Author Topic: 69 302 on pump gas?  (Read 4208 times)

deadmetalprez1952

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69 302 on pump gas?
« on: December 11, 2016, 10:02:49 PM »
Anybody here running their 302 on pump gas? I heard with the stock cam they can run on Super, I have a zip 510 cam and I think I may have to run a mix of 110ll and super...

camaroboy68ss

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Re: 69 302 on pump gas?
« Reply #1 on: December 12, 2016, 05:47:16 AM »
what compression are you currently running? that's a big factor if you plan on running pump gas. My built 350 with 11 to 1 barely runs on super. I usually have to add octane booster to the tank.
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deadmetalprez1952

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Re: 69 302 on pump gas?
« Reply #2 on: December 12, 2016, 01:16:39 PM »
Stock DZ302, just has a bigger cam, so 11.5 to 1?

camaroboy68ss

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Re: 69 302 on pump gas?
« Reply #3 on: December 12, 2016, 08:08:49 PM »
you can try super and if you get detonation, you can mess with the timing then to run on the pump. Although I would still run at least an octane booster in the tank. 
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deadmetalprez1952

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Re: 69 302 on pump gas?
« Reply #4 on: December 12, 2016, 08:39:55 PM »
Ok thanks, I plan on winding it out too like it was meant to be run, I guess I'll try it with super and see how tolerant it is. I have a set of aluminum heads that I was gonna run but they have 210cc runners which are way too big for this little 302...

X33RS

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Re: 69 302 on pump gas?
« Reply #5 on: December 12, 2016, 09:02:12 PM »
Fresh 302 build, everything cc'd, true 11:1 compression using original heads with a slight surface clean up cut and JE original type dome replacement pistons.   Stock solid cam, stock intake and carb, running 36 degrees of total timing all in at 2400 rpms, vacuum advance at manifold vacuum to add an additional ~10 degrees if idle timing.   Runs perfect on 91 octane, driven daily and occasionally romped on.   Plugs show no signs of any detonation.  Even getting 14.2 to 14.7 mpg around town.

deadmetalprez1952

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Re: 69 302 on pump gas?
« Reply #6 on: December 12, 2016, 09:55:27 PM »
Nice, that's what I like to hear! What rear gear are you running? I have an m20 and 4.56 gears. I don't expect to get gas mileage in the teens, haha. The original cam in these cars was the duntov 30 30 right?

X33RS

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Re: 69 302 on pump gas?
« Reply #7 on: December 12, 2016, 10:40:05 PM »
I've been switching rear gears around lately with complete rears I have stashed away.  4.88's were in for a bit, 3.73's, and right now running 3.55's with an M20.   Wife seems to like that the best at the moment.  She drives it daily.

Yes the stock cam is referred to as a 30-30.  I'm running a tight lash version of it (14-14) to keep the valve train beating minimal.

x66 714

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Re: 69 302 on pump gas?
« Reply #8 on: December 12, 2016, 11:18:02 PM »
Mine is set up like X33RS & I have no problems with pump gas. It runs better with racing gas of course. My car is M21 with factory 4.56. Fun in town. Never checked fuel mileage...didn't care....Joe
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deadmetalprez1952

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Re: 69 302 on pump gas?
« Reply #9 on: December 13, 2016, 12:59:58 AM »
Thanks for all the input guys, I won't be daily driving it but don't want it to cost a small fortune every time I take it out.

Kelley W King

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Re: 69 302 on pump gas?
« Reply #10 on: December 13, 2016, 12:34:27 PM »
My 302 and L78 both run OK on pump high test. I try to find non ethanol. But mixing a few gallons of race gas really shows a difference. But with the race gas get out of the shop quick. Stuff really burns your eyes and stinks up anything inside.
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deadmetalprez1952

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Re: 69 302 on pump gas?
« Reply #11 on: December 13, 2016, 01:29:06 PM »
I have easier access to 110ll aviation fuel, and right now it's roughly 4.80 a gallon so that's what I would use if I did use a mixture.

z28z11

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Re: 69 302 on pump gas?
« Reply #12 on: December 13, 2016, 02:24:33 PM »
My 302 and L78 both run OK on pump high test. I try to find non ethanol. But mixing a few gallons of race gas really shows a difference. But with the race gas get out of the shop quick. Stuff really burns your eyes and stinks up anything inside.

At least you know when you're around a Holley burning high octane gas. Not a stink to me, just a mark of GM high performance - lol. Plus an unforgettable odor -

Regards,
Steve
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cook_dw

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Re: 69 302 on pump gas?
« Reply #13 on: December 13, 2016, 03:08:33 PM »
My 302 and L78 both run OK on pump high test. I try to find non ethanol. But mixing a few gallons of race gas really shows a difference. But with the race gas get out of the shop quick. Stuff really burns your eyes and stinks up anything inside.

At least you know when you're around a Holley burning high octane gas. Not a stink to me, just a mark of GM high performance - lol. Plus an unforgettable odor -

Regards,
Steve


   


These are what I run in the blue and green cars...  Along with 90 octane from the local COOP and 5-7 gal of Renegade Racing Fuels Pro110+.  They will both run on the lower octane just have to knock the timing down to around 28 degrees total.. 
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X33RS

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Re: 69 302 on pump gas?
« Reply #14 on: December 13, 2016, 04:12:19 PM »
Wow, that's knocking a lot of timing out of it.

I have had a fair amount of success running high compression engines with cast iron heads on the street with pump gas.   But I'll admit, with pump gas getting worse, I felt the need to cheat a bit with mild modification on this build knowing it was going to see a lot of street miles.   
    So when I built the 302, knowing a steady diet of 91 pump would be used, but not wanting to detune, I took extra precautions.  Making sure piston wasn't in the hole (near zero deck height promotes better mixture motion and fights detonation)  I also removed all sharp edging from the piston crowns, as well as the combustion chambers.  I run a cooler plug, and I also keep engine temps in check with cooler stat.  We were also careful with camshaft position, making sure we had enough off seat timing with later intake closing so as not to build cylinder pressure too early in the rpm range.
  Really have to stay on top of the tune as well.  On the dyno we found 36 degrees to be a happy spot for the engine on 91 octane, where it made best power and no sign of detonation.  Carb jetting was 74-72 front side left to right, and 82-80 rear left to right with the rear power valve blocked.  Stagger jetting helps the lean cylinders and makes a smidge more power.
   Driving the car during the hot desert summer time is where I was most worried.  Hot ingested air and warmer engine temps under load is where I thought I might have a problem.  Engine never ran over 185 shooting with a temp gun, and plugs are showing no signs of detonation.
   I'm willing to bet if I wanted to run some high octane race gas and crank some more timing in it,  38-40 degrees maybe, It might make a few more ponies, but I'm extremely happy with the performance and how the car drives on crap pump gas.   When the car hits the track I may play with timing and fuel just to see if I can find anything.

cook_dw

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Re: 69 302 on pump gas?
« Reply #15 on: December 13, 2016, 04:33:37 PM »
Wow, that's knocking a lot of timing out of it.


They will both run on the LOWER octane just have to knock the timing down to around 28 degrees total.. 

IE lower than 90..  Im not looking for performance on 87 octane.   Im not trying to write an article for Hot Rod or insert magazine here..  I pick a point where there is not noticeable knock and the plugs look decent and run it..  That being said; I try to never run that low of octane for the simple fact I did not wish to constantly adjust the timing..  Im not at the track and neither are the majority of the cars here on the forum..  Im not gonna bore everyone with useless knowledge that doesnt benefit anyone..  Its pointless and most will have glazed over eyeballs..  Original point was to the comment on the smell of the fumes and you can make it more pleasant with fragrance additives..  You can make one of these engines work on watered down 87  if you want but these engines were not meant to be done that way so why try to reinvent the wheel..  Run 90 or 87 or piss...  Get it to run on it and enjoy it..

Im out..
Darrell Cook

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deadmetalprez1952

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Re: 69 302 on pump gas?
« Reply #16 on: December 13, 2016, 05:13:18 PM »
I have 93 octane in a few local pumps here, sounds like a lot of you guys can only get 91 for premium pump gas. Maybe I will try to run the 93 straight and see what happens. As a last resort I can always run 3 gallons of 110ll aviation fuel to a tank.

Kelley W King

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Re: 69 302 on pump gas?
« Reply #17 on: December 13, 2016, 07:27:37 PM »
I hear AV gas is not good. Formulated with high altitude and additives for plane engines. If you are local  to water, boat marinas usually have high octane and most are totally ethanol free, but it ain,t cheap either.
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X33RS

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Re: 69 302 on pump gas?
« Reply #18 on: December 13, 2016, 07:41:47 PM »
Yep 91 here is as good as it gets.   I wouldn't call any of that useless information.  Anyone that calls themselves a true car enthusiast like myself will drive these things and enjoy them.  I already have garage queens and I'm sick of that.  Getting too old to just stare at these things.   My wife loves driving them and this Z was put back on the road for her to enjoy.  Since I had the opportunity to rebuild the engine, I took advantage of some tricks.
  But with that said, being who I am, I won't detune (deface) a real deal Z28 just to run cat pee in it so I applied what most good engine builders know.  I actually built this engine with the intent to run at the PS drags and followed the rules of that class.  The car is still getting a concours type restoration though.  I want the car to look correct in everyway, but it also has to run as good as it looks.  At the same time I had to run pump gas in it.  I was confident that we could run pump with 11:1 comfortably.  It's not a purpose built track car by any means and I hope I didn't come off that way, but I enjoy the hell out of the PS drags, running stock rubber, and that's the only kind of track time the car will see for a little fun.  Not enough 1st gen Z's compete in that class.  But it's still a street car first and foremost. 
I did the same recipe with my 70 Formula about 20 years ago and raced it quite a bit, but it too was primarily a fun driven street car that ran pump gas.  Back then we had 94 Sunoco.  Now it's running on 91 and complaining a bit.  That engine is currently getting some minor changes to make it happy.

I actually find the engine part of the equation just as interesting as the restorations I do and enjoy every aspect of it.  You can really squeak some power out of these things while still looking completely stock.  Fascinating stuff.   So I would tend to think that at least some of the true enthusiasts here would be interested in the same.

bcmiller

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Re: 69 302 on pump gas?
« Reply #19 on: December 13, 2016, 08:29:30 PM »
Engine designs have changed and a lot of us detune for street cruising.

302s had their day. Build a 10 or 11 to 1 small block 406 if you want power from off idle and want to stay small block. 572hp @ 6000 rpm is fairly easy to do. That's not the peak hp yet, just what it was run to on the dyno during break in. And it will rev to 7500 for shifts. :)
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X33RS

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Re: 69 302 on pump gas?
« Reply #20 on: December 13, 2016, 09:16:15 PM »
That's cool, I like that stuff too.  My father built a 571 Pontiac that dyno'd 760 on pump gas.  He's driving that thing everywhere and loves it.  I'm currently doing a 502 BBC with AFR heads that should go over 700hp on pump gas, it will be going in my chevelle street car.

The Z was a different deal.  Running the Pure Stock drags, your stuck with what the car came with and very little wiggle room what you can do with it.  Besides, being a real Z I just couldn't bring myself to run anything but the 302 in it so a bigger engine wasn't in the cards for this car.  Even with it's limited size it still just topped 400 hp at 6700 and carried it to 7,000.  I was happy considering no porting anyplace and a stock type cam.     Given the rules though, The Z isn't the most advantageous car to start with anyway.  My firebird is a much better package for a class like this.  But it's fun either way.

deadmetalprez1952

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Re: 69 302 on pump gas?
« Reply #21 on: December 13, 2016, 09:23:23 PM »
The z motor I'm running is in a 55 Bell Air, it was put together in the late 60s and sat ever since 74. I don't really want to run a different motor because to me this car is a time capsule. It is untouched from the way it was built in the late 60s. I have thought about selling it and building a more street able motor bit that just wouldn't be the same...

bcmiller

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Re: 69 302 on pump gas?
« Reply #22 on: December 13, 2016, 09:55:45 PM »
Nothing wrong with running what you have. Just realize what you are working with and it's limitations.
Bryon / 1968 Camaro SS 396 - now 468 ci, M21, 12 bolt
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X33RS

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Re: 69 302 on pump gas?
« Reply #23 on: December 13, 2016, 10:44:08 PM »
Yeah it's fun for what I'm doing.  Truth be told, if I really wanted to be quick in the class, and run a camaro, I'd build a clone COPO dedicated to the class and exploit all the rules, and have some fun without the collectability worries.  With the Z I'm limiting myself with what it's capable of.  I'm in the same boat with the firebird.   At the end of the day it doesn't matter too much though, they pair you with another car based on qualify time, and then run heads up best 2 out of 3.  So you never know what you're going to get.

X33RS

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Re: 69 302 on pump gas?
« Reply #24 on: December 13, 2016, 10:48:33 PM »
The z motor I'm running is in a 55 Bell Air, it was put together in the late 60s and sat ever since 74. I don't really want to run a different motor because to me this car is a time capsule. It is untouched from the way it was built in the late 60s. I have thought about selling it and building a more street able motor bit that just wouldn't be the same...

Understand totally.  I have a 56 Nomad, that's had a screamin' 327 since the early 70's when my father took possession (already in it so probably longer) and the car is untouched since.  I daily drove it in highschool back then and had a blast with it.  I just refreshed that motor/trans and 4.56's in it.  I have no plans to change the car from what it is/means to me.

Bigblockbird

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Re: 69 302 on pump gas?
« Reply #25 on: January 17, 2017, 01:28:40 AM »
There are so many factors contributing to running Pump Gas or not.
As someone said obviously timing is a huge factor but often people forget about fuel mixture.
By that I mean your Fuel air Ratio.
On my 1969 Z/28 Original 302 Double Hump heads correct factory Cam and a Winters Crossram with those two ridiculously overfueled carbs for a Street Car, I haven't once heard any detonation even under low rpm heavy load.
I do however make sure I buy 93 Octane Ethanol Free fuel.
While Ethanol can reduce spark knock it plays hell on rubber hoses mot made for an Alcohol laden fuel.
Is 10-15% Ethanol enough to be a problem. I don't know, but I will tell you this. Alcohol of any type requires a much bigger jetting and if you run an engine lean it is much more prone to pre-ignition spark knock.

Mike S

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Re: 69 302 on pump gas?
« Reply #26 on: January 17, 2017, 02:55:40 PM »
 Here on Long Island, all gas sold has 10% ethanol. It used to be seasonal but it is all season now. A product like Ethanol Shield will be needed.

Mike
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X33RS

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Re: 69 302 on pump gas?
« Reply #27 on: January 17, 2017, 03:56:02 PM »
I'm probably one of the few, maybe the only one here that is daily driving their Z with it's 11:1 302 on pump gas.

I can tell you all the gas here in AZ is 10% ethanol.  I've also tested the gas with one of those cheap testers you get off ebay and found that even though it's advertised at 10% at the pump, I've found variations as high as 17%.   So each fill up can change slightly.

Ethanol requires a richer fuel mixture.   Normal stoich AFR for real gas is 14.7:1.   With 10% ethanol mixed in stoich is 14:1 so an increase in fuel consumption of .7 is required to maintain stoich.

I use a wideband to dial my cars in and tend to run them slightly rich to compensate for this.  It's the only way to tune these carbs precisely.   I also have the pleasure of dealing with major swings in altitude, living at 5,000 ft and routinely driving as high as 7,000 and down to sea level.   Fun to find a happy medium that works well everyplace.  Lots of practice knowing what works, and can't do it without that wideband. 

What I also do with my gas is mix in 1:5 ratio (1 ounce per 5 gallon of gas) of 2 cycle oil that has TCW3.  This acts as a lubricant in the fuel.  Lead used to be your lubricant but that is now gone.  But it also has cleaning properties and has cut down on carbon buildup on a couple engines I've torn down with long term use.   I'm not sure if this has any counter active affects towards the corrosion of the ethanol but I'm happy to report that after 10 years of using it in 12 different cars here I've never had any fuel related corrosion issues anyplace in the fuel systems.

deadmetalprez1952

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Re: 69 302 on pump gas?
« Reply #28 on: January 17, 2017, 04:31:24 PM »
Thanks for all of the input. I have been researching avgas and I'm gonna try running a premium fuel/avgas mix. The local airport has it self serve for around 4 bucks a gallon and all of the local dirt track guys buy their fuel there instead of the expensive vp fuel.

X33RS

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Re: 69 302 on pump gas?
« Reply #29 on: January 17, 2017, 04:49:18 PM »
Have you tried just running straight premium pump gas yet?  What octane is in your area?

I'd certainly try pump first and save your money.    We have crap 91 here and the Z is doing fine on it.

69Z28-RS

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Re: 69 302 on pump gas?
« Reply #30 on: January 17, 2017, 05:47:53 PM »
... portions removed...
What I also do with my gas is mix in 1:5 ratio (1 ounce per 5 gallon of gas) of 2 cycle oil that has TCW3.  This acts as a lubricant in the fuel.  Lead used to be your lubricant but that is now gone.  But it also has cleaning properties and has cut down on carbon buildup on a couple engines I've torn down with long term use.   I'm not sure if this has any counter active affects towards the corrosion of the ethanol but I'm happy to report that after 10 years of using it in 12 different cars here I've never had any fuel related corrosion issues anyplace in the fuel systems.

Interesting post... :)

but one clarification...  I suspect the addition of any kind of oil to the fuel in a car with a catalytic converter would NOT be a good idea???
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X33RS

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Re: 69 302 on pump gas?
« Reply #31 on: January 17, 2017, 06:27:15 PM »
Good question Gary.    If you look at the Lucas Oil fuel additive it's recommended for all makes and models, as well as diesel.  I don't recall seeing any mention on those bottles about converters.  So not sure what to think about that.  But if I had to do a sniffer test I probably wouldn't have any in the tank for that, lol.

I used to use the Lucas fuel additive for years, but at $30 a gallon and a dozen cars it got too costly.  The mix ratio of the Lucas is also very large, so you use quite a bit more of it.  One thing I also noticed with Lucas, is that there seemed to be no ill affects if you had more than the recommended dose.  It is very forgiving.

The 2 cycle oil I've been doing is basically the same deal.  But I get a gallon of it for $13 and I mix a very small portion (4 ounces will do 20 gallons)   This seems to be the ideal ratio. So a gallon of this stuff will do about 600 gallons of gas.   The drawback is that it's not as forgiving when it comes to the mix ratio.  Get too much in there and you'll notice a little bit of a smoke show out the tailpipes.  Not harmful but performance suffers.

  I mainly started doing this just for the lubricity in the fuel, to lube the upper valve train components (valve guides, seats) as well as the upper cylinder walls as fuel is washed down and combusted.  I also mix an ounce in a 5 gallon can for the lawn equipment.   The 2 cycle oil with TCW3 in it also has mild detergents and cleaning ability (much like Lucas)

I also pick up a small MPG increase while using it.  Usually on average about 1 mpg is what I see. 

BULLITT65

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Re: 69 302 on pump gas?
« Reply #32 on: January 17, 2017, 08:50:48 PM »
Good thread (I just finished reading it).

So I have the original 302 in my car with just under 48k miles on it. To the best of my knowledge, from all the paperwork, and in talking to the original owners family the motor has never been out of it, or had any major service work done( ex: hardened seats installed, or stainless steel valves). My car is in northern Indiana, and the Citgo has 93 pump gas (sorry don't know the ethanol %). I have run that in the car for the last almost 1000 miles (since I got the car), and never had it ping or pre-detonate. Now mind you I am only around the car a couple times a year at best, but I do use it as a driver when I am in town, so I have been in traffic with it and it sees normal street driving. While there is not any hills in indiana to really put it under a load, I do tend to do a couple of hole shots with it on the back roads and the car runs really solid. Again this is with the stock manifolds, full exhaust (even the smog pump).
So as mentioned give it a whirl on the highest octane (91-93) pump gas you have locally and see how it performs. If you need to you can always take out a little timing and run a colder plug, or go the other route with a additive. I agree with Larry (x33RS) if you can see to putting a wide band in your car, you can really dial it in. You will never want to take that gauge out of your car once you install it. It is a great feeling to look over and see it at around 13 ( i have one in my 64 C/10)
Have fun and let us know the results. :)
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dutch

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Re: 69 302 on pump gas?
« Reply #33 on: January 17, 2017, 11:01:21 PM »
Have a friend who runs a 302 configured stock and he uses local airplane (on floats) gas - 100 Low Lead that is mainly for radial engine aero stuff (110 is mostly in non radial engines around here) and he seems to like it.
He said the lead content compares well to older high test fuels for combating valve seat problems and the 100 octane rating is sufficient for use in motors such as his.
Lately the going rate - this is in CDN $$ and imperial gallons and was around $1.30 a liter when our best pump high test crap is in the $1.20 range and probably tainted with varying amounts of ethanol.
Not sure how that works out for a US gallon - but its in the $5.90 range here verses $5.40 - works and is well worth it according to his experiences!
I'm betting $5.90 per any gallon is far and away enough down in the States to buy any type of special or racing fuel - so consider yourselves lucky!   

Z28Project

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Re: 69 302 on pump gas?
« Reply #34 on: January 18, 2017, 04:08:09 AM »
As far as pricing goes, I just bought 15 gallons of Rockett 110 leaded for $6.66/gal. to mix with premium.

I haven't tried to buy avgas for years but when I went to buy some many years ago they wouldn't sell it to me!  Maybe that would be different now.
John

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X33RS

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Re: 69 302 on pump gas?
« Reply #35 on: January 18, 2017, 04:13:32 PM »
Throughout the 80's we would occasionally swing into the local airport and could pump av gas right into the cars.  A couple of local gas stations sold good 110 octane race gas, and at that time it was $4 a gallon.  I used that on occasion.  As the years went on the price increased but what became the biggest issue was that we were no longer allowed to pump directly in the cars at the airport or at the gas station.  Had to resort to filling cans and transferring to the cars.  That gets old real fast.  It also limits the distance you can drive the car.    That same 110 octane is still sold at a couple gas stations but you'll pay $8 a gallon for it now, and you still can't pump it directly in the car.   No thanks.

After all that silliness we quit building ultra high compression engines for the street.   The last one my father had was a 12:1 motor with iron heads.   He was happy to see that engine go.   With the power that can be made on pump gas now we haven't built anything but pump gas engines ever since.  Dad's latest made 760 on crappy 91 pump.   If you truly enjoy driving these cars like we do, and go the distances that we do, making them run on pump gas is a must anymore.

In the case of the DZ engines, I still built mine with 11:1 to keep it authentic, but also because I knew it would run on pump no problem.   The overlap and off seat timing of the factory cam bleeds off enough low speed cylinder pressure that it will run fine on pump at 11:1 with normal timing curves.  Matter of fact, I wouldn't run this cam in the 302 with any less compression than what is advertised, it would just be a dog, with poor throttle response and no low end at all.

Z28Project

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Re: 69 302 on pump gas?
« Reply #36 on: January 18, 2017, 04:26:47 PM »
Good info!  Getting ready to have DZ engine built using JE pistons, stock heads and stock cam.  The piston domes look slightly smaller than the originals so I'm going with .030 head gasket instead of .039.  I'll see how it turns out.
John

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deadmetalprez1952

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Re: 69 302 on pump gas?
« Reply #37 on: January 18, 2017, 04:29:45 PM »
Doesn't the dz come stock with .010 head gaskets?

69Z28-RS

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Re: 69 302 on pump gas?
« Reply #38 on: January 18, 2017, 04:59:41 PM »
Chevy's engine originally used steel shim gaskets, which are generally around 0.020"...
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deadmetalprez1952

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Re: 69 302 on pump gas?
« Reply #39 on: January 18, 2017, 05:05:29 PM »
Have any of you guys milled the heads to use a modern say .041 head gasket but still maintain the factory compression ratio?

Z28Project

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Re: 69 302 on pump gas?
« Reply #40 on: January 18, 2017, 05:09:48 PM »
Oh.  Well I guess I'm not gaining anything at .030.  ;D

I remember using the steel shim gaskets back in the day.  I used to paint them with aluminum paint on both sides before assembly.

I think I like the multi-layer type gaskets better for long term seal.  Any opinions on that?
John

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69Z28-RS

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Re: 69 302 on pump gas?
« Reply #41 on: January 18, 2017, 05:17:38 PM »
If your domes are smaller, your compression will be lower..

If you use a thicker head gasket, your compression will be lower.

There are websites which allow you to put your engine data, including dome volume, head gasket thickness, etc and will compute both static and dynamic compression..

I wrote a very simple spreadsheet to compute static compression ratio which allows me to change any of the variables and see the effect...
Gary W / 09C 69Z28-RS, 72 B 720 cowl console rosewood tint
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X33RS

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Re: 69 302 on pump gas?
« Reply #42 on: January 18, 2017, 07:35:29 PM »
Have any of you guys milled the heads to use a modern say .041 head gasket but still maintain the factory compression ratio?

This is a critical area of the engine build for many reasons.

The factory had the pistons .020 to .025" in the hole.  With the thin metal head gasket and a 64cc head, you would be lucky to see the advertised 11:1 compression ratio.   During tear down this was all checked, with pistons in the hole pretty far, heads that CC a little large because the valves had sunk, my DZ had at best 10.5:1 to 10.7:1 because the deck height was uneven and quench was terrible.  (it's why these engines come apart on day one for stock eliminator blue printing)

Since we are talking about detonation, the ideal situation is to have tight quench.  Most engine builders will shoot for a total of about .40 to .45 quench with steel rods.  The tight quench promotes combustion motion/mixture and fights off detonation, also needs less ignition lead to make power.  Lots of benefits with this.    The worst way to go about this is having the piston in the hole and a thin gasket.
   The best way is to have the piston near zero deck and adjust the quench with the gasket being used.   You can get zero deck a few different ways with rod length and piston pin height changes, but it adds to the cost with custom parts.
    On my build, knowing what we had to start, we decked the block to put the piston .005" in the hole.  But you have to find a machine shop that is willing and able to deck the block without removing your engine stamps.   With that said, I then used a .038" gasket.   .043" quench is what we came out with.   We only gave the heads a clean up mill because we didn't want to shrink the chambers much, and used the JE factory replacement style forged .030" over pistons.  We came out with exactly 11:1 as measured.

Lots of engine building tricks like this, that help make power and in this case, makes the engine a little more octane tolerant.


BULLITT65

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Re: 69 302 on pump gas?
« Reply #43 on: January 18, 2017, 07:39:29 PM »
Good detailed info. thanks Larry
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Re: 69 302 on pump gas?
« Reply #44 on: January 18, 2017, 09:25:29 PM »
Mixing 2 cycle oil into the gas is nothing new.  I have done it in my trucks for years.  Like an ounce per tank.  Doesn't need much.

An old racers trick is to run MMO in aviation fuel if you think it is too "dry".

93 octane pump gas with a 302 can be done, but not universally with full timing.  Usually, as many have stated, you have to back the timing off or mix in some higher octane fuel.

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X33RS

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Re: 69 302 on pump gas?
« Reply #45 on: January 18, 2017, 10:53:01 PM »
An ounce per tank won't do what we are trying to accomplish.  Doesn't hurt but to be more affective a larger dose is needed.  A handful of us experimented, a lot of trial an error, probably a little more than 10 years ago looking for a cheap alternative.  What was found is that an ounce per 5 gallons was about perfect.  Less didn't make a change and more simply caused a smoke condition.   Excellent lubrication properties and cleaning ability with the stronger mix ratio.   But I only brought this up because the discussion turned to the addition of ethanol in the fuel and corrosion concerns, I don't mean to sound like I'm trying to sell this backyard remedy to anyone.  With the horror stories I've read about corrosive ethanol, I've always felt the 2 cycle combats the ethanol corrosion to some degree just based off the dozen cars I use it in and having no fuel related corrosion issues to speak of.   Just a cheap and effective alternative to add to the crap fuel we have rather than buying expensive fixes in a bottle off the shelves. 

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Re: 69 302 on pump gas?
« Reply #46 on: January 19, 2017, 02:34:56 AM »
Oh.  Well I guess I'm not gaining anything at .030.  ;D

I remember using the steel shim gaskets back in the day.  I used to paint them with aluminum paint on both sides before assembly.

I think I like the multi-layer type gaskets better for long term seal.  Any opinions on that?

I build and run Race cars. My current Big block Chevy in my 67 Nova Carbon Fiber/ Fiberglass composite  bodied Tube Chassis drag car is an all Dart 582 inch engine with a net compression of 15.25-1, I run on Methanol with 5% nitro-Parafins in it called M-5 from VP.
I EXCLUSIVELY use Multi Layer Steel Gaskets from Cometic and they never fail, they crush consistently and can easily handle the cylinder pressures of my high compression engine.
I will never use anything other than MLS unless trying to stay true to an all original scenario, even then, who's gonna' see your head gaskets.

cook_dw

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Re: 69 302 on pump gas?
« Reply #47 on: January 19, 2017, 02:56:40 AM »
I EXCLUSIVELY use Multi Layer Steel Gaskets from Cometic and they never fail, they crush consistently and can easily handle the cylinder pressures of my high compression engine.
I will never use anything other than MLS unless trying to stay true to an all original scenario, even then, who's gonna' see your head gaskets.

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deadmetalprez1952

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Re: 69 302 on pump gas?
« Reply #48 on: January 19, 2017, 03:00:56 AM »
I would use MLS gaskets if they were thin enough but that would lower compression too much. I will be using .015 steel shim gaskets. I thought about milling the heads to use thicker gaskets but I don't want to ruin the quench...

X33RS

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Re: 69 302 on pump gas?
« Reply #49 on: January 19, 2017, 04:05:43 PM »
They make MLS gaskets as thin as .027" for SBC with a 4.060" bore.   I think that's about as thin as they get.  They offer a large variety of thickness to taylor quench and compression.   It's a great gasket, I've used them before on LS builds here, but I considered them overkill for my little 302 build when I could use a standard gasket that gave us exactly the quench we were looking for at half the cost, thanks to putting the pistons close to zero deck.  Bischoff recently used MLS gaskets on my fathers 571 pump gas street engine though.  Only 10.84:1 compression on that engine but Tony doesn't mess around.

I'm not sure exactly what you are working with Deadmetal, but if it's a factory deck height block with factory internals you can bet the piston is going to be .020"-.025" in the hole minimum.  Even with the steel shim GM head gasket at .015" these engines when they are virgin don't have the 11:1 compression they advertise (mine didn't)  They usually fall a tad short.  So in that case I agree, I wouldn't want a thicker head gasket on there.  It lowers the compression more, but also hurts quench and can possibly make the engine more susceptible to detonation if it's tuned on the edge.
   The old thinking was putting thick head gaskets on an engine with high compression was the way to make it tolerable.  But smart engine builders quickly found out that was a bad idea.  Especially when dealing with dinosaur cylinder heads with poor combustion chamber design.

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Re: 69 302 on pump gas?
« Reply #50 on: January 28, 2017, 02:41:00 AM »
Looking forward to a 302 build here in the next few weeks and will have to see how this one reacts to pump gas?

The block will be freshly machined before reinstalling the 302 crank with a new set of 4340 competition series I-beam rods and a new set of forged slugs. This one's getting a Lunati .582" @ 254/262 solid roller cam so it should run like a nasty little thing. The best part is I'll then be waiting to take stock in a new set of Trick Flow 186 aluminum heads. They are a few months from being released and I'm pretty stoked to be in line for a set of these new 185cc aluminum castings. Heads flow 254/207 @ .600" and they accommodate a 1.500" spring required for newer solid roller cams. The engine will then be topped with an Edelbrock Tarantula intake and an AED 750 mechanical carb. I'll post a video of it running before I install it into the green car. Should make a fun little motor to rip around in.
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