Author Topic: Engine mod - thoughts?  (Read 13148 times)

bheston

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Engine mod - thoughts?
« on: April 24, 2018, 10:06:08 AM »
My 69 SS has the original 350 numbers-matching block. After looking up the other numbers, I know that the intake manifold and the heads are not period correct. Furthermore, the carb is not correct either. It appears like most of those bits were from 1972 to 1977 donors.

I’d like to rebuild the motor and get a few more ponies but I still want that orange motor with cast iron exhaust manifolds.  At this point, I can’t pull the block, save and buy a crate motor. I’m not flush with unlimited garage space. I’d like to keep the block and maybe the quadrajet carb. I thought about picking up a set of double hump heads with the 2.02 intake valves and putting those on with a DZ aluminum intake and the Holley carb. Not trying to build a Frankenstein but also not trying to put back to original. Any good thought?
« Last Edit: April 24, 2018, 11:52:05 AM by bheston »

Kelley W King

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Re: Engine mod - thoughts?
« Reply #1 on: April 24, 2018, 12:03:25 PM »
I think the quadrajet is fine. I like the L79 350 horse cam. To me the 2.02 valves are the biggest thing you could do along with the cam. If you look for different heads make sure you get the late ones with your accessory holes. Or while rebuilding a good shop can install 2.02 valves in your heads. These mods and some distributer work to help the cam and heads while really lighting things up and look factory. If you want the factory air cleaner look get another bottom and drill air holes where you cannot see them or use the open element type. After this the exhaust will be you main holdback but I think you will be surprised by the power. A set of 3.55 gears and you are set to go.. My 64 corvette has this same setup except a holley and 4.11 gears and it has done well enough to trash some clutches and Muncie gears and it really fun to drive.
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Stingr69

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Re: Engine mod - thoughts?
« Reply #2 on: April 24, 2018, 12:23:41 PM »
I would agree with Kelly - Keep the Q-jet and put some small chamber heads with the 350 HP cam with a later model GM aluminum Q-jet intake.  The DZ Z/28 intake is a great piece but rather pricy these days. 

That 350 HP cam was originally designed for use with a factory restrictive exhaust.  It is inexpensive to install with inexpensive matching valve train and it will last longer with todays lousy oil. Reliable and easy to live with.

I would probably skip adding bigger valves but its your choice. While many shops can change 1.94"/1.5" to 2.02"/1.6" valves, the bigger valves will not deliver more power without additional chamber cutting modifications.  Few shops will know how to do that properly. 

-Mark.


rsms

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Re: Engine mod - thoughts?
« Reply #3 on: April 24, 2018, 04:22:19 PM »
 I also ran an L79 cam in one of my Camaros for years and it is a very good grind.  It will give you good street manners, a good sound and it runs strong thru out the rpm range.  If you use a set of 10 to 1 flat top pistons with a set of stock 461 or 462 heads and a Q jet you will have a very fun car to drive and it will be very streetable.  I ran more compression in mine with a set of angle plug bowtie heads that had a lot of work done to them and a little bit looser torque convertor w/4:11 gears and it would surprise a lot of people.  I will be using that same cam for a L48 car I'm building that will be completely stock except the cam. 

camaroboy68ss

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Re: Engine mod - thoughts?
« Reply #4 on: April 24, 2018, 07:47:41 PM »
I used to run the L79 cam in my 68 L30 327, but a couple years ago went to a Comp Nostalgia 30/30 Hydraulic cam. I have a 69 over the counter aluminum intake and holley carb on it as well dressing the whole thing up like a 302. Setup runs decent, though it could use the pop up pistons instead of the stock flat tops, which i'm looking at installing soon. As stated earlier, just swapping a 2.02 valve into an head that was a 1.94 does not gain anything. I know recently, I think Trick Flow, started making a aluminum head that looks like a factory camel hump head with casting grain and the mold seam down the exhaust ports. The only real change from a GM head was the valve cover gasket surface was a little higher. You could paint the heads and know one would really know the difference. But swapping the heads would probably need a set of headers, which there a few sets out there that look like the stuff you would get in 69 as a day two item and would not look too out of place.
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HustleRussell

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Re: Engine mod - thoughts?
« Reply #5 on: April 25, 2018, 12:37:18 AM »
Build engine to 1969 Corvette L46 specs. 350 HP, cast iron intake and Q-jet carb.
Premium gas would be a must with 11 to 1 compression. L46 is also a/c friendly. 
Russ 
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Kelley W King

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Re: Engine mod - thoughts?
« Reply #6 on: April 25, 2018, 11:58:04 AM »
There are many opinions on valve size out there. Most all GM HP versions included larger valves. On big blocks they say oval ports are better for the street but odd that most aftermarket ovals have the 2.19 valves. I tried to build a L78, cam,intake, carb,ect. with the small valve ovals. Just was not the same until I installed the big valve heads. Did the same thing on a smallblock trying to make a L79.
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Stingr69

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Re: Engine mod - thoughts?
« Reply #7 on: April 25, 2018, 01:03:00 PM »
Factory big valve head chambers.  You can see where the cuts were made around the intake valves to unshroud them for better flow.  You can still find them out there but they are pretty rare.  These were unmolested/uncut originals when I got them but the intake valves were pretty worn so they got replaced.  Original exhaust valves looked fine so they were reused.  New guides all around. 


Sorry, not for sale.   :(



bheston

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Re: Engine mod - thoughts?
« Reply #8 on: April 25, 2018, 01:06:01 PM »
Ohhh, looks cool.  Are those 2.02?

Stingr69

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Re: Engine mod - thoughts?
« Reply #9 on: April 25, 2018, 01:12:13 PM »
Yes, 2.02" x 1.6"

Kelley W King

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Re: Engine mod - thoughts?
« Reply #10 on: April 25, 2018, 05:49:11 PM »
When I am at swap meets my rule of thumb is if the valves look like they touch they are 2.02,s. Any space they are not. They are kind of rare but you would think with all the guys going aluminum there would be some out there.
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69Z28-RS

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Re: Engine mod - thoughts?
« Reply #11 on: April 25, 2018, 05:52:04 PM »
I have one or two extra sets of 186/2.02 heads which have been rebuilt totally... 
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bcmiller

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Re: Engine mod - thoughts?
« Reply #12 on: April 25, 2018, 07:14:39 PM »
When I am at swap meets my rule of thumb is if the valves look like they touch they are 2.02,s. Any space they are not. They are kind of rare but you would think with all the guys going aluminum there would be some out there.

Old rule of thumb, use a dime. If it doesn’t fit between the valves, then it has 2.02 intake 1.60 exhaust.

And yes, they are out there.
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X33RS

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Re: Engine mod - thoughts?
« Reply #13 on: April 25, 2018, 07:37:49 PM »
The 186 and 462 heads are relatively easy to find.  Most are of the 1.94 variant which isn't a big deal.   I never run a set of old heads without completely going through them, and for me that means new valves, seats and guides, positive seals etc...  While doing that it's not a big deal to upgrade to the 2.02/1.60 valve arrangement.   As far as I'm concerned, I'm paying for all this stuff either way so it's a no brainer. 
  So don't pass up a set of heads just because they're 1.94's, chances are they'll be priced cheaper anyway, and smart money says you'll be sending them to a shop for a rebuild so.....   
 

Kelley W King

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Re: Engine mod - thoughts?
« Reply #14 on: April 25, 2018, 09:49:25 PM »
An old round tracker told me about valves, .08 does not seem like much, but when you calculate the circumference of the circle times the lift of the valve the area of flow picks up quite fast. Increase the cam lift and duration and the .08 increases power pretty well.
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