Carburation Ideas

[WaltZ]

If I were to change from my original 780 Holley on my stock 302 69 z, what would be suggested.
Would like to keep it looking proper when air cleaner is on it.
no computer or elect pieces.
Thanks in advance.

[firstgenaddict]

Why change from the 4053? Are you having issues?

[WaltZ]

yes, not totally sure if I will change or keep putting $$s into it until it's off idle hesitation is gone. I have exhausted everything, including sending it out 2 times to a highly recommended carb shop in New Jersey.
Timing spot on and adjusted with vacuum gauge and checked for leaks.
Just looking for a carb recommendation.
So much help offered here on this site and tried just about all of it.

[crossboss]

Use the very common 'aftermarket' Holley and very similar in the looks department would be a 750 cfm 3310 model. Summit Racing and others can sell you one in the mean time while getting the OEM 780 version working properly.

[WaltZ]

thank you

[bertfam]

1. Send your carb to Jerry.
2. The newer 3310 carbs are not the same as the original 3310. The newer 3310 carbs are a 4160 model (instead of the original 4150 model) with a primary metering block but a secondary metering plate. If you plan on using your original fuel lines, they won't fit (Some great info HERE). Not only that, but your automatic choke won't work. The original 3878261-EH 3310 used a hot air choke and the later 3310's use a manual choke, or an electric.
3. Send your carb to Jerry, or find a good used 3878261-EH (3310) or aftermarket 3310-1 core and send it to Jerry if you don't care about the choke.
4. Buy a new reproduction 3923289-DZ.
5. Send your carb to Jerry.

Ed

[WaltZ]

I am thinking about sending it to Jery, but want to be able to put something on to use while he has it, hopefully using the existing fuel lines,
thanks
Walt

[Tinkerr]

Have you checked the points gap. I used to set mine at 30 degrees with a dwell meter. Had a issue with a hesitation turned out to be the points were off. Corrected to 30 degrees and solved the problem.

[WaltZ]

using a pertronics

[GMAD_Van Nuys]

If your valve clearances are set too tight, it can cause a rough idle.

[crossboss]

using a pertronics

Thats most likely a high percentage on your issues. Pertronix has a failure rate of over 50%. 'I' would never use it.

[MO]

I agree with Ed's numbers 1,3 and 5. Let him know the issues you're having and I'm sure you won't be disappointed. As for the Pertronix, I think it's a good choice. I've used it on several cars as well as friends using them without any issues. Then again, some may find problems, but over 50%?

[crossboss]

I agree with Ed's numbers 1,3 and 5. Let him know the issues you're having and I'm sure you won't be disappointed. As for the Pertronix, I think it's a good choice. I've used it on several cars as well as friends using them without any issues. Then again, some may find problems, but over 50%?

Yes, over 50% failures. Other car sites/owners report the same. Many engine builders hate it. Many have failed with in minutes, some failed in weeks. Check the online chat boards...its not good for Pertronix. Remember the ill failed Mallory Unilite? Same as Pertronix. That said, IF you like it, use it. I wont.

[69Z28-RS]

If your valve clearances are set too tight, it can cause a rough idle.

I agree with Ed's numbers 1,3 and 5. Let him know the issues you're having and I'm sure you won't be disappointed. As for the Pertronix, I think it's a good choice. I've used it on several cars as well as friends using them without any issues. Then again, some may find problems, but over 50%?

Yes, over 50% failures. Other car sites/owners report the same. Many engine builders hate it. Many have failed with in minutes, some failed in weeks. Check the online chat boards...its not good for Pertronix. Remember the ill failed Mallory Unilite? Same as Pertronix. That said, IF you like it, use it. I wont.

Where do you get that failure rate Cross?   Do you have the raw numbers you used to calculate it??

[jdv69z]

yes, not totally sure if I will change or keep putting $$s into it until it's off idle hesitation is gone. I have exhausted everything, including sending it out 2 times to a highly recommended carb shop in New Jersey.
Timing spot on and adjusted with vacuum gauge and checked for leaks.
Just looking for a carb recommendation.
So much help offered here on this site and tried just about all of it.

Is your jetting stock 68/76? How about accelerator pump cam? 72/76 jetting works well for my Z, and I changed the accelerator pump cam to initiate the fuel shot sooner. I think the Z had this issue from the factory originally as a result of the emissions tuning requirements. Mine also reacts differently depending on air temperature. Definitely more off idle hesitation when it is colder outside, cold air density is higher; so mixture is leaned somewhat. The carburetor is a compromise of settings trying to cover the different conditions encountered during different driving situations, idle, cruise, accelerate, etc. I believe drag racers are constantly making adjustments to their carbs depending on air temp, humidity, etc. This is what today's fuel injected, computer controlled cars are able to do, make constant adjustments for changing engine requirements.

[crossboss]

If your valve clearances are set too tight, it can cause a rough idle.

I agree with Ed's numbers 1,3 and 5. Let him know the issues you're having and I'm sure you won't be disappointed. As for the Pertronix, I think it's a good choice. I've used it on several cars as well as friends using them without any issues. Then again, some may find problems, but over 50%?

Yes, over 50% failures. Other car sites/owners report the same. Many engine builders hate it. Many have failed with in minutes, some failed in weeks. Check the online chat boards...its not good for Pertronix. Remember the ill failed Mallory Unilite? Same as Pertronix. That said, IF you like it, use it. I wont.

Where do you get that failure rate Cross?   Do you have the raw numbers you used to calculate it??

No, I don't have any graphs, charts or actual data numbers. You don't have to be a rocket scientist to know when over 50% fail its a cause for alarm. Pertronix has admitted to the issues. That said, I have seen it first hand from others, read the comments on the chat boards/other car sites I frequent. Also, many engine builders don't like Pertronix products. Btw, NO racers (that I know of) use them. When people say "Keep an extra set or points in the glove box just in case" you KNOW its unreliable. For GM cars, I would use Accel's electronic conversion, Mopar has their own excellent electronic ign. system, and for the Ford's I use their excellent OEM and dead nuts reliable Duraspark II. Lastly, IF you like Pertronix, and it works for you, by all means keep it. For me, I would throw it in the trash.

[bertfam]

Chat boards are NOT what I would call trustworthy sources and I can find nothing online where Pertronix has admitted to that failure rate so I called them and spoke to the Tech Support department head. He stated that at no time has Pertronix ever admitted to a 50 percent failure rate. As a matter of fact, he said that if they actually DID have that large of a failure rate, they'd probably be out of business!

When I first got my 55 Nomad, I installed the Pertronix Ignitor 2. I had the car for over 10 years and when I sold it, it was still working. I also installed the Ignitor 1 on my 68 Camaro 25 years ago and it was still working when I made the change to the Breakerless-SE a few years ago. The only reason I changed was for the "one-wire" conversion of the SE instead of the two wires of the Pertronix.

Ed

[crossboss]

Chat boards are NOT what I would call trustworthy sources and I can find nothing online where Pertronix has admitted to that failure rate so I called them and spoke to the Tech Support department head. He stated that at no time has Pertronix ever admitted to a 50 percent failure rate. As a matter of fact, he said that if they actually DID have that large of a failure rate, they'd probably be out of business!

When I first got my 55 Nomad, I installed the Pertronix Ignitor 2. I had the car for over 10 years and when I sold it, it was still working. I also installed the Ignitor 1 on my 68 Camaro 25 years ago and it was still working when I made the change to the Breakerless-SE a few years ago. The only reason I changed was for the "one-wire" conversion of the SE instead of the two wires of the Pertronix.

Ed

Ed,
No BS here. Of course the Pertronix tech is going to tell you that. Btw, you were one of the 'lucky' ones. With all due respect, don't say I did not warn you, and come crying to me when yours fails. Like I said, IF you like it, keep it. To each their own...

[bertfam]

You might want to think about retracting some of your comments. People have been sued for MUCH less.

Ed

[crossboss]

You might want to think about retracting some of your comments. People have been sued for MUCH less.

Ed

Ed,
Sorry you feel that way. I can say for certain it is true. Others CAN testify to the comments made. Lets move on...

[bertfam]

It makes me no never mind. I'm just stating fact from Pertronix and my own personal experiences. If you want to continue running down a product based on nothing but hearsay, that's your perogative. But like I said, people have been sued for a lot less.

And I agree. Let's move on.

so.... which carburetor to install? There's also the HOLLEY 4779 carb. It's a 750 double pumper but you would be able to use the stock fuel lines.

Ed

[crossboss]

Why not consider a 650 DP? Might be a better choice for some drivability on the street than the 'larger' carb(s). Most guys aren't racing their Z/28s...just a thought...

[bertfam]

Why not consider a 650 DP? Might be a better choice for some drivability on the street than the 'larger' carb(s).

Now THAT I can agree with! Most people install carbs that are way too much for what they're doing. Heck, even HOLLEY recommends a 650 for the 427 I'm installing in my 57 Chevy!

I sent Jerry a Holley 4777 650 double pumper I plan on trying out and I should be getting it back within the next few weeks. I also sent him two 3310's (both 3878261-EH carbs) that I'll try out and see which I like better, the 650 or the 780. I have a feeling the 4777 650 double pumper will be more in line with the street especially since I don't plan on pushing the RPM's past 5k.

Take a look at the Holley site and be honest with the numbers. If you have a 302 that's stock, but never plan on revving it past 6k, even a 4776 600 double pumper would be good enough! Or, a 4777 650 double pumper if you want a little more.

Ed

[WaltZ]

70 primaries...78 secondaries
timing 10 advanced... total 38@2500rpms
28 squirter, will try a 31 as soon as I get back to my car.

[MO]

By crossboss: Why not consider a 650 DP? Might be a better choice for some drivability on the street than the 'larger' carb(s).

Now THAT I can agree with! Most people install carbs that are way too much for what they're doing. Heck, even HOLLEY recommends a 650 for the 427 I'm installing in my 57 Chevy!

I sent Jerry a Holley 4777 650 double pumper I plan on trying out and I should be getting it back within the next few weeks. I also sent him two 3310's (both 3878261-EH carbs) that I'll try out and see which I like better, the 650 or the 780. I have a feeling the 4777 650 double pumper will be more in line with the street especially since I don't plan on pushing the RPM's past 5k.

Take a look at the Holley site and be honest with the numbers. If you have a 302 that's stock, but never plan on revving it past 6k, even a 4776 600 double pumper would be good enough! Or, a 4777 650 double pumper if you want a little more.

Ed

Great info in both of the responses above. But what about for the person that wants to keep their car stock? My carb was restored by Jerry and went on the dyno with my 302 after he rebuilt that. So, I have no doubt it's perfectly set up.

Otherwise, I think you have to start by checking the float adjustment and move to checking spark plug color. Once you figure that out and know which jets work best for your driving style, you can play with power valves.

[bertfam]

I could be wrong but I think he's looking for something temporary while he gets his original carb sorted out. His only real requirement is that it has to use the same fuel line setup as the DZ carb, which rules out Edelbrock carbs and all Holley 4160 series. It's going to be hard finding something cheap for just a short time use.

Ed

[crossboss]

I could be wrong but I think he's looking for something temporary while he gets his original carb sorted out. His only real requirement is that it has to use the same fuel line setup as the DZ carb, which rules out Edelbrock carbs and all Holley 4160 series. It's going to be hard finding something cheap for just a short time use.

Ed

I agree. The OP was looking for a temporary replacement. However (again, just my opinion), he may actually like the drivability of the 650 DP better...and enjoy the car that way. Obviously, keep the OEM 780 IF you ever choose to sell the car, OR have it fixed in the near future. Some options to consider...

[WaltZ]

great input, thanks for getting back to my needs.
maybe for cheap than I should just out change the gas lines
Thanks again everyone.
will be back to my car in about 10 days, I am sure you will being hearing from me again on this post as to how it's going

[bertfam]

In that case you should be able to get a rebuilt Edelbrock 650 for around $300. Like I stated before though, I'm not a fan of these carbs and have no experience with them, so hopefully someone that has one will chime in on how well they work. The only thing I know about them is that the Garage Squad puts them on EVERYTHING!! (or fuel injection)

Ed

[janobyte]

Dad had a 650 Edelbrock on the 302 when it was doing street/strip duty in the Anglia. Ran great, good manners on the street. I never played with it but said easy tuning,,rods.

Same old carb was on his last project. No issues, no leaks.

[crossboss]

The Edelbrock carbs are made by Weber. They are almost an exact copy of the older Carter carbs. Both versions are an excellent performer, and very reliable...aka 'set it and forget it'. I speak from experience, used many on different makes and engine sizes (CID). That said, they wont have the 'look' for a DZ type of engine though...IF that is a concern.

[crossboss]

Also, Summit makes/sells a close direct copy (with their name on it) version of the old Autolite 4100 series of 4V carbs, known as 'The Cracker Box'. Its a great performer, highly tunable, excellent throttle response, and extremely reliable. Again, it wont have the correct 'look' for a DZ engine. Many choices out there...

[WaltZ]

FIXED: FUEL PUMP
Prior to all the tinkering, adjusting and frustrations I tested the psi, 3 different times,  had 5-6 pounds..
yesterday, the fuel pump decided to leak, quite badly, around the upper and lower sections thru the ring.
An obvious replacement was done and guess what, NO MORE HESITATION.
Totally a bad coincidence; pump started failing when restored 780 was installed.
I guess the assumption that a mechanical fuel pump is either good or bad has not proven to be.
Was so happy that I drove the car like I just stole it!
Thanks for all the help.

[usa1ti]

Great to hear! Sometimes if the mechanical diaphragm leaks externally through the weep hole it has leaked internally into the engine. Change the oil and filter just as a precaution.

[WaltZ]

Thanks, ahead of you on that.

[WaltZ]

Amazing what 100s of an inch can do
found an old 2007 post from Jerry and tried his configuration
72s in the primaries and 76s in the secondaries both with 6.5pvs
no more stutter no more stumble.. A whole new beast to say the least.
tuned vacume on carb as recommended and added 1/4 turn
I run the timing at 10*/ 38 with 93 Sunoco......... temp is about 190* 
tried 77s in the secondaries and above 5000 ran extremely strong, but settled on the 76s for my driving.


Thanks to Jerry's old post and everyone's help on this. Zoom Zoom!

[jdv69z]

Amazing what 100s of an inch can do
found an old 2007 post from Jerry and tried his configuration
72s in the primaries and 76s in the secondaries both with 6.5pvs
no more stutter no more stumble.. A whole new beast to say the least.
tuned vacume on carb as recommended and added 1/4 turn
I run the timing at 10*/ 38 with 93 Sunoco......... temp is about 190* 
tried 77s in the secondaries and above 5000 ran extremely strong, but settled on the 76s for my driving.


Thanks to Jerry's old post and everyone's help on this. Zoom Zoom!

Same setup I run. Works well for me.