Holley Carb Tuning Problems --- Help

[CWPottenger]

[quote="CdnCutlass"Yes I have a 3.5 power valve. The vacuum in gear is only 7-8 inches if it stays running. Holley says divide that number by two and that is the correct size power valve.[/qg


I know this is a pita, but that info brings me back to timing or vacuum leak. For my knowledge @ idle that cam should still make about 12 mmHg. Do you have any other vacuum lines hooked up to carb? If it was me I would unhook and cap all the vacuum ports on engine and carb to eliminate a possible leak. See if it changes how the engine runs. If better I would add vacuum pieces back in till engine got worse. You also state it starts popping at 5500rpm. Does this feel like a backfire or detonation(ping).

 

[CdnCutlass]

The popping at 5500 rpm sounds like more of a backfire, some of it seems to come out the exhaust. I have verified the timing, and even gone to lower octane with no change. That tells me it's not detonation it should have gotten worse.

For vacuum all I have hooked up are the brakes, a PCV, distributor, TCC lockup and the vents for the dash. If there is a leak I certainly can't find it. There was a hissing in the dash and I replaced one of the vacuum operated climate control switches. Even with it disconnected no difference.

I have decided I'm pulling the heads off this winter and at the very least going over everything and resealing the top end. Hopefully I will be able to put a more street friendly set of heads on.

 

[pontiacgp]

do me a favor and rate the valve springs when you get heads off.

 

[CdnCutlass]

do me a favor and rate the valve springs when you get heads off.

Found the card that came with the heads.

Spring Diameter - 1.25"
Spring Type - Single with Dampener
Closed - [email protected]"
Open - [email protected]"
Max Lift - .575" Hydraulic Flat Tappet

Also the new Mallory Promaster coil which is only 4 months old died on me. A replacement is on the way (warranty).

 

[thrasher]

How are you doing on this problem?

The other guys are right, those are some big heads for your combination.
A 400 can live with a 190-200cc intake runner pretty easily and still make good low end torque but 225cc's is pretty far away from where you want to be with that mild of an application.

I've READ about some guys having problems with the Performer RPM/RPM Air Gap intake with heads that have tall runners. Apparently the ports don't seal very well.
What a lot of them ended up using to get them to seal is the discontinued Holley casting# 300-36.
I believe the big thing that I read is that there is more meat to port the manifold when using the Felpro 1206 gaskets and it will still seal.
It's also reported to have a larger plenum volume than the RPM Air Gap. Some people say that engines above 350 cubic inches like that.
The 300-36 was called a few different things over the years and the look changed slightly with age, but it's basically the same intake.
It started out being called the Street Dominator II, then they called it the Contender, then they returned to the Street Dominator name without the II designation before they stopped making it.
Whatever the name is just look for the 300-36 casting number on the bottom of the intake.

If you're wondering about the gasket size I have the Street Dominator version and it fits a Felpro 1205 almost exactly. It's a closer match than my Performer RPM -or my- RPM Air gap.

Early Contender

Late Contender with plenum ridges removed

Street Dominator

It's every bit as tall as a Performer RPM/RPM Air Gap

 

[CdnCutlass]

How are you doing on this problem?

The other guys are right, those are some big heads for your combination.
A 400 can live with a 190-200cc intake runner pretty easily and still make good low end torque but 225cc's is pretty far away from where you want to be with that mild of an application.

I've READ about some guys having problems with the Performer RPM/RPM Air Gap intake with heads that have tall runners. Apparently the ports don't seal very well.
What a lot of them ended up using to get them to seal is the discontinued Holley casting# 300-36.
I believe the big thing that I read is that there is more meat to port the manifold when using the Felpro 1206 gaskets and it will still seal.
It's also reported to have a larger plenum volume than the RPM Air Gap. Some people say that engines above 350 cubic inches like that.
The 300-36 was called a few different things over the years and the look changed slightly with age, but it's basically the same intake.
It started out being called the Street Dominator II, then they called it the Contender, then they returned to the Street Dominator name without the II designation before they stopped making it.
Whatever the name is just look for the 300-36 casting number on the bottom of the intake.

If you're wondering about the gasket size I have the Street Dominator version and it fits a Felpro 1205 almost exactly. It's a closer match than my Performer RPM -or my- RPM Air gap.

Early Contender

Late Contender with plenum ridges removed

Street Dominator

It's every bit as tall as a Performer RPM/RPM Air Gap

Well after getting a new ignition coil under warranty, turns out the Mallory Hyfire 6A box was no good. It's currently out for repairs. Thanks for the info on the intakes I will keep my eyes open for one at the swap meets.

As it stands now my plan for the car is to remove the engine this winter and teardown the motor. I am definitely going to change the heads to something that builds low end torque and is street friendly. I was looking at AFR Eliminators 180's, Dart Pro 1 180's, or Trick Flow 195's.

I would also like to throw in different pistons and bring the compression up to at least 10.5:1 and maybe get a different cam if it would work better with more compression and different heads.

I'm tired of driving the car around the block and making adjustments that result in minimal to no change. I am at the point I would just like to have a street friendly car that consistently runs good, and can be enjoyed.

I am open to any advice on what direction I should go with the motor. Thought about maybe starting a new topic about my parts combination.

 

[pontiacgp]

If I were you I'd look at the cost of a crate engine vs. building an engine and see what you come up with. You'll find you get more for your money with a crate if calculate everything in.

 

[marz442]

Crate engine from what company? Im looking for a 350 or a 455 olds.

 

[CdnCutlass]

If I were you I'd look at the cost of a crate engine vs. building an engine and see what you come up with. You'll find you get more for your money with a crate if calculate everything in.

I understand where you are coming from, and if I were to start over again I would look at that option. Right now I will still be able to rework what I have for far less and I have a couple people that can help me do all the work to the motor.

 

[crotchss]

Just out of curiousity, how did you set the mixture screws? With a vacuum gauge? Like you and I have talked, my pick-up runs close to the same combo with the heads being the only exception. Can't remember for sure, but I believe I started at 1 turn out from fully seated. Then adjusted side to side for max vacuum, all the while adjusting the idle speed to keep it where I wanted, then more mixture adjusting. After I got max vacuum I added a 1/8-1/4 more turn out, because alot of times bigger cams want that little extra fuel to idle. Just wandering because that vacuum is very low in comparison to mine, and yes I would agree the heads are a little on the large size for the combo, everything else looks like it would be a good match with some 180-190 heads. Also I don't know what octane of fuel you are wanting to run, but if you go with a cast iron head and stay with that cam I wouldn't raise your compression any more. If you decide to stick with aluminum I would stay where you're at or you could go up to a 10:1 compression max, to allow flexibility with fuel grade, that's just my opinion and has been my experience. Besides I don't think going up a half point of compression will be something you will notice, especially for the cost of new pistons. Around here it seems like gas companies are trying to make the fuel grade shittier and shittier. So I guess if it were me, I would change out to a 180-195 runner head and sell the ones you have to offset some cost. On another note, since I live in Nebraska and the weather here gets a little chilly, the only issue I've had with the Airgap on my pick-up (which is my daily driver) is it is a little cold blooded. Other than that it works great. Good luck with the switch and tuning