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Dominator - can't even get it to idle

General engine tech -- Drag Racing to Circle Track

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steve cowan
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Re: Dominator - can't even get it to idle

Post by steve cowan »

I found proform 67220 can't find in Australia
QFT Q8-139 I can buy here,
Can anyone verify these part #
Thanks.
steve c
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Re: Dominator - can't even get it to idle

Post by Crew Chief »

I have read through most of the posts here and I have noticed that nobody has mentioned fuel pressure? I have had carb issues in the past and it all lead back to too much fuel pressure. Holley carbs like about 4 to 6.5 PSI. get a fuel pressure gauge and a regulator and check it out. Just another suggestion for you. Good Luck.
steve cowan
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Re: Dominator - can't even get it to idle

Post by steve cowan »

steve cowan wrote: Wed Jun 03, 2020 1:18 pm
shoedoos wrote: Wed Jun 03, 2020 7:26 am bump it up to 30 initial and get back to us with the idling results.....
even more timing if you have to just at idle as to try and isolate the problem,try lowering fuel pressure to 4-4.5psi,
fuel pressure and float level have a influence on idle mixture,
and dont be surprised if you only need the secondry idle screws out a quarter of one turn from closed.
steve c
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Re: Dominator - can't even get it to idle

Post by V12MECH »

He mentioned that carb was used, could their be a casting porosity?
steve cowan
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Re: Dominator - can't even get it to idle

Post by steve cowan »

I have had the carb completely apart,it is brand new,I believe the mods I have done will help alot,in time Chris and I will work on timing curve and PCV as well.
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Re: Dominator - can't even get it to idle

Post by PRH »

Through the years I have had various running issues with Holley or Holley style carbs.
The beauty of the modular carb is that you can swap “known good” parts, one at a time, into the problematic unit to isolate where the problem really is.

In doing that, I have found a variety of different ailments........ which are often in the main body.

We used to build a bunch of oval track motors that had to run 4412 carbs.
It was amazing to me how many of those things just didn’t work right.
The first easy test was to swap the metering block right on the dyno.
That rarely solved it. Then I’d swap/add a different main body so all that was left of the original was the baseplate and bowl.
That basically always fixed it. Then I’d put the original metering block back on with the new body........ which almost always ran fine, but was sometimes down a little on power.

In the OP’s situation where the motor wouldn’t idle at all ..... I’d have started with a swap to a known good carb, to make sure that’s really where the problem was.
Somewhat handy with a die grinder.
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Re: Dominator - can't even get it to idle

Post by 1980RS »

PRH wrote: Sun Oct 04, 2020 1:24 pm Through the years I have had various running issues with Holley or Holley style carbs.
The beauty of the modular carb is that you can swap “known good” parts, one at a time, into the problematic unit to isolate where the problem really is.

In doing that, I have found a variety of different ailments........ which are often in the main body.

We used to build a bunch of oval track motors that had to run 4412 carbs.
It was amazing to me how many of those things just didn’t work right.
The first easy test was to swap the metering block right on the dyno.
That rarely solved it. Then I’d swap/add a different main body so all that was left of the original was the baseplate and bowl.
That basically always fixed it. Then I’d put the original metering block back on with the new body........ which almost always ran fine, but was sometimes down a little on power.

In the OP’s situation where the motor wouldn’t idle at all ..... I’d have started with a swap to a known good carb, to make sure that’s really where the problem was.
You are right about getting a know good carb to try first. This past summer I tried to use the 8896-2 I had and after some changes I got it to idle pretty good but going down track it was an ET pig. I decided to take the 2 circuit 750 and make a new 1050 out of it with billet boosters. When I got it running the new Dommy did not take much to get it idling so I set everything up and took it to the track. The 1st pass was WTF? it fell on it's face, changed out both squirters and made a 2nd pass and the car spun the tires "hard" so I know it works. Now I just have to have a day where the track actually preps the track for racing and not this street crap prep. Either way the new Dominator works great.
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Re: Dominator - can't even get it to idle

Post by steve cowan »

PRH wrote: Sun Oct 04, 2020 1:24 pm Through the years I have had various running issues with Holley or Holley style carbs.
The beauty of the modular carb is that you can swap “known good” parts, one at a time, into the problematic unit to isolate where the problem really is.

In doing that, I have found a variety of different ailments........ which are often in the main body.

We used to build a bunch of oval track motors that had to run 4412 carbs.
It was amazing to me how many of those things just didn’t work right.
The first easy test was to swap the metering block right on the dyno.
That rarely solved it. Then I’d swap/add a different main body so all that was left of the original was the baseplate and bowl.
That basically always fixed it. Then I’d put the original metering block back on with the new body........ which almost always ran fine, but was sometimes down a little on power.

In the OP’s situation where the motor wouldn’t idle at all ..... I’d have started with a swap to a known good carb, to make sure that’s really where the problem was.
Thanks for the information interesting about the main body issues,
You are correct about swapping carbs but the only option was adapter plate and fitting a 4150 carb.
Initially I was helping Chris over the phone and we got the engine to run cleaner with a couple of changes then it broke a rocker stud so Chris dropped off carb to me.
I have done these modifications before on my carbs and other peoples carbs as well with good success,the 950hp holley gets a bad wrap for idle quality and low speed issues, I have done several including my own with great success and I don't think they are a bad carb at all.
As far as the gasket deal i got onto some QFT replacement metering block gaskets that don't have the extra hole for idle vacuum port,I found in one of my holley books this can contribute to overly rich idle mixture where fuel runs down the main body into intake manifold,I have experienced this once before myself.
steve c
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Re: Dominator - can't even get it to idle

Post by PRH »

The other option is take the problematic carb and try it on a motor that runs fine.

For the “known good” test to really be of value, it’s best if the carb is known good on an at least “similar” combo.

I have plenty of carbs and spacers & adapters....... so for the “it won’t run/idle” type of test, that’s usually a quick and easy test.

I prefer to narrow down a suspected carb issue..... to the carb....... before I spend a bunch of time messing with one(and then find out that was never the problem).
Somewhat handy with a die grinder.
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Re: Dominator - can't even get it to idle

Post by JDR Performance »

That should always be the first thing tried. It saves a lot of time.
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Re: Dominator - can't even get it to idle

Post by Freddie »

Steve has been awesome. I’ve learned so much from his experience. We are much closer now and am looking forward to throwing it back on now the mods are completed. I saw a post saying fuel pressure. Has been set at 5psi pretty much from the beginning

Again Steve thank you
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Re: Dominator - can't even get it to idle

Post by PRH »

Through the years, my experience with ootb 4500 carbs is....... they often have low speed/part throttle drivability issues.
However the one thing they usually don’t have a problem with is..... idling.

If the cam is small, and the idle vacuum higher than what would be typical when using a 4500 carb....... you’ll often end up with the mixture screws barely open at all.
Somewhat handy with a die grinder.
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Re: Dominator - can't even get it to idle

Post by steve cowan »

PRH wrote: Fri Oct 09, 2020 10:09 am Through the years, my experience with ootb 4500 carbs is....... they often have low speed/part throttle drivability issues.
However the one thing they usually don’t have a problem with is..... idling.

If the cam is small, and the idle vacuum higher than what would be typical when using a 4500 carb....... you’ll often end up with the mixture screws barely open at all.
Appreciate your input
Before I received the carb we took fuel out of it,went to a hotter sparkplug and increased total timing and the engine started to move in a positive direction as far as start up,idle and cruise.
Unfortunately neither Chris or myself have access to a dyno so we are doing it the old fashioned way.
The main thing we have to realise is this car is street driven and we are looking for a good tune up.
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Re: Dominator - can't even get it to idle

Post by PRH »

I’m not going to go back and re-read 8 pages of posts.......

When you pulled that carb apart to go through it....... did you find something “wrong” with it, to the point where you felt that’s why it wouldn’t run?

If not, and it was just std Holley fare........ and it was that far off from working on that motor combo....... maybe it’s not really the right carb for the application?
Somewhat handy with a die grinder.
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Re: Dominator - can't even get it to idle

Post by Freddie »

PRH wrote: Fri Oct 09, 2020 5:38 pm I’m not going to go back and re-read 8 pages of posts.......

When you pulled that carb apart to go through it....... did you find something “wrong” with it, to the point where you felt that’s why it wouldn’t run?

If not, and it was just std Holley fare........ and it was that far off from working on that motor combo....... maybe it’s not really the right carb for the application?
Great question

It was a bill mitchell world products 632 cube crate motor that came with an AED 1050 3 circuit which was so stupid rich it killed the motor. I never played with that carb as beyond my knowledge and pressed it air bleeds. So with the rebuild I scoped put a good sized 2 circuit that would suit. The 1150 2 circuit kept coming right into range as a good combo

Problem initially was the amount of change in air bleeds IFR and jets to even get it to idle was significant

But we are getting closer thanks to Steve and I do think it will be an excellent carb choice when dialed in

If nothing else. I’ve learned so much I’m no longer scared of complex carb systems. Very very happy yo have gone through this experience
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