[Overbiter]

Not a typical hot rod engine. I have a chevelle with an i6 250. Bolt on upgrades only. 2 barrel holley,offenhauser intake,hei ignition and dual exhaust. I've had tons of trouble getting the idle right, and keeping it running. Typically I would look at a vacuum leak. But it idles very high when I start it and slowly drops until it dies. I can't bring the idle down with any adjustments that don't make it stall. I can blip throttle and it will stay running indefinitely. it doesn't backfire like a vacuum leak. I had the thought to pull the line to vacuum advance the idle instantly dropped,much closer to wear it should be,it idled much better. But eventually did again die. If I advance the distributor it has too much advance to start. The engine kicks back.
Does my distributor need heavier springs?
Maybe its choke related? I'm pretty confused.

 

[RWENUTS]

Which Holley carb?
Give us the list number.
What choke?
Is it hooked up?
What carb to intake adaptor did you use?
How is the carb situated on the intake? Float bowl to drivers or passenger side.

Do you have pics of your motor?

 

[BogiesAnnex1]

Sounds like there may be more than one problem, but for starters it sounds like the base timing is too advanced which likely is a distributor installation problem. Base advance is set with the vacuum disconnected and the source at the carb or manifold capped.

The eventual wind down sounds like a fuel supply problem, especially when you add that you can keep it going by blipping the throttle which is an action that add accelerating pump fuel.

Sounds like you need a timing light and a fuel pressure gauge to see where these things are.

Don’t forget that if the vacuum advance diaphragm is ruptured that makes a vacuum leak.

We could use detail part specs like part numbers for carb and distributor. Keep in mind that HEI distributors use full B+ voltage of 12 to 14. if this came with points there will either be an external resistor that drops the B+ down to 6 to 9 VDC or there is a resistive wire running from the run terminal of the ignition switch to the distributor also providing this low voltage. so if this is a conversion check the volts up to be sure the HEI is properly fed.

Bogie

 

[Overbiter]

I will work on finding the holley carb model, I tried to look on their online catalog but it's none of those, I'll have to look at the engine later today. It has an electric choke that is connected. The carb/intake Adapter plate I used was machined on a bridgeport Mill for this specific application.

The Balancer I am using does not have TDC Mark. I used a vacuum gauge when I did my initial tune.

It could be fuel supply, but the fact that sometimes it will stay running would confuse me but that's not hard.The fuel filter is never full, but since I can keep keep it running indefinately taping the throttle wouldn't that rule it out?

The distributor is a fairly generic in cap HEI. It did originally come with points but the resistor wire was removed at that time.

Thanks for you help guys. More info to come.

 

[johnsongrass1]

I'd use a piston stop to get an accurate TDC position so you know without a doubt where the timing is. Even if that just means a pain mark on the damper and timing over at 10' BTDC.
I think bogie is correct in hos assessment of a fuel issue. I suspect the issue is in the idle metering circuit adjustments or cleanliness rather than the fuel pump.

 

['48 Austin]

Check mechanical advance by removing distributor cap and turning rotor and let it spring back on its' own. If it doesn't move freely and spring back, remove base plate and free up the mechanical advance. Then reset initial timing at idle with vacuum advance disconnected and plugged.

 

[Overbiter]

I got it to idle a bit lower, partially thanks to better timing. I connected a test tach to the dizzy with clip lead and saw 1100 rpm idle.I don't believe it's fuel because the car seems to have very different issue today. Today I could get the engine to idle. I didn't have to fight it to stay running. No creeping idle drop. The fuel filter is full, I could bring the rpm up and saw no issue;no stumbles or pops. I placed an inline spark test on cyl1 and saw no issue. The sporadic stall is still there. I think its an Ignition issue. Suddenly I lost spark when trying to restart after a stall. I ran and bought a new coil,even though in my head I knew that wouldn't fix it. I didn't want to dilly dally testing the coil,intermittent failures rarely show up in these tests.

The new coil did not fix the issue as i suspected it wouldn't. Can GM ignition modules fail intermittently?
Could this be a dizzy problem?

I took pictures of the crusty engine in this car as promised. Carb as well.

 

[RWENUTS]

Looks like a Rochester 2gc, not a Holley.
I see a hot air choke that’s not hooked up.
How are you controlling the choke?

 

[RWENUTS]

More research reveals that to be a Holley 2210. Mostly used on mopar and international trucks.

 

[Overbiter]

I don't remember why I decided onThis carb years 10 ago. It's has electric choke now.

 

[RWENUTS]

What did you use for a gasket to seal the adaptor to the intake?
Could be a vac leak source as could the carb hold down bolts be a leak source.

 

['48 Austin]

RWENUTS could right on the nose.

 

[Overbiter]

I actually had it all apart recently for suspect vacuum leak. I don't believe there is a vacuum leak now. It was much cooler near me yesterday and I suspect a vacuum leak would have been much more obvious in the cold weather. Additionally I placed my hand over the carb inlet and it nearly was sucked in. It was leaking at the manifold last time. The carb adapter is mated using a paper gasket.

 

[JeffB28]

It could be a vacuum leak it looks like you have an Offenhauser 4 barrel intake and are using a 4 barrel to 2 barrel adapter which is never really good news for decent sealing or flow a small 4 barrel like a 390CFM Holley or 500CFM Edelbrock would be a better choice so you can chuck the adapter,most of the time you will be running on the 4 barrels smaller primaries anyway so over carburation should not be an issue.

 

[Overbiter]

While I agree that adapters are not ideal this particular intake is always sold with an adapter. I purchased this intake with an engine and milled my own for my Holley 2GCE equivalent purpose.

 

['48 Austin]

See pic of carb base. Many carbs have milled channels in the base (2 and 4 barrel carbs) that are not covered by the gasket and manifold or adapter. If the gasket covers the channels and the manifold or adapter doesn't, it will leak. A thin steel plate with additional gasket will be required to eliminate the vacuum leak. I've seen this many times. Even with matched manufacturers like Edelbrock carb on Edelbrock manifold.

 

[Overbiter]

Very wise point. I could see how this would be overlooked, I'd like to think this isnt my issue but I will certainly check.

 

[d.b. cooper]

i'm with northern neighbor on this one: Let's make sure the choke is working properly first. Does it open all the way after about 2-3 mins?

The engine is supposed to idle fairly high when first started. Just trying to make clear that we understand this here. Then the fast idle cam follows the choke opening---and then rpm should drop etc. Just trying to make clear.

2) Do you have a tach?

 

[Overbiter]

Yes,choke works

I connected a tuning tach and saw 1100 rpm. I got it down lower to I think 750 or 800 a tad high,bumps going into gear at that rpm. The powerglide always sorta bumps,but this is just a tad harsher. I'd have to look at it again to confirm where my rpm was.