PHARMER

Specifications: MSD HEI ignition , stock GM heads , shorty headers , flowmasters , Edelbrock Performer Plus cam,lifters and intake manifold. Holley 600cfm carb.(double pumper) . Initial timing = 14 degrees , 32 total mechanical . Auto transmission.

Ok ,here is my problem. Having difficulty getting a good stable idle . Would usually set idle at around 800 rpm (park) and 600 rpm drive but idle is too weak at those settings. There is a stumble off idle and the engine rpm drops significantly when shifting from PARK to REVERSE or DRIVE.

Fuel pressure seems OK (occillates from 4-7 psi) with new stock mechanical fuel pump. Intake manifold pressure is steady at 15 with low idle setting (800 rpm) in PARK. In PARK at 1000rpm manifold pressure is steady at 18 (running much smoother). Distributor vacuum is attached to timed port on carb. I used propane test around intake manifold base and carb base and did not detect change in rpm.

I was thinking vacuum leak , but I can't detect one. Float level in carb is appropriate . I adjusted valves after inital start up ,then a mechanic friend of mine did final adjustment. I'm begining to wonder if valves are adjusted properly.

Any help would be greatly appreciated. This is a great forum !

VettePower

A little push for you.....

PHARMER

A little push for me ? Is that your final answer?

SIXFOOTER

Hmm, so how did he adjust the valves?
If they are in to far it won't idle well at all.
SO this is a new motor? Just reworked a bit? Or was it running ok for a while and then this problem?
If its new work, redo the valve adjustment and start from there

mkflanagan

Sounds like your tourque convertor may be staying in lock up.

coda2112

I had the same type of problem on my 1981 zz3 vette. I followed the vacuum lines and found if your headlights don't pop right up, replace those lines. That fixed my problem and made the headlights pop up lighting fast. Just one thing to look at...

PHARMER

Thanks , Ill try adjusting valves with engine running . I replaced vac modulator on transmission , no change. I may have tranny problems , but still have rough idle. Talked to a carb shop and they said they routinely have to modify double pumpers to get good idle with auto trans. Have been considering going with a vacuum sec.carb like a Edelbrock 1405 until I convert to 5 speed.

Tall Boy

Check your head light actuator seals for vacum leaks.
Also when someone said they will give you a little push they mean they will bump your post up so people will respond to it faster

VettePower

As you are a newbie, let me explain. Whe someone says a little push for you, that means he is pushing your thread to the top, so that you get a better chance of getting a good reply. An act of kindness.

MEGALADON

EXACTLY

SIXFOOTER

So whats the status? Find anything yet?

PHARMER

Thanks for all of the help. I adjusted the valve lash with the engine running . I added a quarter turn after rocker chatter subsided. The valves had at least a full turn (some more) past zero lash. This made a big difference. Runs a lot better.

I'm getting idle circuit on Holley DP modified at a carb shop (four corner idle) . Hopefully this will do the trick.

Thanks for all the help.

P.S. Live and learn , now I know what a little push means !

LOL