Idle / Low End Problems on '66 w/ SB and PG

[Dave S.]

Just finishing a body off on a '66 w/ 327 - 300 w/ PG and A/C. Engine was rebuilt to factory specifications with the exception of 0.030" cylinder bore. Correct Holley 3367 carb is rebuilt and has NOS throttle body / base plate. The car seams to run fine at higher RPM, say + 2k, but will not idle below 1,200 - 1,300 RPM. I have the idle set at around 1,300 and when I put the car into gear it drops to less than 600 RPM, therefore I have to "double foot it" to keep it running (keeping the revs higher than 1200 RPM). It really acts like it's loading up with too much gas at the low end.

Any ideas out there to what may be going on? Right now, I'm thinking that the jets may be too large. Does anybody know what size "factory" jets would be on the 3367? Looking forward to any hearing other ideas as well.

Thanks,
Dave

[G B.]

Re: Idle / Low End Problems on '66 w/ SB and PG

Dave, I don't think the primary jet size affects the idle mixture significantly.

When your throttle plates are closed, the carb should be supplying gas to the engine through the idle mixture screw passages and the lower third of the transition slots in the primary venturis. At idle there shouldn't be enough air velocity through the venturis to pull gas up though the jets.

My guess is that your carb rebuilder didn't re-surface the main body of your Holley and that left you with an internal gas leak. In your shoes I would buy a new 3367. I think "The Last Detail" in Atlanta still has a few left for around $520. You won't find any rebuilt Holley that runs as good as a new one.

[Loren L.]

No Vaccuum leaks? *NM*

[Duke W.]

Re: Idle / Low End Problems on '66 w/ SB and PG

It should idle smoothly at about 450 in Drive. Start by connecting a vacuum gage and record the readings you get. At 1200 in neutral is should be about 20".

A vacuum leak is a good first suspect.

Check that you have a correct and properly functioning vacuum advance, including testing it for vacuum holding ability them look at all vacuum lines and the PB booster, if equipped - also check that the correct carb/manifold gasket is installed.

Finally, set the idle mixture screws in the initial position listed in your CSM, then go through the idle speed and mixture adjustement procedure.

If the vacuum advance is correct and properly functioning and you cannot find any vacuum leaks, and adjusting the idle mixture screws has no effect, the carburetor may have some internal defect.

Duke

[Clem Z.]

Re: Idle / Low End Problems on '66 w/ SB and PG

LIST 3367 should have #65 pri jets,-22 secondary plate,#65 power valve. make sure the metering body,the main body or the base plate are not warped as this will cause idle problems because of a internal fuel or vacuum leak