• ODT Gun Show & Swap Meet - May 4, 2024! - Click here for info

1984 Chevy 350 still being a headache to get running right

Vacuum is one indicator of the health of the engine. The more vacuum, the better your air pump is. 15” of vacuum for a stock grind cam is an indication of a bad tune, open vacuum source or mechanical failure such as a blown gasket, bad rings etc.

Hook up a vacuum gauge to a direct intake port. Plug off all other sources including the vac advance on the distributor (diaphragm can be blown and leak) and brake booster. Take a vacuum reading. If its still at 15”, and you’re certain your ignition timing is correct, then you have a bad tune (throw out the edelbrock) or a bad intake gasket etc.


This is on my next steps list. I left the advance hose, brake booster, and PCV valve hose all connected. I did use the intake port on the right side of the carb to check vacuum. Will try this and get a more accurate vacuum reading.
 
Is the choke adjusted on the carb properly ? Pulloff working? I would go to an older emission test station and pay them to take a 5 gas off the tail pipe. Then you can see if its rich/lean and also watch values as you quickly eliminate poss causes.

Other than that....take it to someone who can diagnose it correctly.


Choke is working and adjusted correctly. Going to a emissions place would be nice, but I’m in Dalton so not many close by.


Taking it to someone who knows what they are doing would be nice and why I asked for recommendations. I haven’t found any shops I trust and actually know anything about older cars. Most I have seen just throw parts at them hoping to fix the issue.
 
I know you say all the parts are new, new means new, not good. I have seen way too many new parts be worse than the ones that were replaced. Always check the function, don't be fooled by a bad part just because it is new.

It’s got plenty of fuel being delivered and the pressure it’s being delivered at is on the high side. May need to add a regulator to get the fuel pressure from 7-9psi to closer to 6-6.5.
 
it was still aligned perfectly on the key when pulled off, and then placed back on the key when put back on. Is there something else that could slip?

Yes!

The harmonic balancer is made of 3 pieces. The piece that slips on the shaft, the piece that your timing mark is on, and a rubber insert that goes between them. It is all pressed together. The outer piece can shift in relation to the inner piece causing the timing mark to be meaningless.
 
Yes!

The harmonic balancer is made of 3 pieces. The piece that slips on the shaft, the piece that your timing mark is on, and a rubber insert that goes between them. It is all pressed together. The outer piece can shift in relation to the inner piece causing the timing mark to be meaningless.


Thanks, didn’t look at it that closely. That makes a lot more since. Was more focused on seeing the condition of the chain and alignment of the sprockets.
 
Finding TDC on compression stroke should be easy enough, if align time marks even close you should be able to tell if balance spun.
Choke is working and adjusted correctly. Going to a emissions place would be nice, but I’m in Dalton so not many close by.


Taking it to someone who knows what they are doing would be nice and why I asked for recommendations. I haven’t found any shops I trust and actually know anything about older cars. Most I have seen just throw parts at them hoping to fix the issue.
Unfortunately that is the truth.
Any decent shop should have an anzlyzer to find HC, CO output at idle...2500 rpm....and under load .
Good luck , in for the outcome :)
 
As the vacuum is low and it's running badly above idle you might have an issue with the vacuum advance - a bad advance diaphragm or a leak in the hose to the distributor.
 
Back
Top Bottom