I have a 1979 Olds 350 engine code "R" with a Quadrajet carb

The carb was recently rebuilt. Runs great off idle, etc. But not so good at smog.

I have been extensively testing for vacuum leaks everywhere. I have been using Carb Cleaner to squirt various places and watching a RPMs on a timing light.


When I squirt carb cleaner at the drivers side primary barrel just below where the carb base gasket meets the intake, the engine revs up.

I have measured for straightness on intake base and also carb base, no warp I could find.

I have tried various base gaskets and glues. 5 different tries...


The last try I used a Mr. Gasket 56A base gasket that seals only the outer edge of the carb with a fair amount of Gasgacinch dressing on every side, let set overnight. torqued to 10lbs spec. and checked every 15 min. until it was steady.


I drizzled carb cleaner here and there just to see if it is a casting porosity problem just below the carb base. No problem.

I got needle nose pliers and made the end of the carb cleaner squirt tube face 90 degrees up so I can squirt directly at the part where carb gasket mates with the intake manifold.

When I do it speeds up.

Just wondering what others know.

IS the carb cleaner being sucked through the gasket material? Is there some other entry point of the carb area near this for the carb cleaner to come into the fuel system?

What am I missing??

At my wits end..

Fred

 

Can you post a picture of exactly where you are spraying?

 

worn throttle shaft/ bushing?

Try a propane "leak" off your old torch to better pinpoint the leak.

Or, use a pc of say vacuum line for a stethoscope and listen here and there for the vacuum leak.

From the sounds of it, the flaw is not at the carb base/ gasket/ intake interface. Unless your base gasket is not a match for the carb itself.

 

Can you explain more what you mean by propane "leak"

connect a piece of vacuum line to a propane torch?


How to do this, more info?

Thanks Fred

 

Fred, If you take a small propane torch like a burnzomatic, don't light it, just allow the gas to come out at the point you think your leak is.

Its like your method with carb cleaner, but different.

What results do you get?

I'm thinking it might not be the right gasket match. We'll have to see.

 

what stanley said
unlit propane, directed near the suspected leak

it can still get drawn in "nearby" though so a hose/ stethoscope may still be better.

 

OK

to rule out the gasket leak, I put a new carb base gasket and used Right Stuff on all sides to glue to manifold.

Tried to find using propane.. even reduced it into a small vaccum line hose. No change to speed anywhere....

tried water out of a vaccum line attached to a funnel and dribbled the area, no change to speed anywhere.

Again, sprayed carb cleaner near throttle shaft, if I squirt a little no change but if I REALLY saturate the area it seems to speed up.


COuld it be coming into the carb some other way, like over spray when I am squirting the heck out of it.



how leak proof should the throttle shaft to carb be?? Recently rebushed.....


Fred

 

Sounds like worn primary throttle shaft. Mine was like that, there is a kit that comes with a special drill bit, new bronze bushings. Or get rid of the quad and get a new one of a different make.

I am having issues yet with mine stalling once the choke comes off. It idles when engine is warmed up after some driving, but not to well when choke comes off. Still playing with the idle screws...

 

Do you have a vacuum gauge? Whats the vacuum reading? You mentioned torqued to 10lbs. Is this the torque you put on the carb bolts? This page shows 15lbs. http://442.com/tech/torque.html