78anniversary

The subject of commercially rebuilt Q-jets has been discussed on this forum too many times to count, and it has been determined that these carbs are not reliable after being commercially rebuilt.

The best way to get a reliable Q-Jet is to find a unit that has not been thru a commercial rebuilding process and rebuild that. There are still many candidates out there, eBay usually has several. It does take a trained eye to determine if it has not been commercially rebuilt.

If you are not up to the task of rebuilding one yourself, you could find someone to do it. Lars would be my first choice, although I haven't seen him posting on the forum in a while. I had read someone mentioned that he may not be rebuilding carbs right now. Other names are Ole's carb, Sean Murphy, or Cliff Ruggles.

There is also the option of changing to a Holley spread bore if you didn't want to deal with the rebuild process, as these are still available new.

JimLentz

That fuel pressure seems low to me, but that wouldn't cause it to run rich.

REELAV8R

This should not be possible. It is drawing air from somewhere. If you want a reliable build get one from Cliff Ruggles. I have read the Lars is no longer doing re-builds.

http://www.cliffshighperformance.com/

jotto

So why did you replace old carb if it was running fine?
If you can wind the idle screws in or cover it with your hand and it doesn't kill the engine then you have issues.
Why not just clean up your old carb and try it?

59BlueSilver

Lars has said that about rebuilds many times and he should know. I was desperate for a carb at the time. They guarantee it, and they send me a new carb when I have trouble. Doesn't make sense to me to take rebuild shortcuts from a business standpoint, but...

I bought a carb from ebay a couple of months ago. Tried to rebuild it but it had a frozen power piston and I couldn't free it up without destroying it, so I removed the base plate that had good idle screws and put it on my old quad. Still has issues but may be better to work thru these than mess around with this commercial rebuild.

I like quadrajets, obviously, when they run right. Can't understand why I can't get at least one of these to work. If this doesn't happen, however, then it's Holley time!

BTW, Lars doesn't do rebuilds anymore as of June 1. Guess he's actively retired. Good man, wish him luck.

BKbroiler

As REELAV8R said, this indicates a big vacuum leak. Has nothing to do with rich or lean. Covering the air horn should cause the engine to stall immediately.

59BlueSilver

You guys are right, that should shut down the engine. Gotta be it, but don't know where. Did the propane leak check, may do it again. Is there such a thing as a bad intake, cracked, etc? This one is new. I would think you could hear or see that.

Danish Shark

It is a spreadbore intake, right?
When you said you could cover the carb with your hand and it would make no difference I assumed you meant partially cover the carb?

jnb5101

Remove all the grease and oil from the carb body, then soak it in Rust Evaporator (or equivalent ) for a few days, and the power piston will free-up. I've done a couple that way.

COOLTED

Maybe I missed something, but the intake was changed at the same time, right? Perhaps you have a leak from the intake manifold. I have seen them leak on both the outside and from the valley.

59BlueSilver

I've checked the outside, but not the inside. I'll check that next. Should be a slight vacuum when removing the oil fill cap, right?

COOLTED

In theory, there may be a slight vacuum because of the PCV. However, normal wear will allow blow-by creating a positive pressure in the crankcase that the PCV can't overcome. So... it may or may not have vacuum in the case, but if it were me I would check and see by removing the oil dipstick, it might be easier to tell because of the smaller opening.

You could check the spark plugs and see if any are oily.

I am rambling...

59BlueSilver

I hate the thought of removing that intake again, but I think everyone has agreed there is a vacuum leak, probably internal but I will recheck. I used good gaskets so my first thought is there must be an anglular mismatch between the intake and the heads, although i don't see how. This is a stock '69 engine that hasn't been apart, and the intake is a new performer 2101.
I'll do a clay ball check dry & see what I find. Is this mismatch common? How else can an internal leak happen?

jnb5101

Make sure that the mounting ears on the manifold are not contacting the heads and preventing the manifold from seating. Did you allow the sealant on the end gaskets to harden before setting the manifold. They can shift and cause a leak.

Big2Bird

Don't use the cork gaskets on the china wall. Use RTV. The cork can keep the gasket from seating on the heads. This will cause a big time vacuum leak.

speedreed8

jet performance carb should have an adjustable ATP for the power valve, should be a allen plug at top front of the carb, should be a screw head under it for the ATP.
i would also check to make sure you have the correct base gasket on the carb to intake.

59BlueSilver

I used the best Felpro gaskets and RTV on the ends.

59BlueSilver

I'm using a '73 quad that doesn't have ATP. Impression I see on the base gasket appears to be sealing well.

Big2Bird

Do you have an EGR valve that may be stuck open?

Have you pulled and capped ALL vacuum lines to see if something is leaking?

59BlueSilver

Away from home this weekend but thinking about my possible vacuum leak and have a question.
Can you still have a vacuum leak bad enough to cause all my problems but still pull 20" on the gauge at idle?