vacuum leak from carb to intake. need quadra-experts

[superwade57]

Hi guys I get everything put together on my 73 a couple weeks ago. Have had it out on some short fun runs... its a mild 355 eddy performer spread bore intake and quadrajet carb fresh reman. I was having trouble getting the high idle on the elec choke to work right. Some intermitent unreliable idle problems and an inconsistant fuel starvation/stammer at3-4500 rpm. Checked for vacuum leaks and sure enough carb base to intake 360* of leak that increased rpm when sprayed with ether. I snugged the mount bolts and it helped but still leaking in the front. I used the thick stock gasket for the carb application based on the stamped numbers. I've heard it can be tricky to seal a quad to a performer? Any sugestions?

Thanks a ton.

[Jabes1]

Spread bore intake and the Quadrajet are a nice match, so they shouldn't be hard to get to seal up. Im willing to bet your base on the the quad is warped and not the mounting pad on the manifold. Try to find a new base or get that one surfaced.

[bnoon]

You can true the base of the carb with a file if you check it with a straight edge and notice any warp to it. Otherwise I'd just grab another base gasket and try again. Also, make sure all of the vacuum port tubes are present and plugged in to vacuum too. The Quads have a couple vacuum ports near the base depending on model, and those can fall out rather easily on an older carb. The port that feeds the vacuum diaphragm on my heat riser on the stock air filter housing fell out on mine and needed resealed (dab of silicone) before it would stay in.

[superwade57]

Thanks guys I'm fairly sure its true since it came on a crate motor and the guy I bought from nevet ran it. But ill check. I was thinking a new gasket since who knows how long that one sat on the shelf of a small town parts house. I was hoping someone made a nice silicon hybrid gasket like they make for oil pans and valve covers but no luck.

[Jabes1]

Good point bnoon. I forgot all about those ports... yes, you can dab them with silicone, also give them a nice firm tap with a rubber mallet. It will help them set better and the silicone ensures in nice seal. If you decide to use a file to surface the base, use the largest flat file you can find and file it in an "X" pattern. You can also use a large flat sanding block, same thing use an "X" pattern.

[superwade57]

Originally Posted by Jabes1

Good point bnoon. I forgot all about those ports... yes, you can dab them with silicone, also give them a nice firm tap with a rubber mallet. It will help them set better and the silicone ensures in nice seal. If you decide to use a file to surface the base, use the largest flat file you can find and file it in an "X" pattern. You can also use a large flat sanding block, same thing use an "X" pattern.

I suppose I could rub it in a figure 8 on a full sheet of sandpaper too.. maybe 220 then 1200?

[Jabes1]

Edelbrock and I think Percy's makes reusable rubber like gaskets...

[superwade57]

The thick ones or thinner? I worry about gas boil or vapor lock issues with a quad and only a thin gasket?

[Jabes1]

As long as its a flat surface it will work. Large plate glass works great. Ideally a thicker gasket would be better, however if its not tightened down evenly at all four corners it too can cause a leak. Back in the day I remember a gasket that looked like it was constructed of cardboard fibers with a waxy material it also had what appeared to be torque limiters on it. Those were the best gaskets in the world for any carb, be it square bore or spread bore. I'm not sure if they still make them anymore... last ones I saw were around 97'. Phenolic spacers are something to look into, Wood is best, plastic works and aluminum just gives you more plenum volume, because it too gets hot unlike the previous I mentioned.

[geezer#99]

Leave that file in the toolbox. If you're looking to buy a new carb then by all means get it out and file away.
I've never seen one warped and I've been working on them for 40 years.
They do make those gaskets. Get one and bolt the carb down gently.
Some gaskets here.
http://quadrajetparts.com/advanced_s...asket&x=51&y=9

[superwade57]

That's the gasket I have tightened gently leaked bad tightened a lil more leaks less but still to much

[donut]

Fresh, re-man q-jet. Just for giggles, put a straight edge on the base. Going by the stamped numbers may be a mistake if the base was changed in the re-man process.

I bought a q-jet from a chain auto parts store. The base gasket supplied was the wrong one. (I think there are actually 3, depending on the base)

[78maliburat]

Get a factory replacement thick gasket and coat both sides with vasoline snug carb down

[savatreatabvr]

Originally Posted by 78maliburat

Get a factory replacement thick gasket and coat both sides with vasoline snug carb down

An old foogy from muskogy told me to spray paint the gasket, any gasket! He said especially head gaskets but it makes sense, I'm having problems getting my base gasket to seal properly and I've tried everything else so I'll try spraying it and see what happens.