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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
Just threw on some Jegs heads on my 350 SBC, And it starts up and stalls out due to a huge vacuum leak. Didn't notice it right away, but saw a gap on both sides of the intake, where it meets the heads
It looks like my Edelbrock performer EPS is not wide enough for the Jegs heads...
I called Jegs, they said that it is not a compatibility issue and implied that the deck might've been machined at one point (this is very possible) or the intake manifold might have warped. I had standard GM heads prior to this and never had any issues.
The previous owner possibly did some machine work.
If the deck has been machined, is there any way to fix this issue? A gap can be seen on the top and bottom of both sides of the intake.
Looks like you have heads that want a MUCH bigger intake than the stock replacement one you have.
Standard way of expressing such things is to use the FelPro intake gasket part # for the appropriate size. Your stock intake would use a FelPro 1204 gasket. Looks like the heads are set up for a 1205. (probably even says in the specs or owner's manual or something) REALLY BIG heads use a 1206.
Only problem you have is a parts selection mismatch. Get an intake more suited to your heads. Post the head part # and it won't be hard to pick one.
Thank you for your response. I used the gasket that was provided with the heads. But you're saying a FelPro gasket that is much thicker should fix it? To me it looks like the manifold is sitting to low... I guess a thicker gasket will move it up.
Here is what it came with. Thickness of the manifold gasket is .062"
From the specs for your heads, right off their web site, that you read, understood, asked questions about if you needed to, and compared to your other parts, BEFORE you bought them. Remember?
Looking at the port dimensions for your intake that NightRider posted, not hard to see what the problem is.
You basically have a GIGANTIC parts mismatch incompatibility. There's nothing "wrong" with any of your parts except that they are totally inappropriate to be installed on the same engine.
You need a race sized intake to go with those heads.
Looks like a Performer RPM is about the absolute bare minimum and probably still may not work, since not only do you have to worry about the port dimensions, but also, how far up or down on the surface the ports are located.
well damn... thank you guys for your help. The worst part about this is I called jegs before I ordered and they said that it would match up with my application... AND they are still saying that... I'll be sure to educate them in the same matter that I have been educated today.
Whats weird is it looks like the middle ports/gasket line up.. pull intake and compare port sizes. put a straight edge on intake to make sure its straight...but yeah, sofa and the guys are dead on otherwise. some knowledgeable ***** on this site.
now that i look closer... the first pic, the ports under the carb, you can see the gasket. that looks normal. then on the last pic, same spot but zoomed in, the gasket is gone now... did you pull the intake between pics? like the gasket got sucked in or something unless i am looking at it all wrong.
Yeah unfortunately the "tech" guys aren't always quite as informed as you'd wish... that kinda leaves you in a bad spot, because most intakes that are likely to fit the heads, aren't likely to fit under your hood. Esp since you have a Firebird.
If you have their assurance that it will fit in writing (chat transcript for example) and pictures of what it actually does (doesn't), you'd have a pretty good case for a full refund. Trade em back in on something that fits better. The Edelbrock head suggestion isn't a bad one for example; not the "fastest" heads there are, but a VERY good choice for a nice street machine, and they FIT street-ish motors quite well. Dart would be another good choice, in their 180cc port size, such as part # 127122. http://www.jegs.com/p/Dart/Dart-SHP-...91309/10002/-1
Last edited by sofakingdom; 04-15-2015 at 09:18 PM.
You're very right sofa, those tech guys had to put me on hold like 5 times today and gave me very little ideas of what could be wrong. I doubt i'll get a full refund... We'll see what happens. Thanks for the suggestion on the Dart heads. I'll look into it if it comes to that. Thanks again for everyone's help.
With that NEW manifold, it is still gonna have 3/10" mismatch on the top of the port.
Check the intake gasket against the manifold and the head before bolting it down.
04-15-2015, 05:12 PM
