Engine Gt40 Tubular Install, Now Running Like Crap


New Member
Dec 13, 2010
So i just finished my installation on my new gt40 intake and i supect there is a vacuum leak. When the car is in idle its going from 700-1300 rpm, not jumping but climbing and falling slowly. Ihad to take the stock heads off to get them resurfaced but i dont think thats the issue since I took my sweet time waiting on new gaskets and making sure any gasket mating surface was completely clean. I ordered myself and edelbrock elbow and kept all smog equpiment. I didnt mark everything but I suspect the problem is from when I had to figure out what vacuum lines went where they were supposed to since the tubular didnt have the vacuum fittings in the same place as the stock piece. Im pretty slow when it comes to reading diagrams but if someone could please help me by explaining one or showing a picture of what its supposed to look like I really would appreciate your time. One other thing is I bought hose candy silicone hoses for some of the smaller smog lines that tend to break off and for the FPR. PLEASE HELP!
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Here's a pretty simple diagram. It doesn't really matter how they are hooked up so long as they are not left open. Also, the vacuum leak may be from the intake gasket and not an open vacuum line.

Vacuum Diagram.jpg
Did you use cork gaskets on the back and front surface of the block? Most of us use a generous goop of high temp RTV because those cork gaskets are thin and blow out. Also you can use the T vacuum lines on the stock intake and carry them over to the GT40. Is your fuel pressure regulator vacuum line on? Also you have the vacuum line block by the booster that has 3 vacuum lines on it.
I have the long vacuum line coming off the tree going in on the elbow vacuum adapter hat came off the stock piece. I did use the rubber gasket ends along with a generous bead of rtv on the ends of them.the only cork used are on the valve covers. Could it do with how the distributor was stabbed? I just stabbed it about where it was before... I think. I turned the engine over with a breaker bar reinstalling the roller rockers. Before it was stabbed for the final time I found tdc on#1 compression. Timing off maybe?
anyway here is how my lines are running under the intake
Confirm the timing mark is at "0" with #1 cylinder at TDC and rotor pointing to #1 spark plug.
Confirmed toyman. Thats how I had it when I stabbed it. Since the gears are funny I kind of had to lead it a little but when it stopped turning when it was in all the way it was pointing at #1 spark plug. I rotated the grey part of the distributor a little not knowing it could do it by accident before I locked it down. Also, I bought bolts for the upper from the hardware store and on the bolts there is about 1/8 of an inch of bolt with no threads going thru the bottom of the upper. Does anyone think it could not be sealing properly because of that once the upper and lower are "tightened"?
If I understand you correctly that would be an issue. Are you saying that the shoulder on the bolt (that part without threads) is visible on the bottom side of the upper? The way you have described it would seem to indicate that the intake surfaces can not be drawn together because of the bolt shoulder. FWIW there are more to bolts than thread size. I doubt that the bolts you bought are of the proper grade. Using the wrong grade of bolt can make a big difference in many applications.
Yes, you understand correctly toyman. Good thing you did because im really bad at being descriptive. I guess i'll have to see if Ford still has those bolts available without having to buy a 1/2 inch spacer with bolts and not use the spacer due to the new intake rubbing the hood liner. I guess its homework time.