major vacuum leak

jludorf

Registered User
Over the past week I have had to remove a low mileage 94 engine from a donor car, as my ported/reworked heads were not going to make it here in time for the shootout, and install it in my 94 5 speed. I have added the following components over the past week and when I start it I have the leak explained below.

-80maf
-60lb injectors
-aeromotive fuel pressure regulator
-marshall fuel pressure gauge
-rebuilt transmission
-new slave cylinder
-new aluminium flywheel
-centerforce dual friction clutch
-ported manifolds with scp exhaust
-egr delete
-stock throttle body:( ( I will have an 85mm but won't have it till I get to dayton)
-mpx blower with partially coated rotors( my early blowers all need a rebuilt and the coated rotors were not recommended for the stock long block)
25% overdrive kit with wider belt and heavy duty tentioner springs
-aluminium drive shaft
-255lph fuel pump
-sct chip

Now the problem like I stated in the title is I have a major vacuum leak. I believe it is from the throttle body. I can start the car and as long as I keep my foot on the gas the car runs great but there is a sucking noise. I have checked all the connections and they are all secure so the only thing I can think of it the throttle body as there is very little meat when it bolts to the inlet plenum on the MPX. any suggestions as I would like to take the car for a spin to test out the tranny and get it to operating temps to check for leaks and problems under minimal boost. I am not able to run the car long enough to look at the problem, hopefully I can get a second set of eyes tomorrow but if anybody could confirm that a sucking noise would be indictive of a leaky t-body to the inlet plenum that would save me some time.
Thanks,
John
 
Last edited:
John,

Got your message really late. I only have a 75 mm BBK that I could give you to use.

The stock TB would definitely have a hard time sealing that large inlet. I can bring out a TB when I come out.
 
better but still have a leak

I have resealed the throttle body and it runs better but if I crank it over and it fires it won't stay running unless I keep my foot on the gas and as ,long as I keep the idle above 1200 rpm it stays running. I have check all the connections for the intercooler and have tightened them as tight as I can. The boost gauge stays at 20hg when I hold a steady idle at 1200. I did notice my fuel pressure is pinning my gauge over 60 psi so I will reduce it to 50 psi to see if that will help. I have checked every hose for splits too. I'm at a loss as to what else would cause the car not to hold an idle. Any ideas on what else I can check?
John
 
It was the fuel pressure. It was pegged at 75 lbs. When we backed the pressure off to 40 lbs, she steadied out. Mr ludorf is on his way to kick some American ~~~ at the shootout.:eek:
 
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