Intake blues

[cbodybob]

Ok I swapped out the 383 Torker intake for a 383 Performer RPM on my 400 low deck drag car & now my engine runs like crap & the idle is all over the place making me think I have a big vacuum leak. The guy I bought the car from told me the heads had been cut a lot on the 400 low deck block to raise compression. The RPM intake bolted on nicely & seemed to fit good but I’m thinking the 383 torker was cut as well. Nothing else was done. Just swapped intakes. Any ideas ?

 

[wagonman]

Pull it back off and set it on with no gaskets. Compare it with the Torker. If the block was decked and heads milled you probably need to cut the intake as well. Check the front and rear China walls as well. Some machinests blue on the intake might show some misalignment also.

 

[cbodybob]

Pull it back off and set it on with no gaskets. Compare it with the Torker. If the block was decked and heads milled you probably need to cut the intake as well. Check the front and rear China walls as well. Some machinests blue on the intake might show some misalignment also.

Neither intake has a China wall. See pic attached. Just the side flanges.

 

[Lefty71]

Start it up and spray some WD40 (prefer non-aerosol) along the sides, and under the flange inside the belly pan. The motor will change idle considerably when you get close if its an air leak. Keep in mind sometimes there can be an out of square condition, and it may not leak all along the entire side, but only towards the front/back, etc. If you have one, pull the gaskets and check again with some feeler gauges until you find the location. It's not unusual to have to correct the manifold to fit a b/rb, especially if you've got some budget rebuilt heads, read Pioneer Head Service, etc. Of course, if you find the heads are really the issue, you'll have to decide if you want to ruin a manifold to fit them.

 

[R/T Boy 67]

Agree with above. You don't hear it referred to, (as an air leak) very often, but it is correct.

 

[forphorty]

Make sure the intake is not hitting the bars that hold the valley pan down.

 

[cbodybob]

Start it up and spray some WD40 (prefer non-aerosol) along the sides, and under the flange inside the belly pan. The motor will change idle considerably when you get close if its an air leak. Keep in mind sometimes there can be an out of square condition, and it may not leak all along the entire side, but only towards the front/back, etc. If you have one, pull the gaskets and check again with some feeler gauges until you find the location. It's not unusual to have to correct the manifold to fit a b/rb, especially if you've got some budget rebuilt heads, read Pioneer Head Service, etc. Of course, if you find the heads are really the issue, you'll have to decide if you want to ruin a manifold to fit them.

I checked the intake with a straight edge & the flange is true. I can’t keep it running long enough to spray anything unless idle it up to stay running. I took it all back apart & I think I’ll put a fresh new Valley pan on it.

 

[cbodybob]

Make sure the intake is not hitting the bars that hold the valley pan down.

Yea it’s fine

 

[wagonman]

Neither intake has a China wall. See pic attached. Just the side flanges.

Yup My Bad

 

[Geri]

View attachment 783606 View attachment 783607 Ok I swapped out the 383 Torker intake for a 383 Performer RPM on my 400 low deck drag car & now my engine runs like crap & the idle is all over the place making me think I have a big vacuum leak. The guy I bought the car from told me the heads had been cut a lot on the 400 low deck block to raise compression. The RPM intake bolted on nicely & seemed to fit good but I’m thinking the 383 torker was cut as well. Nothing else was done. Just swapped intakes. Any ideas ?

same carb- different manifold sounds/feels like vacuum leak- it probably is. off chance the newer manifold wants to be richer,I've had that happen years ago, same carb(s) different manifold and extremely lean, back to first manifold and all was well. I didnt have the $$ for bigger better carbs. just spit balling here.

 

[cbodybob]

same carb- different manifold sounds/feels like vacuum leak- it probably is. off chance the newer manifold wants to be richer,I've had that happen years ago, same carb(s) different manifold and extremely lean, back to first manifold and all was well. I didnt have the $$ for bigger better carbs. just spit balling here.

Well after 3 attempts to get the new RPM to work I have given up. The Torker went back on today without the tall spacer.

 

[PRHeads]

Just think of the thousands of RPM manifolds that have been installed on BB mopars.
It’s obviously not a “design” issue.

Did you test fit the manifold to the heads without the valley pan to insure the flanges of the manifold were sitting straight and square on the heads, on both sides?

 

[cbodybob]

Just think of the thousands of RPM manifolds have been installed on BB mopars.
It’s obviously not a “design” issue.

Did you test fit the manifold to the heads without the valley pan to insure the flanges of the manifold were sitting straight and square on the heads, on both side?

I did.
And I’ve installed several Rpm’s over my 40 years of working with MOPARS. Just can’t make this one work. Ran best with fiber gaskets though.

 

[66Satellite47]

Did you try a REALLY thin layer of silicon on the pan gasket too? The .015 or maybe .030 thick "6 Pak" gaskets with a light spray of Peramtex red spray may also work. Just a thought. When I mill the heads, always mill the intake side too. I check as best as I can with welding rod with a small L bend to run down the port to see if there is a mis-match. Hard to do with a dual plane.