Intake exhaust question (1 Viewer)

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Aug 17, 2016
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Location
Massachusetts
Have hopefully a quick intake exhaust question. Pulled intake manifold 76 fj40. Had it indexed. 20 thousandths off between highest and lowest point. Do I need to get this manifold planed, or will the gasket close it up. I'm running a header currently but planning to go back to factory exhaust manifold in the future. Any help on this would be greatly appreciated.
 
That main concern is that the exhaust and intake flanges are the same thickness. (although making sure it's as flat as possible is always a good thing)

Swapping between a header and stock intake might make that problematic..
 
On the '80 & later manifolds, the warp limit is 0.020 in. Theoretically that's the acceptable limit. 0.021 in. would be out of spec. Personally I'd shave it flat. Intake vacuum leaks are no fun.

image.jpeg
 
Thanks so much for the input. I pulled the manifold specifically because I am chasing a vacuum leak. I will get this thing shaved as u recommend. Thanks again.
 
Check for cracks in the manifold as well. I think most vacuum leaks that create a noticible problem, can be traced back to the intake manifold somewhere.
I bead blasted the manifold and checked prett carefully for cracks and such. That isnt to say there aren't any. If you are aware of any typical problem areas, please let me know. Thanks.
 
Look VERY carefully down at the bottom of the intake below where the carb sits for a hairline crack. They can be hard to see at first if you just glance at it. If there is any hint of a hairline crack, have it welded because once the crack starts, it grows uglier by the mile.

Below is an example of a really bad crack. This will be the spot where it cracks. Inspect it carefully.

Picture courtesy of @SAWTOOTH 55 LC


image.jpeg
 
Look VERY carefully down at the bottom of the intake below where the carb sits for a hairline crack. They can be hard to see at first if you just glance at it. If there is any hint of a hairline crack, have it welded because once the crack starts, it grows uglier by the mile.

Below is an example of a really bad crack. This will be the spot where it cracks. Inspect it carefully.

Picture courtesy of @SAWTOOTH 55 LC


View attachment 1430269
Great, thanks. That's a big help.
 
IMG_1183.JPG
Look VERY carefully down at the bottom of the intake below where the carb sits for a hairline crack. They can be hard to see at first if you just glance at it. If there is any hint of a hairline crack, have it welded because once the crack starts, it grows uglier by the mile.

Below is an example of a really bad crack. This will be the spot where it cracks. Inspect it carefully.

Picture courtesy of @SAWTOOTH 55 LC


View attachment 1430269
Ok, hate to be needy here but here goes. i bought this rig because it was untouched original except po, by the way, original owner, changed carb to holly and exhaust to header, deleting all smog. The good news is, he gave me the original Alison carb which I had rebuilt and and everything else he had removed. I posted some pics. I think it's all there. My question is, can I assemble exhaust and intake manifold and have them planed together? Also, can i run that configuration without hooking up all the smog stuff for now?
 
View attachment 1430699
Ok, hate to be needy here but here goes. i bought this rig because it was untouched original except po, by the way, original owner, changed carb to holly and exhaust to header, deleting all smog. The good news is, he gave me the original Alison carb which I had rebuilt and and everything else he had removed. I posted some pics. I think it's all there. My question is, can I assemble exhaust and intake manifold and have them planed together? Also, can i run that configuration without hooking up all the smog stuff for now?

IMG_1179.JPG
 
That looks like a 76 to 79 california smog legal exhaust manifold.

You want to put that on a 60? You'd be better off selling it to a california native and getting a more conventional (stock) exhaust manifold.
 
That looks like a 76 to 79 california smog legal exhaust manifold.

You want to put that on a 60? You'd be better off selling it to a california native and getting a more conventional (stock) exhaust manifold.
Pretty sure. I got the 40 out of Nevada. Could have been purchased in California I guess. And no, I wanna put it in my 1976 40. Am I in the wrong place. Oops. I'm new to this forum and really appreciate the community. Sorry if I messed up.
 
That main concern is that the exhaust and intake flanges are the same thickness. (although making sure it's as flat as possible is always a good thing)

Swapping between a header and stock intake might make that problematic..
I have the original exhaust manifold so the thicknesses are right on.
 
Yeah, you should have originally posted in the 40's section, but the 40 & 60 manifolds are very similar. So is the engine. So yes, the correct way to plane the intake & exhaust manifold is after they've been bolted together. It requires a shop that has done it before so they will know how to deal with the rotating ends.

Yes you can hook up the smog equipment again. But if you don't need to smog it, then there's no point. It's just clutter that gets in the way.
 
Yeah, you should have originally posted in the 40's section, but the 40 & 60 manifolds are very similar. So is the engine. So yes, the correct way to plane the intake & exhaust manifold is after they've been bolted together. It requires a shop that has done it before so they will know how to deal with the rotating ends.

Yes you can hook up the smog equipment again. But if you don't need to smog it, then there's no point. It's just clutter that gets in the way.
Great, thanks for that info. I suspect Id have to block any ports leading to the smog equipt if I don't hook it up.
 
Yeah, you should have originally posted in the 40's section, but the 40 & 60 manifolds are very similar. So is the engine. So yes, the correct way to plane the intake & exhaust manifold is after they've been bolted together. It requires a shop that has done it before so they will know how to deal with the rotating ends.

Yes you can hook up the smog equipment again. But if you don't need to smog it, then there's no point. It's just clutter that gets in the way.
Rotating Ends? Not sure what you mean
 
There is a local cali guy that is drooling over that manifold right now..
 
I would avoid using that ghastly Calif. manifold, unless forced to do so by law. It retains a lot of heat to promote vapor locking and heat soak issues, and has even more places to leak....
 

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