Technical Chevy headers on a Mopar

I have a set of Chevy small block headers and the flanges are pretty close to what the small block Mopar flanges are drilled.Can the Chevy flanges be re-drilled to fit the Mopar head?

 

Bob Glidon said the sbm was a sbc with goofy valvtrain but I've never heard of using headers on one from the other.

 

Use a SBC gasket as a template to check your idea. But..........
Even a 1/8" misalignment of any of the ports to the runners would be a "Do not pass go. Do not collect $200" to me. Unless someone dared you to use them, sell old - buy new (or trade) headers.

 

Get the correct headers, and be done .

 

If you really want to use the headers buy the correct flange and remove the Chevy flange, then make them work.

 

These are fender well headers.I do have a set of Mopar headers but don't want to cut them up to get the flanges.

 

Just buy new flanges.

 

Not saying to do it or not to, but a friend of mine generally used slightly modified Chevy headers on his circle track car running a 340 and/or 360 Mopar. He was pretty successful.

Lynn

 

While you're at it, why don't you try them on a Ford Y-block.

 

I sold a pair of Fat Fender Chevy fenderwell headers to a young guy who was building a Mopar gasser with a 340. He later called me and said they worked great once he welded the Mopar flanges on them!

 

like he said...or buy a set on evil bay

 

I've used sbc headers on a Ford y-block, so why not.

 

Stop the madness......

 

I think my concern would be the Mopar starter clearance with the sbc headers. I suspect the outer two flange holes could be relocated to bolt onto the Mopar head, the flange gaskets would answer that question, and would probably clear up any questions about sealing the exhaust ports to the headers. The next question is if (or which) the headers would fit in the chassis, since we have to guess what you are doing.

Are Mopar headers that had to come by these days? Gene

 

The OP said there fender well headers in a reply post. Shouldn't have any starter clearance issues with those. The only fender well headers I know of for small Mopar are for early A body and are not very cheap.

I agree with the replace the flanges crowd if these fit whatever the OP is building. The tubes and collectors don't know what make the engine is.

 

Neither does the exhaust gas. If you can make it work then why not?

 

Absolutely Slayer. I have 302-351 Ford Headers on my Poly 318 because they were (alot) less expensive and available in stainless. Port center on the worst of the cylinders was only .040" different between the Ford and Poly.

Pre-super-charger pic...

 

Earlymopar,
That Poly looks beautiful,,,,,,and the headers are very slick,,,,,wise decision.
I can’t get over the exhaust adapter,,,,,now that is what I call craftsmanship !

Tommy

 

You should be able to redrill them

if the ports are not off by much snd your not going for 100% all out horse power , run ‘em !

you can always change the flanges and tweak the tubes to your likening.

as has been said tje exhaust gasses won’t know the difference in mopar or Ford .

 

Thanks much Tommy. Interestingly a year or so after I made these, a poly entry in the Engine Masters competition made a similar adapter for sprint car style headers and they found through dyno testing that the length added to the exhaust port by adapter was also an H.P. adder. They also did further research and found that intake port centers are similar to the Chevy LS platform so that opens up a boat load of possibilities.

 

Here is some info
https://www.racemufflers.com/Mopar-Mild-Steel-Header-Flanges-s/2095.htm
and
https://www.jalopyjournal.com/forum...s-and-equipment.235784/page-103#post-12067333

 

After laying a gasket over the flange it looks like I will need new flanges welded on.That's not a real big problem.I was just hoping that I could get away with re-drilling what was there.Thank you to those that posted useful advice.

 

Yeah, that wasn't going to be a drill and go...

 

Prior to seeing the previous post above, I was going to say if you have the time, but not the money, then why not, possibly with the right skills and commonsense it could work.
However after seeing the gaskey mismatch, I'd say I am now not warming to the idea...

 

The chevy ports look awful small compared to the Dodge ones. They would probably hurt HP more than help anything. Even re-flanging them unless you open the tube size they would hurt exhaust flow.

 

Trust me the Chevy headers have huge tubes..They are bigger than the Mopar tubes.These headers were on a 57 Chevy dragster .

 

How about a photo. Sure looks doable to me.

 

Trade the Mopar engine for a SBC.

Seriously, the flange swap work should get you where you need to be.

 

I’ve a set of SBC manifolds and a set of 318 and a set of 360 manifolds. If I can locate an old set of SBC header gaskets I have somewhere, I’ll post pics of them laying on the Mopar manifolds.

 

Due to the angle of exit of the exhaust ports, the size of the opening can be deceiving.
Doing flanges (and forming the pipes to fit) now would be the way to go, especially when you are talking about fenderwell headers, which have a lot more weight offset out from the head, leading to more stress.
I also want to say you have not mentioned what this is going in. If this is anywhere close to a stock body front end, the headers may not go where you need them. You would be better off building from scratch. If it's a freak, and they fit the car and engine except the flange area, go for it!