Hi all - I have a build thread going but thought I would ask it here since it seems to be a common question on Pontiac sites too but no answers. Has anyone installed an Oldsmobile 455 WITH headers, in place of the 403, etc., in a 2nd gen (70-81) Trans Am or Firebird? I have 'small block' manifolds on it now and would eventually like to re-do the entire exhaust. I understand the headaches with headers but believe its worth the HP in this case.

I have heard headers for a 455 Cutlass (74-76 body style) should work best? Does that mean all 69-76 Cutlass 455 headers will work then? I assume 403 headers would not fit due to engine being hire up than original 403? I am using the factory motor mounts on the frame and engine block if that helps.

Any input appreciated! Really appreciate a known brand recommendation (Flowtech, Headman, etc) that is known to be compatible...

 

I know for a fact the 403 headers will not fit without some serious bashing and denting. It’s not worth even trying.

The Hooker headers fit very well. I don’t recall the part number, I don’t think they are the same as A body headers.

 

It's due to the 455 being wider than the 403. That makes the headers hang at the wrong angle off the flanges when bolted to the engine.

 

Ha! Thank you. I thought about trying 403s actually at first. I will look at their offerings..maybe ones for a full size car?

 

Makes sense now that you explained it. Probably hit the steering linkage too. Thank you

 

Found this posting, #21, and will look into some Hedman's with a part number of 58150. I see Speedmaster now offers headers but for the 403...

https://classicoldsmobile.com/forums...90/#post279526

 

The angle of the exhaust port flanges is exactly the same on all 1964-90 Olds V8s - they are parallel to the bore centerlines, period. The difference is the taller deck height, which puts those flanges (and thus the attached headers) both further outboard and higher relative to the crank centerline when bolted to a BBO.

 

If you do a detailed search here you'll probably find the answer.

Maybe these big olds G body since the small olds G is the same pipe in the T/A

OBBG-78178300HR

 

I have searched and confirmed it's possible to have headers but no luck with what car/body style to use.
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Thanks but I think those are for a Chevy engine...

 

Don't think so, that didn't come up last I chatted with them for a starting point set to cut and build for a B Body 69 BBO and I wouldn't have posted it if the pic showed a BBC flange spacing.
It's listed under Oldsmobile which covers a few different cars SB and BB Olds.

Oldsmobile Big Block G , OBBG

 

Look at the exhaust flange. These are Oldsmobile headers.





Now, I have not idea if G-body headers will fit an F-body.

 

Thanks, my mistake. I didn't see a picture originally. I checked the application guide and just saw 78-83 Malibu, 78-87 El Camino , etc but looks like the headers are made for Olds transplants into various cars. They might fit but not worth $1600 gamble to me.

 

They'll answer the phone and help you. Seeing as the SBO G fits your car the BBO G might just do the same and fit mounts loosened to get them in or very close with just a little working.
I've not had both cars side by side to compare but they probably have a TA there , maybe haven't checked it with a big Olds yet.

 

https://americanracingheaders.com/pr...8-1988-headers

https://americanracingheaders.com/pr...03-small-block

https://americanracingheaders.com/co...8-1988-headers



It's be said the 64-76 BBO A fit the BBO F but ...
https://americanracingheaders.com/co...4-1977-headers

 

It can be done with 403 headers but you will have to "make it fit". Will not work with the factory AC Box and you will have to oval the collectors.

 

I have been looking at putting an Olds 455 in my 403 Trans Am since I have one sitting around. Do you have any more pics of how it turned out and how the clearances were around the engine? How did you get your shaker scoop to work out or did you opt to attach it to the hood? Thanks!

 

You can check out my build log and see most of what you need or ask questions there. Get a toronado intake manifold if you want a shaker to work.
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https://classicoldsmobile.com/forums...-455-a-167349/

 

ebay stainless steel 455 / generic headers

Overdue for an update - no luck with the cheap ebay stainless steel headers unless I cut and re-reroute the last two pipes. Based on lots of googling, I may try Headman 58060 since the passenger side routes straight down instead of rearward. Overall, it probably is not possible or worth the effort or costs to run headers on the 455 in a TA. May look for W/Z/X manifolds in the end.

 

I know for a fact someone makes headers for a F body with a 455 Olds. I’d call the major manufacturers and check.

 

Ha, no lie, I just talked to Hedman today. There may have been a manufacturer back then but not now. He couldn't really tell me the dimensions/info of the headers that they had in stock now. He did mention Mondello used to make parts but no tangible info.

 

Thorton just started selling W and Z reproductions that have a 2 1/2" outlet. These will perform better than originals that have a 2 1/4" outlet. They also make shorty headers that might fit and perform well. A cam with a wide LSA like 112 or 114 degrees works best with cast manifolds.

 

Someone on the site has stuffed a 445 olds into a mid 70s Camaro, but I cant remember if they had headers on it.
Might try searching for that.


found it..
Cam for a hot street 455 - ClassicOldsmobile.com
see post #10 he has headers

 

Nice, thank you. I had searched Camaro and skimmed thru 13 pages of results and missed that posting. Unfortunately, he doesn't have AC so no big suitcase to get in the way... Appreciate your help though! The search continues