Does anyone know for sure if these exhaust manifolds will fit a '76 455? Any fitment issues in an A-body ('71 Supreme)?

https://www.opgi.com/cutlass/C240268...8aAs7jEALw_wcB

Many thanks

 

All factory BBO heads have exactly the same exhaust ports, so yes they will fit both the engine and the car.

 

If you are building a modified engine I would strongly recommend a set of long tube headers. Installed properly they will require little maintenance and provide a significant gain in HP and low end torque over the exhaust manifolds.

 

Mac - when I saw this motor it had the exhaust manifolds on it. Did he remove them before you bought??

 

Jmo, but that's a good price with free shipping. Your probably giving up 10/15 hp going with these vs long tube headers.

 

Thanks Joe, I'm new to the 455. And from reading here on CO, I know how you feel about these.

Thanks Eric. I haven't rules this out. Just exploring options right now. Not sure I feel like messaging them in and don't they hang fairly low? Depends on the brand I suppose.

Yeah dude, I have them. Also considering using these and just welding a cap on the crossover. But that just looks like it would introduce unwanted air turbulence. Maybe?

Seemed reasonable to me too. Then again, the budget is getting eaten away quickly, lol.

Thanks everyone.

 

These are repros of the factory W/Z manifolds used on the 69-72 442s. Nothing wrong with them. My issue is with the small block manifolds that are alleged to be "based on the W/Z manifolds". Completely different product.

 

The cap is the way the factory did it for every stock dual exhaust using those manifolds. It won't cause any ill effects.

 

Sorry, no. You are thinking of the SBO manifolds. The OP is talking about a 1976 455. Due to the catalyst, Olds only used a single exhaust with a crossover pipe on every engine that year. The earlier BBOs with true dual exhaust had different manifolds without the crossover provision, thus no cap. Also, the motor is going into a 1971 A-body. Use the correct A-body manifolds. You'll have enough other issues to deal with. Don't create new ones with the wrong manifolds.

 

My mistake.

 

Yup, that's right. I forgot I was reading a thread about a small block. So these manifolds will cause the least amount of (extra) headaches?

No worries, Eric. I appreciate the effort.

 

Yes, they are repros of what the factory used for this application.

 

Thanks dude.

 

I just found these W/Z manifolds on eBay. What is the heat spring for and can it be deleted?

http://www.ebay.com/itm/1968-OLDS-CU...VZYvpd&vxp=mtr

 

Yes - the spring can be removed. You can also cut the flap away from the shaft it's attached to if you want to eliminate that potential restriction. For that matter, you could remove all of it (shaft, flap, spring) and easily tap the shaft holes with a pipe thread type tap and put a couple small pipe plugs in there to block of the shaft holes.

 

Excellent! Thanks, Post.

 

Mac I have those on my 455 in my supreme. I did exactly what Patton described to remove the choke stuff. Idt it's noticeable at all especially once on the car.

I would ask that eBay seller if there are any cracks or other damage to those manifolds as the description is vague w no mention of condition.

 

Thanks Retro, I did exactly that last night. I haven't heard back yet.

Also, over the last few years I've somewhat learned where to worry about looks and where not to. I've spent too many hours cleaning and painting areas that can't normally be seen and that get filthy the first time down the road, lol. Chrome headers, ceramic coatings, yadda yadda. I like black stove paint. It protects against the elements, is easy to touch up with a cheap paint brush, and best of all it's uber cheap, lol.

 

So, last night I emailed OPGI about their manifolds. This was their response:

"thank you for your inquiry,

these will not fit the 1976 455 block. These are designed to fit a 455 block from the years of 1969-1972

thank you for letting us be a part of your restoration."

Is this right?

 

What morons.

One more time: every single BBO has exactly the same external dimensions, including exactly the same exhaust ports and bolt pattern.

Your first mistake was asking them and expecting to get a coherent response. They probably would tell you they don't fit Supremes, either...

 

I guess I'm just used to companies telling me a part fits when it doesn't. Not that it doesn't when it does. Seems like a bad business model.

Joe, I saw an old post of yours where you said that J heads can flow as well as the others with proper porting. I found someone within driving distance that sells ported and polished J heads. This is their claim:

"OLDS 400/455 HI-PERF CYL HEADS PR - Competition Valve Job - Heads PORTED & Blended COMPLETELY w/ ENLARGED Valve Seat Pockets - all new HD VALVE GUIDES - RESURFACE MILLED - Machined for HD Teflon Seals & EXTRA VALVE LIFT Clearance - CRANE VALVE SPRINGS, RETAINERS, SEALS - C.N. 411873, Suffix J - APROX 80 cc - OK Unleaded Gas - HELLUVADEAL ON REALLY GOOD HEADS, w/ Gasket Sets Included Can be used on HP 403 engine"

I thought I might give them a call and see if they'd take my J's as cores. Other heads, C, G, etc. are just too far away. Thoughts?

 

mac i have those manifolds on my 76 455 and they fit nicely .my downpipes needed a little work getting them to fit through the crossmember humps,but this is on my 76 supreme you may not have that issue on your 71.

 

You have the OPGI manifolds or the eBay W-Z's?

I'll have to fiddle with the downpipes as well since I'm changing from shorty headers to the manifolds but I think I have the double-hump crossmember on my '71.

I picked up some heads today from an engine builder that was in the biz for over 50 years. He REALLY wants me to go with full length headers. I know they would flow a little better but are they worth the fitment headaches?

 

Mine are w/z from Fusick Oldsmobile . I did buy a 73 duel hump crossmember for my car . I love headers once they're on , definitely more work.

 

Anyone else want to chime in? The original W/Z's on eBay will expire on about 6 hours so I have to decide. The seller got back to me and claims no cracking anywhere. I think it would be cool to have original W/Z manifolds and it would also save me about $90 (Edit: eBay W/Z's $90 cheaper than the OPGI manifolds). Not a ton but still, every penny....., right?

 

Took one last close look at the eBay manifolds. One has a broken bolt in the exhaust hook-up (collector?). Not a deal breaker, but still, he didn't offer than info in the description or the email.

 

I am actively waiting for the latest batch of reproduction W/Z manifolds to be shipped (I assume on slow-boat from China) to Thornton Reproductions, and then distributed by them to outfits like OPGI, ILT and all the rest, "by the end of July" (as Thornton advised me two weeks ago).

It is my understanding (from Thornton) that all of the retailers are Sold Out and that Thornton is the only authorized manufacturer.

I am looking forward to having new pieces of cast iron that have not endured 45 years of heat cycles and general use/abuse. I just sold a pair of originals that had been repaired for the (at least) 2nd time due to cracking.

I couldn't afford the only set of real, original NOS units I'd be interested in using on a car I actually drove, i.e. manifolds that actually fulfilled their intended purpose.

 

Well then it's a good thing I'm not in a hurry. But I also won't put off the purchase. I passed on the original W/Z's. When I looked at all the pics again it just seemed to me that he was actually hiding the broken bolt. And when he emailed me he said "Oh wow, I never noticed that!". It's possible but not very likely.