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So, Thornton seems to have introduced a new set of headers that fit onto the stock intermediate pipes for a dual exhaust 350. My current long tubes are rusty and a real PITA when it comes to the tension spring and the shifter linkage. I'd like to switch to these new headers and use the stock exhaust pipe routing, but I can't seem to find a supplier of the factory bent intermediate pipes. I've done a search, and the best I can come up with is that the passenger and the driver's side are different pipe sizes on the 350 - 2" vs 2-1/4" - but when I find a supplier of the intermediate pipes, the disqualifier is that I have OAI, which doesn't seem to make a lot of sense. If you have replaced your dual exhaust with the factory style pipes, where did you find your intermediate pipes? Are they the same as the 455? The rest of my exhaust system is excellent - no need to replace anything but the headers and the front pipes. Any help is appreciated!
Last edited by BSiegPaint; February 13th, 2018 at 06:42 AM.
I have no experience with these shorty headers. The outlets APPEAR to be i the stock locations for an SBO, but the ad claims that they accept 2.25" or 2.5" head pipes. The flanges appear to be ball joint and not the stock flare. I'm not convinced that a stock pipe bolts up with no issues.
I have no experience with these shorty headers. The outlets APPEAR to be i the stock locations for an SBO, but the ad claims that they accept 2.25" or 2.5" head pipes. The flanges appear to be ball joint and not the stock flare. I'm not convinced that a stock pipe bolts up with no issues.
Joe, that’s a perfect point. If stock pipes are 2” on the driver’s side, then these wouldn’t fit onto the stock pipes. So I’m sure this is just a “stock location” fitment, and I’ll need a custom bent pipe to meet up with the muffler(s). That was easy.... thank you
A vendor doesn't know what you have, so, if it makes no sense that it has a no OAI restriction, you can mislead them and buy anyway. Might help to ask why in a separate phone call just to make sure.
A vendor doesn't know what you have, so, if it makes no sense that it has a no OAI restriction, you can mislead them and buy anyway. Might help to ask why in a separate phone call just to make sure.
The Parts Book shows different P/Ns for 1970 350 cars with and without O.A.I. (of course, this likely means W-31 and not a non-W car with a W-25 hood).
Non-O.A.I. is 399546 RH and 403413 LH
O.A.I. is 406218 RH and 406219 LH
Unfortunately, the Parts Book does not detail the differences.
OK, I've figured this out. The 1970 A-body 350 cars all use the same exhaust manifolds, so the front ends of the pipes are the same. The 1970 350 O.A.I. cars (namely, the W-31s and Rallye 350s) use different mufflers than do all other 1970 Cutlii. The exhaust pipe difference must be an expanded aft end where it fits into the muffler. Mystery solved.
What about the Pipes down pipes or ask Thornton what pipes they have fitted to their headers. Nice to see these as nearly ever other make has bolt on shorty headers to stock or stock replacement exhaust. I assumed they were doing a SBO version of that tubular header, not a regular shorty header.
Last edited by olds 307 and 403; February 15th, 2018 at 05:46 AM.
I ordered up a set of these for my 85 442 that currently has crappy long tubes going into a full 2.5" Pypes system (X-Pipe, dual mufflers and tail pipes). I'm planning on junking the beat up leaky long tubes installing some universal Pypes Cats, the Pypes G-body SBC downpipes connected to the Thornton Headers. I'll let everyone how the install goes.
Originally Posted by olds 307 and 403
What about the Pipes down pipes or ask Thornton what pipes they have fitted to their headers. Nice to see these as nearly ever other make has bolt on shorty headers to stock or stock replacement exhaust. I assumed they were doing a SBO version of that tubular header, not a regular shorty header.
I asked Thornton if they'd work with Pypes DGU10S down pipes but got no answer. Pypes lists that # as compatible with SBC powered G-bodys but they also offer the same DP with a 3 bolt flange, seeing as the Pypes are 2 bolt flange as well as the headers being 2 bolt they might work and I'll take my chances. Best case scenario is the headers bolt right up to the down pipes and I just have to do some cutting to fit up to the cats & xpipe. Worst case scenario is cutting the flange off of the down pipes and welding on a new one that is the right size. Cutting and welding flanges is a lot easier than bending exhaust tubing. The Pypes are mandrel bent and you won't find many muffler ships with a mandrel tube bender.
And if you're not concerned about having a Mandrel bent exhaust system any muffler shop should be able to fab up a down pipe. The ball socket on the end of these headers is a pretty universal design and any muffler shop stocks the flared exhaust tube, they just weld that to a bent up section of pipe and slide on the flange with holes in it to bolt up to the header. Shouldn't cost much at all to have fabbed up.
Last edited by rogue_ryder; February 15th, 2018 at 02:14 PM.
This'll is the down pipes you want to try. The sbc ones probably won't be close, a member modified a sbc G body Y pipe, it needed a lot of modifications. Pretty sure Thornton headers will be based on pre 75 non catalytic converter exhaust manifolds. The DOF10S are the ones to try, read the 13 reviews, multiple 350 owners have used them with success. Get both sets and see which ones will work better. https://www.summitracing.com/parts/pye-dof10s
Last edited by olds 307 and 403; February 15th, 2018 at 04:30 PM.
I contacted Thornton, and they suggested I contact a place called Never Rust in Pittsburgh, PA - so in other words, they don't have a real answer for the headers they're selling. I checked on the Summit Racing parts and those that used them with the 350 seemed to have excellent reviews, so maybe these are the answer! Thank you
Well, I'll dig up this thread for an update.... I ordered the Thornton headers and I ordered the down pipes suggested above. Good reviews on everything I found so far, so I'll see if these work as well as I hope. At the very least I want to gain some room underneath so I can properly adjust the shifter linkage and install the return spring onto the starter bracket as it's supposed to be. I think they will look a lot better than the painted long tubes I have in there now as well. I'll let you know how it goes!
I was looking at Thorntons "350JR" cast iron manifolds on their E-pay site a while back & they said to use big block 2 1/4" head pipes for them but all their regular website says is the manifolds have 2 1/4" outlets?? I would have to think the same is true for these new shorty headers. I can't believe they can't tell you what pipes to use on the manifolds they made(or had made)? I'm interested in these "headers" for a '69 W31 4spd clone that I'm helping my friend Craig build. I used inlines pipes for my '68 442 & the fit was excellent. I guess we'll order the big block front pipes for his & see how they fit but we're still a long ways off from this build. He's got to finish his new shop first.
February 13th, 2018, 06:39 AM
