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Thornton stainless shorty headers on 1972 455 automatic Cutlass 442
Hi:
Anyone here install Thornton stainless shorty headers on 1972 455 with 400 TH automatic in a Cutlass 442? I have regular long tube headers but want to swith to the shorty headers. I have a full 2 1/4 inch FloMaster dual exhaust and just need the pipes for bith sides from the shorty's to the FloMaster pipes. I guess I need what's called down pipes? Any one know the best place to get these pipes? How tough is it to get the shorty's installed. Am I going to need the motor mounts undone and an hoist of some type?
You'll need an exhaust shop to bend up the new bits for you. You can't buy something like that off the shelf. *supposedly* the thortons exit at the same spot as the stock manifolds, so you could buy a stock fitting kit, try to cut it up to match what you have. But that would cost far more and be way more difficult than going to an exhaust shop. I think those thortons have 2.5" exit, but stock fitting pipes are 2.25" (or 2"!). Seriously, any exhaust shop could whip up those little connecting pieces and get them installed in less than half an hour.
Installing the thortons will be easier than removing the full length headers. The difficulty of removing those headers just depends on what they are. I assume you haven't done it on this car? Usually they need to come out the bottom, so need to lift the car pretty high in the air. I end up getting the headers pretty low, then pulling the collector towards the middle of the car. That gets the flange to turn and fall out.
Most headers require the starter and oil filter adapter to be removed. That should be it, though. Don't normally need to mess with the steering shaft or anything. Get a new gasket for the oil filter adapter!
I have a 2 post lift at home so getting them out the bottom will be doable. I put the headers on around 20 years ago but it's all a haze in my memory. I remember it wasn't fun since I didn't have a lift back then. Now that I'm in the final stretch towards 70, things are more intimidating than they used to be. Trying to do things to get this one done sometime next year! I was hoping that I could order the down pipes from FloMaster and they'd be close.
I'm not sure how different the clearances are on the 455 models, but I installed the Thorntons for my 350, and used the Pypes downpipes with a small adapter to fit into my existing pipes (formerly with long tube headers). I'll get it to an exhaust shop next spring, but for now, everything fits. I had a header clearance issue above my oil filter housing that I had to heat and beat to fit, and I needed to flatten a tube on the passenger side to clear the crossmember. The passenger side went in from the top, the driver's side from the bottom. Honestly, pretty straightforward. Wish I had a lift!!!
Interesting there was interference on the oil filter housing. You are talking the exhaust pipe or the header that needed flattened to clear the crossmember? Maybe issues with the jig being used to make them? I know Sanderson had quality and fitment issues with their headers a few years back. My 3 sets were fine, someone else got three bad sets in a row.
I've frequently offered my opinion on this, so sorry for the repetition. (OK, no, I'm not sorry. )
Shorty headers give you all of the problems of full length headers (annual gasket replacement, leaking collectors, etc) with none of the pesky extra horsepower. If you're prioritizing convenience over performance, just get W/Z manifolds and be done with it. The W/Z manifolds have individual runners and frankly are probably no worse than those shorties.
Interesting there was interference on the oil filter housing. You are talking the exhaust pipe or the header that needed flattened to clear the crossmember? Maybe issues with the jig being used to make them? I know Sanderson had quality and fitment issues with their headers a few years back. My 3 sets were fine, someone else got three bad sets in a row.
The header itself had to be flattened at the edge of the collector for the oil filter housing, and just past the first bend of the cylinder 4 pipe to clear the crossmember. And Joe is right (as usual) in that I've gotten rid of that pesky horsepower I used to have. If I didn't have an issue with the fitment of the long tubes and my shifter adjustments, I wouldn't have made the changeover. And I thought the chrome looked better than the factory pieces. Of course one drive down the block and the chrome is solid brown now. I'm guessing next year I either do some serious research into long tubes that fit or go full factory pipes block to bumper....
I'm really surprised the small collector version had any fitment issue. No wonder you lost power if you had to flatten tubes to make them fit. I'm going with the BBO Chinese stainless full length on my 70 Cutlass S. They will hang low with a 350 but will fit and I have a ton of ground clearance.
What are the odds that to get my long tube headers off that I'll need to disconnect the motor mounts? My car is a 455 with automatic transmission. I have the car on my two post and would love it if I could wiggle them out of there without unhooking the motor mounts!
I may get the headers off and send them back to Jet Hot and have them re-coated and put them back on.....per Joe's recommendation. I'd then sell off the Thornton's. Not sure what I'll do. The car will be in the lift bay until I get it done so....I have time(as far as I know....LOL)!
If I were to get the Pypes Stainless Steel Exhaust Downpipes DOF10S to use with the Thornton short stainless headers, do I need any type of donut gasket to seal them or do they just bolt up metal to metal? What type bolts to make the connection?
About 100%. You'll also have to remove the dipstick tube.
I guess I'll set it on the ground, unbolt the motor mounts and stick a couple small wood blocks in both sides, remove the dipstick and then raise it on the lift & remove the headers and send them back to Jet Hot. After I do all that, I will most likely put them back on and sell off the Thornton's! Decisions! It's not like the car is going anywhere for a while. Just need to find my Jet Hot headers info in my pile of receipts...LOL! Thanks Joe!
Been a long time remove oil filter, starter and dipstick tube. Get the car up on stands on all four higher the better, drop and install through the bottom. This is what I did with my dipstick tube. Hope this info helps.
Been a long time remove oil filter, starter and dipstick tube. Get the car up on stands on all four higher the better, drop and install through the bottom. This is what I did with my dipstick tube. Hope this info helps.
September 26th, 2020, 12:15 PM
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