Cutlass Supreme Exhaust System Questions

[olds307 and 403]

I think those old headers were for a firebird with the 403. The guy I bought this car from had a half dozen discobirds; but who knows...

The Thorntons bolted up fairly easily. They were nice enough to include gaskets and bolts BUT on each header 1 tube was blocking the bolt hole and I used a couple I took off which were shorter and had 3/8” heads vs 7/16”, so I could squeeze them in. Passenger side barely clears the top of the upper control arm on my car.

These headers are very nicely made. The welds are good and the chrome finish looks great. I’ve seen better but not at this price. Yeah the collectors are pretty tiny compared to the long tubes but these should flow plenty for a stock or mild small block.

Still waiting on my down pipes so I can’t say how they sound yet.


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Glad to hear, they are a needed product for us Olds V8 guys. I would buy a set over my Sanderson shorties but I have them and custom front pipes.

 

[WanaBa442]

They look like a good fit. If you used the supplied gaskets let us know how they hold up.
They're on my radar for this spring, adding in a dual crossmember and complete duals out the back for the mighty 260....
Keep us posted on how you make out with the downpipes work out, or what you had to modify.

 

[Gozer442]

I've got a 403 with 455 heads, and old set of Hedman headers. I don't know the PN#, but they fit with no "adjustments" at all...but it's a real tight fit. To remove the stock style starter, I have to unbolt the header, pull the motor mount bolts, raise the motor up, pull the motor to the passenger side, lower the header, then pull the starter. Yes, I should get a mini starter...

 

[rogue_ryder]

They look like a good fit. If you used the supplied gaskets let us know how they hold up.
They're on my radar for this spring, adding in a dual crossmember and complete duals out the back for the mighty 260....
Keep us posted on how you make out with the downpipes work out, or what you had to modify.

The DPs finally showed up on Friday Night. I got the Driver's side installed no problem. The Passenger side is gonna take some bending or cut/weld to get to fit right. The SBC must have both exhaust manifolds flanges at equal angles, wheres the Olds is different driver to passenger side. I actually got the passenger side to bolt up but it won't fully seal due to the difference in angles between the header flange/collector and the DP.

Believe it or not the gaskets are really nice, they're super thick all metal. There was no leaks between the header and the head on my initial fire up. I'll update when I get the system fully fitted up. I'm probably going to have the Down Pipe modified at a local shop that can do a cleaner welding job than I can (all I have to cut is an angle grinder and a flux core Mig which does not generally produce the nicest welds).

 

[olds307 and 403]

You should have tried the other down pipes I mentioned, they should have bolted right on. The Olds V8 and sbc are very different, surprised the driver's side bolted up. Is the sbc passenger side a 90 degree angle? Your old 307 manifold is, the Thorton isn't. Remember Thornton's headers are based on early precat manifolds and so are the Pypes head pipes, even though they say 400 through 455 and only through 72.

 

[DoubleV]

Yep. Olds engine. Olds down pipes. Why did you try cobbling Chevy pipes onto Olds manifolds?

 

[WanaBa442]

You should have tried the other down pipes I mentioned, they should have bolted right on. The Olds V8 and sbc are very different, surprised the driver's side bolted up. Is the sbc passenger side a 90 degree angle? Your old 307 manifold is, the Thorton isn't. Remember Thornton's headers are based on early precat manifolds and so are the Pypes head pipes, even though they say 400 through 455 and only through 72.

Are these the ones you're thinking of?
https://www.lmperformance.com/26646/dof10s-pypes-442-2-bolt.html

 

[olds307 and 403]

Are these the ones you're thinking of?
https://www.lmperformance.com/26646/dof10s-pypes-442-2-bolt.html

Yes, they may need some cutting and adding but will at least bolt on. I moved my custom dual exhaust from my G to A body, except the tail pipes. I didn't try the tail pipes but they have fit as well with some mods.

 

[WanaBa442]

Thanks. Trying to come up with a "recipe" with all the parts to order a complete system with the Thornton shorty headers.

 

[rogue_ryder]

You should have tried the other down pipes I mentioned, they should have bolted right on. The Olds V8 and sbc are very different, surprised the driver's side bolted up. Is the sbc passenger side a 90 degree angle? Your old 307 manifold is, the Thorton isn't. Remember Thornton's headers are based on early precat manifolds and so are the Pypes head pipes, even though they say 400 through 455 and only through 72.

I had already ordered up the Gbody ones at that point. Looking at the reviews on Summit for the Abody parts it looks like some mods are needed to use on a Gbody too.

The Driver Manifold was a direct bolt on, the passenger's side is at an angle. From what I've read about the Abody Olds Pypes DPs on Summit is they need massaging for the Gbody too. Probably would've worked out perfect if I could have ordered 1 chevy DP and 1 A body DP! The local exhaust does great work and is super cheap. I had a full 2.5" cat back built for my Jeep and it was $80! So I don't think he'll charge me too much to hack off the flange and tig it up at the correct angle.