Thornton exhaust manifolds (SBO) on a G-body
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If you want to keep the emissions stuff intact do you not have to keep the exhaust manifolds?
Or can you get rid of the air injection pump? Or did the 307 not have one ?
Or can you get rid of the air injection pump? Or did the 307 not have one ?
Small block Chevy, yes (though I've seen headers with AIR tubes as well).
Oldsmobiles are separate, and screw into the cylinder heads straight in from the side, flow upward and into a single pipe that goes between the firewall/bellhousing and straight into the catalytic converter. Check valves and a diverter solenoid control where the air is pumped and when. The exhaust manifolds are attached to the heads at an angle, pointed towards the ground. I don't see there being any interference issues, headers/Thornton manifolds.
Keeping the emissions equipment isn't so much a "want", as it is a "need". There are no visual inspections (yet, although they've always had visual inspection upstate). But anything not tagged as a classic has to be tested with a sniffer. Not an issue, it's not a hot rod, won't be a hot rod. All the equipment is there, it's not going anywhere. The car will never be dyno tested, so I won't be concerned about making 185 horsepower vs. 180 by keeping the stuff on there.
Or whatever power it will make. Don't know, don't really care number wise. Making a 7hr. trip, not using a case of oil, and having adequate power is fine. It's a $700 car that's lasted 10 years, and should last many more.
Thanks for all the replies. My main concern was whether or not the large ports on the manifold would seal against the small ports on the heads. It sounds like it should.
i used their big block manifolds when i put the 455 in my 79 cutlass. they work very well, a little restrictive on a 455, but cheaper than custom headers.
joe
is there a benefit to the 3in cats attached to manifolds that are 2-1/4in? am i missing something?
joe
If you are using the previous 85 heads I see no problems. But if your using the 86 and up swirl ports then it's hard to say.
I know that they can't seal the intake manifolds when going aftermarket.
I know that they can't seal the intake manifolds when going aftermarket.
That was my concern, but apparently "RunawayNJ" is using them, been driving for a while with them. I'll have to check back in personally with him to see what complications there were/are.
https://gbodyforum.com/threads/1986-oldsmobile-442-build.46606/page-20
Might be, I originally got the catalytic converters to mount right behind headers (with 3" collectors). They're a restriction no matter what, so I wouldn't see the problem one way or the other.
And the plan is to use 2-1/4" exhaust yes. Tailpipes anyway, was thinking 2-1/2" intermediates from the cats, then 2-1/4" tailpipes (which I already have, custom manderal bent in stainless, purchased lightly used). Not 100% sure yet, and I'm not an engineer.
The intake seals, there is just a big port mismatch. A member used a Performer 500 cfm intake and these manifolds on 7A head 307 HO along with a rebuild, tune and dual exhaust, he gained a lot. Olds gained 30 hp by adding shorty headers with anti reversion cones, a Y pipe, Corvette cat and a ram air set up similar to the 1970 set up. This was the 1985 FE3X prototype. Too bad it didn't make the changes for the 86 442 along with the 5spd option. It just shows how poor the factory exhaust was.
I used my shorty headers, X pipe and 2.5" dual exhaust on my Olds 260. I lost no bottom end and gained a little up top. I went back to the 2" dual exhaust with cast iron 260 manifolds. Even that, along a 2004R and 3.42 gears make it driveable and still should be able to get 30 mpg imperial, got 26 on a cool windy day. The 3.42 is a nice gear with OD, 1850 rpm at 60 mph with stock tire and launches the car much better.
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