wjustinmartin

1969 98, 455

Currently stock manifolds running to single pipe and a glass pack of some sort.

I am considering having true dual exhaust installed, but I recall something about there being a special manifold required for the left/drive's side of the engine. I did a few searches, but I was never able to find any previous topic addressing this question; please pardon if this has been asked before.

Additionally, is it practical or possible for headers on that car/engine combo?

Texas Jim

I think it's that you need to cap off the "cross-over" hole in the passneger side manifold. If you do that, you could run dual exhaust on the car. I just pulled a 455 from a '71 98 and that had the said manifolds. If you could find headers, they'd let the engine breathe more. You'd have to do the search f/ the headers. Good Luck.

rocketraider

65-70 B/C cars use a specific LH exhaust manifold. It can be done without it, but the pipe will be up in the starter and steering linkage. The "S" manifold is available reproduction and to me is the only way to go.

Texas Jim

What about getting a cap on the RH manifold? I don't think that turning that LH pipe in the needed direction would make any difference in exhaust flow. If you were going to spend money on another cast manifold, you might as well get headers and let the engine breathe. Yes, the LH head pipe (cross-over) runs over the starter...

rocketraider

Factory capped the RH manifold crossover port on these DE applications, but the LH DE manifold exit point is different. The S manifold is a rear exit and angles over the steering box for clearance. The single exhaust piece is a center dump. You try routing the LH dual pipe to it and it's gonna be all up in the starter and steering linkage. The rear steering box location is what makes fitting headers to these cars difficult.

wjustinmartin

I knew there was something, but was not able to fins a thread - thanks for the info

The "S"manifold - is that as in Cutlass Supreme? I am super green when it comes to engine/oldsmobile shorthand, forgive me.

Olds64

This is what you are looking for:

http://gawain.membrane.com/~thornton/manifold.html

svnt442

66ninetyeightls

Here you go.

http://www.themotorcompany.com/Full-...d-p-16158.html

wjustinmartin

I searched and searched Google and this place, but I guess I don't know enough about it to even know what to search for.

Thanks for the help and input, Olds peeps.

Texas Jim

The manifold posted by SVNT sure eliminates the covering up of the starter, and evidently the over-all steering mech. Very nice. Rocketraider, I understand your point f/sure, no doubt. I think I'd go w/ a header kit, where you can cut and weld the tubes to shape the headers how you need/want/ them. They are alittle higher priced than the "run of the mill" types, but they'd surely be worth having, f/ a number of different reasons. If you were going all original and no mods, the different manifold would throw a monkey wrench into your game plan anyway.

I just went over the pics I have from when I pulled the 455 from the '71 Olds 98. You mentioned that the (I'm sure you meant the pass. side w/o reading it over again) manifold was a center dump. I'm sure you know that I was saying that the center dump should be capped. But still the driver side manifold has a rear dump, not as friendly as the one posted by SVNT, but I'd think a muffler shop could bend a head pipe to suffice, and therefore eliminate buying another manifold The driver side manifold does help w/ the covering up of the starter which sucks, to say the least. Like I saaid, IMO I'd go w/ the header kit, as the wrong manifold will not get it if you're looking f/ going all original. Like I said, just my opinion. And obviously, Rocketraider, you're way more knowledgable than I when it comes to what manifolds are available and applicable. Thanks f/ the input trading and opinion swapping.

Olds64

If you get the reproduction manifold from Thornton you should have the driver's side manifold welded. Welding the crossover will prevent a cap from leaking.

Texas Jim

That's like saying, weld the exhaust together so that the crappy work you do doesn't leak. 15 or 20 dollars compared to 250. Cut and clean a cap, use an exhaust gasket, and be done, correctly, and f/ a fraction of the price. And, a header kit would be the best way, especially since you're now talking about spending hundreds of dollars anyway.

You mean "passenger side," don't you?????? You mean, to weld the cap on?????? And welding old cast manifolds is something I don't like to depend on. Been there w/ some old ones before, both intake and exhaust.

Olds64

I say that because I've had work done on the passenger's side exhaust manifold before. I've heard numerous people say you can have the crossover pipe going to the passenger's side manifold "crimped" and welded shut. If that isn't WT then I don't know what is. IMHO, the "right way" to have the passenger's side manifold "capped off" is to remove it and take it to a good welding shop so they can weld it shut. I've done it before and it works great if you find a shop that knows how to weld.