nukesec1

I discovered the other day that I have a passenger side exhaust manifold gasket leak on my '73 CS. Now is as good a time as any to go with dual exhaust, but I don't want to use that block off plate for the crossover pipe. Is there a stock cast passenger side manifold I can use?

Don L/442

If you get a new exhaust from the manifolds back that will replace the "Y" pipe and the need of a block off plate

74 Omega

Look at this link to an older post.
https://classicoldsmobile.com/forums...manifolds.html
In the forth post I have some pics....not sure if it is what you are after or not...

joe_padavano

There are no exhaust gaskets on a 73 Olds motor, unless someone put them there. Both the manifold-to-head and pipe-to-manifold seals are metal-to-metal. It's possible that the manifold has warped or cracked.

All factory SBO dual exhaust setups used the cap on the passenger side manifold, even the W-31s. The aftermarket manifolds are expensive and frankly don't look to be shaped any differently from stock. Your call as to whether or not they are worth the money. The cap is cheap.

nukesec1

I did not know this Joe. Guess I'll pop for the $40 cap. This happened after I jacked the car up to change the oil.

Warhead

Pay your exhaust guy the $10-$20 to cut the crossover pipe to a short stub, and weld a round cap on it.
$40 is waaaaaay out of line for this part.
Good luck

Jim

jag1886

I put a set of Thornton manifolds on my 65 a month ago they are a true dual exhaust manifolds (no second cross over hole on the PS) that where cast from the BBO from what I under stand they are much bigger inside (more volume) than the stock manifolds and they have a much larger exit hole where the pipe goes on than the stock ones, my local shop put on a 2 1/2 exhaust system behind.
They are very well made and fit perfect.

nukesec1

I gotta weigh my options here. On one hand, after talking with a few old timey retired GM mechanics that are friends of the family (WHAT a WEALTH of knowledge these old guys have on 60's and 70's GM cars), they both suggested as a quick cheap fix to drop the manifolds and install a quality gasket. Certainly that is the cheap route to a fix, but I'm not sure how "quick" it would be as that's at least a 2 man job because everything has to move at the same time on both sides of the engine. But then again they warned that this may or may not fix the problem and I'm back to square one. Then on the other hand my engine builder says to get the Thorton manifolds and he will give me the dealer cost on a Pypes exhaust, installed (if I bring the Sam Adams). Oooh, what to do!

joe_padavano

They're not and they don't.

RAREoldsmanifoldsRH.jpg

Don't get too excited over that center divider. It only goes about an inch or so deep. The BBO manifolds have true divided runners.

RAREoldsmanifoldsRH2.jpg

RAREoldsmanifoldsRH3.jpg

RAREoldsmanifoldsLH1.jpg

RAREoldsmanifoldsLH2.jpg

And for comparison, these are real W/Z BBO manifolds - no, you can't use them on an SBO.

OLD SKL 69

That's what I have on mine. Worked out great and I would recommend that as well.

74 Omega

That is what I did until I got headers.....

Omega 012.jpg

jag1886

I think you need a new pair of glasses, I agree they don't look much different on the out side but when you look inside they are defiantly bigger. The DS dump is larger (you have to look at the inside not the outside) than stock and if you don't think getting rid of that stupid looking 1/2 horseshoe on the PS doesn't help then I give up, your pictures are shot a a deceptive angle, if you had shot them from the top so you could see how much wider they are the would tell the real story. I was just trying to help.

joe_padavano

Yes, the outlets are larger than stock. Frankly, the internal volume of an exhaust manifold is not an indication of it's scavanging or flow potential. And I have physically held these manifolds and examined them. My only point is that in my opinion the advertising hype and price far outweigh the actual benefits. You may spend your money any way you like, but make an informed decision. If they were $150 a pair, my opinion might be different than at $300-$400 a pair.

nukesec1

My opinion is this. Not having actually handled these manifolds, I do like the fact that it has a center runner (No matter how deep it is or is not). I like the fact that the bolt holes look a tad beefier than the stock ones. I like the fact that unless someone from this site judged my car they would most likely not be able to tell they are not GM issue. Price is what you are willing to pay. I agree with both of you at least on some aspects of both of your arguments.