Exhaust Riser Question

"Have 89 454s FWC and last spr

"Have 89 454s FWC and last spring complete R&R on engines, new manifolds, risers & elbows, R&R coolers, new hoses and much more, installed. Engines run great, temp steady @ 165 to 170 +/- and laser temps show 75 or so on risers & elbows and manifolds run around 175. So here is the question. When I put the elbows on the risers I used the gasket that only has one hole at the top instead of the 3 hole gasket (that was how they were on old set-up)when engines are warmed up I get some steam out of the exhaust, not really bad but none the less it steams, should I have used the 3 hole gaskets for increased water flow through the elbows?
Also on the Port engine only after sitting for a few weeks I get a big rusty colored discharge upon starting then it clears. I am thinking its coming from the exhaust collector box ( 2 - 3" hoses into one 4" hose system) and not from the new risers & elbows installed. Any thoughts on this?

Thanks for the suggestions."

Sounds like your engines are v

Sounds like your engines are very happy. The temps are great. A little steam is normal. Since I don't have a collector box on my 90 454s I can't really say but it sounds like you might be on the mark. Be happy you got those puppies right where you want them.

"Had to laugh upon reading you

"Had to laugh upon reading your post!

On mine, the old gasket (manifold/ riser) had 4 holes in it where the new one had only one hole. It turns out that the other 3 holes were made by the engine! The gasket was covering up holes in the manifold that are there for core removal at the time of manufacture. In use, the gasket gradually wears away where those core holes are, revealing the extra holes. Had a merry time trying to explain all this to the OSCO tech rep.

Perhaps that's the case here as well?

Jeff"

So does that mean that the sin

So does that mean that the single top hole is the correct gasket between the riser and elbow for this application? OSCO gave me some three hole gaskets in my purchase of all these parts.

Thanks for the help

Robert

On my 454 the gasket that goes

On my 454 the gasket that goes between the riser and the exhaust elbow has three holes (Crusader pn 96108) and the hole in the riser that gets blocked off is the bottom hole. The explanation that I got was the bottom hole is blocked off to insure the water flows thru the upper part of the riser. Is this correct?

Suggest a call to the manufact

Suggest a call to the manufacturer.

Jeff

"Call Osco they are very helpf

"Call Osco they are very helpful. On my 1988 454s when I replaced riser and elbows last year the directions matched what you did. Single hole that goes on top. As it was explained to me the purpose is that the entire riser will fill with water and then force it out the top hole. The riser being "full" of water helps to keep it cool.

We get the exact same steam, in fact we get some steam at all speeds and it is noticeable running. It dissipates about 20' behind the boat. From everyone I have spoken to this is normal. I will post a picture when can find it.

Also did you install the metal plate between the two gaskets between the manifold and riser?"

Thanks for your feedback on yo

Thanks for your feedback on your installation of top hole only gasket. Yes the metal plate was installed between the two gaskets on the manifold / riser connection.