454 exhaust manifolds

[CharlieN]

I have used up two sets of Osco manifolds and two sets of Mercruiser cast iron sets, I need to replace them again. I use 3 inch spacers on a 268 Searay on a 454 with raw water cooling on the manifolds. I have been looking at the newer 8.1 aluminum manifolds with stainless risers and a DRY joint between. I compared the old Mercruiser cast iron manifold, 3 inch spacer and stainless steel riser with the newer 8.1 aluminum manifold and stainless steel riser. They are very close to a bolt in replacement. From my initial measurements, it looks like 1 inch would need to be cut from the down pipe and the more critical inside riser height above water line is less by about 3/8 inch. I will try to post a picture. Has anybody else done this conversion? I would fresh water cool the aluminum manifold and raw water cool the risers. Any thoughts out there? Thanks in advance.

 

[tdschafer]

I don't know much about the conversion. There is another CSR member who got SS riser/manifold combo from an outfit in Australia. Here is their link:
http://www.hitekmarine.com.au/

If you're interested you can pm rcknecht and ask his opinion. Good Luck!
Todd

 

[CharlieN]

I have been talking to Hitek Marine also about their manifolds and also talked to a few of their customers in US. There is a report on the Baylinger owners forum about performance gains using Hitek manifolds. A lot more expensive than the aluminum Mercruiser units but with a 5 year Warrantee , it may be worth it. I could also raw water cool the SS units from Hitek.

 

[tdschafer]

This is all true. They even said avg lifespan was approx 20 years! I know Rod, rcknecht, was able to talk the price down quite a bit by going back and forth with them. Like you said, could be worth looking into. My mechanic had already ordered my new setup before I got a response from them. The lead time was also a problem for me as it was midseason when my old ones failed. Had it been the off season I would have given them greater consideration.
Todd

 

[G Wilikers]

I have used up two sets of Osco manifolds and two sets of Mercruiser cast iron sets, I need to replace them again. I use 3 inch spacers on a 268 Searay on a 454 with raw water cooling on the manifolds. I have been looking at the newer 8.1 aluminum manifolds with stainless risers and a DRY joint between. I compared the old Mercruiser cast iron manifold, 3 inch spacer and stainless steel riser with the newer 8.1 aluminum manifold and stainless steel riser. They are very close to a bolt in replacement. From my initial measurements, it looks like 1 inch would need to be cut from the down pipe and the more critical inside riser height above water line is less by about 3/8 inch. I will try to post a picture. Has anybody else done this conversion? I would fresh water cool the aluminum manifold and raw water cool the risers. Any thoughts out there? Thanks in advance.

First off, I hope this is not a thread jacking and if it is I apologize. I have a similar dilemma right know that I am looking for answers on and viola, I see this post. So here goes.

I have a 88 268 454 & cast iron manifolds. They do not have the 3" riser cast into the manifold. There was a separate spacer between the manifold & elbow. The elbow & spacers are gone (that's the way I bought the boat) & was contemplating a similar setup as seen in the picture. Except I would use my cast iron manifolds instead of the 8.1 aluminum units. It would be very easy to machine a spacer down ( instead of modifying the elbow) to get the correct height I need for the elbow. I would be open to hear if there is a problem with set up or line of thinking.

Thank you,

Greg

 

[CharlieN]

G Wilikers:
The 3 inch spacer (you called it a riser) is a separate piece that bolts between the manifold and risers(elbows). The later Mercruiser risers(elbows) are stainless which is better. I have not had a lot of luck getting these two joints to seal. The heating and cooling, extra long bolts, rusting surfaces, then throw in a little salt water. The newer Mercuiser gaskets-metal with shiny surfaces seem to work better. I have tryed all types of sealers and no sealer-I finally settled on the Ultra Black. The surfaces have to be absolutly flat and smooth. The good thing about the manifolds is they have a little trough in the bottom that catches small amounts of water from small leaks.
I just need to try something different. Good luck with yours.
Charlie

 

[G Wilikers]

I have used up two sets of Osco manifolds and two sets of Mercruiser cast iron sets, I need to replace them again. I use 3 inch spacers on a 268 Searay on a 454 with raw water cooling on the manifolds. I have been looking at the newer 8.1 aluminum manifolds with stainless risers and a DRY joint between. I compared the old Mercruiser cast iron manifold, 3 inch spacer and stainless steel riser with the newer 8.1 aluminum manifold and stainless steel riser. They are very close to a bolt in replacement. From my initial measurements, it looks like 1 inch would need to be cut from the down pipe and the more critical inside riser height above water line is less by about 3/8 inch. I will try to post a picture. Has anybody else done this conversion? I would fresh water cool the aluminum manifold and raw water cool the risers. Any thoughts out there? Thanks in advance.

G Wilikers:
The 3 inch spacer (you called it a riser) is a separate piece that bolts between the manifold and risers(elbows). The later Mercruiser risers(elbows) are stainless which is better. I have not had a lot of luck getting these two joints to seal. The heating and cooling, extra long bolts, rusting surfaces, then throw in a little salt water. The newer Mercuiser gaskets-metal with shiny surfaces seem to work better. I have tryed all types of sealers and no sealer-I finally settled on the Ultra Black. The surfaces have to be absolutly flat and smooth. The good thing about the manifolds is they have a little trough in the bottom that catches small amounts of water from small leaks.
I just need to try something different. Good luck with yours.
Charlie

So besides the sealing surfaces being flat & getting the joints to seal, this set up will work? I own a machine shop, so the flatness part is not a problem. Any idea about the reversion issue I have heard so much about with the 454 engines? Is it any better, worse or the same with these stainless risers?

Thanks,

Greg

 

[Capt Duck]

I have a 34 with 454 and they ned to be replaced, I have removed 7 of the eight bolts on each side and yes there is one to go on both sides. The bolts head are rusted and the socket keep slipping, I am thinking about using a grinder to remove the head and then manifolds are off I will hopefully be able to remove the headless bolt. Has enyone done this, it is just a painful situation

 

[Air O'Nautical]

I have a 34 with 454 and they ned to be replaced, I have removed 7 of the eight bolts on each side and yes there is one to go on both sides. The bolts head are rusted and the socket keep slipping, I am thinking about using a grinder to remove the head and then manifolds are off I will hopefully be able to remove the headless bolt. Has enyone done this, it is just a painful situation

Common problem,

Hammer on a smaller socket and spray with penetrating oil.

Or, get the grinder out.

Good luck.

 

[CharlieN]

G Wilikers:
My understanding of reversion is an engine with long overlap on valve timing causing cooling water that should have been expelled to get sucked back into the manifold exhaust causing water ingestion. I don’t really know much about it, maybe one of the other guys has more to tell.

 

[blackbeard]

I put those ss manifolds from hy-tek on my twin 350s.I like them.More power and wont have to mess with them anymore.

 

[Leafy Isle]

I put those ss manifolds from hy-tek on my twin 350s.I like them.More power and wont have to mess with them anymore.

how much did you have to pay for the hitek manifolds? I saw them at a show a few years ago in canada and the guy wanted many$$ for them...

 

[blackbeard]

well,they are expensive but my engines needed servicing and I know I will be keeping this boat for awhile.Replacing manifolds and risers twice ,plus labor pays for ss manifolds.I am not getting any younger and installed these myself with no experience.I like them.Runs cooler,more power and Ill never do that job again.