Older stainless Marine exhaust
11-10-2005, 03:51 PM
#1
Charter Member
Older stainless Marine exhaust
I bought 2 sets of the older SM exhaust with alum. risors, to replace my stock cast iron exhaust. Would have prefered Gils, but the price was right. 
These manifolds are basically the same design as the stock manifilds: open manifolds, no dividers.
I'm expecting zero performance gains, which is fine. Reasoning for the change is to eliminate 160# , and eliminate the chance of the leaky risor to manifold gasket.
Is there any reason not to use these? Motors will never be modified. 502MPI's
These manifolds are basically the same design as the stock manifilds: open manifolds, no dividers.I'm expecting zero performance gains, which is fine. Reasoning for the change is to eliminate 160# , and eliminate the chance of the leaky risor to manifold gasket.
Is there any reason not to use these? Motors will never be modified. 502MPI's
Last edited by US1 Fountain; 12-02-2011 at 11:15 AM.
11-14-2005, 08:45 AM
#4
Registered
Re: Older stainless Marine exhaust
Those aluminum risers CANNOT be used on a high performance engine. They are cylindrical (no nozzle) and will hoover water at idle. Great and long lasting for STOCK engines with non-lumpy cams.
11-15-2005, 07:13 AM
#6
Registered
Re: Older stainless Marine exhaust
Chit! I didn't realize that these two messages were from the same guy. No! Don't use these risers on that engine. I recommend long risers for the 502 MPI. Call me at 305-681-7892 for more info.
11-15-2005, 04:36 PM
#7
Re: Older stainless Marine exhaust
Brownie, tried to call, but no answer.
Guess I'm not following here. They would seem like a direct replacement for what I have, stock cast iron merc exhaust with silent choice. I understand that longer risors are preferred, but everyone has short risors for use of silent choice on BBC's. I must not be seeing the whole picture.
Will try to get ahold of you Wed morning to talk in detail.
Thanks,
Jerry
Guess I'm not following here. They would seem like a direct replacement for what I have, stock cast iron merc exhaust with silent choice. I understand that longer risors are preferred, but everyone has short risors for use of silent choice on BBC's. I must not be seeing the whole picture.
Will try to get ahold of you Wed morning to talk in detail.
Thanks,
Jerry
11-16-2005, 07:04 AM
#8
Registered
Re: Older stainless Marine exhaust
The difference is backpressure. Ours (or anybody elses besides Merc) are free flowing. Freeflowing = larger area. Same amount of gas, larger area = lower gas velocity. Low gas velocity can't push the cooling water as far. Your engine is a high performance engine. If you want a performance manifold on it, you will be forced to use either a longer or a nozzled riser. My cellphone: 305-332-7611.
