www.iFourWinns.com :: View topic - 1989 5.8l manifolds

Graham R wrote:

Regardless of where they are made or by whom, I thought they were all made of cast iron. Why the OEM and aftermarket people don't cast them from aluminium I don't understand (why; lighter, lower melting point so cheaper energy and tooling, despite the higher price of aluminium, better thermal conductivity) Maybe they'd last too long !

Lower melting point is exactly why they cannot be made from Aluminum. Aluminum melts at around 1300 deg-F. Aluminum also looses it's temper (it's hardness condition) at temperatures as low as around 700. Exhaust gas temperature coming out of the engine can exceed 1500 deg-F. Of course the manifolds are water cooled, but they would melt and/or erode right at the engine exhaust exit.

Author:	Jesse [ Mon May 21, 2012 11:53 am ]
Post subject:	1989 5.8l manifolds
Has anyone done the conversion on the exhaust on one of these? What did you use and where from?

Author:	rpengr [ Wed Aug 15, 2012 10:03 pm ]
Post subject:	Re: 1989 5.8l manifolds
I would contact: http://www.marinepartsexpress.com or http://www.ebasicpower.com

Author:	Sanmiam [ Thu Aug 16, 2012 3:52 pm ]
Post subject:	Re: 1989 5.8l manifolds
I second ebasicpower. Ordered risers/manifolds at the beginning of the season and they shipped out quick. There are only three companies I know of other than OEM that make replacements (OSCO, BAR, GLM). I am 99% sure OSCO and BAR are made in the US and GLM is overseas junk (inferior materials and cast). Give them a call, they seemed to know what they were talking about when I ordered from them.

Author:	Graham R [ Thu Aug 16, 2012 4:30 pm ]
Post subject:	Re: 1989 5.8l manifolds
Regardless of where they are made or by whom, I thought they were all made of cast iron. Why the OEM and aftermarket people don't cast them from aluminium I don't understand (why; lighter, lower melting point so cheaper energy and tooling, despite the higher price of aluminium, better thermal conductivity) Maybe they'd last too long !

Author:	Sanmiam [ Thu Aug 16, 2012 6:37 pm ]
Post subject:	Re: 1989 5.8l manifolds
Graham R wrote: Maybe they'd last too long ! BINGO

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Author:	rpengr [ Fri Aug 17, 2012 6:15 am ]
Post subject:	Re: 1989 5.8l manifolds
Graham R wrote: Regardless of where they are made or by whom, I thought they were all made of cast iron. Why the OEM and aftermarket people don't cast them from aluminium I don't understand (why; lighter, lower melting point so cheaper energy and tooling, despite the higher price of aluminium, better thermal conductivity) Maybe they'd last too long ! They are all cast iron, but their still can be quality differences in the iron composition, as well as the casting process (temperature control, pour procedure, controlled cooling rate, etc), so when comparing these aftermarket companies, it is best to read forums like this one to see what their track record is. Lower melting point is exactly why they cannot be made from Aluminum. Aluminum melts at around 1300 deg-F. Aluminum also looses it's temper (it's hardness condition) at temperatures as low as around 700. Exhaust gas temperature coming out of the engine can exceed 1500 deg-F. Of course the manifolds are water cooled, but they would melt and/or erode right at the engine exhaust exit.

Author:	Graham R [ Fri Aug 17, 2012 7:28 am ]
Post subject:	Re: 1989 5.8l manifolds
rpengr wrote: Graham R wrote: Regardless of where they are made or by whom, I thought they were all made of cast iron. Why the OEM and aftermarket people don't cast them from aluminium I don't understand (why; lighter, lower melting point so cheaper energy and tooling, despite the higher price of aluminium, better thermal conductivity) Maybe they'd last too long ! Lower melting point is exactly why they cannot be made from Aluminum. Aluminum melts at around 1300 deg-F. Aluminum also looses it's temper (it's hardness condition) at temperatures as low as around 700. Exhaust gas temperature coming out of the engine can exceed 1500 deg-F. Of course the manifolds are water cooled, but they would melt and/or erode right at the engine exhaust exit. I believe a company called PPT makes aluminium ones, but only for Mercruiser applications. Ceramic coated to protect against corrosion and perhaps localized heat; but haven't aluminium alloy cylinder heads been used for quite a lomg time now, their exhaust galleries seem to survive quite happily. Aluminium is much better comnductor of heat than cast iron, so the manifolds should run cooler I expect for any given water throughput. edit; looking into it, there are a number of suppliers of aluminium marine exhaust manifolds and risers (in the US), some even have anodes for additional corrosion priotection All for Mercruiser as far as I can tell; does anyone know how far apart the outlets of a Mercruiser and VP riser are? The V8 heads are the same, so the Mercruiser manifolds should bolt straight onto the VP heads.

Author:	rpengr [ Fri Aug 17, 2012 1:50 pm ]
Post subject:	Re: 1989 5.8l manifolds
I stand corrected.

Author:	LouC [ Fri Aug 17, 2012 2:14 pm ]
Post subject:	Re: 1989 5.8l manifolds
I don't know why they don't either, in light of the fact that the exhaust section of all outboards is aluminum, and I noticed in the exhaust section of my Cobra there is almost no corrosion to speak of. So I don't get why, other than the thermal expansion difference between the cast iron head and the manifold (poss gasket issues) it could not be done.

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