[DeTomaso] NPC indeed, marine engine problem

[Julian Kift]

Mikael,
Marine engines with blowers are notorious for overheating exhaust valves as a marine engine is in 'boost' all the time. If you have a water cooled exhaust then the problem is worse as the slightest bit of water vapor and the valves are subjected to thermal shock. Boost should also be less than you'd use in an automotive application and when installing blowers you should at the same time change exhaust valves to hardened (Inconel) ones. They are going to be $800 an engine, but it's $800 now or $8,000 later.
I suspect your friend already has exhaust valve damage and valve heads that are now possibly tulip shape.
I dropped an exhaust valve last year that went through the piston and cracked the block. I'm just finishing re-installing the engine now and installed the Inconel valves and I'm still normally aspirated.
Julian

> From: mikael_hass at mail.tele.dk
> To: detomaso at poca.com
> Date: Sun, 16 Jun 2013 10:46:38 +0200
> Subject: [DeTomaso] NPC indeed, marine engine problem
> 
> Being around V8s for decades I thought I had seen it all, but I need help on
> this on. One of my boating friends put blower kits on his twin 454+ Chevy
> Marine powered boat. 78 mph at 5400, all fine, that was last year. This year he
> can only get it to 72mph at 4900, and the valve covers get very hot. Reason for
> that is rockers (still stamped steel) get so hot they turn blue and had to
> be refinished. Many clever people have tried to help him with suggestions,
> the rockers overheating has happened 4 times.
> 
> My immediate guess would be oil starvation or water in oil. But I wouldn't
> know why this happened and why only this year, and why only one engine. The
> oil pressure on his gauges is fine, on both engines.
> 
> I'm just throwing this problem to this forum if anybody has experienced
> something similar.
> Thanks
> 
> Mikael
> 
> 
> _______________________________________________
> 
> Detomaso Forum Managed by POCA
> 
> DeTomaso mailing list
> DeTomaso at poca.com
> http://poca.com/mailman/listinfo/detomaso