Re: Proper gas for 374 engine
Posted by Craig Hendrickson On 2011/2/24 12:35:06
Jack Vines wrote: Quote:
I pounded in the stock exhaust valve seats on my 55 Pat driving from Las Vegas to Reno (840 miles round trip) in August 1999, just keeping up with traffic. I had a set of 56 heads rebuilt with hardened exhaust seats and haven't had a problem since. Here's the valve recession chart I've posted before. The gray bar at about 19 lb/hp is my 55 Pat, so 85mph sustained (trip above) will definitely do it (click for larger view).
Craig
Exhaust valve recession is caused by long, high speed hard pulls where the heat build to extremely high levels. Ask yourself how often your Packard V8 pulls a trailer across the Grapevine.
I pounded in the stock exhaust valve seats on my 55 Pat driving from Las Vegas to Reno (840 miles round trip) in August 1999, just keeping up with traffic. I had a set of 56 heads rebuilt with hardened exhaust seats and haven't had a problem since. Here's the valve recession chart I've posted before. The gray bar at about 19 lb/hp is my 55 Pat, so 85mph sustained (trip above) will definitely do it (click for larger view).
Craig
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