Join Date: Mar 2001
Location: Peoples Republic of Vermont
With any used parts choice you're taking a risk. If I was going to look for a set of "P" heads I'd probably try to score the complete "P" engine, knowing that the heads hadn't been pulled, checked, found to be crap and then eBayed. Other choices would be heads accompanied by a machine shop's bill of goods showing work done to some degree. As a minimum I'd like to see a set of "loose" heads that had been magnafluxed and, perhaps, had the valve guide clearance checked.
To be safe, build into your desired acquisition cost the cost to replace the guides with new press-in ones and to replace the valve springs if you plan on any cam more "radical" than an "RV" cam and a 5,000 rpm redline.
If you think you're up to a little "DIY" porting and port matching then scrap the GT40P's and put the money into your existing heads. Yeah, you'll need to consider milling them to reduce the combustion chamber size and installing some larger valves but you already own them.
Of course, the big question is "what are you looking for" as far as performance is considered? Yes, heads, particularly the exhaust-side are the big "bottleneck" on the SBF, but how does the rest of your motor factor? What pistons (style/compression height) are currently installed? Are you looking for more power production at higher rpms or more low-end "grunt"?
What, me worry?
- Alfred E. Neuman