I did a search but still have some questions.. Im thinking about getting a pair of GT 40 P heads. As far as bolting these to a carburated 70's 351 W block, what would need to be changed / modified? Also would running Hi-Po valve springs be a problem with a stock/mild cam?
the "P" heads use a 7/16" head bolt where the 351w uses 1/2" head bolt your better off looking for a set of gt40's from a first gen lightning which have the 351w
The P heads were used on the Explorers in the late 90s. They have a different angle to the spark plug and tend to have header to spark plug clearance problems when used in non stock applications. They also use a plug with a longer reach. They are pretty good heads. It is not uncommon to drill the head bolt holes out to accommodate the bigger bolts. Any machine shop can do it, but most people do it themselves.
Im not too worried about the spark plug and header issues.. So besides the head bolts whats else do I have to look out for? What about push rods? Intake?
Pushrods, intake, etc. are all the same. They are really good heads for a production head. Even for fuel injected applications the GT 40 "p" intake is essentially a Cobra without the EGR plate built in. I have had a lot of Mustangs and built quite a few for others and using these heads are a real bang for the buck.
I have stock heads on my 351W. Is this a worthy upgrade if I come across either a GT-40 or GT-40P heads in the junkyard?
If you have a 69-70 Windsor then NO, It would actually be a downgrade, the 69-70 Windsor heads actually have bigger valves if im not mistaking, flow just as well and have smaller CC's wich means higher compression... If you have a later Windsor (like me) then YES!
p heads have a 1.84 int valve and a 1.5 exh valve and have 62cc-64cc seen them both the spring retainers are different from the int and exh valves. i had a trick flow valve spring kit installed on a set and my machine shop guy said they went together good.
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