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I have read alot about this topic over the years and I have done this mod in the past but, I personally didn't see any advantage to using the 351W heads on my 302. In my opinion that seemed to be a step backwards.I didn't really notice any major power gains after doing the swap. It wasn't until I started doing some research that I found that most all of the early 351W heads have a larger combustion chambers which will effectively lower the compression ratio.'69-72 351W heads have a 60.4 cc combustion chamber as compared to a '68-70 302 2V which has a 58cc chamber or a '68 302 4V which has a 53.4 cc chamber. See the difference? So if all I was going to gain was the larger valves,then why not just put the larger valves into a set of 302s? I'd get the compression I needed and the flow capabilities I desired. I do this sort of thing for a living and I have compared the early 351s with the early 302s and in most ways the two are identical, with the exception of the valve sizes,cobustion chamber volume,and head bolt diameter. Runner volumes appear to be the same as well as port configuration. So after I did my research I went ahead and built up my 4V 302's.I did a mild bowl blend and port match, just like I had done on the 351 heads, and used the 351W valves,springs and hardware. With the extra compression, I noticed a major power increase right away,which is what I was after in the first place. This is only my theory and I'm sure someone will tell me that they have had great success with the swap, but in my own experience I didn't acheive the power gains that I was expecting and it left me a little disappointed.
Every day is a holiday if you love your job.
Current projects: 65 Fastback, 68 Coupe Oval Track Racer, 64 Galaxie 500 XL, 54 F-100 Pickup
Every day is a holiday if you love your job.
Current projects: 65 Fastback, 68 Coupe Oval Track Racer, 64 Galaxie 500 XL, 54 F-100 Pickup