GT40 / GT40P

TRBenj wrote:    For a 400+ hp build, I'd think differently.

Yea like I'm not wasting a 400 + engine on a 16 foot Mustang

I am pretty sure Tim knows what boxes fit what.

We should measure the width and length of a wood vs a 'glass box. I only have about 1/4 to 1/2 side clearance on mine til the manifolds hit. Not sure if PCM's are narrower,I suspect they are,but in my case I sure would not give up the HM's just so I could have a 351. Maybe those squared off newer style ones,like the one John has would clear better,I don't know.

I know the 351W is slightly larger, Are the old dog houses that tight?

A little quote from the internet,

"Here’s even more cool stuff about the 351W: It is only 1” wider (approximately), and 1” taller than a 289/302 and almost all of the outer bolt-on’s are the same, from the motor mounts, to the valve covers, to the water pump, to the bell housing bolt pattern, to the exhaust bolt pattern, to the spark plugs, to the heads, rockers, timing cover and so on….. all the same as ANY 289/302.

Put a 289 / 302 side by side with a 351W and take a few steps back. It’s VERY hard to tell the difference between the two. The best part is; it’s a completely bolt-in swap for any early Mustang from 65 on-up, and any early Falcon, Galaxie, Fairlane, Cobra kit car, 5.0 Mustang, or pretty much anything that had a 289/302 sitting in it. Usually all it takes to swap out a 351W with a 289/302 is nothing more than a set of retro fit headers and a low profile air cleaner and you’re good to go. Hedman makes a great set of retro fit headers for early Mustangs, Falcons, etc..

So, without even spending any extra money on expensive stroker parts, a stock 351W has a MUCH stronger block and lower-end, a better deck height, and a better rod angle without even doing a thing to it, plus it is already larger in displacement than both the 331and 347 strokers! Remember that saying? “There’s no replacement for displacement”? Right from the get-go it’s bigger and it’ll make more power, plus it’ll handle that additional power MUCH better (and much more of it) than ANY 289/302 based stroker ever will!

Now here’s an even better part. One of the best all around strokers you can build is a 408 cubic incher based on a 351W block. So consider this, you can either spend all of your money building a weak little 331 or 347 stroker, or you can build a nice 351W and turn it into a monster 408 cubic incher for about the same amount of money, which will absolutely eat-up and spit out the other two on ANY given day!"

The 351W uses a much longer connecting rod, this takes a lot of stress out of the engine with less piston side wall loading and helps with durability.

Get a bigger doghouse!

If you are building a new engine why not find a 351W and build it rather than stroke a 302. I think you could make more power and do it for less money. Or stroke the 351W and make even more!!! Power always brings smiles in boats.

I want to say Reid is running one on his 347 '73 HM. Similar to a performer rpm iirc, the extra $ might be worth tj for the look!

True, mine are on studs and those '66 valve covers were very small.

My rollers are 1.6. They will required taller valve covers, which are very close to the exhaust manifolds.

gun-driver wrote: Those are the heads I have on the '85s RR motor. Do0E mildley ported with bigger valves.

Those are 79 nautiques old heads.

Those are the heads I have on the '85s RR motor. Do0E mildley ported with bigger valves.

John,
If you decide to go with stud mount roller rockers I have a set of 1.6 Scorpions I would be willing to sell.
I only put a couple of test hours on them before I changed them for a set of 1.7s

Yes, it hit 56.4 with a little stainless 2-blade, about 1mph better than the Acme 1210 could muster. It has an edelbrock performer rpm intake on it, if I remember correctly.

It's very well behaved... As are all modified correct crafts I've encountered thus far. Even Joe's 83 and our bfn start reliably and idle nicely down at normal rpm's (650ish). The bfn sounds lumpy with the 4" exhaust and big cam, but it is perfectly functional for putting around and pulling skiers, which is it's primary purpose. It just goes faster when the throttle is pushed further. You'd really have to build an extreme motor, or at least be mighty careless in component selection to diminish overall usability of these boats. They're very light and with prop slip essentially have the equivalent of high stall torque converters, so there's no need to be concerned with a potential drop off in "off idle" power, unlike a heavy muscle car. I've never seen an engine built with midrange to high end power in mind that also didn't improve holeshot (usually significantly). I think people are generally too conservative, as remarks like "build for low end power" or "water tractor" are pretty common- and only serve to limit your options (with no benefit).

John, you are not "limited" to .500 lift with p-heads... They just don't flow significantly more at higher lift in stock form (Google gt40p head flow data and you'll see what I mean). They're a very good stock replacement head but they do have their limitations. They are probably not a good choice for BIG power (>1hp/ci) given the rpm range we tend to run (5k or so).

That said, they're a great choice for a mild build. Even going with the "biggest" RH cam currently available (cam researches popular .460 grind) and the biggest rocker ratio (1.72) and you won't quite reach .500 at the valve. I'd say you would be happy with 1.6's- my uncle built a p-headed 302 for his ski Tique with that cam (stock 1.6 rockers) and the dyno said the combo was good for 290hp or so. It pushes the boat 54-55, it's quite the little rocket.

I put a Clevite came in my Mustang. It changed the firing order to that of a 351. Roller rockers made a big difference in the mid-range power.