1974-351 windsor intake

I don't know if this makes a differnce but I'm running stock mannifolds with straight pipes.

81nautique wrote: I was expecting more out it than that even with the gt40p heads. I would still give Scott a call and see what he thinks of it.   The lift numbers seem to be decent but the timing events are different than ours.

Wow, thats quite a bit different than the one you ran for me (stock exhaust). With the P heads and my Cam Research stick (.490/.490, 218/222), my peak power was 311 @ 5000 and max torque was 396 @ 3000rpm. What a difference a cam can make!

Much better than than the 280ish hp with the Comp, and a huge difference in the torque numbers as well (or was the scale on the right different?).

Tim, I was going to say the same about the cam, it'snot a bad piece but no matter what I do in Desktop dyno it's not performing with those old heads. It's making about the same power but has moved it in a higher rpm range.

Stock 351


Clarks 351 with the comp cam and performer intake, stock heads



Clarks 351 with gt40p heads, comp cams and performer intake


It has certainly broadened the torque curve though. I was expecting more out it than that even with the gt40p heads. I would still give Scott a call and see what he thinks of it.   The lift numbers seem to be decent but the timing events are different than ours.

Cslaten33 wrote: Gary what does all that mean?

Bottom line it means I spent some money and got nothing--- yet. So I have to spend some more

Gary what does all that mean?

What is a set of brand new 351W heads worth?? Never ran. Straight from the factory? If someone needs them or wants them. I will sell them so I can get the GT40P heads.

Thanks Clark Slaten

PAPA wrote: Clark, believe it or not, guys were putting in cams and intakes on this motor for over twenty five years before the GT40P heads even came out and I am sure a lot of them got more than a 15-20 horsepower pick up.

The heads in question arent the P heads- its the terrible flowing 302 based E7 ones that came on the stock 351w marine engines! Better heads have existed for the 351w since the very early days- the 1969+ D0OE heads come to mind. You dont have to take our word for it though- Alan will run the desktop dyno once he is given the cam specs.

Gary S wrote: Some time I have to have you run mine Alan, after all that work I did on mine last spring I didn't even pick up 1 mph.Low to midrange seems to have picked up. I need to get ahold of Reid or Matt to see about a prop next. What info do you need to run it?

Didnt you try a 12x13 OJ, Gary? That prop should have pushed the boat well. I like the Acme 1210 better on my Skier, but both are good wheels.

The one detractor to installing the P heads on the earlier 289/302 is the drop in compression you'll see. Flow should be much better. I think if you tell Alan which intake youre using and get him your cam specs, he can run the software.

Cslaten33 wrote: The engine going back into the boat is a LH rotation the sa e that came out. The cam is to as well

So the engine that came out wasn't the original engine ether.

I'm waiting to see what the cam specs are and I was going to run a desktop dyno for him with the stock heads and the a comparison with the gt40p's.

I'm with Tim on this because you get 2 things with the Gt40p's, one being better breathing and 2 being almost a full point increase in compression ratio. The heads alone are worth approx 40hp. The cams not going to make a huge difference if the restrictions are there with stock heads, you could do a little home porting on the stock heads but it's not going to get you much.

Without changing heads I would not spend the money on an aftermarket intake. I took some heat for stating that on another thread but I still feel it's a waste of money even if this is a hobby.   

When it comes down to decision time on the intake I prefer the RPM over the standard performer BUT I like Summits clone of the RPM because you don't need the crappy adapter plate for the square bore Holley carb eliminating a possible vacuum leak and a second gasket. I know Tim runs a Stealth and I don't think you need the adapter for that intake either. I stay away from Edelbrocks simply for that reason.

Tim, as Clark said, he has the new cam, so why not put on the RPM? He can always do the heads or other more aggressive upgrades later and then you already have a good intake. As you said, not much to be gained if putting it on by itself with stock everything else. As for the K&N; my boat had a huge 5+ inch flame arrestor probably put on by a previous owner for some reason and I needed the clearance on my application. You have to admit it sure looks better than a stock one.

Clark, I put a Edelbrock Performer RPM on my 1977 with a K & N #59-3264 flame arrestor to make sure the engine box cover would still fit.

that was my first thought Pete, if i were a betting man....

The more I research the more I want the Weiand Stealth. What kind of gain will the have over the stock intake?

Critter I have already paid for a better cam and lifters. They are sitting in the shop ready to go in. I will tell you what the cam is tomarrow. I can not remember off the top of my head and I really dont want to go out to the shop and look right now. Although it is warming up here in Tulsa, OK.