Gt40/gt40p Heads On A 351w Questions

[sneaky98gt]

Hey all. I know this is a "5.0" section, and I rarely post over here, but I'm doing some inquiring for a cousin of mine. If this is in the wrong section, please feel free to move it.

He has a '89 F150 with a '91 351W (carbed) in it right now. He's looking to put a set of heads and a cam in it for as cheaply as possible, so expensive cams or aluminum heads are out of the question right now. He's found a set of GT40P heads and GT40 intake for pretty cheap.

A few questions:

1. Are the GT40P heads worth anything significant over the stock heads on a 351W?

2. Would you bother porting them?

3. What's a decent sized cam for those heads on a 351? He's got his eyes on a Lunati cam, 227/233 duration at .050, .522/.538 lift, 110 LSA. The advertised RPM range is 1800-6200. It sounds a little big to me, but I know nothing about non-modular motors. I've heard that the GT40Ps are gonna be done by 4500-5000, so I'm thinking that extra 1200 rpm from the cam is being wasted and could be better suited in the lower rpm range.

4. Anything else technical related he needs to know about it? Certain valves to use/not use? Certain lifters? Etc. From what I've read, the only changes required is to drill out the head bolt holes to 1/2 and get a set of headers that will fit.

5. What's a decent flywheel horsepower/torque number to be expected from this combo (GT40P heads, GT40 intake, decent cam, long tubes)? Is 300/350 out of the question?

Thanks Stangnet!

 

[foxna6]

Yeap p heads aren't much good over 5000 rpms the cam is a little big there gonna need valve springs and the bolt holes are gonna have to be machined for the 1/2 head bolts on the 351 porting will help any head flow better so there's always room to improve and I would think they will be an inprovment over the stock heads as always these are just my thoughts on it though

 

[srtthis]

Copy a lightning motor

Gt40 heads gt40 intake...
Get a stock 302HO cam and a set of 1.72 roller rockers or go cheap and get a set of junk yard 460 rockers

 

[NIKwoaC]

A 351 with small heads and intake is going to want a lot of cam to get any power out of it, put a small cam in it and it'll just be a turd. I wouldn't be afraid to run a cam with a little duration to it, just make sure your valve train is built well and your valves clear the pistons. I'm assuming it is a flat tappet engine. I'd like to see him convert to roller but probably out of the budget...?

If you or your cuz can port, I say port away. The more flow you get through those parts, the better.

 

[srtthis]

Nik I think it's a roller from the factory...

Also to the OP... Did he actually find a gt40 lightning lower? Or is it a 302 gt40 lower?

 

[NIKwoaC]

Nik I think it's a roller from the factory...

Also to the OP... Did he actually find a gt40 lightning lower? Or is it a 302 gt40 lower?

I thought they weren't roller until after 92?

 

[srtthis]

i thought it was 90... but you may be right.

 

[rd]

As noted, this is looking like hes building a 351 Lightning truck motor, which is a good way to go. I used Lightning heads on my 302, (GT40 not P) with stock rockers on a flat tappet engine. Runs well. Note the head bolt hole issue, some GT40 iron heads had 1/2 holes, if not they will need to be enlarged.

 

[68stang351]

94 was the first year for a roller 351w.

 

[sneaky98gt]

A 351 with small heads and intake is going to want a lot of cam to get any power out of it, put a small cam in it and it'll just be a turd. I wouldn't be afraid to run a cam with a little duration to it, just make sure your valve train is built well and your valves clear the pistons. I'm assuming it is a flat tappet engine. I'd like to see him convert to roller but probably out of the budget...?

If you or your cuz can port, I say port away. The more flow you get through those parts, the better.

Yea, that's the cam argument that he was using to justify a cam that big. And I thought that that could be true, but I just don't know a whole lot about these older motors.

I know he's putting new lifters in, and pretty sure springs as well. I'll ask for sure about the springs and rockers.

And yes, it is a flat tappet. He'd like to go to roller, too, but just isn't gonna spend that money on this motor.

Nik I think it's a roller from the factory...

Also to the OP... Did he actually find a gt40 lightning lower? Or is it a 302 gt40 lower?

I'm not sure. What's the difference? The ad says "GT40P heads and GT40 Explorer intake". I emailed him asking for some pics, but haven't heard back yet.

 

[NIKwoaC]

Yea, that's the cam argument that he was using to justify a cam that big. And I thought that that could be true, but I just don't know a whole lot about these older motors.

I know he's putting new lifters in, and pretty sure springs as well. I'll ask for sure about the springs and rockers.

And yes, it is a flat tappet. He'd like to go to roller, too, but just isn't gonna spend that money on this motor.



I'm not sure. What's the difference? The ad says "GT40P heads and GT40 Explorer intake". I emailed him asking for some pics, but haven't heard back yet.

It's definitely a 302 lower intake then, which will not fit on a 351. The 351 uses a wider lower intake, though the upper intake is interchangeable.

 

[NIKwoaC]

94 was the first year for a roller 351w.

This is actually what I was thinking, but I couldn't remember for sure. I knew it was later.

 

[srtthis]

It's definitely a 302 lower intake then, which will not fit on a 351. The 351 uses a wider lower intake, though the upper intake is interchangeable.

what he said... if you actually come across a 351 GT40 lower expect to pay between 300-400 just for the lower

 

[NIKwoaC]

what he said... if you actually come across a 351 GT40 lower expect to pay between 300-400 just for the lower

Yep. That's why I'd go aftermarket. Or maybe a ported stocker...?

 

[srtthis]

Yep. That's why I'd go aftermarket. Or maybe a ported stocker...?

ported stock truck lower and system max upper

 

[NIKwoaC]

ported stock truck lower and system max upper

I believe there is some extensive port work in matching up the runners, but that would be cool!

 

[sneaky98gt]

Yep. That's why I'd go aftermarket. Or maybe a ported stocker...?

So could he run the stock 351 lower with the GT40 upper? Or is that not very productive?

 

[NIKwoaC]

Stock lower and 40 upper will not work together.

 

[f8tlfiveo]

So could he run the stock 351 lower with the GT40 upper? Or is that not very productive?

yes it will work

 

[68stang351]

yes it will work

No, it won't.

A stock 351w truck lower has oval shaped ports, inline with each other, much like a 302 Mustang lower. The GT40/Cobra/Explorer upper and lowers have round staggered ports.


It will not work.