"New" GT-40P heads purchased, what now?

BTW, with your .471 lift cam, a set of 1.7:1 rocker arms will put the valve lift right at .500 which is max for the P head.

 

What happens over .0500? Is that the end of travel for the valves, or does the airflow become restricted after that?

 

Yes and yes.

 

Hmmm ... by the time you spend all the money on the heads, parts, work and special headers wouldn't it be easier to buy a nice set of E7's already done and use Hooker 6901's?

 

Or buy a set of Roush heads or edelbrocks

 

So far, I have 3 hours and $185 on these heads. AND, technically, I could install them right now and drive off.

I will be waiting for new gaskets so I can spend another 1-2 hours gasket-matching, and $150 for headers. Also another 2 hours of grinding the bumps off the other head, and done!

Total for heads, $185 plus $40 gaskets, and 7-8 hours head work (total under $250 for the pair). The rest is just the installation and headers.

I figure that $250 for a clean set of good flowing heads is a good price. Yeah, these are no edelbrocks or roush, but I don't really want to mess with aluminum heads (water port corrosion, higher compression, stripped bolt holes, etc.).

These heads were useable with good flow when purchased. I just wanted to try my hand at minor porting and polishing work, just so I can say "I mildly ported and polished them!"

 

Not a bad price.
I meant Roush 200 heads, they are cast heads. My buddy has a set and I like them, and will prob buy them from him if he keeps them when he sells his car.
But for what you got, very good price

 

Here are the oval port gaskets (pn MRG-5928) from Summit for $20.00 if you are still looking for them

 

Hooker 6901 are "Same as Production" port, which is square, isn't it? What model would be oval ported?

Or, do I just ignore that my oval port is squirting out into a larger square hole and suffer the minor power loss (which will still be an increase over manifold!)?

 

I have GT40 heads. I looked for GT40P's but could not find any. Boy I'm glad I didn't. Central Coast Mustangs & I think Mac Performance have headers for GT40P heads, they are for classic mustangs. I think they will fit our cars. You do not want to get over .500 lift either unless you change the internals. They guys on here really know what there talking about. It's a pain.

 

Will cutting .025" off the base of the heads increase my lift? I would like to increas the compression a bit.

Seems that putting the rockers closer to the lifters (by making the head thinner) would cause more lift.

Do I have this right?

 

No, because the camshaft lift and the rocker fulcrum ratio determine the valve final lift minus the hydraulic lifter take up.

You seem to be missing some info on the relationships involved with this head change.

Milling the heads moves them closer togather on the block.

This begins to change the holdown bolt location centers on the intake manifold such that the holes have to be enlarged.

The valley gasket surfaces might have to be milled or they will cause too much distance between the port mating surfaces for gasket seal..

The valve stem tip to rocker operating point could change because the push rods now become longer than needed unless the rockers are adjustable out/upward.

All these relationships must be "hearded" togather at the same time or things just don't work correctly.

You would have been much better off with a set of 69/70 351w 4 barrel heads with larger ports and not have to do any more work to get better performance than the heads your trying to work with. Just a bolt on deal.

Sure you want to keep investing the time and aggravation setting up these late heads on an early stock motor application?
They are fine on a late 5L motor and an improvement but not on an early block.
Windsor Jr. heads would be even better and get performace for the money invested.
Going in another direction; when you improve airflow, more fuel is needed to support the power increase and more cam duration which raises rpm power points and on and on.

 

true 15 years ago

"You would have been much better off with a set of 69/70 351w 4 barrel heads with larger ports and not have to do any more work to get better performance than the heads your trying to work with. Just a bolt on deal."

Round and round we go, eh? This is covered in various other threads with links to flow charts on all the stock heads. The GT's flat out outflow the old school DOOE heads, often even after the DOOE's are ported. And you get a more efficient chamber to boot. Header fit is do-able, and they are way cheaper than aftermarkets.

 

Actually the P heads pretty significantly outflow 351W heads even before porting.

 

I have mine set up with 266 extreme HR comp cam at .555 lift int. & .565 lift exh. true I did use the recommended springs but these heads will flow and the valves are long enough.