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Discussion Starter #1 (Edited)
It's winter and I'm bored :D so I'm considering an engine buildup with some parts I've accumulated.

.030 stock block with new stock crank, stage 1 Summit rods, Keith Black hyper pistons. I have a set of stock GT-40P heads off a low mileage crate motor, the FRPP 1 /8" P-headers, and an untouched Cobra intake. This engine will have the usual bolt ons (24 lb injectors, 65 mm TB, 75 mm MAF, cold air kit, pullies, Crane Hi-6 ignition, etc...). The exhaust is 2.5 MAC 2 cat h-pipe and MAC 2.5 after-cat.

I've read a great deal about P-head porting and camming these head on the forum but I can't seem to pick a direction that will meet my needs so here's my questions:

The engine will go in my 93 LX which needs to be a reliable daily driver (80 mile highway roundtrip), so drivability and fuel economy are important. The car also needs to pass emissions. The goal is to approach 275-300 rwhp N/A meeting the above criteria. The car currently has 3.73's but I'm considering a swap to 3.55's, unless the 3.73's are better for the overall combination.

Should the heads be shaved to bump compression as the car will be N/A? If so, by how much?

How important is basic home porting (gasket matching, minor polishing, etc.) to these heads?

Are stock valve sizes OK?

How important is gasket matching / porting to the Cobra lower?

OTS Cam suggestions? Also, rocker choices and ratios? I'm not ready to call Ed just yet... :D Primarily because I haven't learned enough cam theory yet to speak the same language.

Should the heads be machined for stud mount rockers or will pedestal mount be acceptable?

Any other thoughts or suggestions would be appriciated. If nothing else, it'll be an interesting discussion...
 

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I'll throw out my opinion on a couple of your questions.

The P head intake ports are real hard to improve on for a home porter. But the exhaust are easy to increase flow if you feel the need. It depends on what you want your I/E ratio to be. I feel 70% to no more than 80% max (75% nominal in my opinion) is suitable for the P unless a power adder is in the plan. For all this I think the stock valves are fine.
 

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The chambers are a bit tighter than the E7TE, E7TE=65cc, GT-40P=60cc, so you can expect up to a half point increase in CR. I wouldn't change the valve size, the Intake is plenty 1.84, and the exaust ports have been revised and improved over the regular GT-40 for overall effency so the even with the exaust valve being small (1.46) they still out flow the GT-40's out of the box. Your looking at a 40+CFM increase they are capable of 300+ HP with supporting bolt ons. These are a great cylinder head for the price they offer a substantial performance increase over E7TE's they also get great mileage, and drivability. Attached is a link to anything you ever wanted to know about them. Good luck w/ your build up





http://www.geocities.com/MotorCity/Pit/5755/gt40p.html
 

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Wrong.. the E7TEs have 62cc Chambers.. and the Gt-40Ps have 64 or 65cc chambers..
 

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My GT-40p

My chambers sizes were

61 - 60 - 61 - 61
59 - 60 - 61 - 61

This was after some cleanup around the valves and smoothing. I believe nominally they were 60 fromt he factory NOT 64-65.
 

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My "P" heads were cc'd at 61cc.

"P" heads run about 59-61cc chambers.

E7 heads run in the 61-64cc range.
 

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Hmm That Article I read about the "P" heads must have been wrong then? Sorry for the bad Info.. I know the E7s are 62 to 63cc... : )
 

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Discussion Starter #8
Is gasket matching / cartridge rolling worth the effort, or should I just bolt 'em on?

How about cam selection? Anyone?
 

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No Numbers yet

But I will be taking my first EVER trip to a drag strip in March. It should be fun as the motor feels really strong and I have no experience :)
 

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Re: No Numbers yet

Bobasaurus said:
But I will be taking my first EVER trip to a drag strip in March. It should be fun as the motor feels really strong and I have no experience :)
LOL, my first run at the track was humiliating. I spun the tires all the way down the track and got like a 17 something :barf: I still suck - I should be low 13's. Now I'm bolting on a blower :rolleyes:
 

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I wanted to mill my heads, but I wasnt sure if I would have to mill the intake as well.
 

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st5150....i ran 115.1 mph with ported p heads,f303 cam and poerted performer rpm intake.

best 60ft from combo 1.58

best et from combo 11.94

fun setup.
 

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stang7089:

I made 267 rwhp & 301 rwtq with un-touched P heads & Cobra intake on the stock cam & a few bolt-ons (see sig). You're going to need some light clean-up on the heads & a mild cam to the get 300 rwhp.

I wouldn't mill 'em for street use on pump gas. As other have said, they already raise your CR ratio. Keep in mind that the extra 4 cubes from your 306 will also help raise the CR a little bit.

I can't help much with a cam. I'm still undecided on that too. Pedestal mount rockers will be fine if you keep the revs at a resonable level. Unported Ps probably wouldn't make power much past 6000 rpm anyway.

The Ps are an efficent head so MPG shouldn't be a concern. My heavy pig gets 19 mpg with mixed driving and a lead foot. I pull down 25+ MPG on the highway, even with the 3.73s. A mild cam would probably lower those numbers a little.

When you figure out your cam selection (ed curtis) and clean-up those heads I think you'll meet your goals.
 
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