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Discussion Starter #1
Replacing intake with Perfromer RPM and Holley 600CFM. Have top end tore down and want to do heads and cam. Cam definatley and looking for recommedations on Cam. Also head wrepalcement. Worth gt40's for $200 or a/m. Will get much gain on hp from heads with that combination? Any advice appreciated. Mike
 

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Are you going with GT40's or GT40P's? Are you staying stock manifolds or using headers? Is the block a stock 68 302 (i.e. no rotating assembly changes)?

Going GT40P's and retaining a 9.5 to 1 compression with the use of headers nets 5.0 mustang guys 30-40 hp. They are roller engines though, so there may be some variation. Cam selection is key to this swap (as well as some other things that require answers to the first questions I posted).

What you actually end up getting out of the heads is going to be affected by the cam as well as what kind of powerband and drivability you are looking for.
 

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And what is a/m, did you mean aluminum?
 

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Thanks for the response. I am not sold on replacing the heads but thought should at least explore. Haven't decided on cam and guess it matters on if the heads are switched. Any recommendations on cam?
 

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Discussion Starter #5
The block is 68 302-2v stock with only change is dual exhaust. Had headers and they didn't fit so looking for new ones.
 

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GT40P's are the cheapest in overall price, many would argue that going aluminum is better, depends on what you want your car to do, how much you want to spend and how far you want to go.

Assuming you were at the stock 210 HP and 295 tq numbers you car came stock with, with GT40P's and a close to stock cam, you will see roughly about 10-20hp with a cam and head swap. Don't stop reading here, just bear with me. I would suggest going with Comp Cams PN 31-234-3 Grind XE256H with those heads, nice under the curve power band and will net you about 20hp with those heads.

NOW, assuming you didn't get depressed with those gains, if you upgraded the carb and intake with those other 2 you would see closer to 50-60 hp out of the deal. It's a package though, only going with the intake and carb will net you 10-20 hp. All 4 together though and you'll see closer to 60. Last but not least, adding headers last would net you another big chunk with the other 4, possibly even 30-40 hp (headers aren't doing it, it's what you should have been seeing from the other 4 things combined that the manifolds were restricting). I'd say with all 5 youwould be looking at around a 100 hp difference, torque might not gain much though (prob. around 30-40), as essentially you are making the gains in breathing up top.

This is all speculative of course. I ran the numbers through Camquest and based off the reading I have done on GT40Ps and their supporting mods, it looked fairly accurate.
 
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