Thoughts on Direction for Engine Project - Page 2 - Vintage Mustang Forums
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post #16 of 25 (permalink) Old 04-24-2019, 04:20 PM Thread Starter
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Word back form the machine shop - crank good, pistons good, block to be rehoned and decked, 1 head is cracked. So , now the search for some budget heads...
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post #17 of 25 (permalink) Old 04-24-2019, 08:42 PM
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Just a thought. If one the available cam grinds suits you, you can score a bargain flat tappet cam from Summit for around $65-75. Add a set of house brand lifters and you're in for under a $150. Back when PAW was still doing Ford stuff they used to sell house brand cams for $50 and a matching lifter set for another $50. I still have those parts in my '67 from like 15 years ago and still like it just fine. The world didn't always revolve around $200 roller cams.
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post #18 of 25 (permalink) Old 04-24-2019, 08:44 PM
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For cheap heads of good quality, it's mighty hard to beat GT40P's. If you're wanting headers though, keep in mind you will need to deal with the weird plug angles.
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post #19 of 25 (permalink) Old 04-24-2019, 08:58 PM
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P heads ,according to @Huskinhano work good with off the shelf MAC longtubes
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post #20 of 25 (permalink) Old 04-24-2019, 08:59 PM
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For cheap heads of good quality, it's mighty hard to beat GT40P's. If you're wanting headers though, keep in mind you will need to deal with the weird plug angles.
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post #21 of 25 (permalink) Old 04-24-2019, 09:00 PM
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P heads ,according to @Huskinhano work good with off the shelf MAC longtubes
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post #22 of 25 (permalink) Old 04-24-2019, 09:09 PM
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Quote:
Originally Posted by katwalk View Post
Word back form the machine shop - crank good, pistons good, block to be rehoned and decked, 1 head is cracked. So , now the search for some budget heads...
Okay... If you can find another E5 head for short money then fine, but if not, my pick is STILL the GT-40P. Why? Very readily available, relatively inexpensive. Perfectly fine for your power range. Running the stock cam I wouldn't even bother changing the valve springs or rocker arms.

Now, have you ID'd the pistons? The reason I ask is that you should determine what their compression height is before having the block decked to optimize how much you'll be taking off. Your pistons, depending on what was put in, could be 1.585, 1.60, 1.605 or even 1.608" CH. This will make a difference in not just static compression, but quench distance. You really want a quench around .040-.045" if possible. Also, if the pistons are dished you DEFINITELY want to consider another set. The Silv-O-Lite 3101HC is, IMHO, a good choice for the money.

https://www.summitracing.com/parts/uem-3101hc-030

Those pistons with 60cc GT-40P's, a head gasket with a 4.1" bore and .040" compressed thickness will yield a 9.25:1 static compression ratio with a nice .045" quench.

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post #23 of 25 (permalink) Old 04-24-2019, 09:25 PM
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Originally Posted by 2nd 66 View Post
P heads ,according to @Huskinhano work good with off the shelf MAC longtubes
Here’s a top view of the MAC header on the P head. With a 90* plug boot doable. I also used boot protectors and have had zero issues since putting the motor in 2 years ago. The P head is a significant improvement over the average sbf head. I’m more then pleased with the performance. About the only way I’d put aluminum heads on is if someone gave me a good new set. How ever like any other factory cast iron head by the time you start doing work to them, you’re approaching the cost of a set of good aluminum heads. These heads really shine if you find a good used set cheap. You can’t beat them for the price.

As far as the MAC header, I really like them. Well made, tuck up to the floor, easy to install especially on the driver’s side as tube #5 slips in. They clear the PS ram without a drop bracket, plenty of access to the starter and the clutch linkage as well. The only hiccup with the clutch linkage I had to slightly dimple one tube for the Z bar shaft which was a easy fix.

Another aspect of the P head. Very efficient combustion chamber. The GT40 head was no longer able to meet new exhaust emissions. The P head did and did it without a smog pump and made more power. It needs only 28 to 30 degrees total mechanical timing. With 87 octane no matter how hard I lug it, I can’t get it to rattle.

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Last edited by Huskinhano; 04-24-2019 at 09:33 PM.
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post #24 of 25 (permalink) Old 04-25-2019, 11:42 AM Thread Starter
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Great info guys, thank you.

re: heads - I am leaning toward some GT40 or GT40Ps. I found a set of Ps locally already rebuilt and ready to bolt in for $450. Still researching this to get my head wrapped around it.

re: cam - I found a good deal on a Comp cam that focuses on low RPM drivability, which is what I am after (not drag racing, etc). Here is the can card for it - thoughts? One thing, I bought this cam when I had plans to continue to run the SROD that is in it now, but have since picked up a T5 that will be going in with the new motor, so may rethink the cam choice.

re: pistons - I already bought a set of 3101HCs. I told the machine shop to go ahead an recondition the rods but he wants to wait to touch the block until I bring him the pistons, so I need to run them over there.

re: headers - I am currently running some Sanderson block huggers on the 302 that is in the car. I found an old post from one of the forums that said these heads will work with the GT40P heads - I hope so because i really like them. For s**ts and giggles, here are a couple of pics of the headers today and the relationship to the spark plugs.

Thanks again and please keep the feedback coming. - Farrell
Attached Images
File Type: jpg cam card.jpg (72.4 KB, 2 views)
File Type: jpg headers1.jpg (76.1 KB, 1 views)
File Type: jpg headers3.jpg (65.0 KB, 1 views)
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post #25 of 25 (permalink) Old 04-25-2019, 12:07 PM
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Great info guys, thank you.

re: heads - I am leaning toward some GT40 or GT40Ps. I found a set of Ps locally already rebuilt and ready to bolt in for $450. Still researching this to get my head wrapped around it.

re: cam - I found a good deal on a Comp cam that focuses on low RPM drivability, which is what I am after (not drag racing, etc). Here is the can card for it - thoughts? One thing, I bought this cam when I had plans to continue to run the SROD that is in it now, but have since picked up a T5 that will be going in with the new motor, so may rethink the cam choice.

re: pistons - I already bought a set of 3101HCs. I told the machine shop to go ahead an recondition the rods but he wants to wait to touch the block until I bring him the pistons, so I need to run them over there.

re: headers - I am currently running some Sanderson block huggers on the 302 that is in the car. I found an old post from one of the forums that said these heads will work with the GT40P heads - I hope so because i really like them. For s**ts and giggles, here are a couple of pics of the headers today and the relationship to the spark plugs.

Thanks again and please keep the feedback coming. - Farrell
From what Im seeing I think those will work just fine with the P head. On the drivers side, if you can get a deep socket on the rear bolt of each header tube, youre good to go. It means the tube comes far enough out in a straight line and the socket mimics the plug in a more severe example.

The GT40 has a 65cc combustion chamber while the GT40P has a 60cc chamber. The 289 head is 55cc. The GT40P will lower compression by about 1/2 point and the GT40 by a full point. The better breathing of either head will offset that loss of compression but I think the GT40P is a better balance. You could have the P heads cut slightly to get 55cc. The P head also breathes a little better and has no smog ports to plug. The GT40P is a modern designed head with modern port and combustion chambers. The GT40 is not. When I first drove my car with the GT40P I was caught off gaurd at how quickly it went to 5500 rpm with a mild cam. Theyre probably at least 30 hp over the older heads.

Tom

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