Ok, here's the deal: I have the block and heads for my 72, and read that they came with 300 hp. But all this is in dire need of a rebuild. Its all rusty and messed up. I recently pulled a 400 from a 76 T/A and got the tranny with it, which to my knowledge should be a TH350. I also read that these engines came with 185 hp4. This engine is an Interrim engine because I can't really afford to rebuild the other engine. I've heard that the 76 heads are crappy, and I'm wondering about rebuilding the 72 heads and using them. What do you guys think?

Tom

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I gotta get to work on my car!! Stupid school...

 

72,

The older heads more likely have a much better port and chamber design, and a bit better control over core position, so porting is a lot more possible.

Incidentally, the '76 TA 4BBL was good for 185 HP, 310 ft/lb @ 1600 RPM. Even the cam in the '72 was a little better (0.410"/0.415"), but only by a few thousandths lift, so the change really isn't worth the time.

The '72 heads should have been rated at 8.8:1 compression, while the '76 heads are rated a disappointing 7.6:1 compression ratio. For the cost of hot-tanking and magnafluxing the older heads, then lapping the valves, I would say the fuel mileage difference alone would be worth the effort - even in the interim. The time and money you'll spend in prepping the older heads can be used as a foundation for a later buld of the bottom end, but the Poncho crank areas are pretty stout right out of the box. The mains are a lot bigger than SBCs, and even the two-bolts are fairly rigid castings.

Another plus for the older heads is that while the intake valve sizes were the same for both years (2.110") the exhaust valves were 1.775" in 1972 and were reduced to 1.660" in 1974. Poncho builders crave the older heads for just that reason (and the extra iron surrounding the valve seats). Unless you find a crack or really bad guide wear in the '72 heads, I'd use those over the newer ones without a doubt. Hardening the valve seats can be done by any well-equipped shop if necessary.

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Later,
Vader
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"I'm'a do Things My Way - It's My way or the Highway."
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