Which way to go ?

Originally Posted by Ausgal67

Is it worth chucking a set of GT heads on, am i really going to get any benefit concidering i am bumping up the comp with pistons.
And should i beef up the rods, with H or I beam.
Any thoughts?
David.

Probably not. Don't get hung up on the GT branding of the heads. We've gone round and round here about interchangeability and for the most parts the heads are really close to each other with the exception for exhaust bolt holes and exhaust port location. Since your doing mild porting it won't really matter. The exhaust ports on the GT heads will be off of what your headers will probably be at, so you'll find it hard to match the gaskets and header pipe location.

A 398ci will be just fine with the stock rods. Ford didn't beef up rods until the SCJ and the 427s. If you have a machinist thats good with the numbers(and cranks) you can increase the stroke just a hair too when the cranks turned. Just do the math before you order pistons. I had my crank indexed(extra $) that made sure that my stroke on all four journals was the same and that they were in fact 90* off of each other.

I'm leaving a lot out but at least it's something. Hope this helps.

.

When we did ours i did two price lists. one with special rods and forged pistons. and one with the stock stuff. I was nervous about the early 390 i had the rods looked like 352 rods. When everything was added up, it was only a few hundred dollors more to go with the scat 432 stroker rotating assembly, through summit. Hope this helps bob

My 2 cents.

Great plan with a couple gotchas.

1 - I think 10.5:1 is too much compression with the 280H. You will have to slow the timing down to the point that the extra compression will have minimal gains. Be sure to calculate it exactly, as most iron headed Ford chambers are much bigger than advertized AND most pistons are deeper in the hole, but just the same, I'd limit it to around 9.5:1

2 - Go with a 750 vac sec.

3 - A little looser converter would make you happier. Stock C-6 of that era was 1800-2000, so you aren't gaining much. I'd go with a 2400 stall with a name brand company. The little extra torque multiplication of the looser converter will make it much happier down low.

4 - Just to be clear, the ports themselves don't need much grinding, and it's a waste of time if you don't address the weaker areas first. Its the bowl and guide area that needs help, especially the transition to the valve seat and even more importantly, the big honking valve guide bosses on the C6,C7, and especially C8 390 heads. On the exhaust side they almost block the bowl area.

BTW, to make you feel better about not using a "GT" head. ALL heads are GT heads from 67+ except for CJs. Just some have a few extra holes drilled for unibody manifolds.

The GT head is the same head used on pickups, full sized and non-CJ unibody cars, all exactly the same, except for a couple extra bolt holes

FYI Your motor plan is nearly identical to the one in my 71 4x4 shortbox F100 and it'll tear your head off, it awlays amazes me that such a mild combo pulls so hard.

Thanks for all the info guys.
With comp ratio, the pistons i am looking to go with and the original heads will give me around 10-1.
Good info on the stock convertor, never really thought what stock was.
Couple more questions before i order the parts.
Would you recomend a Melling HV oil pump with stock oil galleys or would i be best with standard.
And is there any benefit in H beam rods over the stock rods, i will be going 0.20" under, is that ok with the FE?
Thanks again for the input.
David.