The problem with pickup 390s is sunken pistons. Ford used the Mercury 410 spec piston to lower the compression in those motors. The piston runs a little over .100 down the hole. Compare that to the spec of .015 down the hole for car motors. Here is a chart with car cylinder head specs for car engines:

FE Cylinder Head I.D. and Application Chart

But the heads you have already may be in the 68 to 72 cc range, or maybe 74. I can't find anything "trustworthy" on that. Plus you have hardened valve seats, which early car motors will not have. Add the cost to rebuild those heads and it's not a cost effective action.

Decent 4bbl manifold, carb and headers will gain you noticeable power. Performer manifold is said to work well.

This forum is full of FE performance threads, keep scrolling and find dozens.

 

Do you have any info for the C4AE-G heads setting on a 390, 20 over flat tops at .015 deck.
CR = ? Approx. Only work to the heads, new bronze guides, hard seats, new standard size valves.

 

1) Start a thread on this for your specific questions.

2) https://www.summitracing.com/newsand...ion-calculator

 

OMG, thread police. Really. Since the conversation was about a 390, types of heads, deck clearance, types of pistons berween a truck and car - AND you think my question is out of line to the conversation.
You posted a data sheet with such info listed but it did not list the C4AE-G. I was simply asking if you also had detail on the 'G' head and pertaining to this conversation. Perhaps you should engage your thought process before posting 'thread hyjack'
Amazing

 

 

The pistons are the real problem. As to aftermarket heads, that will be pretty expensive. What is the condition of your current heads? If you just need valve seals, that's an easy fix. If they are in need of major rework, then it's a real question of that cost vs. the cost of aftermarket heads. As to older heads, I would expect most to need some rework and hardened seats added.

If your heads are ok, the intake/carb/headers will be more than "a little (more) power".

 

 

Maybe do a compression test first. If you are good on cylinder pressure on all cylinders, then other than valve seals, it would probably be best to let them be.

The Performer intake is well spoken of here, carb, maybe a 650 CFM vacuum secondary carb.

Factory iron manifolds work just fine also, but you need a crane to install them.

How is the timing set and ignition?

 

About 10 to 10.5 to 1 with .020 thick steel shim gaskets, that's what the 4 bbl engines came with. But there were two different flat tops used in the 60's. The early ones were true flat tops with no valve reliefs,(circa 1964 or thereabout) the later with reliefs circa 1968 or so. The actual ratio will depend on the exact pistons and gaskets used

 

You could do a cam swap to improve the performance with the setup you have now. Something with a wider LSA to raise the dynamic ratio, that works with a low comp ratio, like a Comp 268H, basically an EFI or RV grind is what you'll need.

 

 

Definitely.