Instead of getting some Afrs I think I will get some Performer Rpms and upgrade the pistons while the engine is broken down. The pistonsI will be getting will up the compression 10 to 1 according to the jegs guy. After putting the pistons and rings will there have to be anything else upraded internally?

 

If you go with the RPMs, which are good heads, call Edelbrock direct and order the new Pro Port CNC RPM heads, they blow away pretty much anything else in their size class. It's basically a new CNC port design that totally kicks butt. As far as pistons and compression, be careful, it works with the cam also, and if you need to run pump fuel with a street cam, you'll prolly wanna be more like 9.0-9.5:1 compression. Static compression means nothing, dynamic compression is what matters, and cam timing affects that. You'll also wanna at least upgrade the connecting rod bolts with the good ARP bolts, or get better rods if you plan on turning higher rpm or making a lot of power(turbo, nitrous etc). ARP head, rod and main cap bolts are definately prefered, especially on an engine with good heads that's making more power than stock. Also get a hardned oil pump drive shaft, either from Melling or ARP. New cam/lifters won't hurt, will do wonders if matched to the heads/intake.

 

My son's truck did really well running on premium pump gas with 10 to 1 compression, aluminum heads,and a mild performance cam. We have since put a much warmer cam in and we can run a little more timing on it now.

The 66 is running about 11 to 1 with a very warm cam no issues at all.

We are at 4,000 feet elevation though.

Aluminum heads will normally allow a CR of about one point... ie: if you can get away with 9 to 1 with iron heads, you should be able to get away with 10 to 1 with aluminum.

IMO you can get away with 10 to 1 on premium pump gas with aluminum heads with practically any cam warmer than stock..... I think...

 

The cam is only a comp cam 270h, so it is a mild cam, What kind of intake do you have in the 66 with a 408?

 

We are running an RPM Air Gap.

With your 270H you should not have any issues with 10 to 1 with aluminum heads, this is very close to my son's first cam in his truck.... You will pretty much need to buy premium gas though.

 

What really matters with the cam, is when the intake valve closes. The later after BDC it closes, the less dynamic compression. You could take a stock cam and retard the timing and it'll bring the dynamic compression down. That's why you can get away with pump fuel on higher compression engines when you have a bigger cam. There are online calculators that'll compute dynamic if you know the cam specs, rod ratio etc. Street use and pump fuel, a rule of thumb is around 8.0-8.5 dynamic max for pump fuel. Rod ratio and qunech will affect detonation resistance as well.

A good example of everything coming together is(again) GM's LS7, it's like 11.0 or 11.5:1 static compression, and it runs on pump fuel with a totally crappy rod ratio(it's like 1.58 I think). EFI helps though, with a knock sensor. Obviously though, there's something going on internally to keep it from blowing up on pump fuel.

Anyway, if you follow the reccomendations on compression ratio and rpm range for the cams/intakes/heads that the manufacturers have, you'll do fine. A good way is look at the cam, like the 270H, and see what Comp reccomends for rpm range and compression, then select heads, pistons and intake based on that. That way everything comes together and runs very well, and you won't have issues(if it's assembled properly at least). Just pick a cam that operates in the rpm range you need, street, strip, oval track etc. The 270H is a good street cam.