early heads on a late block

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grendel

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So, I am back... built a 500 for a C20 Longhorn I converted to 4wd with help from y'all about 8 years ago. Got into LS motors for a bit. While building the other 500, I acquired parts for my brother, who just finally forked them all over as he wasn't using them.

What we have, I think, is a 1973 complete motor. I also have a set of high compression early heads and an edelbrock intake. Plan is MTS roller shaft mounted rockers and a roller cam with lifters. Maybe the high compression heads... but as I recall, that nets some really high compression???

What do y'all think?

Would like 400hp and be a torque monster.

I know, it's been asked before but search sucks wind these days.

So, do I need to buy and swap pistons and stay with the 73 heads?

What's the best combination for a 91 octane gas stump puller to haul around a race car behind a pick up with Holley EFI.
 
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For a goal of 400 hp, either heads will meet the need.
Use the 75 heads with flat top pistons, or if you want to use the early heads get pistons with more dish to them.
Check the cc math before ordering.
It's tough to see the big picture having the most expensive cam and valvetrain possible and at the same time only having a goal of 400hp without wondering what is being considered for the rest of the components and machine work?
 
Quick and dirty look at wonderful moroso slide chart, assuming 8.5-1 for a late engine, and 124 and 78cc chambers [-46cc], CR would go to around 12.3-1.

Recipe for disaster unless you plan to buy gas in a barrel.

Egge has copies of the '70 piston, which in real world give 9-1, maybe 9.3-1 with tight quench. They are really proud of them though. Hard to find useable original '70 pistons.....
"Vendors" have forgings to give you whatever you want.

Although a copy of a 70 engine would do better, I had a re-ringed '75 engine that went 12.97 at 100 in my truck, on 87 gas, with points, a '76 caddy QJ on an edel. Only non stock original 1975 parts were Howards .536" cam, toll steel rocker tees, yellow GM beehive springs and the intake. Lots of time porting, but stock valves. The block was decked .013" for zero and heads cut a little. CR was 8.7-1. Ran best shifting at 4800. I wish that I would have kept it.
Dave
 
I think I'd like to be around 10:1 compression and run it on 91. Seems like either head would do what I need, just have to swap out pistons.

Who should I send the heads and intake to for porting? Looking at them, they have a lot to give.
 
Does that mean you're selling head work, Dave? :) I don't have the time to do it. Thought about aluminum heads, but not enough gain for a truck motor. Thanks for the reminders on your thread. I did reply to it about 7 years ago.

I do have a set of stainless LS headers here, to cut up and add cadillac flanges to, including the anvil to square the tubes.

I'd happily pay someone for a recipe: What pistons, how much to take off what set of heads, what roller rockers, what roller cam, what roller lifters, what valve springs etc. I have a machine shop that is top notch, but they don't race or run Cad500's.

Total engine budget is about 3500. I have the motor, low and high compression heads, headers, Edelbrock intake, rhe right oil pan for the truck, etc.

If I can get more out of it, great, if not, I err on the side of reliability.
 
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oh and an HEI distributor with an MSD box.
 
10-1 is still risky without a pretty big cam, but good thing you have the valvetrain to handle it.
The way to reliably get more out of it is to tone down the compression a bit and deal with the airflow.
More cam and airflow will quickly exceed the Performer intake.
 
No head work guy here. LOL. I enjoy it much less that I did when I was young.

I'm with f-85, 10-1 is pushing it on 91 esp with that cam [a good towing cam imo].
Fwiw, Potter's crate engines were 10-1 and he used a flat tappet 232/236 at .050", .550" ish lift 112* lsa.

Iirc, summit can have whatever you want ground. I have a howards lobe list if you want it. More fwiw, I would go tighter on lsa.
 
I ended up sending this out to 8ad-f85 who's working it over... well that and an LS2.

The Cad is going into this... chassis is ready. Once I get the motor in and running, it gets painted.

The LS2 he's working over goes into a jeep of all things... on corvette suspension.
 

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Well, we sent him everything motor related we had. :)
 
Can't wait to get them back and into the trucks...
 
I don't know - I sent a Cad and LS2 engines to 8AD-F85 in March. Waiting to get 'em back.

I sent both types of heads I had. Tony, which ones were used? You might contact him about a set.
 
dave brode said:
Quick and dirty look at wonderful moroso slide chart, assuming 8.5-1 for a late engine, and 124 and 78cc chambers [-46cc], CR would go to around 12.3-1.

Recipe for disaster unless you plan to buy gas in a barrel.

Egge has copies of the '70 piston, which in real world give 9-1, maybe 9.3-1 with tight quench. They are really proud of them though. Hard to find useable original '70 pistons.....
"Vendors" have forgings to give you whatever you want.

Although a copy of a 70 engine would do better, I had a re-ringed '75 engine that went 12.97 at 100 in my truck, on 87 gas, with points, a '76 caddy QJ on an edel. Only non stock original 1975 parts were Howards .536" cam, toll steel rocker tees, yellow GM beehive springs and the intake. Lots of time porting, but stock valves. The block was decked .013" for zero and heads cut a little. CR was 8.7-1. Ran best shifting at 4800. I wish that I would have kept it.
Dave
Click to expand...

So, would e-85 run perfect on 12.3 to 1 compression ?
Just sayin’
 
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