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Author Topic:   Small Block Chevrolet Compression ?
Dirt Forum Champ
Total posts: 569
posted April 19, 2005 09:19 AM  
How much compression is too much?

I'm looking at a Classic Series Jr Motorsports 406 (hypertech pistons, Scat crank and "race prepped" stock 5.7 rods) with 13:1. My last motor was the same motor with 11:1 and I liked it but wonder if I'd be happier with more compression. I had a 360 a few years ago with 12:1 (from another builder) that was not too good - little power, tough to start and just generally a dog. I always attributed this to too much compression, but maybe I was wrong.

Here are some particulars - the heads are Dart iron eagles (64 cc chambers and 215 cc runners), 3000 lb car and 750 dbl pump Holley running on Sunoco racing fuel (110 octane I believe). Also, the rpm range is 4500 to around 7000.

Is 13:1 a sensible ratio?

Dirt Forum Champ
Total posts: 2007
posted April 19, 2005 09:24 AM  
more compression = more power.

I think it sound like your 360 had other problems. That would be a pretty healthy 406 combo, the only thing i would be concerned with is getting it to live W/ hyper pistons and stock rods i think its on borrowed time.

Dirt Roller

Total posts: 8
posted April 19, 2005 12:23 PM  
tried the old hyper pistons with x rods and 13.5 to1 wont live only buzzed it 6000 to 6500 longest one lasted was 6 races. spend the money on good parts and they will pay for themselves in no time at all just think what it will cost to rebuild when you need new pistons rods block and crank when it comes apart!!!

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