12 1/2 -1 compression on the street?

[tufrat]

Just a question but how many 427 c.i. motors on the street have 12 1/2-1 comp for example the ZL-1. Does this motor run hot (200 +)or the timing way down? Reason I ask is I'm building a ZL-1 for the street and not to sure of the piston and comp, I want. Any information would be great and concidered thanks

[COPO]

I have a couple of cars that have 11:1 compression. None of them will run on straight pump gas. With super 104+ octane booster and 93 unleaded I can usually keep the timing close to stock and no problems with over heating w/the 4 core radiator. Unless you have easy access to racing fuel 12.5's are not streetable. I bet you only lose around 30 ponies going to 10.5 or 11:1. I think you'll be happier if you plan to drive it on the street and no one will know anyway.

[Chevy454]

The aluminum heads will help the compression issue a little bit, as aluminum can take a little more than iron. But, like COPO said, I would probably drop the compression about a point or so. Then, I would call the cam manufacturer of your choice, tell them what combo you are running, and let them put it in the computer and find out what you need. With the lesser compression, the original cam would be a real dog. Go with an aftermarket grind. Oh yeah, make DARN SURE you have a 4-core radiator and a good waterpump/thermostat!

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Rob Clary
'70 LS-6 Chevelle
Numerous Yenkos
Interested in COPOs, Yenkos or other dealer built muscle cars then go here: https://www.yenko.net

[micky69396]

Unless you want to run cam2 all the time, I would at least drop back to 11-1, you can still run a L-88 cam or something aftermarket(roller?)to get the lope you want, run a mixture of racing gas and premium fuel. Timing shouldnt be that big a deal unless you plan on racing it, then you can kick it up a notch.

[JoeC]

Chevy made two prototype 1969 ZL-1 Camaros under COPO # 9567 with 11:1 compression. According to one Camaro book they were "intended to provide a more streetable car with more expressive graphics then the regular ZL-1 Camaros".

[Charley Lillard]

How much are you going to be driving the car ? I have a ZL1 and a ZL1 replica. I add 5 gallons of race gas and then fill with Premium Unleaded then keep topping off tank with Premium when it gets down a little.