Sonix

iTrader: (1)

I'd want to know all the numbers you used to calculate the 11:1, and how you got each number, before trusting you have an 11:1 engine. 64cc heads doesn't get you there unless you're using domed pistons, and you said you have flat tops, so something doesn't add up.

No change in hell you're going to run an 11:1 engine on 87 octane, 92 minimum, with a big cam. But I don't really think you've got 11:1, 10:1 if you've decked the block a bit, but I still want proof.

The compxe274 is a proven winner. With the ballpark compression you've got, that's still what i'd pick. That's enough cam that you won't enjoy daily driving it, but you CAN. With anything bigger it'd be next to impossible. (next to, as in "good lord do you really want to drive that thing again today?!? Bus seems great...")

stevenb

I dont know how I'm going to get 11:1....that is just what my valve guy said. He said with the World Sportsman 2 64cc heads with .40 flat top pistons thats what I'd run

Sonix

iTrader: (1)

Ok, then that's BS.

Are you currently building the engine now? Measure the deck height, and get the valve relief size from those pistons.
Use this calc;
http://kb-silvolite.com/calc.php?action=comp

I'm seeing 9.7:1 using numbers that i'm guessing you'd have. Unless you've modified something (decked the block), then this is most likely what you're at.

That's assuming a 1.56" compression height, it could actually be less.

F-BIRD'88

I hope your "valve guy" is a little more precise in doing your valve job than he is at calculating an engines compression ratio. He is way off.
Sonix has pretty well nailed it for ya.

If you follow my previous recomendations for setting up the cam in the motor and setting up the timing, carb power valve, rear gearing and torque converter selection, it will run very well at the track and drive well on the street.
You cannot change the LSA of a camshaft once it is made. The LSA is the distance in degrees of the intake and exhaust lobe of one cylinders cam lobes. (in your cams case 108deg )You can advance or retard the cam timing of a camshaft by moveing the camshaft in the motor relative to the crankshaft. By doing this you can fine tune how the motor will run with a particular camshaft. (enahance the low end of the usable rpm range or enhance the top end.) Advancing a camshaft in a motor makes the timing points occur earlier (most important is the intake valve closing point) Earlier intake valve closing helps build cylinder pressure early and enhance low top mid range torque. It has a small effect on the top end power.
Your cr is just right for premimum pump gas. But, I would dial in the camshaft you bought as I described before, to optimise the overall performance. You do not need a new cam unless you won't be buying a high stall converter and high ratio rear gearing. Or do not want a "rough idle cam".
Your cr is not too high. The stuff you bought can work very well for you once dialed in. Its up to you to do the "dialing in".

stevenb

Yeah the guy is "shady" at what he does but good at it if that makes sense lol

Well thanks a lot for the help everyone, I am probably gonna look into another cam when money comes around

F-BIRD'88

Good at, being shady?......
Read my post again. If you want to build a motor that will do what you stated you wanted to achieve before, then you have the right camshaft and the right compression ratio (for pump gas). You just need to take care of the details.

stevenb

So I cannot use regular unleaded with a cr of around 9.5ish:1?

Sonix

iTrader: (1)

That's dicey. Maybe.
Pump gas, as F-bird is talking about is 91-92 octane. 94 if you're lucky and can find it. He means you don't have to run 110 octane race fuel.

87 octane is for boats and trucks, it has no place in the high performance community for the most part. A few exceptions for TBI motors, etc. Wave goodbye to it and forget about it.

F-Body Demon

iTrader: (1)

Open headers will make it nice and choppy

stevenb

Doesn't Sunoco have 94 oct?

Sonix

iTrader: (1)

I guess, you got Sunoco near you? There's only one place in my city that I know of that has 94 octane, and it's kinda far, (maybe 15kms away).

stevenb

It is about two miles from my house

F-BIRD'88

In Ontario, (Canada) Sunoco "Ultra" is 94 minimum Octane. Used to be called "Gold" Good for 10.5:1 compression . on many small blocks. A little less on BBC's Some people, not all with aluminum heads get away with 11:1. 10:1 cr works very well.

Sunoco does not give a "maximum recomended compression ratio limit" that this fuel is good for. They simply state that as long as your car does not ping, detonate or knock,or run on using this fuel with proper ignition timing and AFR , your fine using it.
It's up to you to determine the octane requirement of your specific motor and driving style.