Hi , I am trying to raise the comp. on a 1995 750. I have 1mm oversize Wisco piston & some head work. I'm getting ready to put in new rings and a .006 thinner base gasket. I checked and have plenty of piston to valve clearance. Looking at my head the valves are almost at the gasket surface, so I do not think I can mill any off of it. My question is, can I mill the top of the cylinder, and how much is safe? Also how much squish band is needed with this motor? One more thing, by taking off this material will this retard my cam timing? Thanks for any advice!

A few questions:

How much CR do you want to run? ...are you planning to stay with pump gas (12.0 - 12.5 is getting to be about all you can stand) or are you planning to run a steady diet of race gas and/or alcohol?

What is the CR now? Going up in displacement will, by itself, raise the CR since you're now packing a larger swept volume into the combustion chamber.

How far are the pistons below zero deck (down in the cylinders) at TDC? ....I may be overly conservative but like to stay in the range of 0.040" as a minimum piston-to-head clearance; if you have a few thickness options available for the head- and basegaskets for your engine you should be able to juggle a little to find a usable combination.

How much- exactly- piston-to-valve clearance do you have at the cam timing you plan to run?

Really the fundamental question is- why? ....raising the CR bumps up torque somewhat but doesn't add any large amount of power; if your piston kit puts you in the 12:1 range right out of the box you are probably going to see a rather modest return if you're chasing raising the CR another half-a-point. What's your true goal?

Oh- and yes... dropping the cam centerlines closer to the crank centerline will retard the timing.

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Thank you for your help. This 1995 750 motor is being used in a TQ Midget car. My main objective is to get more torque and horsepower to come alive out of the corners quicker. The car belongs to my father and I am trying to help out the best I can from out of state. This is not a high budget project and there are some modification rules but I am trying to get as much out of the motor as I can. For instance, 1mm oversized pistons is as large as you can go.

The stock compression ratio was 11.1:1
Wiesco said with the new pistons it would be 11.8:1

I measured my valve to piston clearence at 10 degrees ATDC on the intake and had .140"
I measured the exhaust at 10 degrees BTDC and had .150"

I didn't measure deck height and can't readily do that since I don't currently have access to the motor. My plan was to reassemble the motor when I visit them at Xmas time. I do have a '93 750 motor with stock pistons available, would it be accurate enough to measure that motor?
I hope that this information will help you help me.
Thank you very much.

Well, you're certainly safe on piston-to-valve clearance. Since you don't have hands-on access to the engine you're going to have to play it safe regarding piston-to-head clearance... any chance you can arrange a deal with your supplier to let you pick up a couple of different thicknesses of headgasket, use whichever works best, and return the others without a restock penalty?

If the budget will stand it, you might at least take a light pass off the deck surface and cylinder-head face to give the headgasket a fresh surface to bite into... even if you can't eke out appreciably more CR at least you'll know that the surfaces are true, and it will (hopefully) help the engine stay nice and tight under race usage.

What are you planning to run for an ignition system? ...will the rules (and/or your wallet) let you run a Dyna2000?

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