I am ready to put the cylinder head on my 1g Laser soon. Previous owner claims that the engine was bored 30 over.

Previous owner has lied about many things and the bottom end looks like it has never had anything done to it so I am willing to bet that the bottom end has never been bored over.

Any reason that I can't use a Harbor Freight Digital Micrometer?

I'd like to know because I want to make sure the stock style Felpro Composite head gasket I intend to use is going to work just fine.

Thanks!

Stock is 85mm / 3.346" so .030 over would be 3.376" or 85.75mm
A bore gauge is much more precise but probably not something everyone has.

HF Dial Caliper says 3.3375"/84.77mm...

Would you say it has stock bores and call it a day or?

Kinda hard to be SMALLER than stock. Do you know a machinist that you could "borrow" a bore gauge from. It sounds stock bore but you really don't know until you use a tool that is really accurate in the measurement that you are taking. It would suck to stick stock pistons in only to find out they are way to small, you get the drift.

1990TSIAWDTALON said:

Kinda hard to be SMALLER than stock. Do you know a machinist that you could "borrow" a bore gauge from. It sounds stock bore but you really don't know until you use a tool that is really accurate in the measurement that you are taking. It would suck to stick stock pistons in only to find out they are way to small, you get the drift.

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Nope, don't know anyone. I figured that it is just a gauge inaccuracy....like you said kinda hard to be smaller than stock. The pistons aren't out BTW. I just turned the crank and brought the piston down to take a measurement.

This was just a head swap.

I don't have a manual in front of me. Could someone remind me what the bore tolerance is? I'd imagine something like +/-.03 mm, which means the lower spec limit is 84.97 mm, but I'm just guessing on the tolerance.

iceguru1114 said:

I don't have a manual in front of me. Could someone remind me what the bore tolerance is? I'd imagine something like +/-.03 mm, which means the lower spec limit is 84.97 mm, but I'm just guessing on the tolerance.

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Good point. Was using the calipers wrong. It is actually 84.95mm. Don't ask me how I could be using them wrong, .

Do not use calipers to measure bore diameter! You need a cylinder dial bore gauge.

the very top of the cylinder is always the smallest, by fractions i know, but still. the caliper is fine for your goal, you are not trying to buy pistons based on the reading just figure out if it has been bored. so according to your numbers it has not been bored.

You can use calipers to get a ball park, but be careful of the ridge at the top you may be measuring.

diambo4life said:

Do not use calipers to measure bore diameter! You need a cylinder dial bore gauge.

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I use them all the time to check if a block has been bored, as I only buy virgin blocks. You have to clean the carbon buildup off first.

Of course you wouldn't use one to measure ptw for a build.

A bore gauge doesn't actually measure the bore anyway. It measures the difference between what you zero it out at and the bore diameter. You measure the piston with a mic, zero the bore gauge out in the mic, then measure how much bigger the cylinder is than the piston with the bore gauge.

donniekak said:

I use them all the time to check if a block has been bored, as I only buy virgin blocks. You have to clean the carbon buildup off first.

Of course you wouldn't use one to measure ptw for a build.

A bore gauge doesn't actually measure the bore anyway. It measures the difference between what you zero it out at and the bore diameter. You measure the piston with a mic, zero the bore gauge out in the mic, then measure how much bigger the cylinder is than the piston with the bore gauge.

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^^^ Exactly, most people wouldnt even be able to use a bore gauge if they even had access to one, they arent all that simple, its not a matter of a direct reading from the tool as the calipers or micrometer would be. The top of the pistons should have overbore numbers on them if the block has been bored, clean the top off of one of the pistons really good and see what it says.

Thanks for the extra comments everyone.