Bore Gauge in cold weather ?

happyhoppy

Measuring my AMC 401 with a bore gauge in 15 Degree weather the cylinders are actually .0015 under standard. Is it possible there will be that much difference when I get it to room temperature? (Wife won't let it in the house under any circumstances!)

fifesjeep

It'll make that difference... Especially if the bore is still tight to original specs. Here's something to considering, most fine measuring equipment should be calibrated Or are supposed to be calibrated @ 68* F... Both part and instrument should be at the same temperature while measuring, ideally 68* or there abouts. This could be part of the problem. Bring the block in (While she's not home and Hide it! :idea: ) let it sit at room temperature... then check it. Also, did you measure the pistons and get the piston to cylinder clearance?

happyhoppy

Thanks - feel better about that. I usually hit pretty close to what the machine shop gets. I have the heads off and measuring the bore with the pistons at bottom of the stroke. Kinda new at this but learning fast but I have another question. Do I need to take the pistons out to measure the piston to bore clearance or is there a way to measure with them in the bore accurately? Another quick question - the AMC service manual said to bore if the bore exceeds .005. Is this realistic? Not going to see any high rpms or many high performance add ons. This is a super well maintained engine with 55000 miles and I'm wondering how far I want to go with this rebuild. Read a little more and found answer to piston to bore clearance - dumb question after seeing how easy it is.

fifesjeep

happyhoppy wrote
Thanks - feel better about that. I usually hit pretty close to what the machine shop gets.
I have the heads off and measuring the bore with the pistons at bottom of the stroke.
Kinda new at this but learning fast but I have another question.
Do I need to take the pistons out to measure the piston to bore clearance or is there a way to measure with them in the bore accurately?
Another quick question - the AMC service manual said to bore if the bore exceeds .005. Is this realistic?
Not going to see any high rpms or many high performance add ons.
This is a super well maintained engine with 55000 miles and I'm wondering how far I want to go with this rebuild.

Read a little more and found answer to piston to bore clearance - dumb question after seeing how easy it is.

What made you tear into the motor? Honestly, if all looks good and measures out to be fine, button her back up! But, before doing so purchase a new timing set. :t: look into and through the lifter valley and inspect the lobes of the cam makes sure the top of the lobe isn't rounded or on it's way to being rounded... it should look similar to an egg (Sort of).