That's what the factory spec is for a 318.
3.910 + a few lines
- Thread starter Princess Valiant
- Start date
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So then what am I looking for?
Well since the factory standard spec is 3.910, measure what you "have" and find the difference. What did you say it measures now? 3.9113?
So 3.9113 - 3.910 = .0013, or heading toward one and a half thousandths.
Yup. 3.910 would be the factory unworn bore and 3.912 would be the factory maximum before you need to bore it. So, if it's 3.9113, that's still below maximum spec. Although, not by a whole lot.
Then I need to finish measuring it and forget the machine shop and put it together.
I am looking for a commuter engine that will never see the race track. Valiant Propellant to go work, grocery shopping and back.
That means i need to take the video down, revise and rebuild
I would at the very least double and triple check. Where in the bore are you taking your measurements? The "proper" and "correct" way really, is to take a measurement at the top (under the ridge) middle and bottom (but not out of the ring travel) and then add them together divide by three and get an average. Most people don't do that, but that is the correct way by the book.
the snap gauge and micrometer showed 3.9113 ...but the bore gauge showed, 3.906 + .006 = 3.912 just shy of 3.912
Part Duex tomorrow
I was measuring just under the ridge on the worst cylinder.
now this changes things because at 3.906 it was way out spec but in light of 3.910 ....this changes things a lot.
I was measuring just under the ridge on the worst cylinder.
now this changes things because at 3.906 it was way out spec but in light of 3.910 ....this changes things a lot.
Dan the man
Well-Known Member
3.912 doesn't require boring. That's only 0.002. A good quality honing should take care of it.
Dan the man
Well-Known Member
I took the time to check out cylinder taper for a cylinder needs to be bored and I found that it's 0.005". Some say that you can get away with 0.007 - 0.008. I've re rung many a engine with a 0.006 taper and got great service from them.
3.912 is the factory spec for the maximum bore size. That's right out of the service manual above ^^^^^
It's totally dependent on what piston you're using. Factory cast style pistons require much tighter tolerances than a forged piston in comparison, so if she's using a factory cast piston, the "go no go" tolerance for bore should be adhered to by what's written in the factory service manual. If she was running a forged piston, they require a good bit more clearance, since they have a greater rate of expansion. I believe she is going to either use the original cast pistons or a factory replacement type cast piston, so she needs to pay attention to what the factory service manual says.
The pictures of your cylinders, are they before and after honing? If you did run a hone through them, was it a stone hone or a dingle ball hone?
Dan the man
Well-Known Member
Do you think that if it's a standard rebuild that 3.912" would be acceptable? I mean with using new cast pistons
After starting hone but didn't finish... stone hone
Dan the man
Well-Known Member
Thanks for the information.
Dan the man
Well-Known Member
What over bore do you think would clean up the bore?
Dan the man
Well-Known Member
I don't mean to highjack the op thread, but is it a good idea to have a block bored and honed with torque plate's? I'm asking because a machine shop not to far from me doesn't use torque plate's for either honing and boring
.020 would likely do it.
A lot of people insist on torque plates on any level build they do. I think it boils down to personal preference and build type.
Dan the man
Well-Known Member
That's good to hear.
Dan the man
Well-Known Member
Thanks RustyRatRod for answering my questions.
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