Don Terrill’s Speed-Talk

Had my 351w aligned honed and came back from shop with 2 out about .0002 loose and others in on Big side of tolerance. Its too late now but my mechanic friend and mentor who i worked for as a teenager and who I trusted. Who usually is on top of things related to machine work decided it would be better off sanding caps down a half thousands as measured with bore gauge and not have perfectly round but would have more crush instead. Since we had plenty of oil clearance and it would be a performance build his reasoning. Two things Made me agree to it was the fact it had 3 inch mains that will see 7,000 RPMs regularly and feel it needs more crush and that I used Kings bearings with the extra thick layer of SI alloy so it won't be into copper if it wears in correctly He used a piece of fine wet sandpaper on a machined flat surface and carefully flat sanded them. Heard stuff like this is done but usually honed afterwards lol. Think After careful break in and street miles I will be good?

do I think it will be ok?
don't think man, check it.
Check the crush

How do you measure an error of 0.0002 inch?

I know I can't.
Maybe with a high tech laser tool?

A change in temperature of a few degrees will make an error like that.
But still..........how do you measure it?

You should be ok, but I would pin the upper Bearing just to be on the safe side.

joe 90 wrote: ↑Sun Apr 08, 2018 5:24 am How do you measure an error of 0.0002 inch?

I know I can't.
Maybe with a high tech laser tool?

A change in temperature of a few degrees will make an error like that.
But still..........how do you measure it?

With a dual bore gauge!

What do I win?!?

Warp Speed wrote: ↑Sun Apr 08, 2018 6:56 am

joe 90 wrote: ↑Sun Apr 08, 2018 5:24 am How do you measure an error of 0.0002 inch?

I know I can't.
Maybe with a high tech laser tool?

A change in temperature of a few degrees will make an error like that.
But still..........how do you measure it?

With a dual bore gauge!

What do I win?!?

A 2 point dual bore gage for that. Them bores look perfect

Well if you are worried, bring it back to the shop. DO NOT SAND THE CAPS. You paid for work, and if it is unacceptable let the shop deal with it. If a customer never told me tight or loose. I'd hone it to the middle. But then again if it is ,0002" too big. Why bother, if your clearances are loose, that's why they make different size bearings. I don't set engine clearances with housing bore size.

Then again call the bearing company and ask, after all they designed the bearing.

One thing to rember is that if u decrease the the vertical bore diameter by .0005 the bore diameter
at the parting line has changed very little. Maybe in the order of 6/7 decimal places.
The point is the housing bore has not gone out of round very much probably less than .0001.
John

jed wrote: ↑Sun Apr 08, 2018 11:56 am One thing to rember is that if u decrease the the vertical bore diameter by .0005 the bore diameter
at the parting line has changed very little. Maybe in the order of 6/7 decimal places.
The point is the housing bore has not gone out of round very much probably less than .0001.
John

I wouldn't suggest that to anyone inexperienced. Id rather have a round hole, vs one that looks like a figure 8. Maybe he should just remeasure it. Recalibrate the db gage and measure again before doing anything.

would check measurements with another bearing, I have gotten rod bearings that when you snapped them in place you could turn the cap upside down and they would fall out. Never had to measure anything to tell they were made wrong.

Your machinist let you have your block like it was because he knows that it would of worked fine, measure how much crush (bearing sticking above the block and above the cap) you have on each set of bearings and put the tightest (most sticking above the block and cap) ones in those holes. Your machinist most of rolled his eyes when you brought this "problem" to him.

Headguy wrote: ↑Sun Apr 08, 2018 12:14 pm
I wouldn't suggest that to anyone inexperienced. Id rather have a round hole, vs one that looks like a figure 8. Maybe he should just remeasure it. Recalibrate the db gage and measure again before doing anything.

Actual bearing surface is just that figure 8, and milling caps a little bit increases that eccentricity a little bit. Probably works just fine - on the other way if shells are left loose it decreases that eccentricity - totally round bearing surface won't work.

I trust clevite when it comes to crush and thickness because I never found a single one that was off, but I can't say the same for other bearing companies.

modok wrote: ↑Sun Apr 08, 2018 2:55 am do I think it will be ok?
don't think man, check it.
Check the crush

I said it was checked with bore gauge and used a Sterrit mic to set it. He said when I picked it up that a couple was out .0002 and we confirmed it and bearing clearance to crank and it was 3.5 on a 3 inch main. Kings had a whole point more built into them then clevite. We hold mic in a towel in vise and everything at room temp as his garage is heated 24--7. I didn't like the bearings bores being bigger then specs or out .0002 with a 1 thousands window on bore/crush limit and being a little bigger then 003 I wanted on them oil clearance wise. Crank turn very freely. Just wanted thoughts. He should of called and said it needed aligned bored , not sure why, took a long time to get back first time, guys old enough to retire. Usually does excellent work.

If you buy a new set of of $500 rods, what is the tolerance on the big end bore?