[PontiacLars]

Machine shop aligne honed and installed splayed 4 bolt mains. I see they made the bores on the upper limit, around 3.1890.
Cap number 4 is outside toleranse at 3.1894.

I get these main clerances now with std 113M bearings:

1 .0043
2 .0047
3 .0035
4 .0051
5 .0035

What to do now?
I can only find 0.0010 bearings. With 0.0020 and 0.0030 also I could fix this.
Dont want to grind my brand new, perfect, Molnar crank if I dont have to.

[PAUL K]

Ask your shop first.... If the housings are over spec you will loose needed bearing crush. Being at the big end of spec usually won't make the clearance that large. Is your crank small?

[steve25]

Bring it back to that shop and while you are have them check it and then compare with your results.

If they are at fault have them buy you a set of .010” bearings , set them in place and then see how the clearances look.

If they look like they will work then have the shop pay for cutting your crank.

If there at fault then it’s this way or they find you another block and do all the needed machine work for free to get you back to where you where before the main cap work.

[Gary H]

Originally Posted by PontiacLars

Machine shop aligne honed and installed splayed 4 bolt mains. I see they made the bores on the upper limit, around 3.1890.
Cap number 4 is outside toleranse at 3.1894.

I get these main clerances now with std 113M bearings:

1 .0043
2 .0047
3 .0035
4 .0051
5 .0035

What to do now?
I can only find 0.0010 bearings. With 0.0020 and 0.0030 also I could fix this.
Dont want to grind my brand new, perfect, Molnar crank if I dont have to.

That's a BIG variance from main to main. If those numbers are accurate, I would take it back to the machine shop and see what's up. Just a FYI, Clevite bearings generally will measure thicker than Sealed Power by .0005 to .0007. Keep that in mind if you need to tighten the clearances up after getting you align home issue straightened out.

[PontiacLars]

I will remove bearings and messure bores myself to check actual diameter of the mains and compare to numbers given by machine shop.
Crank messures 2.9994. Same on all mains. Is this small?

What Are typical variation in clerance? Are the bearings perfectly identical from production?

[mgarblik]

Originally Posted by PontiacLars

I will remove bearings and messure bores myself to check actual diameter of the mains and compare to numbers given by machine shop.
Crank messures 2.9994. Same on all mains. Is this small?

What Are typical variation in clerance? Are the bearings perfectly identical from production?

The housing bores need to be verified for size and taper first. 3.1885-3.1887 would be ideal. Taper of .0002". Housing bore size should be +-.0002" through the 5 mains. These dimensions are not hard to achieve with a decent line hone mandrel and a skilled machinist. If the housing bores are not within these dimensions, have the caps re-cut and line honed again until they get it right. No bearing changes will correct the results you posted. Now, once the line hone and housing bores are correct, move to the crankshaft and see if it was ground and polished correctly. It needs to be within factory tolerance +- .0002" and consistent through the 5 mains. Lots of Chinese cranks need to be ground to be close enough to use. With a good crank and block, oil clearance will be within .0005" difference max. through the engine with 113M bearings. King bearings are a little better at around .0003" good luck with it.

[Gach]

When you had the block line honed did you bring them the crank, usually you bring them the crank and the bearings. Its a Chinese crank ! and you can’t trust them with out checking them. Usually they take .003 off the caps before line hone. Of cruse they can re-due the line bore but if the crank is off, it won’t solve your problem.

[Dragncar]

You can send bearings out to Cailico and have them coated. .0005 and .001 coatings are available but it will not take care of bearing crush issues or your variances.
My engine had .003 rod clearance and I brought it down to .0025 with coated bearings.

[Formulas]

Another aspect to ponder Iff they were lacking talent in the machinery department..... Along with bore size issues are they straight front to rear?

[mgarblik]

Virtually all line honing is done using a Sunnen mandrel, regardless of the machine. Kwik Way, Van Norman, and many other brands buy the Sunnen mandrel and adapt it to their machine. The secret is the guides and stones need to be in good shape, be kept adjusted, (tight), and be kept clean. If a crash occurs and 1 stone is damaged, all the stones and guides need to be replaced at once, (around $1000.00). So many shops don't do a good job keeping these up. Then you get weird, inconsistent sizes front to rear. Also during honing, the block needs to be flipped front to rear a few times to get best, round, no taper results. This all takes time. It's a skill operation. 3" Pontiac blocks are fairly easy. 3.25" are more difficult.

[chiphead]

The 4040m bearing come in a .001 thicker version. Had the same thing happen to me. I had them re do the line hone. I find that shops will set the home to the larger side. The excuse I got is it keeps the bearing clearance from being tight. I call bs.

[PontiacLars]

Looks to me like machine shop screwed up.
Bore 3 is 0.002755 out of round.
Overall the bores vary about 0.00157 in diameter.
What do you guys think?
If the block is already at or over Max tollerance, can this be fixed or is my block scrap now?

[Formulas]

Sad state of affairs, instinct says get your moneys worth take it back, thinking above that they already screwed it up once take it to a better shop so you can actually have a useable block later that doesn't need a 1 inch shorter timing chain when its done

[i82much]

Originally Posted by PAUL K

Is your crank small?

Just a tough question for a lot of guys to answer honestly on a public forum.

[Gach]

Originally Posted by PontiacLars

Looks to me like machine shop screwed up.
Bore 3 is 0.002755 out of round.
Overall the bores vary about 0.00157 in diameter.
What do you guys think?
If the block is already at or over Max tollerance, can this be fixed or is my block scrap now?

It’s a tough call, obviously their experience is not good. You have one or two options, have them correct it or take it to another more experience shop. It’s going to take one hell of an education on your part to make sure that it’s corrected right. Either way you’re definitely looking at a shorter time in chain how much, who knows they come .005 and I believe.010 shorter. But good luck on getting a good one with shortness you need. Went through that with a friend he ended up with 3 sets timing gear sets That could be whole another nightmare. You definitely have the capability of measuring correctly. Personally before you go any further, I would definitely take the time and check that Molar crank, check the Mains..Rods journals and check it for straightness. Just for peace of mind. Just don’t trust any Chinese Crank. I don’t care what anybody says how good the tolerances are. Personally I would look for another block that doesn’t need line bore and cut your losses. You may have already checked the crank out but would be kind of nice to let us know if you have.

[mgarblik]

OK, lets try to clarify a few things about your block. First, the block can be fixed absolutely, the sky is not falling. Second, about 80% of the housing bore needs to be round and to tolerance. As you measure, your looking for vertical oil clearance, straight up and down. Then as you rotate the gauge toward the parting line, the bore should stay round to about 1/4-3/8" on either side of the parting line. At that point, the housing bore will get big by as much as .001" or even .0015" That is normal and not a problem. This is so when under load and the caps are being stretched and pushed down, the sides will not be drawn inward, pinch the bearings and spin them. It is pretty clear the block needs to be re-line honed. No idea if this shop is the ideal place to have it re-done. Pontiac blocks are not especially difficult or special in any way to line hone. Any good race shop should be able to hit the numbers. The caps will need to be cut probably .005" and then hone away. Timing chain should not be an issue. Generally, if done properly, a Pontiac block can be line honed 3-4 times before a short chain is needed. Have it re-line-honed and if the chain seems loose, PM me and I can fix you up with a -.005" or a -.010" chain. You will need Cloyes brand sprockets for proper fit. You want that brand anyway because they are the best, not Chinese crap. Let us know where you are located and maybe members here can recommend a quality shop to get you fixed properly.

[Gach]

PM me and I can fix you up with a -.005" or a -.010" chain.

Thats nice your offering him that opportunity. If need be he won’t have to Chase the correct one down. Being it’ll be second time being line hone.

[hurryinhoosier62]

Originally Posted by PontiacLars

Looks to me like machine shop screwed up.
Bore 3 is 0.002755 out of round.
Overall the bores vary about 0.00157 in diameter.
What do you guys think?
If the block is already at or over Max tollerance, can this be fixed or is my block scrap now?

Find a new machine shop. No, your block isn’t scrap; it can be re-honed after the caps have been cut around .005-.007. Mike is correct; on a 3” main block I like to see the main saddle bores at 3.1880-3.1885. A COMPETENT engine machinist should be able to accomplish this relative simple operation without screwing it up,

[hurryinhoosier62]

Originally Posted by Gach

It’s a tough call, obviously their experience is not good. You have one or two options, have them correct it or take it to another more experience shop. It’s going to take one hell of an education on your part to make sure that it’s corrected right. Either way you’re definitely looking at a shorter time in chain how much, who knows they come .005 and I believe.010 shorter. But good luck on getting a good one with shortness you need. Went through that with a friend he ended up with 3 sets timing gear sets That could be whole another nightmare. You definitely have the capability of measuring correctly. Personally before you go any further, I would definitely take the time and check that Molar crank, check the Mains..Rods journals and check it for straightness. Just for peace of mind. Just don’t trust any Chinese Crank. I don’t care what anybody says how good the tolerances are. Personally I would look for another block that doesn’t need line bore and cut your losses. You may have already checked the crank out but would be kind of nice to let us know if you have.

Gach, if they are taking .005 to .010 out of the bottom of the saddle they need to have their heads examined. A proficient align hone operator shouldn’t be taking more the .002-.003 out of the saddle. Align boring a main saddle should take just enough material to ensure the saddle is “cleaned up” and it is concentric. With either operation, a maximum out of round of .0005 is what I look for.

[Gach]

In my initial post I said they take .003 off the cap. Mike was one I think said .005 off cap. I do agree that taking .003 off cap and then line honeing should have any effect on having to run a .005 shorter timing chain, but if it has to be done again ( line honed ) then the possibility of a shorter chain is definitely there.