EarlyC34me

So at what point does it affect timing chain slack? Camshaft timing? My block was bored and crankshaft polished he recommended the main caps shaved and fresh align bore back to spec shape and size. There was only one cap/main that was out but i was curious how much material does it take before this matters. I ask because this was a thread topic not long ago and there was debate about chain stretch or geometry? At what point should i be concerned?

Vortecpro

The timing chain play is effected when the caps are cut to much. If the person doing the line hone is savvy theres not going to be a problem. If the person doing the line hone is a savage theres going to be a problem, and not just with the timing chain. Typically I cut the caps in the following:

Cap 1 .003
Cap 2 .004
Cap 3 .004
Cap 4 .004
Cap 5 .003 Oil pump torqued

Cutting double that much above could result in timing slack.

2airtime2

I think I commented in that other thread. For timing chain tension to change, the position of the crank has to change. Why would anyone "align" hone out of original factory alignment? Whoever is doing the "align" honing, should maintain the center point of the crank. When material is removed, larger bearings should take up that space and position the centerpoint of the crank right back where it was from the factory. I don't understand at all why the crank has to change position in relation to the cam or anything else just because it's bore is straightened.

EarlyC34me

I am just attempting to better understand why, and how these things are done and what impacts someting may have going forward. It is entirely possible i am using improper terminology. This is my second engine build with the last being 1992 so i forgot most of what i may have learned on that one. Based on what I have been told this is a very minor amount of material and will not have any impact to be of any concern. My machine shop is a race engine builder so i am trusting his professional opinion and experience. Based on my own personal experience I have learned verify, verify, verify and things dont always go as planned. I am very greatful for the collective knowledge here on the forum

derekderek

I have never heard of bearings with a larger outside diameter to compensate for machining the block.

resdoggie

When I blew my engine years ago it was the result of oil starvation in the lower end - a couple main/rod bearings melted and two of the main caps were over heated. The machinist during the rebuild recommended an align hone, not an align bore, was needed. The align bore being considerably more expensive. Anyway, the crank journals were turned down 0.020" and oversize bearings installed. This was over 20 yrs ago and 35K miles later and the lower end of the L-82 is still holding up. No effect on the timing chain or timing.

EarlyC34me

So my crankshaft is good rod journals std. post polish the mains are .001 under so we are using over sized bearings there. He said on the block though #1 main .001 out, #2 is .001 out #3 .0022 out ect. The align hone will take this back to stock size and shape of the main journals.

I am just trying to not cut any corners because these parts are very hard to find in original condition. I am not doing this twice.

So my understanding is if the caps are shaved .01 (I dont know what he is doing just hypothetically speaking) then the crank moves .005 closer to the cam and introduces slack in the chain. This would also by a smaller margin reduce top end clearance? .0025ish?

JoeMinnesota

Align honing does not require machining the caps. It is a HONE, to get everything straight and to the appropriate size. Align boring involves cutting the caps first (to undersize the mains) and then bore back to the correct main size for straightness and uniformity.

As pointed out already, honing is common, boring less-so and more expensive.

"Undersize" (actually, oversized/thicker) bearings are to tighten clearances. Standard .010 or .020 under bearings are to accommodate crank undersize (NOT oversized mains - the O.D. of the bearings should be standard). Cranks are commonly ground at 10 or 20 under to clean up. In my case I used 0.001" undersize bearings on a standard crank to tighten my oil clearances after crank polishing and align honing.

There would need to be a major amount of change in the crank centerline to cause excess slack in a timing chain. I would question whether that's even a possible cause with the small dimensions we're talking about. A change of 0.020" is only 0.010" on a side. There is slack designed in the chain set to begin with, so how much slack do you have? Have you tried a different timing set? Maybe it's the tolerances in whatever set you're using.

PAmotorman

if you do not cut the caps to make the main bearing bore oval shaped honing will cause the maim saddles to be too large in diameter and you will lose the bearing crush which holds the bearing in place.

JoeMinnesota

Noted. So with honing a little bit comes off of the caps. My point was that boring is a more involved/severe process than honing.

One thing I have also read, but not experienced personally, is that there are variations in crank-to-cam centerline evident in blocks from the factory - sometimes severe.

Your machine shop should be able to provide you an accurate cam-crank centerline measurement to decide if that's your issue.

Sounds like you don't have an issue, though, and simply asking whether align honing should be a concern? NO. Lots of us have that done as a regular part of the rebuild.

PAmotorman

there are timing gear sets made for line bored blocks to take up the center to center distance change

Vortecpro

All I can say is wow........

jim2527

Come on...spill it!!!

EarlyC34me

Ok.

Pop Chevy

I have to have my blocks line BORED when I convert 2 bolt blocks (454) to 4 bolt , then they finish up with a line HONE. Like a cylinder overbored. No you should not need a diff timing chain, I haven't.

CanadaGrant

This just boggles my mind. How do you get or buy a timing chain that is a few thousand's shorter, or even why? It isn't like piston rings or bearings. Pop Chevy is correct.
This is crazy for any engine without an idler and isn't needed there either. I would be more concerned about my chain stretching a quarter inch or more from wear than a couple of thou on a line bore/hone.

derekderek

Back to OP's engine. Your crank is good? Came out of this block and does not need machined? Then the main bores don't need machined either. It is really only necessary when a main bearing dies and damages the hole it sits in.

PAmotorman

http://www.jegs.com/i/Cloyes/220/9-3...xoCGTcQAvD_BwE

Vortecpro

Not exactly. Lets take a big block Chevy for instance, there is a housing bore spec for the mains, 2.937-2.938 many times the factory will go bigger than this spec, it is made up for with a over size outside diameter bearing not available to the public. When the housing bore goes outside this spec above its line hone time...if you want proper bearing crush and clearance.



The line hone/bore timing chain: The chain is not shorter, the upper gear is bigger, they come in .005 and .010 tighter and are used when the line bore/hone operator does not know how to perform this operation, or there was severe damage to the housing bore. I can get into exactly how a line hone is done if any ones interested.

derekderek

So how do they work? .005 smaller diameter sprockets with a tiny bit shorter chain pitch?