Line honing crank journals

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harrisonm

harrisonm

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If I understand the line honing process, the cap's surface gets ground down a bit and then they are bolted and torqued to the block and honed to the correct diameter. Here is my question. If a few thousandths is honed from both the cap and the block surface, wouldn't that bring the center of the crank a few thousandths closer to the cam? And could that cause the timing chain to get a little loose? Or is it too little to worry about?
 
yes , it causes crank to cam centers to be closer. cloyes makes chain sets to take up the slack. align bore is way better, block is cut about a .001 rest comes out of cap. align hone takes equal amount from both . besides you can/t bore with a stone !!!
 
No. Not at all. Not if it's done correctly. The proper procedure is to measure first. Then, remove a small amount of material from the main cap mounting surfaces.

Once that is done, the align hone or boring bar is positioned so that it removes most of the material from the main cap half of the bore, while barely skimming the block itself.

Doing it in this way affects the crank to cam relationship either very small or none at all.
 
RustyRatRod said:
No. Not at all. Not if it's done correctly. The proper procedure is to measure first. Then, remove a small amount of material from the main cap mounting surfaces.

Once that is done, the align hone or boring bar is positioned so that it removes most of the material from the main cap half of the bore, while barely skimming the block itself.

Doing it in this way affects the crank to cam relationship either very small or none at all.
Click to expand...

Not true. There is no way to make honing stones take material off one side only. They take an equal amount off the block and the caps. If you line bore it, yes you can bias it toward the cap.
 
lilcuda said:
Not true. There is no way to make honing stones take material off one side only. They take an equal amount off the block and the caps. If you line bore it, yes you can bias it toward the cap.
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I am fully aware they take an equal amount off. The bar is round. I simply said to bias it toward the main caps more, which you certainly can do. I have aligned probably over 150 blocks when I was working in the machine shop. I have hands on experience with it.
 
good chains come in undersizes for line honed blocks. Run a STD chain and an MP tensioner, case closed. Your going to have maybe a degree difference at the cam as the links dont get smaller, but the distance does, by thousandths.
 
A proper align hone job takes so little out its not even worth thinking about. The distance between the crank and cam centerlines will be reduced by a couple thou at the most. The factory machining isn't even consistent any way. When I built my left over parts 360 a few years ago it got a heavy line hone job. In spite of this the timing chain went on as tight as a piano wire. This chain had been used in my 340 for 6 years. When new it went in the 340 it was very loose about 15 degrees of slop, had to use the T chain tensioner. That motor had never been align honed.

As has been mentioned one can buy shorter chains for the cam to crank centerline issues, wish I had known that when I built the 340.
 
They mill a bit off the mains and caps, then there is enough meat in the mains and caps to re-machine a new crank bore in the original position if you have a good machinist.
 
skrews said:
A proper align hone job takes so little out its not even worth thinking about. The distance between the crank and cam centerlines will be reduced by a couple thou at the most. The factory machining isn't even consistent any way.
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x2^^

I have every engine I build align honed. I know the shorter chains exist but I've never had an issue with a sloppy chain. The hone process does not remove much material. Think of it like the final steps of a cylinder hone - you're removing less than a thou of bore size. It's more to flatten the surface and leave the right finish for the bearing to seat against.
 
How's a tensioner going to "fix" a possible timing issue? If the distance between the two gears is too close with a standard chain, the chain is too long. I don't care if the chain is pulled taut by the tensioner or by natural forces, the chain is still too long which throws the timing off a little. Obviously a shorter chain is the only real answer, or you can start playing around with the gearsets that have offset keys/keyways.
 
harrisonm said:
If I understand the line honing process, the cap's surface gets ground down a bit and then they are bolted and torqued to the block and honed to the correct diameter. Here is my question. If a few thousandths is honed from both the cap and the block surface, wouldn't that bring the center of the crank a few thousandths closer to the cam? And could that cause the timing chain to get a little loose? Or is it too little to worry about?
Click to expand...

I can appreciate the post, & attention to detail...
However, & forgive the crude pic, just something scribbled up from My old memory...

View attachment 1714847992

Non issue! really! With RESPECTS !!!
There are chain/gear mfgrs around that can supply .002, .005, .006. .007, .008 lengths
Moreover the same mfgrs can provide gear combos with modified 'pitch' gears... same roller size on the 'true roller' chain...

Apologies Honored Posters, Thx for the grace. I suck as an artist :D
 
Thanks for all the great posts. I was wondering about this issue, and now I know a lot about it. This is the BEST forum ever.
 
Math is not my strongest suit but.. Using the drawing & estimating lengths to indicate the trend...
A = distance from crank CL to cam CL: 7.000"
B = distance from cam CL to chain CL (call it the radius of the cam gear): 2.750"

A^2 + B^2 = C^2
49.00 + 7.5625 = 56.5625
Take square root = 7.5208

Change A to 6.998:
48.972 + 7.5625 = 56.5345
Take square root = 7.5189 Difference of .00185. And that's if they screw up and the crank CL moves .002". Short chains are really intended for reusing damaged blocks where one or more of the main bores needs to be repaired due to damage (bearing spun in saddle, etc). That can really move the centerline.
 
It never seemed like much to worry about. I know I never even thought about this when rebuilding engines. But if you degree-in your cam like you are always supposed to, if it's wrong you'll fix it anyways, I believe.
 
69_340_GTS said:
How's a tensioner going to "fix" a possible timing issue? If the distance between the two gears is too close with a standard chain, the chain is too long. I don't care if the chain is pulled taut by the tensioner or by natural forces, the chain is still too long which throws the timing off a little. Obviously a shorter chain is the only real answer, or you can start playing around with the gearsets that have offset keys/keyways.
Click to expand...
A chain tensioner stabilizes the cam timing at what ever value it ends up at with the tension side of the chain pulled taut. Any corrections to timing are made with offset keys, etc. A tensioner would be worthwhile IMO if you moved the crank CL a lot, just to help keep timing from jumping around, and keeps the tension on the chain smooth and even. (But I don't know how much tension the aftermarket SBM ones provide, and thus how well they can stabilize cam timing.)

As far as the math..... if the crank CL moves up .010" into the block, then the cam timing is retarded by about 0.21 degrees with the SBM cam sprocket sized as it is..... yeah, pretty much a non-issue! (If you are curious, it can be easily approximated as the acrtangent of [the CL move divided by the cam sprocket radius].)
 
The tensioner just stops the undriven (slack) side of the chain flopping around and creating noise and oscillations. It has zero to do with keeping cam timing events aligned.
 
I think that should be clarified. It's not that it has nothing to do with it, it does have an effect. The tensioner affects the cam timing by reducing the possibility of slack being introduced into the drive side as the chain wears - it reduces cam timing variance over the service life.
 
moper said:
Math is not my strongest suit but.. Using the drawing & estimating lengths to indicate the trend...
A = distance from crank CL to cam CL: 7.000"
B = distance from cam CL to chain CL (call it the radius of the cam gear): 2.750"

A^2 + B^2 = C^2
49.00 + 7.5625 = 56.5625
Take square root = 7.5208

Change A to 6.998:
48.972 + 7.5625 = 56.5345
Take square root = 7.5189 Difference of .00185. And that's if they screw up and the crank CL moves .002". Short chains are really intended for reusing damaged blocks where one or more of the main bores needs to be repaired due to damage (bearing spun in saddle, etc). That can really move the centerline.
Click to expand...

Yep, 7.000" CCL/CMCL OR SO lmao stock "A" block tolerances float around like a bb in a coffee can.
With the ? factory ? constant of the production 2.750" radius cam gear pitch & same for the crank gear...

Point is 'bearing' speed of the chain v/s torsional wind up of the cam is inconsequential
on a street build.
Maybe + or - 3/4 deg timing change at 3k rpm (total 1.5 deg).

Now on a 'balls out artificial atmosphere build' 1.5 deg is to much...

Crap, I am rambling again, Apologies Honored Posters, Back on topic :D

harrisonm
Great Topic, thx added, to reiterate, yes the center lines will move,
on a stock build not an issue... ahahahahaha, there was this 'ol' limerick... < 2(.002) no harm on You,
3-5 (.003-.005) no worries live, 5-7 (.005-.007) running for heaven, over 7 (.007) Find a Machinist,
not a Priest...
I'm out Folks My 'little grey cells' hurt

P.s,
Always A Pleasure Honored Posters, I consider Myself ---way down on the food chain---
compared to Ya'll.
 
moper said:
I think that should be clarified. It's not that it has nothing to do with it, it does have an effect. The tensioner affects the cam timing by reducing the possibility of slack being introduced into the drive side as the chain wears - it reduces cam timing variance over the service life.
Click to expand...
Sorry your incorrect. It's the resistance of the cam and valve train, that keep any slack being introduced into the drive side of the cam chain, in a SBC V8. If the cam was to keep more momentum than the crank at deceleration( try to spin faster than the crank) and effect cam timing then it would be a mute point because your not under power. Also who's to say that the spring in the tensioner would be able to resist that force anyway.....
 
moper said:
I think that should be clarified. It's not that it has nothing to do with it, it does have an effect. The tensioner affects the cam timing by reducing the possibility of slack being introduced into the drive side as the chain wears - it reduces cam timing variance over the service life.
Click to expand...
Not making sense..... the tensioner only takes up slack on the slack side of the chain. Wear/stretch will occur all along the chain, and will show up in the drive side and allow cam timing to slowly retard as the chain wears/stretches. If you mean variance as it runs, then agreed. The cam load varies a lot as it rotates, and the chain will whip around quite a bit when it gets an slack in it. But the aftermarket tensioners for the SBM are pretty wussy IMO; engines that have more serious tensioners have oil pressure activated tensioners that apply more tension as the oil pressure and RPM's rise..
 
I look at tensioners as sort of an anti wear device. Think about it, if the slack side is constantly hammering against the gears isn't it going to wear faster?

I know there will always be wear, but I think that little device would subdue it some.
 
Bad Sport said:
I look at tensioners as sort of an anti wear device. Think about it, if the slack side is constantly hammering against the gears isn't it going to wear faster?

I know there will always be wear, but I think that little device would subdue it some.
Click to expand...
Maybe 'slack dampener' would be a better name...
 
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