what constitutes line hone vs line bore?

[Blazer406]

OK guys.... spun my #3 main bearing.... trying to decide if the block is worth machining.... dial indicator (I know you really need a dial bore gauge... but this is all I have for rough measuring) shows about 2.689 on # 1 and #2.... but #3 is about 2.695 or 96.... looks like it is about 6-7 thousandths oversize from the bearing spinning....

I am assuming you could line bore.... which I also assume would require a small amount machined off the pads where the cap sits... and a small amount machined off the bottom of the cap.... then re bore to the proper size... If my #3 is .007 oversize.... I take say .007 off the block... and .007 off the caps.... it would effectively move CL of the crank .007 toward the cam.....

It would seem the tensioner would have no problem taking the .014 of extra slack up (.007 per side of the chain)....

I'm just thinking out loud..... Need input if this is logical......


As far as the thread title.............how much meat does one typically hone off? .0005? At what point do you do a bore (obviously the boring tool is different than the honing tool).....???

 

[BadAssGN]

Line boring is common when installing Billet centre mains, the problem like you already stated, once you cut into the register you will need a shorted Timing chain,

every block is different, if i measured any in the past I don't remember gow much,

I know there are shorter timing chains sold to accomodate this procedure.

 

[Blazer406]

OK guys.... spun my #3 main bearing.... trying to decide if the block is worth machining.... dial indicator ........

Sorry guys... it was late... I had a brain fart.... I meant dial calipers..... I do have a dial indicator.... but it is obviously not for measuring a diameter....

 

[Nick Micale]

There is no short cut to fixing your block. A line bore may, or may not, fix your problem. You do not machine one cap to fix this problem, if the cap can even be re-used? From the sounds of the damage, the cap register may be off enough to trash it. In that case you would need a new cap or both the 2 center caps.

To do a proper line bore, the set up and machining takes about half a day, it is not simple or easy.

As far as the tensioner taking up the slack, this is NOT the proper way to do this. You need to use the proper undersize timing set to maintain proper cam timing.

 

[noslo6]

There is no short cut to fixing your block. A line bore may, or may not, fix your problem. You do not machine one cap to fix this problem, if the cap can even be re-used? From the sounds of the damage, the cap register may be off enough to trash it. In that case you would need a new cap or both the 2 center caps.

To do a proper line bore, the set up and machining takes about half a day, it is not simple or easy.

As far as the tensioner taking up the slack, this is NOT the proper way to do this. You need to use the proper undersize timing set to maintain proper cam timing.

How does moving the bottom sprocket a few thousandths change the ratio? You may be right that the proper way to do it is to use an undersized timing set, but I don't see the cam timing changing. The factory gears wear, the timing chain wears and the tensioner takes up the slack. It was designed to take up the slack in the chain. The sprockets follow the ratio set in the gear cuts & chain links... it doesn't matter if they are 1 inch apart or 1 foot apart.

 

[VadersV6]

A good shop can do a line hone in a couple hours, not a day. Also, by far, the majority of metal removed is from the caps, not the block. The cap gets ground square on both sides, and then the mating surface gets ground down. The caps are torqued down and then you start line honing. You stop every several passes and check each bore with a dial indicator. More metal will be removed from some vs. others. Those caps get loosened so no more metal is removed. make a few more passes until all the caps are the same number. then you re-tighten those caps and make some more passes. Check the bore diameters again. then loosen the caps that are bigger than the others. Because the mating surfaces were ground, the bores arent round, so you also have to keep an eye on that while you're doing it...its a gradual process. It doesnt take a long time, but it does take someone with skill and experience. I could line hone with the best of them, and get REALLY accurate numbers, but I have seen some done by shops who didnt know what they were doing. Bores out of round, some tight, some loose, loose main caps, etc. Make sure all the caps seat tightly in the block when you get it back from the shop. You dont want any that barely drop right in. They need to be tight enough that it takes a rubber mallet to seat them on the block.
A line bore is done when you're dealing with a virgin block and for whatever reason, you may want to open the main bore diameter, and also when you buy steel caps, the radius of curvature is alot smaller than the others. So you have to mount all the caps, with the stock ones on the ends and the steel ones in the center. You find the centerline of the bore with the stock caps, and use that to locate the boring jig. Then you bore out the steel caps until the radius ends up about .005" smaller than the stock caps on the ends. Then you grind the stock caps down to get them roughly the same as the others.
When you're all done, the witness marks from the line hone will show that the leading edge of the bores in the block, are not even touched...just the extreme edge is showing no grinding marks. This shows that the centerline of the crank hasnt moved much, if at all. if the machinist knows what he's doing, there is nothing to worry about. That centerline is pretty much still where it was before.

 

[Nick Micale]

I do not want to start a "spitting contest" with anyone here as I am just trying to help by answering the original post.

Here is my opinion on your problem. When you have spun a main bearing, this is serious, and both the crank and block are suspect and need to be closely checked before even considering using them again.

If you line bore, you will move the crank centerline. We always use a undersize timing chain set when this is done.

The tensioner may take up slack in the chain, which we do not use with a quality roller set, but being loose, it will still put your cam timing off.

Again, I do not want to debate this, but I just replaced a chain set so worn out, the car would no longer run. The tensioner was in place, but the cam was WAY out of time.

The tensioner does take out slack, but does not keep the cam in the proper position.

 

[Blazer406]

I do not want to start a "spitting contest" with anyone here as I am just trying to help by answering the original post.

Here is my opinion on your problem. When you have spun a main bearing, this is serious, and both the crank and block are suspect and need to be closely checked before even considering using them again.

If you line bore, you will move the crank centerline. We always use a undersize timing chain set when this is done.

The tensioner may take up slack in the chain, which we do not use with a quality roller set, but being loose, it will still put your cam timing off.

Again, I do not want to debate this, but I just replaced a chain set so worn out, the car would no longer run. The tensioner was in place, but the cam was WAY out of time.

The tensioner does take out slack, but does not keep the cam in the proper position.

Point taken....Thanks Nick for weighing in..... I am somewhat confused... if you only take off like .007...... that you will even see much difference in what the stock chain would look like.... maybe I am thinking about this all wrong....

In the end... I will trust my machinist to tell me if it is too bad... or... no problem.........

 

[Blazer406]

I guess I should also say.... I am not considering at this point using the crank.... haven't even put calipers to it to see if it even looks like it might go 10/10 .... I do have 2 other rolled fillet cranks.... one I am almost positive it will go back std/std .... the other will need to go 10/10 ... I don't think it will polish....

 

[VadersV6]

If the main journal on the block is really damaged, throw the block away and start over. You can line hone it, and if there are still some scratches left on the journal, its ok as long as they arent too big. The bearing will sit in there...its not like the crank is riding on the block.
Also, if you're worried about cam timing being retarded, you can always get a cam that has some advance already ground into the design, like most comp cams are.

 

[noslo6]

The tensioner may take up slack in the chain, which we do not use with a quality roller set, but being loose, it will still put your cam timing off.

Again, I do not want to debate this, but I just replaced a chain set so worn out, the car would no longer run. The tensioner was in place, but the cam was WAY out of time.

The tensioner does take out slack, but does not keep the cam in the proper position.

I do want to debate this: moving sprocket centerline longer or shorter will not change the ratio of the gears turning. Explain how this is possible. The wear of the chain links, rollers and sprockets can change the timing, but a new chain & sprockets, even if moved slightly on a shorter centerline, will follow the exact same timing and ratio of the designed chain/sprocket profile... and the tensioner keeps it tight. This is not a pissing contest, I just simply disagree with you. This does not need to turn into anything other than a simple debate.

 

[VadersV6]

If the crank centerline is brought up further toward the top of the engine, cam timing WILL be retarded. Imagine the timing chain installed. Feel the chain. its nice and tight. Rotate the crank a little. The cam immediately starts turning along with it. Start over, and now move the crank centerline up a tad. The timing chain is loose. Start rotating the crank. The cam isnt moving yet..the crank has to move a little more before the cam starts turning. The cam will always be a little behind, no matter what you do...add a tensioner..it doesnt matter. What I was saying in the earlier thread, is that a line hone job will move the crank centerline in tenths of a thousandth...not thousandths. Its negligible.

 

[noslo6]

All things being equal you are correct, but we're not talking about the chain being loose. The tensioner takes up the slack in the chain. The chain has designed length links as does the sprockets. When the tension is maintained on the chain, the chain turns the sprockets the designed ratio and speed regardless of how long the chain is. That's the way I see it and have designed chain driven swing arm ATV's. I'll just agree to disagree...:biggrin:

 

[VadersV6]

All things being equal you are correct, but we're not talking about the chain being loose. The tensioner takes up the slack in the chain. The chain has designed length links as does the sprockets. When the tension is maintained on the chain, the chain turns the sprockets the designed ratio and speed regardless of how long the chain is. That's the way I see it and have designed chain driven swing arm ATV's. I'll just agree to disagree...:biggrin:

Yeah I know the ratio remains unchanged...how could it be?...same number of teeth and links regardless. The speed and ratio will never change. But Im talking about the intake and exhaust events occuring a couple degrees later than before. But my point is, that the crank centerline isnt really going to move anyway, with a line hone. The ratio has nothing whatsoever to do with the advance or retardation of the timing events. Thats what offset crank woodruff keys are for. Making a chain and sprocket setup for ATv's isnt even comparable. Start trying to time the rotational position of the rear sprocket with the crank sprocket within a degree and you'll see what Im talking about. But you would never ever ever have a reason to do that on an ATV. Yes, I know that the tensioner will return the cam sprocket back forward in timing, but it will be different, dynamically, than it would be had the crank centerline never moved. The tensioner will not always maintain a constant and reliable level of tension on the chain as the engine revs up. It will bounce. The cam timing will be altered throughout the rpm range. It wont be a static change, is basically what Im saying. But the crank centerline would have to move alot for any of this to be a reality. And once again, a line hone isnt going to move the centerline, unless you really botch the job up. The goal is to have the chain as tight as possible from the get go, and use a quality chain that wont stretch much, so you dont need a tensioner.

 

[Razor]

If it spun mains or cam bearings, get another block from the boneyard.

Not worth the trouble. Unless the block you have has had lots of custom machining and the costs associated and risks outweigh one another.

Example its been bored, decked, bushed, filled, ground, etc.. lots of money tied up.

A run of the mill 109.. go get another one.

 

[turbodave231]

My advice, take the block to a good machinist and ask his opinion. If the #3 main saddle is really scored up, you might be better off trashing the block. If the damage is minimal, and the cap registers are ok, magnaflux the mains for hidden damage.

If no major damage exists, it is no big deal. Lots of guys are replacing #2 and #3 caps and installing girdles. There is no more work involved in line boring your damaged cap(s) than installing billet caps.

BTW a good machine shop with a CNC machine center (Rottler or RMC) can set up and perform a line bore/hone in one operation. No honing required.....and it doesn't take all day (sorry Nick).

Shortening the center to center distance between the crank will have a small affect on cam timing if it is not adjusted for by the indexing of the cam and crank sprockets. Any competent engine builder will compensate for this when he degrees the cam.

 

[Nick Micale]

....BTW a good machine shop with a CNC machine center (Rottler or RMC) can set up and perform a line bore/hone in one operation. No honing required.....and it doesn't take all day (sorry Nick)...............

You should be sorry for mis-quoting me, I said "about half a day"!:biggrin:

 

[noslo6]

But Im talking about the intake and exhaust events occuring a couple degrees later than before.

The chain would have to be pretty loose to disrupt a "couple of degrees" of timing. The chain stays "relatively" tight with the tensioner and the forward drive of the crankshaft sprocket putting tension on the trailing side of the chain... miscut line bore on the extreme of .025" would not change a thing (using a tensioner). The keyword here being "tensioner". You are describing a chain that is so loose it's bouncing around nearly falling off. That being the case, I agree with you 100%.

 

[VadersV6]

The chain would have to be pretty loose to disrupt a "couple of degrees" of timing. The chain stays "relatively" tight with the tensioner and the forward drive of the crankshaft sprocket putting tension on the trailing side of the chain... miscut line bore on the extreme of .025" would not change a thing (using a tensioner). The keyword here being "tensioner". You are describing a chain that is so loose it's bouncing around nearly falling off. That being the case, I agree with you 100%.

Have you ever degreed a cam? Having the crank bore misaligned .025" would **** everything up, not just cam timing. Like the thrust bearing not sitting right, and the piston depths being all over the damn place. But like I keep saying ad nauseum is that a line hone wont change a thing even if Ray Charles was doing it. I also said it would have to be "pretty far off" for anything weird to happen.

 

[noslo6]

Ok, strictly talking about cam timing, never said anything about piston travel outside the block etc. (yes that is likely with a hugely miscut line bore closer to the cam bore)... Hone is cool, nothing changes. I'm speaking in hypotheticals here, leaving all other variable out such as those you stated. I'm done, you can argue til you're blue in the face, I was simply talking about cam timing and that alone. A small miscut on the line bore will not change a thing including cam timing with the use of a chain tensioner... If you would rather use a shorter chain than a tensioner I'm sure that is probably a better fix anyway. It's all cool Vader, this is friendly... no need to get nauseated