Cylinder hone or bore oversize?

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ValiantOne

ValiantOne

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Working on a 360 magnum for my 68 val. I am hoping to do a hone job and use the original rotating assy. Someday I want to do a 408 stroker, but that is 3-5 years off...yadda, yadda...

I just measured the cylinder wear with a freshly calibrated dial bore gauge. (I am a machinist, jut not automotive) and this is what I got

Cylinder: max/min oversize from 4"
1) .002-.0015
2) .0015-.005
3) .0025-.001
4) .002-.0005
5) .0025-.001
6) .002-.0015
7) .002-.0005
8) .002-.001

So .0025 seems to be the most wear, and .0015 the worst out of round. I haven't looked in the manual to see what the max wear limit is, but what say you all?

Even if I am right up against the max wear I am tempted to hone it and run it because I only put a few thousand miles a year (if that) on the car, and am looking at going stroker in a few years.

Thoughts?

Thanks,

CE
 
ValiantOne said:
Working on a 360 magnum for my 68 val. I am hoping to do a hone job and use the original rotating assy. Someday I want to do a 408 stroker, but that is 3-5 years off...yadda, yadda...

I just measured the cylinder wear with a freshly calibrated dial bore gauge. (I am a machinist, jut not automotive) and this is what I got

Cylinder: max/min oversize from 4"
1) .002-.0015
2) .0015-.005
3) .0025-.001
4) .002-.0005
5) .0025-.001
6) .002-.0015
7) .002-.0005
8) .002-.001

So .0025 seems to be the most wear, and .0015 the worst out of round. I haven't looked in the manual to see what the max wear limit is, but what say you all?

Even if I am right up against the max wear I am tempted to hone it and run it because I only put a few thousand miles a year (if that) on the car, and am looking at going stroker in a few years.

Thoughts?

Thanks,

CE
Click to expand...
From experience, build it once and build it right. Bore it, stroke it and be done. Saves time and money in the long run
 
ValiantOne said:
Working on a 360 magnum for my 68 val. I am hoping to do a hone job and use the original rotating assy. Someday I want to do a 408 stroker, but that is 3-5 years off...yadda, yadda...
you're within limits for honing. for a casual street engine, it'll work just fine. hone out as little as you can, final finish, use a 400 grit, and moly top ring. it will seal fast and stay sealed. BTW, I'm a machinist, auto.
I just measured the cylinder wear with a freshly calibrated dial bore gauge. (I am a machinist, jut not automotive) and this is what I got

Cylinder: max/min oversize from 4"
1) .002-.0015
2) .0015-.005
3) .0025-.001
4) .002-.0005
5) .0025-.001
6) .002-.0015
7) .002-.0005
8) .002-.001

So .0025 seems to be the most wear, and .0015 the worst out of round. I haven't looked in the manual to see what the max wear limit is, but what say you all?

Even if I am right up against the max wear I am tempted to hone it and run it because I only put a few thousand miles a year (if that) on the car, and am looking at going stroker in a few years.

Thoughts?

Thanks,

CE
Click to expand...
 
hi, you're within limits for honing. hone as little out as you can. final stone, use 400 grit and use moly top ring, will seal fast and stay sealed, BTW, I'm auto machinist.
 
While I just always go for fresh bores and pistons anymore, the numbers don't look all that awful.

From your description, it sounds like you measured out-of-roundness only. Did you measure bore taper from top to bottom? Excess bore taper will flex rings constantly as they move up and down and tend to wear them out quickly. If this includes taper, then overall it doesn't look to bad to me. (You can get this much distortion in the cylinders just torquing down the head bolts or even bell housing bolts.)

Also, you need to measure the ring side clearance in the piston ring grooves before you have a full picture of the existing parts. Loose ring side clearance will allow ring twisting which will result in poor ring sealing.
 
Okay, just looked at a 2000 service manual. It gives a bore size of 4.000 to 4.002.

Max out of round .0005 max taper of .001

I didn't keep track of taper and out of round. I just did max and min measurements..... back out to measure again!
 
Those sound like NEW bore numbers, not 'service' numbers, which are the maximums that can be 'lived with'. (However, sometimes 'service' limits are too sloppy for good work; they are just for 'getting by'.)
 
nm9stheham said:
While I just always go for fresh bores and pistons anymore, the numbers don't look all that awful.

From your description, it sounds like you measured out-of-roundness only. Did you measure bore taper from top to bottom? Excess bore taper will flex rings constantly as they move up and down and tend to wear them out quickly. If this includes taper, then overall it doesn't look to bad to me. (You can get this much distortion in the cylinders just torquing down the head bolts or even bell housing bolts.)

Also, you need to measure the ring side clearance in the piston ring grooves before you have a full picture of the existing parts. Loose ring side clearance will allow ring twisting which will result in poor ring sealing.
Click to expand...

Okay, I will measure ring side clearance today too. I was going to go with new rings, but of course I'll have to measure with the old rings today. I am wondering if the engine crud is going to give me erroneous readings?
 
perfacar said:
hi, you're within limits for honing. hone as little out as you can. final stone, use 400 grit and use moly top ring, will seal fast and stay sealed, BTW, I'm auto machinist.
Click to expand...

By the way, I've only ever honed small power equipment bores where I just eyeballed the crosshatch angle. Should I have the local machine shop do the honing to be sure that the crosshatch is correct? Or can I just try to match the existing crosshatch that I can still see in the bores and diy it?

Thanks,
 
perfacar said:
hi, you're within limits for honing. hone as little out as you can. final stone, use 400 grit and use moly top ring, will seal fast and stay sealed, BTW, I'm auto machinist.
Click to expand...


An auto machinist and a nice guy? How often does that happen.

Perf is correct. Just get some crosshatch in the bore and go. If you didn't use a torque plate your numbers are probably not that bad.
 
ValiantOne said:
Should I have the local machine shop do the honing to be sure that the crosshatch is correct?
Click to expand...

I dunno, I did a quick dingle ball hone on mine, looks like it will work. :D

crosshatch1-jpg.jpg


crosshatch-jpg.jpg
 
You can dingle berry the bores. I've had to. It will work if you don't have a rigid hone. It won't remove material if you are trying to straighten stuff up.
 
ValiantOne said:
Okay, I will measure ring side clearance today too. I was going to go with new rings, but of course I'll have to measure with the old rings today. I am wondering if the engine crud is going to give me erroneous readings?
Click to expand...
Yes, you need to clean out the grooves before measuring ring side clearance. There are tools for that, but you can usually do a decent job by breaking a ring in half and using that as a scraper.

BTW, there are all sorts of moly top ring sources. RcokAuto and everyone sells them. FM, Hastings, etc.
 
I'm going to be in the minority here, but what else is new. I say it looks great, but I would pay to have it machine power honed with a torque plate. It's worth it, and you can afford it, you're not buying new pistons.
 
nm9stheham said:
Yes, you need to clean out the grooves before measuring ring side clearance. There are tools for that, but you can usually do a decent job by breaking a ring in half and using that as a scraper.

BTW, there are all sorts of moly top ring sources. RcokAuto and everyone sells them. FM, Hastings, etc.
Click to expand...

I just went ahead and wiped the pistons down and did an initial ring clearance measurement. I measured at the top and bottom of the piston (thrust faces?) of the 1st and 2nd ring. They were all pretty much the same. .003 on the top ring and .002 on the bottom. Some were a little looser or tighter, but none of them took the next feeler gauge up. .004 and .003 respectively.

I think that is pretty good. I'm guessing that will loosen up some with cleaning, and then tighten up again with new rings ??
 
nm9stheham said:
From your description, it sounds like you measured out-of-roundness only. Did you measure bore taper from top to bottom?
Click to expand...

I went back and measured for out of round and taper separately. Looks like max out of round was .0015. Max taper was .001.

So looks like oor is out of spec by .001 and taper is right at spec.

Not too bad I guess
 
It all depends how money you want to put into it. Xoxo amount of money will get you either a better than was performance but ultimately won't go the mileage the fresh overbore will, performance naturally will be a Lil better than the dingle balled hole because it will be more round and seal better.

Realistically you can run around another 50k on those bores dingle balled, it really depends on how you drive...but the last 10k know itll be burning some oil.
Don't have the money? That's okay, it'll run good dingle balled and be some time before you word need to go through it...besides, you're saving for a stroker, right?
If you do have the money, go for it, you have a great spare motor to sell to finance/recoup cost of the stroker. Bore n hone is around 250.00+/- bucks, depends..
 
ValiantOne said:
I just went ahead and wiped the pistons down and did an initial ring clearance measurement. I measured at the top and bottom of the piston (thrust faces?) of the 1st and 2nd ring. They were all pretty much the same. .003 on the top ring and .002 on the bottom. Some were a little looser or tighter, but none of them took the next feeler gauge up. .004 and .003 respectively.

I think that is pretty good. I'm guessing that will loosen up some with cleaning, and then tighten up again with new rings ??
Click to expand...
Good for you for taking the time to measure everything in detail. That is not bad wear at all. You just don't want them getting up in the .005" or more range. In the old days, you could get the pistons 'grooved' (grooves machined wider) and then put in ring spacers to tighten them up. It was usually only the top grooves that needed that.

And your out-of-round and taper look good. I just did not want to see you have taper in the .005" range... I honed and re-ringed one engine with tapers up in the .004 to .010" range once. (I was still working through college.) It ran but was pretty darned weak on a couple of cylinders.
 
I just measured the crank and frankly I am astounded. This engine had 110K on it when pulled.

main journal spec is 2.8095 to 2.8105 stock. Mine were all either 2.8095 or 2.810. .005 variance? really? with no perceivable taper or out of round
rod journal spec is 2.124 to 2.125. Mine were all 2.124 on the money, also with no perceivable oor or taper.

Technology must have gotten WAY better over the years. When I measured my 68 273 steel crank at 135K on the odo, there was several thou of orr and taper on every journal.

I do have one question though. I can feel some really small grooving on a few journals with a fingernail. Should I give 'em a tiny polish with a strip of emory paper? if so, what grit should I use?
 
Fuel injection ends up with less gas in the oil, and that helps lower wear. Yeah, it is pretty amazing.

240 or 320 grit wet or dry will take care of the scratches. But they don't need to come all the way out.
 
Dingle ball hone with a 400 hone. Just did the same thing with comparable numbers. Changing from a dish to flat top piston for a couple of points of compression. No blow by or excessive oil consumption. Mine is also a stop gap motor also.
 
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