914-SHO Motor teardown & inspection
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First run at Cylinder bore taper results (based on ring gap measurements). I actually like this method better than using the inside gauge and a micrometer - its easier to control so improves repeatability and precision.
The taper service limit for 3.0/3.2 is 0.0008in
On my 3.2 I got the following using the ring gap method:
Note - I'm dividing the gap difference by 3.1416 to get the diameter distance since the gap is measured on the circumference.
So at least the taper portion is within spec. I'll measure this again using the gauge & micrometer just to compare any differences.
One down, two to go.
The taper service limit for 3.0/3.2 is 0.0008in
On my 3.2 I got the following using the ring gap method:
Note - I'm dividing the gap difference by 3.1416 to get the diameter distance since the gap is measured on the circumference.
- Cyl-1: (.0005/3.1416) = .00016in
- Cyl-2 thru 6: (.001/3.1416) = .00032in
So at least the taper portion is within spec. I'll measure this again using the gauge & micrometer just to compare any differences.
One down, two to go.
Off Road SHO
Moderator
Great taper results, but I would still do them again with the inside micrometer. So you know that the first measurement should be 3/8" to 1/2" down from the top of the top ring's travel, and the bottom measurement should be the same from the bottom compression ring's lowest travel point. This gives you amount of wear from the ring's rubbing action from the hottest part of the cylinder, to the coolest part.
If your micrometer test validates the ring gap version, I would ball hone that block, and install new rings. I have a ball hone (multiple sizes in fact) if you need to borrow them. My wife is heading to Tucson and could drop them off at Brock Technologies for you.
Tom
If your micrometer test validates the ring gap version, I would ball hone that block, and install new rings. I have a ball hone (multiple sizes in fact) if you need to borrow them. My wife is heading to Tucson and could drop them off at Brock Technologies for you.
Tom
Well I've got some dimensions, but I'm not sure I want to make any decisions based on them. The gauge I'm using is a little flacky and if I tighten it incorrectly it changes the gauge setting. I had to redo each measurement several times to make sure the gauge fit snug again, after I removed it.
The cylinder bore diameter rubydist provided me was - 3.6220". But I don't know if that's the max or the min. If its the min, then adding the tolerance of .0012" gives me a max diameter of 3.6232".
I made two measurements near the top. One (A) at .25" below the bottom edge of the chamfer - where the cylinder coating material starts. The other (B) is .75" down from the face of the block. This is equivalent to top travel of the oil ring.
EDIT: Remeasured using Tom's inside mic as a gauge then measured using my outside mic, and at the position he suggested (top ring - 3/8") and averaged for perp & para measurements. I updated the numbers above.
The cylinder bore diameter rubydist provided me was - 3.6220". But I don't know if that's the max or the min. If its the min, then adding the tolerance of .0012" gives me a max diameter of 3.6232".
I made two measurements near the top. One (A) at .25" below the bottom edge of the chamfer - where the cylinder coating material starts. The other (B) is .75" down from the face of the block. This is equivalent to top travel of the oil ring.
- A) = 3.6229 (.0003 under max)
- A) = 3.6225 (.0007 under max)
- A) = 3.6229 (.0003 under max)
- A) = 3.6224 (.0008 under max)
- A) = 3.6230 (.0002 under max
- A) = 3.6231 (.0001 under max)
EDIT: Remeasured using Tom's inside mic as a gauge then measured using my outside mic, and at the position he suggested (top ring - 3/8") and averaged for perp & para measurements. I updated the numbers above.
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Off Road SHO
Moderator
I'm not sure that you took those measurements in the right location for "B", however less than 5 ten thousandths is darn good. I could live with half a thousandth all day long and twice on Sunday.
Do you want to borrow my ball end hones? Mitzi is getting ready to head South.
Tom
Do you want to borrow my ball end hones? Mitzi is getting ready to head South.
Tom
Tom, yeh - go ahead and send it south. So this is a 92mm hone -right?
So are you saying I should go with these and just hone?
A few of the cylinders look really good. It's the others that have be bugged. I've edited the previous posting to show the "over" cylinders.
The reason I took the .75" readings was because I noticed there appeared to be a slight taper from that point to the top of the cylinder lining where it meets the chamfer at the top. This seemed to be consistent with all cylinders except #5.
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Off Road SHO
Moderator
They are on their way.
Tape up the entire top of the block and valley with painters tape, might have to clean the gasket surface with alcohol or paint thinner to get the tape to stick. Lay clean rags everywhere you don't want gritty oil because the hone MUST be spinning before you insert it in a cylinder and after you remove it. On my last hone job, after I taped off the passageways on the block, I cut a square hole in the bottom of a cardboard box and placed it over the cylinder openings. You will be amazed at how much oil is flung from the hone.
The small one is 92 and the large one is just in case you have a stubborn glaze. Run the hone in a drill on very low speed at the same time you are moving the hone in and out of the cylinder, do not stop the drill until the hone is completely out of the cylinder, otherwise you will leave vertical scratches. Slow rpms and never stop in the cylinder is key.
Ideal angle of the crosshatching is 30-45 degrees off of horizontal. Use a 5 lb coffee can full of very thin oil like kerosene or diesel fuel, dip the hone, then immediately two or three passes in and out of the cylinder, no more. Clean off the residue with a clean lint free shop towel and inspect for proper cross hatching down the entire cylinder. If not clearly visible, dip the hone again and do a couple more passes, clean and check again.
It goes without saying but you will need to rinse out the bottom end of the block thoroughly after doing this. If you still have the crank in, it is important to not let the gritty oil get in the crank's oil passageways or between the main bearing journals. I used spray bottles full of paint thinner until I got smart and bought a pump action weed sprayer. You cannot clean the bottom end too much. I used sheets of copier paper to test for residue in the runoff, works well.
Call ahead to Brock Technologies.
Good luck
Tom
Tape up the entire top of the block and valley with painters tape, might have to clean the gasket surface with alcohol or paint thinner to get the tape to stick. Lay clean rags everywhere you don't want gritty oil because the hone MUST be spinning before you insert it in a cylinder and after you remove it. On my last hone job, after I taped off the passageways on the block, I cut a square hole in the bottom of a cardboard box and placed it over the cylinder openings. You will be amazed at how much oil is flung from the hone.
The small one is 92 and the large one is just in case you have a stubborn glaze. Run the hone in a drill on very low speed at the same time you are moving the hone in and out of the cylinder, do not stop the drill until the hone is completely out of the cylinder, otherwise you will leave vertical scratches. Slow rpms and never stop in the cylinder is key.
Ideal angle of the crosshatching is 30-45 degrees off of horizontal. Use a 5 lb coffee can full of very thin oil like kerosene or diesel fuel, dip the hone, then immediately two or three passes in and out of the cylinder, no more. Clean off the residue with a clean lint free shop towel and inspect for proper cross hatching down the entire cylinder. If not clearly visible, dip the hone again and do a couple more passes, clean and check again.
It goes without saying but you will need to rinse out the bottom end of the block thoroughly after doing this. If you still have the crank in, it is important to not let the gritty oil get in the crank's oil passageways or between the main bearing journals. I used spray bottles full of paint thinner until I got smart and bought a pump action weed sprayer. You cannot clean the bottom end too much. I used sheets of copier paper to test for residue in the runoff, works well.
Call ahead to Brock Technologies.
Good luck
Tom
Tom, I still need to measure the pistons but don't know the correct location for diameter measurement. It's not in the SHO engine book. Any ideas?
Also, was I correct in adding the tolerance to the nominal bore dia?
Also, was I correct in adding the tolerance to the nominal bore dia?
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Off Road SHO
Moderator
Yes, maybe I didn't explain it properly above. The distance between the two measuring points is equal to the stroke minus 3/8"from the top rings stopping point and 3/8" up from the bottom compression ring's bottom stopping point.
You do it this way so that you are sure to be in the top and bottom compression ring's travel area. Never measure too close to where the compression rings are changing directions. The reason you do it at the top AND bottom is to determine the difference between the highest wear point (also the hottest part of the cylinder) near the top of the stroke, and the lowest wear point (the coolest part of the cylinder) at the bottom of the stroke.
Don't do the ball honing until after you mic the cylinders because it will throw off the measurements.
I should have sent down my inside micrometer set also.
Tom
You do it this way so that you are sure to be in the top and bottom compression ring's travel area. Never measure too close to where the compression rings are changing directions. The reason you do it at the top AND bottom is to determine the difference between the highest wear point (also the hottest part of the cylinder) near the top of the stroke, and the lowest wear point (the coolest part of the cylinder) at the bottom of the stroke.
Don't do the ball honing until after you mic the cylinders because it will throw off the measurements.
I should have sent down my inside micrometer set also.
Tom
Off Road SHO
Moderator
You will have to make arrangements to pick up the hones this coming week. The following week they are doing flight testing.
They live in Vail, which might be closer to you.
Tom
They live in Vail, which might be closer to you.
Tom
I multiplied x .0045 top and .0055 for the 2nd to get the gaps. I went with a slightly larger gap just to be safe. The DNJ's out of the box gave me .0014 and .0016 from what I recall. I ended up with .0017 and .002.
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jimtash, was your a 3.0 or 3.2?
It's a 3.2L. The bores were in good condition finish wise so I just cleaned them up. I remember now using the formula the total came out to .0016 for the top ring but I went ahead and took it up to .0017.
I have a tapered 92mm piston ring compressor/installer if you want to use it. I literally just pushed the pistons in with hand pressure.
I have a tapered 92mm piston ring compressor/installer if you want to use it. I literally just pushed the pistons in with hand pressure.
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Thanks for the tip - just not there yet. The heads just prep'd and waiting for the cam seals to come in.
OK, revised the cylinder bore numbers. Tom had a cylinder micrometer which had very good feel with no variation like the gauge I was using. The mic was only good to .001, so I used my outside mic to get the measurements.
See post #104 for the revised numbers.
Next are measurements on a another set of used 3.2 pistons. I hope I get lucky.
See post #104 for the revised numbers.
Next are measurements on a another set of used 3.2 pistons. I hope I get lucky.
Off Road SHO
Moderator
Gerard,
I don't see those diameter numbers as bad at all. The largest bore at 1 ten thousandths shy of the maximum is still going to leave plenty of tension in the rings, more than enough to keep the pressure on the top side.
Let's see what those other pistons mic out to.
Tom
HooRa! - got some used pistons :woo-hoo: Rich to the rescue!
Thanks Tom & Rich. Both had sets but Tom's were only a partial fit & Rich's were a near perfect fit. All measured in at the low end of the clearance range - which works great since I still have to hone the cylinders and will loose a few .0001's.
Guess I know what I'm doing the rest of this weekend. Got DNJ rings ordered, finished assy on the left head, and located some head bolts to replace 5 or 6 of mine that were mucked-up.
Hope to be up & running again in a couple of weeks.
Thanks Tom & Rich. Both had sets but Tom's were only a partial fit & Rich's were a near perfect fit. All measured in at the low end of the clearance range - which works great since I still have to hone the cylinders and will loose a few .0001's.
Guess I know what I'm doing the rest of this weekend. Got DNJ rings ordered, finished assy on the left head, and located some head bolts to replace 5 or 6 of mine that were mucked-up.
Hope to be up & running again in a couple of weeks.
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