Engine Rebuild Questions 172cid Sleeveless

[LarryMaine]

Having engine on my engine stand finally for my 1964 ford HD industrial, I have a couple of questions as this is my first sleeveless engine rebuild. Acquired tractor not running. It was not seized but prior owner suggested valve problem. On exam it looks as though head gasket blew between the center two cylinders, with these valve seats also very heavily pitted. Most valve springs also had shims (from a prior rebuild by some prior owner). All the main and crank bearings were stamped -0.01, with nice even wear on one side with little wear on the other half bearings. Cylinders are sleeveless and bore gauge a fairly consistent 3.928". A couple were narrower, but these were where there was a slight top rim which will be honed down to match 3.928. Pistons all measure exact 3.900". Crankshaft also very even 0.01" wear with no need for regrinding. My question is, should I go with oversize rebore pistons that measure 3.920", or, should I try to use standard replacement pistons of 3.900" but use .02" oversize piston rings. Not sure which are even available. Machine shop will plane the deck, replace valve guides, and replace valve seats, but will not work on the block. I feel good that my measurements are all correct. Before anyone asks, no, I do not want to have to have the block rebored, as the measurements are quite consistent. Any advice would be really helpful and appreciated. Thanks, Larry. P.S. If the original cylinder was exactly 3.900, then wouldn't the original pistons be a bit under 3.900, suggesting my existing pistons are already oversize???

 

[shaun wallace]

Do not know hard its going to be used. I would replace seats,valves,giudes, springs and surface head. Put bottom end back with what it is or standard.

 

[LarryMaine]

shaun, not sure of your meaning. Of course I am doing a full rebuild of the valve train, but have decided to do full rebuild of block as well. Makes no sense to replace the existing worn -.01 bearings with std bearings, and not sure why I would use standard size pistons and rings on an engine with cylinder sizes of 3.028. Also, how hard it is going to be worked is a bit irrelevant to me, as I am not going to go through all this effort of removing engine from an HD Industrial to do a mediocre job (tho I am sure that is not what you really meant to suggest). Also, are pistons of 3.900 original to this engine, or are they considered oversize as the original cyl was 3.900 as well. Larry.

 

[mhb@ufe]

Having engine on my engine stand finally for my 1964 ford HD industrial, I have a couple of questions as this is my first sleeveless engine rebuild. Acquired tractor not running. It was not seized but prior owner suggested valve problem. On exam it looks as though head gasket blew between the center two cylinders, with these valve seats also very heavily pitted. Most valve springs also had shims (from a prior rebuild by some prior owner). All the main and crank bearings were stamped -0.01, with nice even wear on one side with little wear on the other half bearings. Cylinders are sleeveless and bore gauge a fairly consistent 3.928". A couple were narrower, but these were where there was a slight top rim which will be honed down to match 3.928. Pistons all measure exact 3.900". Crankshaft also very even 0.01" wear with no need for regrinding. My question is, should I go with oversize rebore pistons that measure 3.920", or, should I try to use standard replacement pistons of 3.900" but use .02" oversize piston rings. Not sure which are even available. Machine shop will plane the deck, replace valve guides, and replace valve seats, but will not work on the block. I feel good that my measurements are all correct. Before anyone asks, no, I do not want to have to have the block rebored, as the measurements are quite consistent. Any advice would be really helpful and appreciated. Thanks, Larry. P.S. If the original cylinder was exactly 3.900, then wouldn't the original pistons be a bit under 3.900, suggesting my existing pistons are already oversize???

3.928 bore measurement would make me believe The block had been bored .020 over plus wear getting to 3.928. 3.900 pistons would be very loose in that bore. I can't find a spec for the standard piston diameter but there would have to be some clearance or the piston would seize if you could even get a 3.9 piston in a 3.9 bore. Used pistons in a used bore recommends 0.003 clearance. new piston in a new bore recommends 0.0015 clearance.

Mark

 

[Mad Farmer]

Do you have a shop manual? From your measurements you have 0.028" clearance. I'm guessing it should be closer to 0.002-3" The manual should give clearance and where to measure it for P/C (usually on the skirt 90 o from the pin bores)

You also should check for out of round and taper, 6 spots top middle and bottom, 90 o offset at each height. Check the pistons in several spots too.

 

[Btzj02]

A standard 3.90 piston is actually 3.871 at the top and 3.873 at the skirt and the cylinder should measure 3.900. So, please someone correct me if I am wrong, you already have oversize pistons.

 

[LarryMaine]

Do you have a shop manual? From your measurements you have 0.028" clearance. I'm guessing it should be closer to 0.002-3" The manual should give clearance and where to measure it for P/C (usually on the skirt 90 o from the pin bores)

You also should check for out of round and taper, 6 spots top middle and bottom, 90 o offset at each height. Check the pistons in several spots too.

Thanks, I already did all of the measurements you indicate, I used a digital bore gauge and a micrometer. Taper is not an issue, if it were I would find the money to have the machine shop do the rebore. The only issue regarding measurements is the slight ridge at the top of the cylinder beyond the play of the piston top, and I can hone those down myself. The 3.928 number is pretty consistent for all 4 cylinders, so I suspect it had been rebored not all that many years ago. This idea is supported by the crankshaft that is also quite consistent and only 0.01 under. Thanks for the reply.

 

[LarryMaine]

A standard 3.90 piston is actually 3.871 at the top and 3.873 at the skirt and the cylinder should measure 3.900. So, please someone correct me if I am wrong, you already have oversize pistons.

Thanks, that was the info I needed. I have ALL the shop, parts, and ops manuals but they suggest using a feeler gauge with a pull gauge between cylinder and rings to determine the correct piston to cylinder clearance, which means I might have to buy multiple pistons and rings iunti

 

[LarryMaine]

Sorry, I hit the wrong button and posted prematurely. Should read, "until I get it right" If those numbers are correct, then a new engine has a clearance between 3.900 cylinder and 3.872 piston of 0.028". Right now using my existing 3.900 pistons and 3.928 cylinder, my existing clearance between cylinder and piston is the exact same as a new engine, at 0.028". So, although I am going to replace my pistons, rings, pins and bearing, I think I will replace them with the same 3.900 pistons with correct rings for that oversize piston, unless someone suggests I may be wrong in my math. Thanks all, Larry. You guys saved me a real headache and possibly a number of returned parts during the rebuild. Oh yea, the actual clearances on each side of the piston to cylinder are half the numbers used because we are talking about a cylinder.

 

[Mad Farmer]

Thanks, I already did all of the measurements you indicate, I used a digital bore gauge and a micrometer. Taper is not an issue, if it were I would find the money to have the machine shop do the rebore. The only issue regarding measurements is the slight ridge at the top of the cylinder beyond the play of the piston top, and I can hone those down myself. The 3.928 number is pretty consistent for all 4 cylinders, so I suspect it had been rebored not all that many years ago. This idea is supported by the crankshaft that is also quite consistent and only 0.01 under. Thanks for the reply.

Thanks, that was the info I needed. I have ALL the shop, parts, and ops manuals but they suggest using a feeler gauge with a pull gauge between cylinder and rings to determine the correct piston to cylinder clearance, which means I might have to buy multiple pistons and rings iunti

Use a ridge reamer to get the ridge out. If you give it a hone and put the larger/oversize pistons in you should be OK.

I found a shop manual for the 600-900 series . They have a strange way of setting clearance without using mics. A feeler gauge slipped in the bore with the piston then some sore of spring scale to measure the tension at 5-10 lbs. I couldn't find a free manual for your exact tractor, but I did find had 172 ci motors. Was 1964 the last year they had the 4-cyl motors?

A standard 3.90 piston is actually 3.871 at the top and 3.873 at the skirt and the cylinder should measure 3.900. So, please someone correct me if I am wrong, you already have oversize pistons.

That still seems like a lot of piston clearance? 0.013" I used to set up SB Chevys and they were ~0.002-3" cast pistons, 0.0045" forged

0.017 or 0.028" is too much unless I'm missing something? Anybody checked these with the pull scale and a feeler then took a measurement?

 

[mhb@ufe]

Sorry, I hit the wrong button and posted prematurely. Should read, "until I get it right" If those numbers are correct, then a new engine has a clearance between 3.900 cylinder and 3.872 piston of 0.028". Right now using my existing 3.900 pistons and 3.928 cylinder, my existing clearance between cylinder and piston is the exact same as a new engine, at 0.028". So, although I am going to replace my pistons, rings, pins and bearing, I think I will replace them with the same 3.900 pistons with correct rings for that oversize piston, unless someone suggests I may be wrong in my math. Thanks all, Larry. You guys saved me a real headache and possibly a number of returned parts during the rebuild. Oh yea, the actual clearances on each side of the piston to cylinder are half the numbers used because we are talking about a cylinder.

That still sounds like an excessive amount of clearance to me. I would recommend you look at your service manual in regards to checking piston to cylinder clearance.

Mark

 

[LarryMaine]

Use a ridge reamer to get the ridge out. If you give it a hone and put the larger/oversize pistons in you should be OK.

I found a shop manual for the 600-900 series . They have a strange way of setting clearance without using mics. A feeler gauge slipped in the bore with the piston then some sore of spring scale to measure the tension at 5-10 lbs. I couldn't find a free manual for your exact tractor, but I did find had 172 ci motors. Was 1964 the last year they had the 4-cyl motors?


That still seems like a lot of piston clearance? 0.013" I used to set up SB Chevys and they were ~0.002-3" cast pistons, 0.0045" forged

0.017 or 0.028" is too much unless I'm missing something? Anybody checked these with the pull scale and a feeler then took a measurement?

Thanks for the info. As you know, we are measuring the total width of the cylinder and the total width of the piston at .028", so the clearance between piston wall and cylinder wall on each side is only 0.014". Not perfect, but good enough for a 60 year old tractor. Besides, there are not a lot of available oversize pistons and rings for this engine. Regarding other question, I think yes. My model tractor was only produced in 1963 & 4. Starting in 1965 Ford switched to the slightly larger cid engine with 3 cylinders, also available in gas and diesel. The 172 sleeveless engines only came out during the later years of production and ended in 1964 as I recall. Having done a rebuild on my 195X Ford 850, that one was the more common dry sleeve engine, which makes life actually a bit easier.

 

[TheOldHokie]

Thanks for the info. As you know, we are measuring the total width of the cylinder and the total width of the piston at .028", so the clearance between piston wall and cylinder wall on each side is only 0.014". Not perfect, but good enough for a 60 year old tractor. Besides, there are not a lot of available oversize pistons and rings for this engine. Regarding other question, I think yes. My model tractor was only produced in 1963 & 4. Starting in 1965 Ford switched to the slightly larger cid engine with 3 cylinders, also available in gas and diesel. The 172 sleeveless engines only came out during the later years of production and ended in 1964 as I recall. Having done a rebuild on my 195X Ford 850, that one was the more common dry sleeve engine, which makes life actually a bit easier.

Piston clearance is measured on the diameters as are the bearing clearances.

Dan

 

[LarryMaine]

Piston clearance is measured on the diameters as are the bearing clearances.

Dan

Dan, not sure what you are referring to "measured on the diameters". From my internet searches, there seem to be a lot of clearance variations, depending upon piston composition, ie cast metal, forged metal, aluminum. If my ford originally had cast pistons, but were replaced with oversize aluminum pistons after a rebore, then the desired clearance would be different than original. Also, they refer a lot to clearances "per inch of diameter" which I take to mean if clearance is supposed to be .003 per inch, then a 3.9 inch bore would yield a recommended clearance wall to wall of about .012". Is that what you are referring to? The only thing I am concerned about is piston slap if I am wrong.
Thanks, Larry

 

[TheOldHokie]

Dan, not sure what you are referring to "measured on the diameters". From my internet searches, there seem to be a lot of clearance variations, depending upon piston composition, ie cast metal, forged metal, aluminum. If my ford originally had cast pistons, but were replaced with oversize aluminum pistons after a rebore, then the desired clearance would be different than original. Also, they refer a lot to clearances "per inch of diameter" which I take to mean if clearance is supposed to be .003 per inch, then a 3.9 inch bore would yield a recommended clearance wall to wall of about .012". Is that what you are referring to? The only thing I am concerned about is piston slap if I am wrong.
Thanks, Larry

All of thos clearances are diametral. Measure bore. Measure piston. Subtract piston from bore and you get clearamce.

SInce you have a bore gauge measure piston diameter with a micrometer and lock it. Use micrometer to zero bore gauge. Use bore gauge to directly read piston clearance in bore.

Dan

 

[LarryMaine]

All of thos clearances are diametral. Measure bore. Measure piston. Subtract piston from bore and you get clearamce.

SInce you have a bore gauge measure piston diameter with a micrometer and lock it. Use micrometer to zero bore gauge. Use bore gauge to directly read piston clearance in bore.

Dan

Dan, as mentioned previously in this thread, I have already done all the measurements. Since this is a rebuild, and I am going to replace pistons and rings, what I am trying to determine is what is the correct clearance versus the actual clearance I already know, so I can buy the correct size pistons and rings for the current bore of 3.928". Its only complicated because this engine was already previously re bored and already has an oversize piston. The question really is, is a clearance of 0.014: inches cylinder wall to piston wall acceptable, or is it way too much. This clearance of 0.014 seems to be the same as an original new engine, but people seem to think that it is just too much.

 

[TheOldHokie]

Dan, as mentioned previously in this thread, I have already done all the measurements. Since this is a rebuild, and I am going to replace pistons and rings, what I am trying to determine is what is the correct clearance versus the actual clearance I already know, so I can buy the correct size pistons and rings for the current bore of 3.928". Its only complicated because this engine was already previously re bored and already has an oversize piston. The question really is, is a clearance of 0.014: inches cylinder wall to piston wall acceptable, or is it way too much. This clearance of 0.014 seems to be the same as an original new engine, but people seem to think that it is just too much.

YOU ARE MISCALCULATING CLEARANCE.

Apparently the stock bore is 3.901 Accordingly a stock piston is finished undersize to provide the proper clearance. The piston OEM will decide the clearance needed based on their choice of materials.

As the engine builder your reference dimension for selecting and ordering parts s the bore in the block. According to your measurements your block is at 3.928.which is .027 over factory. Accordingly a .030 over piston (readily available) matches your block bore.

Its as simple as that.

Dan

 

[Mad Farmer]

Thanks for the info. As you know, we are measuring the total width of the cylinder and the total width of the piston at .028", so the clearance between piston wall and cylinder wall on each side is only 0.014". Not perfect, but good enough for a 60 year old tractor. Besides, there are not a lot of available oversize pistons and rings for this engine. Regarding other question, I think yes. My model tractor was only produced in 1963 & 4. Starting in 1965 Ford switched to the slightly larger cid engine with 3 cylinders, also available in gas and diesel. The 172 sleeveless engines only came out during the later years of production and ended in 1964 as I recall. Having done a rebuild on my 195X Ford 850, that one was the more common dry sleeve engine, which makes life actually a bit easier.

Slap slap slap.....of the pistons. On 2-stokes two strokes the skirt breaks off.

"Is that a valve maki"ng noidts...?

 

[TheOldHokie]

A standard 3.90 piston is actually 3.871 at the top and 3.873 at the skirt and the cylinder should measure 3.900. So, please someone correct me if I am wrong, you already have oversize pistons.

You sre correct.

A 3.873 piston in 3.90 bore is a "standard" piston in a nominally standard bore with .007/.008 clearance baked in by the maker of the piston.

A 3.920 piston in a 3.928 bore is almost surely a .030 over piston in a .nominally .030 over bote and has .008 clearance baked in by the maker of the piston and/or rebuilder. It cannot be a .020 over piston in a badly worn engine because it would never have fit a fresh .020 overbore. An overhaul reusing those pistons would require .030 over rings.

TOH

 

[Destroked 450]

A standard 3.90 piston is actually 3.871 at the top and 3.873 at the skirt and the cylinder should measure 3.900. So, please someone correct me if I am wrong, you already have oversize pistons.

There’s something wrong with these numbers
A block bore of 3.901 minus piston diameter 3.873 equals 0.028 clearance.
Actual clearance should be 0.0015-0.0035
Generally on a rebuild with a fresh overbite and new pistons we shot for .002-.003 piston to bore clearance using cast aluminum pistons