Piston/bore differance ?
Trying to correct some sloppy machine shop work . One out of 6 pistons not showing any drag , one just about seized . Thankfully no serious damage done , I shut it down as soon as I noticed it was tightening up . When a shop that says they do these old engines a lot can't get it right I begin to wonder if I can and want to be sure I'm on the right track . . ---Would like a little input to see if I have this read right from the manual and figured out right . --Using a mic on the pistons and a bore gauge what is the correct difference for a 212 engine . Gonna have to fit each one with a ridged hone . THANKS , BUD
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There's not much clearance in there with the original type T-slot pistons, just .0015". However, the bores were originally diamond-bored, according to Hudsons sales splurge, and this is purported to be much more accurate than most boring bars can achieve.0
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I forgot to mention, the pistons must be cam-ground, with around .008" minimum clearance fore-and-aft.0
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Thank you Geoff , I've had so much trouble with machine work on this engine I'm afraid I've become a bit paranoid . No 2 holes the same--no 2 pistons the same . What I came up with is those with just a bit of scuffing have about 2 1/2--3 thousandth clearance and if I went to about 6 thousandths difference in the bore and piston {what I use on modern engines , but these Hudsons seem to me to be a bit of a different critter } that it would come out OK without any clatter or scuffing . Dang , if they did these things in '37 why can't they do it with todays equipement ? No pride in their work , run it thru fast and out the door . Any other opinions out there , these are not stock pistons, McQuay Norris aftermarket ? BUD0
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37 Terraplane#2 wrote:
Hudsons are hard blocks and all machine shops today do Chevy's and bore 0.030 in one cut. Hudson blocks can only be bores 3 to 5 thousands at a time. They tried to cut your block say 10 and the tool bit wore before it reached the top and that is your problem. Try honing each cylinder to it's piston till you have 0.0015 clearance. What bore size did they come too. Sorry to say, but 0.030 is maximum for a 175 or 212 block, anything our can cause heating problems. Walt.Thank you Geoff , I've had so much trouble with machine work on this engine I'm afraid I've become a bit paranoid . No 2 holes the same--no 2 pistons the same . What I came up with is those with just a bit of scuffing have about 2 1/2--3 thousandth clearance and if I went to about 6 thousandths difference in the bore and piston {what I use on modern engines , but these Hudsons seem to me to be a bit of a different critter } that it would come out OK without any clatter or scuffing . Dang , if they did these things in '37 why can't they do it with todays equipement ? No pride in their work , run it thru fast and out the door . Any other opinions out there , these are not stock pistons, McQuay Norris aftermarket ? BUD0 -
Thanks Walt , that may be part of the problem, had to go .040 over to clean the block up and getting more heat / less cooling at the cylinders which would call for a bit more clearance . Any suggestions there ? And your right about HOW to bore a Hudson block . {tool bit } I have high/low spots all over the thing but they will come out with the ridged hone . BUD0
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37 Terraplane#2 wrote:Thanks Walt , that may be part of the problem, had to go .040 over to clean the block up and getting more heat / less cooling at the cylinders which would call for a bit more clearance . Any suggestions there ? And your right about HOW to bore a Hudson block . {tool bit } I have high/low spots all over the thing but they will come out with the ridged hone . BUD
OUCH! I'd lay money that said Walt's gonna say, "Sleeve it and do it again or find another block."0 -
RL Chilton wrote:
Not just yet, try honing it for a smooth surface and you will be OK if you end up with 0.005 clearance. Hello Russell. hold the money till he answers. Walt.OUCH! I'd lay money that said Walt's gonna say, "Sleeve it and do it again or find another block."0 -
walt's garage-53 wrote:Not just yet, try honing it for a smooth surface and you will be OK if you end up with 0.005 clearance. Hello Russell. hold the money till he answers. Walt.
Doin what you said Walt, man that thing is HARD , almost to .005 on the first one , high/ low spots are comeing out , should I quit there or go for .006 as was my original thought ? gonna be a while before I get them all done . I've got a Ford tractor radiator and a big fan in the car that'll cool anything , with out the thermostat it won't even warm up good so engine overheat I'm not worried about , ---BUD0 -
37 Terraplane#2 wrote:
Doin what you said Walt, man that thing is HARD , almost to .005 on the first one , high/ low spots are comeing out , should I quit there or go for .006 as was my original thought ? gonna be a while before I get them all done . I've got a Ford tractor radiator and a big fan in the car that'll cool anything , with out the thermostat it won't even warm up good so engine overheat I'm not worried about , ---BUD
Gonna quit at the .005 and work on the others untill Walt gets back on here .0 -
Sorry to say, but at .005" you are going to hear those pistons.0
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Geoff C., N.Z. wrote:Sorry to say, but at .005" you are going to hear those pistons.
Geoff-
Out of curiosity, couldn't he solve his dilemma with oversized rings?0 -
Geoff C., N.Z. wrote: »I forgot to mention, the pistons must be cam-ground, with around .008" minimum clearance fore-and-aft.[/QUOTE
CONFUSED ---the pistons were cam ground , no 2 are the same as are the bores , gotta have a clearance that will work all around . No Russel , oversize rings will not remove piston slap , worn pistons that chatter are knurled to do that . COME BACK WALT , don't leave me now !0 -
Cam grinding means there ismore taken off the front and rear of the piston skirt to allow for expansion around the wrist pin holes, as there is more metal here. With .0015" clearanc einitally laterally, and .008" fore-and aft (It can be evenmore here), the piston will expand with no ill efect, as the T-slot will close up slightly to take any lost clearance. Any expansion around the pin boss is allowed for with the cam grind. If the pistons were ground exactly round, the operation heat would make them expand oval, as expansion is greater around the pin boss, and you would have to allow much more clearance, which would make them noisy.0
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Geoff C., N.Z. wrote:
HI GEOFF , yes I know what - where - why the cam grind is . Problem is the machine shop work has a lot to be desired . New pistons just been ground , "T" slot not cut thru at bottom , was advised by very reputable source not to --new bore job -new line bore . None of it done with care . NEW HOLE BORED IN MY POCKET . MAMA SAYS SHE AIN"T AGONNA MEND IT ! Can't start over so gotta come up with something that will work . Gotta give somewhere . I have my own thoughts but on this one I think I would like all the input I can get from guys with more experience than I . And I thank you all . BUDCam grinding means there ismore taken off the front and rear of the piston skirt to allow for expansion around the wrist pin holes, as there is more metal here. With .0015" clearanc einitally laterally, and .008" fore-and aft (It can be evenmore here), the piston will expand with no ill efect, as the T-slot will close up slightly to take any lost clearance. Any expansion around the pin boss is allowed for with the cam grind. If the pistons were ground exactly round, the operation heat would make them expand oval, as expansion is greater around the pin boss, and you would have to allow much more clearance, which would make them noisy.0 -
I'd just like folks to note that with regard to cylinder boring there's really nothing special about these Hudson splashers except for the important bit Walt stated about the block hardness. Any competent shop should be able to bore one properly. Certainly nothing new about cam-ground pistons. It IS important to get the pistons first and bore the block to a good fit for those pistons, rather than fitting the pistons to the bore.0
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Thanks for the input PARK . I did get the pistons and took them to the shop . As said no 2 pistons are the same , bad job#1 , then the shop probably only measured one and went to boreing , From the result of that it looks like they did what WALT said don't do , cut it all in one shot , that resulted in low/high spots all over . Bad job #2 . I've got a little hobby lathe I play with and even a dummy like me can tell when the bit is dulling . Lesson hard learned , take a Hudson to someone you KNOW has experience with them , shops will tell you anything to get the job . Now I gotta do a getby job with hand tools or trash it . I'm gonna try the getby aproach and hope it works , not much choice .
BUD0 -
Geoff C., N.Z. wrote:
Cam ground is side to side, not for and aft. 4 thousands is plenty of clearance with todays gas as it burns much hotter. This is the reason a lot of old cars are over heating. WaltI forgot to mention, the pistons must be cam-ground, with around .008" minimum clearance fore-and-aft.0 -
37 Terraplane#2 wrote:
Try honing till you get cylinders smooth enough, but do not exceed 5 thousands. Then have the pistons knurled which brings out about 3 to 5 thousand, now this is done on the front and rear side of the piston. This will help with a little less clearance. Are your piston 4 or 3 rings? Do not cut the skirts as they will break off and then you have real troubles. Make sure you fill the top tray before you install the crankcase, as the engine must be upright, or after the engine is in the car, pour 2 quarts through the valve chamber, 1 in front and 1 in rear as this will fill the mains also. I would suggest you use Castrol 20-40 when finished. Set your valves cold at 10 intake and 12 exhaust, there is Walt's 2 cents worth as this is what I would do if you brought it to me after they get it a screwed up. Walt.Thanks for the input PARK . I did get the pistons and took them to the shop . As said no 2 pistons are the same , bad job#1 , then the shop probably only measured one and went to boreing , From the result of that it looks like they did what WALT said don't do , cut it all in one shot , that resulted in low/high spots all over . Bad job #2 . I've got a little hobby lathe I play with and even a dummy like me can tell when the bit is dulling . Lesson hard learned , take a Hudson to someone you KNOW has experience with them , shops will tell you anything to get the job . Now I gotta do a getby job with hand tools or trash it . I'm gonna try the getby aproach and hope it works , not much choice .
BUD0 -
HI WALT , Screwed up is putting it mild . Gonna try what you say here , sounds like the best option . Pistons are 4 ring with one oil ring below the pin . They are bigger by close to .008 side to side than they are front to rear . Does this change any advice above ? What is the minumum clearance to go for or should I get them all the same ? After knurling do I need to do any more fitting or just put them in , bear in mind the crappy work I've been getting and may happen with the knurling . THANKS , BUD0
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WALT , update , here's where I'm at now . TIRED !! Gonna delete this and do the measureing again in the morning , think I must have wrote some notes down wrong BUD0
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37 Terraplane#2 wrote:
Again, I will say this. Where the wrist pin goes through the piston, is where it's cam ground. In front of the wrist pin is fore, and behind the wrist pin is aft, and this is where you have the 0.0015 clearance. A cam ground piston is egg shape. The top of the piston, where the rings go, should be 0.005 smaller and round.If your clearance is in front of the wrist pin and behind, you are in trouble. Back in those days even the factory didn't get it right the first time and had to diamond hone the cylinders to clean up. Look at the bottom ridge in the valve chamber and you will see letters stamped in, those letters meant the finish size of that cylinder. Example, A- 3.000, B-3.005, C-3.001, D-3.0015 and goes right up to code FF-3.22 oversize. If you have the 1934 to 1937 repair manual go to engine page,section 7 page 3 and read. Remember, cam ground is clearance on the sides of the skirt. Walt.WALT , update , here's where I'm at now . The bores straightend up at .004 side to side clearance with a ridged hone . . If I understand it right this is a good place to stop honeing , not be concerned with the fore and aft clearance as the pistons are .008 smaller here , and now have the pistons knurled on the fore and aft sides , and do not cut the expansion slot thru to the bottom of the skirt . BIG question on when and when not to knurl . Fore/aft clearances are not the same on all cylinders . What would you say is MAXIMUM clearance to say knurl this one and the minumum clearance to say , leave this one as is . In other words ---this_____ or under leave it alone and the minumum here or this_____or over knurl it . Again , thanks for your advice on this ..
BUD0 -
walt's garage-53 wrote:Again, I will say this. Where the wrist pin goes through the piston, is where it's cam ground. In front of the wrist pin is fore, and behind the wrist pin is aft, and this is where you have the 0.0015 clearance. A cam ground piston is egg shape. The top of the piston, where the rings go, should be 0.005 smaller and round.If your clearance is in front of the wrist pin and behind, you are in trouble. Back in those days even the factory didn't get it right the first time and had to diamond hone the cylinders to clean up. Look at the bottom ridge in the valve chamber and you will see letters stamped in, those letters meant the finish size of that cylinder. Example, A- 3.000, B-3.005, C-3.001, D-3.0015 and goes right up to code FF-3.22 oversize. If you have the 1934 to 1937 repair manual go to engine page,section 7 page 3 and read. Remember, cam ground is clearance on the sides of the skirt. Walt.
WORE OUT, ME. --Pretty sure I got my notes mixed up , forget what I posted above , and gonna do the measureing again in the morning . The fitting method in the manual deals with factory parts made to Hudson's specs and won't work on this mess . Have to find a compromise . BUD0 -
I'm afraid our terminology is somewhat skewed, perhaps between imperial and republican, I don't know, but most pistons have "front" stamped on them with the arrow pointing towards the front of the engine. Hence I understand that fore and aft means the ends of the piston pin holes, and the sides are the solid and split sides of the piston. The split goes to the side opposite the camshaft, so the solid side is taking the thrust on power stroke. To say fore and aft, meaning sideways doesn't make sense to me. Sorry Walt!0
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New day and I'm wide awake . Haveing a bit of trouble with terms myself . This is what I have for sure . From one side of the engine to the other is where I have .004 clearance . Would like any/all opinions on whether that is acceptable . From front to rear of engine is where I've got big time trouble . Due to the crappy bore job I've got--.016---.010---.007---.017---.005---.009 . This is front to rear of engine orientatation . Expansion slot is not cut thru to bottom of skirt , would cutting it help take up some of the excessive clearance in the front to rear of engine area ? . In my opinion this excessive clearance front to rear might cause some oil consumption for quite a few miles untill rings wore in but not cause a lot of chatter as the piston movement is side to side of the engine . Any opinions/solutions on what to do here no matter how wild/wierd are welcome from anyone . BUD0
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The front-to-rear clearance is of no consequence. This where the expansion is taken up, and has no influence on oil control - this is done by the rings. .004 is probably fine, but you may notice a slight noise when the engine is cold. Do not cut the slot through. The original T-slot pistons have the cut finishing at the bottom oil ring.0
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Geoff C., N.Z. wrote:The front-to-rear clearance is of no consequence. This where the expansion is taken up, and has no influence on oil control - this is done by the rings. .004 is probably fine, but you may notice a slight noise when the engine is cold. Do not cut the slot through. The original T-slot pistons have the cut finishing at the bottom oil ring.
The above is what I think , I've had so much trouble with this thing I feel much better having some reliable confirmation . Knurling is not too expensive a job , what are the thoughts on this to take up a couple thousands on the side to side clearance . And on the other hand a little noise while warming up is not an issue with me except that if it is there it may not be too many miles before it gets to a point it has to be taken care of or risk skirt breakage from hitting too hard . I intend to get this thing on the interstate roads , got it geared high , 307 rears , to cut down on rpms . May be too high on the rears , only trying it will tell if it will work in my area , not too many big hills but we won't get into that , first gotta get it running decent .
IDEA : what about putting ring expanders under the 2 oil rings,
theory-remove any free space between ring and piston by tension and take some of the TEETER-TOTER effect of the piston on the pin off to reduce/eliminate any cold start chatter ? Hey GEOFF , how you like that for automotive terminology , best I could do ? BUD0 -
O.K. guys , a little parts trial fitting puting expanders under rings not intended for them makes the tension much greater , how much I have know way to determine , and I can still push the ring into the groove about 1/32 or a bit less below the piston surface . Plan is to put them under the rings just above the pin and the bottom ring . I would think things would pretty well ride on the rings due to the increased tension holding the piston in a more central location , and with this excessive clearance I have all around , things should not get too tight . WHATCHA THINK ? BUD0
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DON'T use expanders in the bottom groove. Only the oil groove above the pin. Expanders on the bottom groove, below the pin, puts excess pressure on the skirt, and could cause it to collapse.0
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Geoff , this ring set has expanders under the top oil ring , after reading your post I went out and put a piston in without an expander under the bottom ring and one with expanders in both , no rods. The without I could move up and down , the with I had to put a 1/4 inch nylon rope around the pin and give it a pretty healthy yank to get it back out . Best I trash that idea , don't think the starter would even turn it over , put the thing together and hope it don't sound like a rattlesnake den . IF it does I'll just have to pull the engine again and knurl or see if an old block I have in the back shed is salvageable. Thanks for your input on this mess . BUD0
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I hope you get it worked out, but if you decide you need to start over I have a set of NOS .030-over pistons that I believe are for a 212. They are unground and have instructions for grinding. They were made by Toledo.0
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