plasti gauge ?

[can whlvr 993]

so i have been working on my m 12,bored 10 over,turned crank,had the parts and the machine shop had them to do the machineing as per usual,ive read here about the plasti gauge and wondered if i need to do this even though the shop is very reputable and does great work,i didnt on my last 10 hp build and had no problems and that motor runs as new,and has alot of power for a 10,any thoughts,my machinist said i dont need to,they allready measured everything and if i do need to where do you get it,and do you use the new torque ratings or the used torque setting after you take the plasti out,and how do you measure it,a micrometer which i dont have?

[CRE1992 135]

I used that stuff in high school when we were rebuilding car engines. I absolutely hated that stuff! Sucha pain! But to almost guarantee precise measurements needed for the rebuild, that's what is used. When I did it, you would put it on the crank journal and tighten up to factory specs, then take it out and measure it. There were two ways of measuring it that I remember 1 was with a micrometer, and another was a chart on the envelop they came it. I think you can get it at most autoparts stores? I don't know, I've never bought it myself. By the way, it looks almost like green dental floss, and be careful not to "smoosh" it if you do buy some.

[Cole 25]

you should use plasti gauge to be shure that the "gap" is right but you also dont have to if you trust the machine shop and if they did it right so its up to you.

[JMW 3]

I would say use it.I've had cranks and rods come back from the machine shop done properly only to find a problem with bearings being marked wrong.This was with car engines but the little extra time it takes is piece of mind.

[TT-(Moderator) 1,147]

I have a lot more faith in precision measuring instruments than a piece of smashed plastic "string".

I've never used Plastigauge in the last 30-plus years and I doubt that I will in the future - unless I run out of dental floss. :D

[KC9KAS 4,744]

I too used it in mechanic's class back in high school...man that was long ago...Any-way, the implement dealer in town still uses the Plasti-Gauge when they rebuild agriculture engines.

[rmaynard 15,916]

For $1.75 US, it is a nice security blanket. I am working on a K301 that only has 100 hours on it. When I took it apart to inspect it, I was amazed at the lack of wear. I took out the piston and connecting rod to inspect the rings, and with the intention of replacing the crankshaft if necessary. There did not appear to be any wear, so I Plastigauged it just to see what the actual wear was. The gap was .002. In the specs sheet, .001/.002 is the allowable clearance for a new rod and crank. I buttoned the engine back up and was very happy.

As they say, "an ounce of prevention is worth a pound of cure".

[can whlvr 993]

my machineist basically said the same thing as tt said,he has very expensive and acccurate measuring tools,and thats why i took it there,but if i was checking a rod for myself i might try it since i dont have the measuring tools

[sorekiwi 761]

OK I'm gonna go the other way!

If you dont have the inside and outside mics to check your numbers then I would definately use it, Don. My opinion is that the guy assembling the motor has the responsibility to check the clearances as he puts it together. I use mics to get my numbers but I have used plastigauge in the past, and I probably will use it on occasions in the future.

The packet has a scale on it that you compare to the squished up "string" and will give you your clearance to 1/2 a thousandths or so. It comes in 3 different sizes for measuring .001-.003", .002-.006" and .004-.009. I dont remember the color of the packages but I'd buy a pack each of the 2 smaller sizes for checking your con-rod clearance.

I measure everything when I am putting an engine together, no matter who did the machining. I've had bad days when I've screwed something up or read a mic wrong, and I know some very very good machinists that have missed the mark on a piece every now and again. And I guess I like to know what my numbers are, and also where I am taking an (educated) gamble!

The following is not aimed at you in any way Don, but while we are talking about putting engines together, there is something I would like to throw out there...

If you look at the "Engines" section here, and look at all the "I just rebuilt my engine, and something is not right, and it must be crappy parts" threads you will notice that in 99% of these cases people didnt check things. The manuals spell it out for you, they tell you what to check and how to check it. They give you the numbers you should see, and they tell you how to put it all back together. It seems that there are a large number of people that think that all you need to do is get a big pile of pieces and bolt them together and then you can call it a rebuilt motor.

One guy in the last year had his engine get tight when he was torquing up his con rod bolts so he decided to just loosen them off until the crank was free again. Others talk about their fully rebuilt engines and then ask how to check their valve clearances. People putting engines together and not setting up (or even checking) the endfloat on the crank, or the gaps on the rings, or the side clearance of the rings in the piston, the widths of their valve seats or any other of the critical clearances.

Sorry about the rant here, I am just dont understand why people dont bother to read the manual or do what it says, and then have the nerve to come to a public place (on the internet) and complain about "cheap aftermarket parts" or "bad machinists" or "badly designed engines".

It's not that hard to put one of these little engines together, but there are a ton of things that can wrong as well. Maybe that mechanic down the road isnt as stupid as he looks after all.

End of rant... :hide:

[Martin 2,133]

i totally agree with sorekiwi here on all points. ive assembled enough of these things in the last six months to almost know the kohler manual reconditioning and assembly section and clearances by memory. that manual is the best way to learn about these things.

it also never hurts to check things twice. its easier to do while the engine is apart than when its back together running with a problem..........

[buckrancher 2,694]

food for thought plasti-gage will not check out of round

Brian

[rmaynard 15,916]

food for thought plasti-gage will not check out of round

Brian

That is true if you only do one test, but you can rotate the crankshaft 180 degrees and do a gauge on opposite sides of the crank pin. That will show a difference if it is out of round.

[can whlvr 993]

i fully agree mike,i have the manual and have read it alot and printed out a copy,now i will print the one bob placed in the files area,so i still ask about the torquing of the rod bolts after you take the plasigauge out,is it used or still new,and the machinest says that it was checked by a different person than did the machining and they do this with all there stuff,they dont do too many small engines as compared to hotrods,tractors,machine engines,but they do all the small stuff in our town,they are the only ones left,thanks for the input guys,it helps and thats why i asked,but im not sure about the gauge because i really dont want to untorque the new rod bolts,is it ok or not to do this is the question i ask,i wish i had a good mic,cant afford it now,im rebuilding this motor to sell the tractor,im out of work and work for myself so i need the bucks,i couldnt sell it the way it was,i never saw an engine smoke so bad,one day a good mic is in order,but then you need one large enough to do the piston,and the gauge to read the bore,etc

[Rooster 191]

Engine clearances are machined by machinist.

No machinist worth his salt would ever use it.

Just my opinion, and only my opinion, I know others have theirs and I respect that..but in my opinion if you are going to be building engines you should have the tools to do it with. You cannot build an engine without mics.

If you just want to build your own engine, you can take it to a machine shop and have it checked if you do not have the tools, most machinist are happy to do it for you for little or nothing.

[305 380]

regardless who did the machine work and how accurate they can measure...it is still up to the guy assembling the motor to make sure everything is correct. call it a final inspection. i prefer using micrometers myself

plasi gauge can be bought at any O'Reilly auto parts

[squonk 42,534]

Another thing about plastigage. If you decide not to use it and then not pay attention and put the rod cap on backwards you would not even know it. If you were using plasti gage it could very well show up. When I sold crank kits at Napa I can recall 2 times when I got a call about "Your crank and bearings are no good" "I plastgaged it and the clearence is off" Come to find out both times they had a cap on backwards.

[TT-(Moderator) 1,147]

you can rotate the crankshaft 180 degrees and do a gauge on opposite sides of the crank pin. That will show a difference if it is out of round.

You have now torqued those same fasteners three times......... what torque spec do you use after the first time - new or used?

What method do you / would you use to lock the crankshaft? Even the slightest rotation of the crankshaft will smear the Plastigauge and the "reading" could be inaccurate.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Come to find out both times they had a cap on backwards.

Sounds like another reinforcement to Kiwi's post...... there are experienced people with the proper resources/facilities, there are parts changers, and there are people who can't tell a carburetor from a fuel pump.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Before anyone schedules me for castration, my first post in this topic merely states my method of determining rod to crankpin clearance.

I am fortunate enough to own and/or have access to precision measuring tools, engine assembly tools, etc. Doing this for yourself is one thing (and your money) but when you do it for others, you better make sure it's done properly or your reputation / job is at stake.

As I have said in the past, these engines are not puzzles or Legos - you can't keep guessing or trying different ways to put them together until you get it right. :thumbs2:

[rmaynard 15,916]

you can rotate the crankshaft 180 degrees and do a gauge on opposite sides of the crank pin. That will show a difference if it is out of round.

You have now torqued those same fasteners three times......... what torque spec do you use after the first time - new or used?

What method do you / would you use to lock the crankshaft?

You asked "what method do I use". Since I have only worked on the K-Series and never had a rod that uses Posi-lock nuts, my info is based on standard cap-screws. The Kohler K-Series manual states that in the final assembly, you should over-tighten the cap-screws by 20%, loosen and then re-tighten to the correct torque. New rods or used rods have the same 285 in. lb. torque value, K241 through K341. When I use Plastigauge, I only torque to 285 in. lb., remove the cap and check the gauge. Final assembly is done as stated previously.

As far as how to lock the crank, if the flywheel is on, I lock the crankshaft by attaching vice grips to the starter ring gear. If the flywheel is off, I clamp the vice grips to the counter weights on the crank.

The M-12 may be a different procedure, but I am only offering my experience.

[buckrancher 2,694]

food for thought plasti-gage will not check out of round

Brian

That is true if you only do one test, but you can rotate the crankshaft 180 degrees and do a gauge on opposite sides of the crank pin. That will show a difference if it is out of round.

still really does'nt tell you anything.How round is your rod? is the problem the crankshaft ? and Bob that should be 90 degrees not 180 degrees

you can pick up cheap chinese made mic,s for $20.00 and thier still better than plasti-gage

Brian

[rmaynard 15,916]

...and Bob that should be 90 degrees not 180 degrees

Brian

If you want to get the top and bottom, it's 180 degrees. Turning it 90 degrees will only get the side.

[buckrancher 2,694]

...and Bob that should be 90 degrees not 180 degrees

Brian

If you want to get the top and bottom, it's 180 degrees. Turning it 90 degrees will only get the side.

top and bottom ( 0 & 180) is the same thing your still only checking one direction you have to rotate 90 degrees

and check on the 90 or 270 degree side to see out of round (the differance between the two readings)

[can whlvr 993]

so i didnt know such a debate would come of this,its a great question,what torque rateing do i use,i went to the machineshop today and talked to one of the machinists because i couldnt find what torque setting to use if i plastigauge it,he said new specks,they recommend torqueing the rod down 3 times,to properly stretch the bolts then set them at new rod setting,he said its up to me to decide about the plasti,like he said its better than nothing if you dont have a mic,inside and out,i read here where a cheap micrometer read incredibly wrong and created problems,i got it done from a very good shop,i do trust them but im going use the gauge,its only 4.50 for a strip,great food for thought this thread ended being,keep the thoughts coming

[rmaynard 15,916]

top and bottom ( 0 & 180) is the same thing your still only checking one direction you have to rotate 90 degrees and check on the 90 or 270 degree side to see out of round (the differance between the two readings)

Point taken.

However what I was trying to point out is that when the crankshaft is in the up position (ATDC), and the spark plug fires, that is when the connecting rod is rammed down against the crank journal. That constant pounding tends to flatten that portion of the journal more so than the 90, 180, or 270 degree sides which only get rotational wear.

So comparing the 0 degree measurement against any of the other three areas will reveal an out of round condition.

[can whlvr 993]

so i was reading the kohler manual again(for the tenth time this week)and it says dont take off the posi nuts,i guess they are a one time deal?so now im relly torn,what do you guys do,dont check or do i have to order more nuts,if you r supposed to check shouldnt they give you spares?

[buckrancher 2,694]

the spark plug fires before top dead center so what you are saying does not apply as the rod is never rammed down on the crankshaft

it is always in contact with the crank journal

Brian

top and bottom ( 0 & 180) is the same thing your still only checking one direction you have to rotate 90 degrees and check on the 90 or 270 degree side to see out of round (the differance between the two readings)

Point taken.

However what I was trying to point out is that when the crankshaft is in the up position (ATDC), and the spark plug fires, that is when the connecting rod is rammed down against the crank journal. That constant pounding tends to flatten that portion of the journal more so than the 90, 180, or 270 degree sides which only get rotational wear.

So comparing the 0 degree measurement against any of the other three areas will reveal an out of round condition.