The Ford Barn

Roadster Rich · 09-13-2015, 07:35 PM

I have a 1930 engine to check out before trying to fire it up. Found a cracked cylinder head and have been convinced to move up to at least a 5.5 compression head rather than use a standard cylinder head I have. Now I have dropped the pan and the oil looks quite good, no sludge to speak of and no particles. I have used plastigage in the past and always just put one piece lengthwise along the journal of the rod or crank. What is the best way to use this to check if journals and Babbitt are good? How many pieces, what orientation, etc. If I check the rods and find them pretty good, should I also pull the crank bearings to plastigage those? I checked my other car engine last year when I opened it up for the first time since I did the rebuild in 1966 and just checked with one length of plastigage, but now I am not sure if that is the best way.

DougT · 09-13-2015, 08:16 PM

Plasti-gage is OK for a quick check but I wouldn't bet the farm on it either. There are cases that can make it inaccurate. They claim that stuff that's been around a while may not be it's original shape or thickness. That will change the final squeeze size. The other thing would be how you tighten it. Don't put the plastic on the cap and then pull the piston out of the bore with the rod nuts. Push the piston with the crank and then put the rod cap up. If you check at 1/4 revolutions of the crank it might show out of round but it really should be checked in the same spot in the cap

Patrick L. · 09-14-2015, 06:04 AM

I just use one length of plastic-gauge. Just remember to oil it. I haven't found much issue with the rod bearings and I like them at .0015". The center and rear main wear the most requiring the most attention. I also set them at .0015" and the rear maybe a little tighter.
I'll give it 1/4 turn and check again, if the same I leave it alone.

bobH · 09-14-2015, 10:21 AM

Opinion here... And, elaborating on post #2, which I believe alludes...
I believe the 'idea' is to get the 'clearance' all on one side, the side where you are using the plastigage. Doug posts how to do it for the rods. I would add, for the mains, some guys like to put a little piece of cardboard (matchbook cover, or business card) under the main caps that you are NOT checking, then plastigage the cap WITHOUT the cardboard. The idea being, push the crank upward, measure on dowward (cap) side.
As said, only a thought & opinion.

Kohnke Rebabbitting · 09-14-2015, 10:26 AM

1. Always use the cap when using Plastigauge, never on the rod, or at 1/4 turns, as it is a useless reading.

2. Always use 2, or 3 drops of oil in the cap so the Plastigauge spreads out, rather the digs into the babbit, and it will when used dry.

3. Never read the Plastigauge in the cap, always on the hard surface of the crank.

4. If Plastigauge dosn't work for you, you are doing something wrong.

5. Always use a piece cut in half, one on each side, as the middle tells you nothing, and the x grooves, and the dipper hole is there.

6. If you want to check roundness, use a Mic.

7. Age of Plastigauge makes no difference in working, but if brittle, yes, get new.

Jim Brierley · 09-14-2015, 10:42 AM

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Do as Kohnke says, it works and works well.

Roadster Rich · 09-14-2015, 12:06 PM

Thanks to Kohnke for a great tutorial that answers all my questions. So great to have all of you to answer the questions that some of us feel may be showing our stupidity (or at least lack of knowledge).

Patrick L. · 09-14-2015, 12:50 PM

I probably should have mentioned a couple more things.
I put light hydraulic jack pressure against the crank when checking.
I have had troubles in the past peeling shim packs and have had some with solid shims, so, I don't mess with that. I just sand them on a sheet of glass and measure the ends and center to make sure they are the same.
I look at what the plastic-gauge says, measure the shims, figure out how much to remove and sand away. I keep the shims the same on each side. [ I know you don't have to, but,,,,,]

aermotor · 09-14-2015, 01:12 PM

How much difference can you have with shim thicknees different on each side? It seems to me that at some point the nut and head flats of the bolts will cause the bolt to bend from the flats not being parrallel.

Tom Wesenberg · 09-14-2015, 02:16 PM

Quote:

Originally Posted by aermotor

How much difference can you have with shim thicknees different on each side? It seems to me that at some point the nut and head flats of the bolts will cause the bolt to bend from the flats not being parrallel.

Yes, you should be able to keep them equal side to side by no more than .002 difference.

Kohnke Rebabbitting · 09-14-2015, 06:01 PM

Pulling shims from both sides, is to much of an adjustment, unless they are wore that bad, but still start with one side, so you don't have to back track.

Normally, .003 are on the mains, and .002 on the rods, but it doesn't make one harder then another.

You want to pull a .002 shim on one side, and try the crank and see if there is a bind on the pull. If there is, and you think the .002 is too loose, to put back in, then make a shim out of .001 brass stock, and that should be exactly where you want it.

If you pull a .002 shim out, and put in a .001, it will drop the clearance by .000-50.

Herm.

09-13-2015, 07:35 PM	#1
Roadster Rich Senior Member Join Date: May 2010 Location: Alpharetta, Georgia (Atlanta) Posts: 272	Plastigage Bearings? I have a 1930 engine to check out before trying to fire it up. Found a cracked cylinder head and have been convinced to move up to at least a 5.5 compression head rather than use a standard cylinder head I have. Now I have dropped the pan and the oil looks quite good, no sludge to speak of and no particles. I have used plastigage in the past and always just put one piece lengthwise along the journal of the rod or crank. What is the best way to use this to check if journals and Babbitt are good? How many pieces, what orientation, etc. If I check the rods and find them pretty good, should I also pull the crank bearings to plastigage those? I checked my other car engine last year when I opened it up for the first time since I did the rebuild in 1966 and just checked with one length of plastigage, but now I am not sure if that is the best way.

09-14-2015, 06:04 AM	#3
Patrick L. Senior Member Join Date: May 2010 Location: Largo Florida Posts: 7,225	Re: Plastigage Bearings? I just use one length of plastic-gauge. Just remember to oil it. I haven't found much issue with the rod bearings and I like them at .0015". The center and rear main wear the most requiring the most attention. I also set them at .0015" and the rear maybe a little tighter. I'll give it 1/4 turn and check again, if the same I leave it alone.

09-14-2015, 10:21 AM	#4
bobH Senior Member Join Date: May 2010 Location: so cal, placerville, vegas Posts: 1,394	Re: Plastigage Bearings? Opinion here... And, elaborating on post #2, which I believe alludes... I believe the 'idea' is to get the 'clearance' all on one side, the side where you are using the plastigage. Doug posts how to do it for the rods. I would add, for the mains, some guys like to put a little piece of cardboard (matchbook cover, or business card) under the main caps that you are NOT checking, then plastigage the cap WITHOUT the cardboard. The idea being, push the crank upward, measure on dowward (cap) side. As said, only a thought & opinion.

09-14-2015, 10:42 AM	#6
Jim Brierley Senior Member Join Date: Jun 2010 Location: Temecula, CA Posts: 4,085	Re: Plastigage Bearings? Sponsored Links (Register now to hide all advertisements) Do as Kohnke says, it works and works well.

09-14-2015, 12:06 PM	#7
Roadster Rich Senior Member Join Date: May 2010 Location: Alpharetta, Georgia (Atlanta) Posts: 272	Re: Plastigage Bearings? Thanks to Kohnke for a great tutorial that answers all my questions. So great to have all of you to answer the questions that some of us feel may be showing our stupidity (or at least lack of knowledge).

09-13-2015, 08:16 PM	#2
DougT Member Join Date: Dec 2014 Posts: 53	Re: Plastigage Bearings? Plasti-gage is OK for a quick check but I wouldn't bet the farm on it either. There are cases that can make it inaccurate. They claim that stuff that's been around a while may not be it's original shape or thickness. That will change the final squeeze size. The other thing would be how you tighten it. Don't put the plastic on the cap and then pull the piston out of the bore with the rod nuts. Push the piston with the crank and then put the rod cap up. If you check at 1/4 revolutions of the crank it might show out of round but it really should be checked in the same spot in the cap

09-14-2015, 12:50 PM	#8
Patrick L. Senior Member Join Date: May 2010 Location: Largo Florida Posts: 7,225	Re: Plastigage Bearings? I probably should have mentioned a couple more things. I put light hydraulic jack pressure against the crank when checking. I have had troubles in the past peeling shim packs and have had some with solid shims, so, I don't mess with that. I just sand them on a sheet of glass and measure the ends and center to make sure they are the same. I look at what the plastic-gauge says, measure the shims, figure out how much to remove and sand away. I keep the shims the same on each side. [ I know you don't have to, but,,,,,]

09-14-2015, 01:12 PM	#9
aermotor Senior Member Join Date: Mar 2015 Location: Greenville, SC Posts: 1,099	Re: Plastigage Bearings? How much difference can you have with shim thicknees different on each side? It seems to me that at some point the nut and head flats of the bolts will cause the bolt to bend from the flats not being parrallel.

09-14-2015, 06:01 PM	#11
Kohnke Rebabbitting Senior Member Join Date: May 2010 Location: 60615,330th Ave.,Clare, Iowa, 50524 Posts: 1,457	Re: Plastigage Bearings? Pulling shims from both sides, is to much of an adjustment, unless they are wore that bad, but still start with one side, so you don't have to back track. Normally, .003 are on the mains, and .002 on the rods, but it doesn't make one harder then another. You want to pull a .002 shim on one side, and try the crank and see if there is a bind on the pull. If there is, and you think the .002 is too loose, to put back in, then make a shim out of .001 brass stock, and that should be exactly where you want it. If you pull a .002 shim out, and put in a .001, it will drop the clearance by .000-50. Herm.