What color plastic gauge do I use to measure the clearance of the rod caps caps
I think it's green
Will, Use the green version. It measures between .001" - .003" which is what will work perfect for most engines.
Green is the correct range for rod caps.
Take your pick.
I use aluminum foil. Depending on the thickness of your foil, a folded square about 1 X 1 inch, 2 to 3 layers thick works great.
If you use the plastic gauge don't use it dry. In a shell bearing with just a thin coat of babbett dry works, with full babbett bearings I have found that working dry it wants to imbed rather then spread. Green would be correct for rods or mains.
Will : I use the green one's ,and then for the mains and rods .0015
Related question, does Plastigage go bad? The strips I have are 20 years old, are they still usable?
I needed Plastigage so I check it on-line and learned that they had it at my local AutoZone store.
When I told the Kid that I wanted plastigage he drew a complete blank.
I then told him that it is used to measure clearances of bearings.
That didn't help!
He finally said that they don't have plastic bearings and started to walk away.
I stopped him and said that it might be a good idea to look in his computer.
In the end I got the plastigage and he actually learned something -- MAYBE
Yew Plastigage does go bad, it get hard.
Plastiguage is not useful for measuring worn bearing caps. It only measures clearance in one spot. The bearing wears egg shaped, unevenly. Measuring clearance in one tiny spot tells you virtually nothing.
Plastiguage is useful for checking clearance on freshly machined bearings in a modern engine where all surfaces are concentric.
Model T bearings are best checked and adjusted without use of plastiguage. Proper technique is to use Prussian blue to check even contact pattern on a bearing if it is scraped or adjusted. The engine operating will cause proper clearance to happen through wear.
A 3/4 X about 2 3/4 inch strip of newspaper was used in the old days to check the rod bearing clearance.
If the crankshaft was difficult or impossible to turn over with the strip in place and turned free with the strip removed, the clearance was just right.
Evidently old news print paper was about .001 inch thick.
Royce - Oh my! You said, "The engine operating will cause proper clearance to happen through wear."
I guess my thought about that is,......gosh,....if only it were that easy! Ha, ha,.....I guess I'd have to say that that makes about as much sense to me as the method of fitting new bearings by "burning them in" by forcing rotating a new stiff engine by machine driving the crankshaft until the heat of friction "breaks-in" new bearings. (???)
What Royce said is absolutely true with poured babbit bearings. A bearing which requires a "slight tap with a hammer" to move along the crankshaft (after adjusting rod bearings), will move freely the next time you check. It only takes a minute or two of running to relieve to proper clearance.
I purchased a sad little runabout which had no shims and very loose rods. Careful filing of the caps created enough room for a short shim stack. Scraping/fitting the bearing caps left good bearing coverage on the caps/crank and snug fit on the crank when assembled (tap with hammer). Drove for a week. Checked rods and were loose. Pulled a shim. Now it's snug again (tap with hammer). Drove another week. Rods fit fine. 4-5K miles and rods are still silent.
With clean oil and a good crank, the bearings will form to fit and clearances will become nominal.
You didn't mention if the engine is in the car or out on a stand.
When I adjusted my rod caps (engine in car)I found it VERY difficult to hold the plastigage, tighten the caps, put in the spacers, and find that tiny piece of plastic once the cap came back off.
Long story short I finally used the method in the mtfca engine book (I think that's the one) which is to tap the rods with a small hammer and observe the sideways movement. Although it seems a bit imprecise, it worked extremely well and was orders of magnitude simpler.
The tapping with a hammer method is described in the Ford shop manual. It works perfectly. No plastiguage required.
Bud, The engine is out of the car. I checked all four rod caps and they were with in spec's. Thats good. But that said there are no shims at all left.