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Perkins Piston clearance

A

Anonymous-0

Well-known Member
Just tore down my 354 Perkins, had a high RPM knock/rattle in #2 Cylinder. Expected to find a broke piston or rings but everything looks great in #2 hole & rod. I'm trying to find maximum allowable piston to liner clearance. My service manual says .006 with 5-7 lbs pull but that's on a new piston/liner. There has to be a max allowable amount of clearance? Mine measures .009 which I think is fine, can't believe that would make the pistons slap. Wishing I would have swapped injectors first...
 
Two things.

First re swapping around a couple of injectors - you live and learn. Best to check out the easy/cheap possibilities first and diagnosis is important.

Secondly, if it were number two clearance, how does that pot compare with another? If clearances are all the same, it ain't likely to be the problem.

Piston slap usually goes away as the engine gets towards working temperature from cold, so would be much more noticeable at cold start up. I would be asking an engine reconditioner the question. It could be a piston pin and that is usually a distinct rattle rather than a knock.

While it is apart I would be checking ring to groove clearance and ring end clearance for wear. Clearances for pistons and rings are usually quoted as a minimum and maximum per unit diameter for most all engines. I always remember, from way back when, ring clearance was 2 1/2 thou per inch of bore but I now use metric as they are so much more universal and generally easier.

RAB
 
yeah, lesson learned...I do know it was # 2, I cracked injector lines and the noise quit as soon as 2 was opened.
 
I'm not sure if I want to take the other cylinders apart to compare it, they all look really good and weren't making noise. As far as the hot vs cold, it actually didn't make the noise until it warmed up, once hot it became very noticeable above 1700 RPM
 
It might still not be too late to rule out the injectors. I would pop test them just to see what pattern they spray and pressure they crack at. Most dealer shops have an injector tester.
You can buy a pretty good tester on ebay for about $200 that is made in China. But, the working parts are usually Bosch(made in Germany).
Also, have seen guys post making them out of hydraulic bottle jacks. If someone had the time it seems like a good way to make a cheap tester.
 
I will second that. One time we had an engine with quite a bit of piston clearance(can not remember how much). Heated the piston with a torch and measured it. Again can not remember how much it expanded, but it was signicant.
Just thinking, when you put it back to together check the piston at top of stroke with a depth gauge and compare to other pistons.
 
Another thing you might want to do is put the engine back together. Had an engine doing something similar one time. Changed the timing a little bit until it went away.
Remove the cover on the pump drive. There are three allen bolts that hold the gear on the shaft. The holes in the gear are elongated and pump drive can be advanced or retarded with bolts loosened a little.
 
Would that change just one cylinder? Wouldn't that affect all six? I know it was the #2 cyl knocking...I'm hoping to have the injectors tested tomorrow at our local Deere dealer, assuming they have the adapters to hook up to my injectors.
 
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