overbore .020 Does the FSM - - -

[1stgen4evr]

Changing to a new shop for our machine work. Machinist doesn't have specs. What is the new piston to cylinder clearance for the B series. Is this info in the FSM?



1stgen4evr

James

 

[Grey Wolf]

James,



Per the FSM: Oversize pistons and rings are available in two sizes - . 50 mm (0. 0197 Inch) and 1. 00 mm (0. 0393 Inch). If over 1. 00 mm then you have to sleeve the block.

 

[1stgen4evr]

clearance

Grey Wolf, I am good to go on the sizes. What I am looking for is the difference between the piston size and cylinder size. The piston is smaller than the cylinder bore. I was hopeing that the FSM had some specs in that regard. We have the first oversize and want to know what to bore/hone the block. We have been using a shop that has done a very good job but is slow to get the work out. The shop we plan to use does not have the data on the Cummins specified clearance. The new shop has Powerstroke experience but no Cummins experience. We have settled on 5 to 7 thousandths for clearance.



Thanks for your reply

James

 

[Paychk]

James



The best I could figure is 0. 0093" - 0. 0115" for clearance on the piston.



These are the dimensions used to arrive at this:

cylinder bore max.

4. 0203"



piston skirt dia. min.

nom. 4. 0110"

worn limits 4. 0088"

 

[Grey Wolf]

OK James,



Boring Diameter Dimensions



1st. rebore - 102. 469 mm (4. 0342 inch)

2nd. rebore - 102. 969 mm (4. 0539 inch)



Honing Diameter Dimensions



1st rebore - 102. 520 plus or minus 0. 020 mm (4. 0362 plus or minus 0. 0008 inch)

2nd rebore - 103. 020 plus or minus 0. 020 mm (4. 0559 plus or minus 0. 0008 Inch)



Chamfer Dimensions



Approx 1. 25 mm (0. 049 inch) by 15 degrees



All of the above (per FSM) is for the . 50 mm first rebore and 1. 00 mm second rebore.



Sorry that's all I could find, which is more than the Cummins repair manual had in it... ... ...



By the way the information was in my 1993 FSM.

 

[1stgen4evr]

clearance

Thanks to Grey Wolf and Paychk. That is ecactly what I wanted. Looks like we had better raise the clearance from the 5 to 7 thousandths we first considered. Might not get run in before too much heat and disaster.



James