The Ford Barn

Brendan · 05-15-2010, 12:59 AM

hi, i have a 35 21 stud motor, it was rebuilt about 35years ago, and was installed in a truck and it has about 2 hr run time on it. i pulled the heads off and was checking it out. i noticed that on cylinders 1 through 4 the pistons are marked front, and pointing to the front of the motor. 5 through 8 the front mark is pointing to the rear. is this something that i should worry about ? dose it make a difference? please help
thanks Brendan

Brian · 05-15-2010, 02:26 AM

Yes mate, it does make a vast difference! Ask yourself- if the pistons could go in either way, then why has the manufacturer taken the trouble to mark a specific direction [front]? Normally they have a split skirt on the non thrust side; this allows for thermal expansion. Placing the piston in backwards places this split side, which is weaker, on the side that is receiving all the side thrust. I am surprised that with two hours running already your pistons are still intact! I found this all out the hard way!! Remedy this situation immediately!! Brian

Barry WNY · 05-15-2010, 07:28 AM

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Yikes, that finally makes sense, what Brian said, seem's important. The marking of rods R & L besides numbering still doesn't to me, and when using reconditioned sets of oddball rods the correct placement was not possable for me.
When pulling the pistons I would look them over good, like ring gap arrangement, full float fit, pin & clip fit, placement.

05-15-2010, 12:59 AM	#1
Brendan Senior Member Join Date: May 2010 Location: At my kitchen table in Santa Rosa, Ca Posts: 2,905	35 21 stud hi, i have a 35 21 stud motor, it was rebuilt about 35years ago, and was installed in a truck and it has about 2 hr run time on it. i pulled the heads off and was checking it out. i noticed that on cylinders 1 through 4 the pistons are marked front, and pointing to the front of the motor. 5 through 8 the front mark is pointing to the rear. is this something that i should worry about ? dose it make a difference? please help thanks Brendan

05-15-2010, 02:26 AM	#2
Brian Senior Member Join Date: May 2010 Location: Masterton, New Zealand Posts: 3,859	Re: 35 21 stud Yes mate, it does make a vast difference! Ask yourself- if the pistons could go in either way, then why has the manufacturer taken the trouble to mark a specific direction [front]? Normally they have a split skirt on the non thrust side; this allows for thermal expansion. Placing the piston in backwards places this split side, which is weaker, on the side that is receiving all the side thrust. I am surprised that with two hours running already your pistons are still intact! I found this all out the hard way!! Remedy this situation immediately!! Brian

05-15-2010, 07:28 AM	#3
Barry WNY Senior Member Join Date: May 2010 Location: Sinclairville NY Posts: 230	Re: 35 21 stud Sponsored Links (Register now to hide all advertisements) Yikes, that finally makes sense, what Brian said, seem's important. The marking of rods R & L besides numbering still doesn't to me, and when using reconditioned sets of oddball rods the correct placement was not possable for me. When pulling the pistons I would look them over good, like ring gap arrangement, full float fit, pin & clip fit, placement.