Thread: I need to know

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I have a new set of pistons sitting here and i cant find out what they fit. Can someone help me please? they are TRW part# 3942546 and thats all i know about them, they are for a small block, but i dont know which one. thanks

Mike, I can come close but not exact. My lit. has a 3942543 which is piston for a 30 over 350 that yields 11:1 compression with a 64cc head. This piston is listed as a hipo piece that came in 1969 L46 engine. But as you know, that one # difference may make a world of difference in specs.

Originally posted by shevy not heme
Mike, I can come close but not exact. My lit. has a 3942543 which is piston for a 30 over 350 that yields 11:1 compression with a 64cc head. This piston is listed as a hipo piece that came in 1969 L46 engine. But as you know, that one # difference may make a world of difference in specs.

im doing this for someone else so i dont know much about them .we thank they fit a 327 so i really dont know now. thanks for trying and if you run across anything new let me know.

The part number is a GM number, not TRW since ( I think) the TRW numbers start with the letter "L" and have 4 digits.

Try having the GM parts guy run a history on the part number....or does anyone have an older parts book (paper) that could be used.

mike in tucson

Originally posted by robot
The part number is a GM number, not TRW since ( I think) the TRW numbers start with the letter "L" and have 4 digits.

Try having the GM parts guy run a history on the part number....or does anyone have an older parts book (paper) that could be used.

mike in tucson

i really dont know, but they are in a trw box. its a old # hes had them for a while. thanks

Another thought.... if it is a GM part number, the 39xxxxx numbers are usually 1969 and later.....327 stuff should start with a 37..... you can measure the pin to piston topand tell if it is a 327 or 350 IF you knew the dimension......let's see

9.050 deck height (is this right?) less 5.7 rod equals 3.35

Then 3.35 is the sum of half the stroke plus the pin to piston top.

For a 350, the stroke is 3.48 so the pin to top is about 1.61 (center of pin to top of piston)

For a 327, the stroke is 3.25 so the pin to top is about 1.72

your numbers will vary, not valid in the southern hemisphere, void where prohibited, no cash value.

mike in tucson

Originally posted by robot
Another thought.... if it is a GM part number, the 39xxxxx numbers are usually 1969 and later.....327 stuff should start with a 37..... you can measure the pin to piston topand tell if it is a 327 or 350 IF you knew the dimension......let's see

9.050 deck height (is this right?) less 5.7 rod equals 3.35

Then 3.35 is the sum of half the stroke plus the pin to piston top.

For a 350, the stroke is 3.48 so the pin to top is about 1.61 (center of pin to top of piston)

For a 327, the stroke is 3.25 so the pin to top is about 1.72

your numbers will vary, not valid in the southern hemisphere, void where prohibited, no cash value.

mike in tucson

is that to the top of the pin?
i dont have the pistons, ill have to call him. if its wrong i wont charge you for the troubles ive had. thanks

Originally posted by robot
Another thought.... if it is a GM part number, the 39xxxxx numbers are usually 1969 and later.....327 stuff should start with a 37..... you can measure the pin to piston topand tell if it is a 327 or 350 IF you knew the dimension......let's see

9.050 deck height (is this right?) less 5.7 rod equals 3.35

Then 3.35 is the sum of half the stroke plus the pin to piston top.

For a 350, the stroke is 3.48 so the pin to top is about 1.61 (center of pin to top of piston)

For a 327, the stroke is 3.25 so the pin to top is about 1.72

your numbers will vary, not valid in the southern hemisphere, void where prohibited, no cash value.

mike in tucson

mike the piston mes. 11/8"??????

Robot is right, that is a GM # , I forgot to mention that.