Fox T-Bird/Cougar Forums

Technical => Engine Tech => Topic started by: jcassity on June 24, 2006, 12:43:51 AM

Title: STROKER issues
Post by: jcassity on June 24, 2006, 12:43:51 AM
Ok,,
so if you stroke an engine then basically the center line of the crank journals are further from the center line of the rod journals due to how the crank is made.  Therefore,, the rods must be longer and pistons will be shorter.

So if you were to compare two sepeate engines,, say a 3.8L and a 4.2 liter,,, and you have any one piston all the way down,,, wouldnt you expect the 4.2L to be sitting deeper in the cylinder than the 3.8?

My factory shop manual for the 3.8L calls out the stroke of a 3.8 to be about 3.3 inches.

I measure on the 4.2 liter from the block deck to the top of the piston and i come up with 2.9XX

Whats going on here?  Its seems the stroke is shorter on the 4.2 compared to the 3.8!!!
Title: STROKER issues
Post by: Thunder Chicken on June 24, 2006, 01:22:49 AM
The stroke of a 4.2 is 3.74 inches. Better get that tape out again :D
Title: STROKER issues
Post by: jcassity on June 24, 2006, 01:28:43 AM
I am measuring from the deck to the piston top,,,,

i used my depth guage on the dial caliper

sorry but i really am confussed here ,,,badly
Title: STROKER issues
Post by: Tbird232ci on June 24, 2006, 07:15:55 AM
I have a friend who is an engine builder, ill ask him how to measure stroke, because i dont think thats the proper way.
Title: STROKER issues
Post by: jcassity on June 24, 2006, 04:19:21 PM
of course thats the way you measure stroke,, the center line of the crank to the center line of the rod journals.  Now having said that,, the distance of the centerlines has no choice but to be transfered to the distance from the deck to the top of a piston that is BDC.

IF,, for instance, you have a crank to rod centerline distance of 1",, then the piston would only be able to move a full two inches of distance if you measure from the deck to the top of the piston when its down.
Title: STROKER issues
Post by: Haystack on June 24, 2006, 05:22:55 PM
Have you gotten anywhere else as of yet? I will have my yahoo on later tonight if you get bored again.
Title: STROKER issues
Post by: Haystack on June 27, 2006, 01:02:23 AM
find anything new out?
Title: STROKER issues
Post by: Haystack on June 27, 2006, 01:08:48 AM
oops found it in the other thread. Good luck!