4.1 question

[adturbo]

rebuilding a non turbo 4.1 v6 engine ...what is the max this can be borred ? what about the stock cam specks ? i read in kb info that any lift above i think above 420 you have to cut the guides doun . so i need a starting point ...thanks

 

[Intercooler]

Don't think so on the guides. The walls are thinner to start with due to siamese bore. I would throw it away at anything over .030" if you plan on going 11.0's or faster on a daily or often basis. Now if you are going slower it may be fine.

 

[FJM568]

A lot of guys go out to a max bore of .035 over, which would give you a 4.000 bore, and then have custom pistons made...The reason being is there is a lot greater choice of piston rings in that size, due to it being the same bore as a Chevy...

Before you ask, NO, you cannot use Chevy pistons if you do bore it to 4.000...You still need to have custom pistons made...But you will save a little money on the piston rings because of the cheaper price, more selection and greater availability of the Chevy sized piston ring...

Also, you will find that a cam like a 212/212 or a 218/218 which is almost too big for the 3.8L will really wake up the 4.1L because of more cubic inches in the 4.1L...Also keep in mind that since the motor is about 10% bigger, you will need to use at least 50# injs or bigger and you will also need a bigger turbo than what you would think...

 

[Whitettype86]

U need to do alot of research on the 4.1. What are your plans like is it going to be street car or a strip car? Max Bore would be .035 I would not go any more due to the thin cylinder walls that a 4.1 has. I wouldn't go with a stock cam go with a 210/214, 212/212,
218/218, 224/224. What FJM568 says is true with cams and 10%
biggier than a 3.8. U need to check the deck for cracks and clean up the nasty casting flash in the lifter valley. Make sure u the head bolt holes have been radised and stress relieved thats were
they end up cracking. There is no turbo oil return prevision either u can drill return into the block or go into the oil pan which ever u like. I'd also go with center steel mains or a girdle to keep the bottom end toghter. There is alot of detail to these blocks compared to its smaller bother the 3.8. Do alot of research like said.