LQ4-E39

iTrader: (7)

recently blew a hole in the side of my stock 2003 LQ4 block. I was running a completely stock bottom end (crank, rods, dished LQ4 pistons). The only internal modifications were a 228R TSP cam. Heads were 317s milled .026" for a 66cc chamber to bring compression back up.

Now that the block is toast (along with 1 smashed piston and broken rod), I'm tossing around the idea of throwing in flat-top pistons to raise compression even more. Here are my questions:

1. Provided I can pick up a used set, would a set of stock flat top LS2 or LQ9 piston/rod assemblies bolt up to a stock 2003 LQ4 crank? I would be installing new bearings for peace of mind. I also would not be trying to retrofit LS2/LQ9 pistons onto LQ4 rods (I'm aware of the pressed/floating wrist pin difference) - it would be an LS2 or LQ9 rod/piston factory assembly going onto the LQ4 crank.

2. One of the 317s was trashed when the valvespring broke (valve gouged the combustion chamber). One option I have is to buy another 317 head cheap and have it milled to match the good one on the motor. If I go with this route, will I have to worry about PTV, given a 228R cam (.588 lift) and flat tops?

LQ4-E39

iTrader: (7)

anyone?

dw456post

I used LS2 rods and Flat top Wiseco pistons in a LQ4 with .585/585 lift cam with no problems. Heads were stock 317, but I don't think you will have ptv clearance problems. I'm getting ready to put a set of 2005 GTO LS2 rods for sale on here tomorrow.

LQ4-E39

iTrader: (7)

I have a line on some piston/rods, but just in case that falls through, PM me what you're looking to get for the rods.

Did you have to rebalance the new pistons/rods to match the old stuff?

farmington

iTrader: (14)

If you are looking to a factory piston, consider a LS3. Since you are using an iron block, it would just be a bigger overbore and get you 18 more cubic inches and less valve shrouding

dns87ss

iTrader: (3)

OP, did you end up installing the LQ9 piston/rod in your LQ4?

LQ4-E39

iTrader: (7)

No, I had the new block bored .030" over and used new pistons.

dns87ss

iTrader: (3)

ok thanks. Was thinking the same lq9 rods/pistons in lq4.

dawgs74

which pistons and rods did u use...I'm doing the same with ls2 flat tops .030 over and gen 4 rods, did you have to get balanced or did you simply swap them?.....

G Atsma

3-year old thread; you MIGHT get an answer.

dawgs74

Yea I just noticed that after I had posted. .....Opps

LQ4-E39

iTrader: (7)

Here is my detailed build for that engine. Don't own the car anymore

https://ls1tech.com/forums/generatio...ld-my-bmw.html