THEFERMANATOR

New here but not new to wrenching and swaps, some may even recognize me from the diesel forums where I've been the most active the last 15 years. I recently picked up a 99, 2 door, 2 wheel drive, 5.7l, Tahoe to drive while I get my 95 Duramax Suburban fixed back up, then I was planning on swapping it.

I already did the 0411 swap, marine intake(was a freebie from a friend), and dual electric fans(controlled by the 0411), but the L31 has decided it wants more love. It only has 159k miles on it, but several lifters have started ticking BAD, it's burning some oil, and I don't want to put any money into this engine.

I've been bouncing back and forth between either using a low mile 638 4 bolt main block I already have to build a 383 vortec for it, or do an LQ4 or LQ9(LQ9's are cheaper at the junkyards) 6.0l swap with a 4l80e behind either one. To me the SBC just doesn't make sense as it is a direct bolt in, but it won't have the power potential of an LQ9.

Since my current L31 vortec has decided to bump up my time frame, I've started looking at some lower cost alternatives. I started looking through car-part and LM4's can be had pretty cheap. So now I'm torn between building an LQ9/4l80e or an LM4/4l65e. What are REALISTIC power goals of each with just basic bolt-ons, head porting, and cam swap? And how well will a mild built 4l65e hold up to a basic LM4 build?

I know these are 2 fairly different builds, but I'm trying to decide if it's worth pushing my L31 hoping it will hang on, or just do what I can get done sooner. Thanks for any insight you can provide.

G Atsma

There are a LOT more LQ4's than LQ9's. Usually the LQ4's are cheaper by a decent amount. Both are iron blocks. Must be different in your area
Also, you should be able to find iron LM7's far more easily and less expensive than aluminum LM4's.

tfi racing

iTrader: (2)

LQ4/4L80E is my pick, unless a LQ9 falls into your lap for the same money,hard to justify the extra cash for the aluminum block in such a heavy pig of a vehicle,the few pounds saved mean very little in this big scheme of things.Since you are 75% of the way there with the 411 swap,it makes little or no sense to waste any effort on chasing more power on a L31 build.

THEFERMANATOR

Checking car-part.com, LM4's are going for $650-800 by me, LM7's are going for $800-1100, LQ9's can be found for $1100-1400, LQ4's are going for $1350 and up, and L33's are bringing LS1 money. Even on facebook and craigslist everybody is wanting $1300-1800 for LQ4's with DBC. It surprised me to to see LQ9's for less than LQ4's.

G Atsma

Then get an LM4.