I recently swapped to a LSX 376 with rectangle port heads. I am running a Vortec V7 YSI. Currently cylinders 1 and 3 are showing lean when I pull the spark plugs. The plugs in cylinders 5, 7, 2, 4, 6, and 8 look good after a run. I have swapped sides on injectors and coils and the problem stays on cylinders 1 and 3. I have been running around 16 lbs of boost. I tested a smaller pulley this week to see what the supercharger was capable of and logged 23 lbs of boost. All plugs minus 1 and 3 looked great. 1 and 3 showed obvious signs of detonation.

Anyone have any ideas what could be causing this other than the intake (see below)? E38 ECU in a 2008 Silverado.

I am starting to think the problem could be related to the intake I am running. It is a made in China sheet metal unit (3rd? version with bell mouths on longer runners). It kills low end power so I am looking to swap it anyway. I don't have a stock L92 unit to run (I'm not a fan of the looks, but I know they perform well). I am running ID1000s and a fuel system with a return regulator (and two 340 LPH pumps fuel pressure is rock steady).

If you had to buy an intake and planned on running 20+ lbs of boosts what intake would you buy (something that will work with my current fuel set up and to pick up some of the low end I am giving up with the current intake as well)? Also I will eventually be swapping in a cam (the LS7 cam is a mediocre boost cam).

HI-RAM
LSXR (I wish there was a rectangular port LSXRT)
STOCK LS3 or L92 (that leaves me cash to buy a cam)
Something else that I am not aware of?

Other factors:
3800 stall
I have a set of AFR cathedral port heads that I think would be as good or better than the rectangle port heads, but I like the idea of keeping the 6-bolt heads.


Thanks,

Mike

 

I have a hi ram for my Chevelle and I plan on 20 PSI.

What is your fuel system, and how are the lines ran? Is there any way you can measure fuel pressure at the front of that rail?

Was any work done to the heads?

 

When you say lean, are you sure you know what youre looking for when reading a plug

I recently had a cold hole and found out my injector was clogged....tested this with a temp gun on primaries

A proper fuel reading on a plug shows very little color but a hot cylinder can resemble lean

As for detonation look at the timing mark on strap if you are so far past the bend that your mark is into the base your way to hot as either plug range or timing


Get yourself a heat gun and read primaries

Next get a volt meter and put it across the injector plug and see what voltage is while running...this will tell you if pcm is commanding the ground and if that plug is seeing 12v+

 

No head mods. Under boost I feed the back of each rail. My regulator is on the front loop between the rails. Yes I can measure fp at the front of that rail.

 

After 1 wot pull on new plugs 1 and 3 have small aluminum specs (detonation). I assumed it was from a lean condition. On the plugs I pulled that with the fried ground all but 1 and 3 look to have a good burn. I'll check voltage at the injectors next. I have a heat gun I'll check the primary's temp.


One other thought, I could have the plugs for 1 and 3 injectors swapped.

 

Detonation shows up as black specs on the porcelin
The strap will be distorted