Mike192

Hey everyone! My name is Mike and I'm not really terribly experienced with the LS platform but for the past month or two I've done extensive research and feel as if I have come to a solid understanding of these engines.

little background I guess, I'm a BMW enthusiast for better or worse, i drive an e39 540i that's been pretty modified and it's amazing seeing how much power people get out of the LS engine family. For the price of what I'm doing to this lq4 and getting +100hp I'd get around 25 hp on my engine lol.

Anyways time for my questions.

My little sister drives a 2007 2500hd classic (basically the same thing as a 2006) so it has the lq4 6 liter. The engine has around 280k miles on the clock and while it runs fine and has good oil pressure it's on borrowed time. It periodically looses oil pressure or will get gnarly lifter tick as if the lifters are starved of oil. I'm pretty sure it has some variety of oiling issues whether it be a failing pump, bad pickup tube o-rings, or clogged oil passages. Anyways its getting a rebuild.

A little power gain while I'm in there would also be nice so here is my plan.
Im keeping the 317 heads because I see no point in rasing the compression to run 93, that stuff is much more expensive then regular these days and she's 17 so she can't afford it.
I got a set of heads off of a friend that are 317 castings that had new guides, a fresh valve job, resurfaced, and with pac .600 lift beehive valvesprings in them for 300 bucks so that's what the cylinder head situation is looking like. I've ported many heads so I just cleaned up the castings, smoothed out the bump in the intake port where the rocker bolt goes and did around a 84% bowl cut, pretty mild port job.

Cam specs are the btr truck norris camshaft 212/22x, .552/.552 with a 107 lsa.

Bottom end is just stock rods with new bearings and .030 over pistons.

here is where the questions come in.
If i put lq9 flat top pistons in that raises the static compression ratio to around 10:1, I'm thinking in a heavy truck on a hot day with a load behind it that will quickly start sending the pistons out of the exhaust in little chunks on 87 octane so I don't think that's a viable option. I could lower the spark tables to keep it safe but I'd loose way more power then if I just ran stock compression right? Only issue is finding lq4 dished pistons has seemed to be an issue, this is a late lq4 with floating wrist pins and all the pistons I find are press pin. Any advice here?

I'm going to do a trunion upgrade, how necessary is that with this camshaft? Is it an issue in the stock engines or does it only rear it's head with larger camshafts?

If I spin the engine to 6800 rpm with ARP rod bolts how reliable will that be? The camshaft pulls to around 6500 rpm so I figured I'd allow a couple hundred rpm over that for shift points and all.

Is it true that a high volume oil pump will pump the pan dry before the oil can drain back out from the heads?

Would it be stupid to not replace the wristpin bushings while I'm in there? I'm not really sure how long they last as I've never rebuilt a super high mileage engine before.

This cam isnt hot enough to reasonably lower the dynamic compression ratio enough to run 87 with flat tops is it?

I'll probably post a couple more questions as i think of them later, thank ya'll in advance!

grinder11

iTrader: (1)

I only quoted you to see the questions, as you have several.

If LQ9 pistons are readily available, and LQ4 pistons aren't, why not go with LQ9s and source thicker head gaskets thru Cometic? Just a thought.....

Wrist pins I don't have any advice, but I'm sure someone here will....

DO NOT do the trunnion "upgrade." In most cases, it's a downgrade. This cam is a fairly mild cam, and Ive put 10s of thousands of miles on a 232/236/.610" lift cam and dual 921 Comp springs that were setup (by AFR) .100" too stiff!! Never had any issue with stock trunnions. The fact.your OEMs went almost 300 thousand miles should answer that one.......

ARP rod bolts are as good as, or better than, any. Even if you're a millionaire. You should be fine.

FALSE on the HV Melling. Especially if running the stock pressure relief spring, which I recommend.....

Without a thicker head gasket, the flat tops are probably too much for 87 octane WITH THAT CAM.....

Hope this helps you out.....

Mike192

I appreciate the advice, I'll stray away from the trunion upgrade. So factory replacement rockers should do me just fine. I'm finding mixed info on the 8.1 injectors, some people say they only for on >2005 trucks and some people say they work for all of them. I know the stock injectors can basically handle no extra power.

grinder11

iTrader: (1)

IDK the flow rate of your injectors, as in how many lbs/hr they flow, but I'd hold off going with larger injectors until you know you have to go that way. It's not like you're going to have a 100hp gain. Research injector size requirements here on the forum. A good tuner should be able to answer the flow questions. Keep in mind the 300,000 miles that the injectors have on them now. It would really suck to have a fresh build damaged by a failed/plugged injector. Considering the 300,000 miles on them, I'd probably buy new ones. A tuner should be able to tell you what size you need! Best of luck to you....