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I have a 5.3 lm4 from a 2003 GMC Envoy. Took forever to find the aluminum 5.3 so I'd really like to take care of it and not have a rod clearance the block. It has 211k on it but is very clean inside and it ran well. I wouldnt have torn it apart but it did have some oil leaks i wanted to fix. I plan on installing it and a t56 into an old Bimmer I've had behind my house for a while. The car will be mostly a dd with hard weekend runs up some local roads peppered with a few track days. The only modifications will be a ls6 cam and springs. Otherwise I plan on using the vortec intake and heads and converting to drive by cable. I may also run an oil cooler.
GM does a pretty darn good job of designing and building engines so I'd like not to replace anything I don't have/need to. With that being said, I have a few questions.
1. Upgrade oil pump or no? I've read all about the Mellings pumps but nothing about why to pick one over the other ( high volume high pressure vs. High volume normal pressure vs. High pressure normal volume). Should I just get a stock replacement?
OEM part number
2. Should I buy new timing gear set or just a chain. Sprockets show some light wear but teeth look good.
3. Should I run a chain tensioner? Ls2 or ls3? Why?
4. Cylinders still have cross hatch but show some very light streaks on the back wall. So light they almost rub out with a clean clothe but not quiet. What do you guys think?
5. I've read about high flow pumps running the oil pan dry. Is there a way to improve drain back in the heads? The old sbc stuff could have the drain holes drilled and the valley deburred. The performance GM pump says not to use without high capacity pan. What's high capacity? I'll be running a canton 6.5qt pan.
If it were mine, I would go with TSP's ported LS6 oil pump, LS2 timing set, LS7 lifters, new hardened pushrods, and the LS6 or GM Hotcam (for the sound mainly).
If it ran good when pulled, I would just leave the short block alone. As long as there are no deep scratches that you can feel with your fingernail, I wouldn't think there's any reason to worry.
EDIT: My old LQ4 had the TSP pump in it with a stock F-body oil pan. After MANY 7K rpm runs, never once saw any indication of the pan being run dry. Ran a pretty consistent 60psi of oil pressure.
If it were mine, I would go with TSP's ported LS6 oil pump, LS2 timing set, LS7 lifters, new hardened pushrods, and the LS6 or GM Hotcam (for the sound mainly).
If it ran good when pulled, I would just leave the short block alone. As long as there are no deep scratches that you can feel with your fingernail, I wouldn't think there's any reason to worry.
EDIT: My old LQ4 had the TSP pump in it with a stock F-body oil pan. After MANY 7K rpm runs, never once saw any indication of the pan being run dry. Ran a pretty consistent 60psi of oil pressure.
Are you suggesting to replace the lifters or upgrade? The ls7 and ls1 lifters are the same performance wise aren't they? Only the ls1 lifters are nla.
Same performance out of the lifters Hard to replace in the future. With that kinda miles it would be a good idea if it's in your budget.
budget...hmm. The original goal of the whole project was to do it for net 0. I picked up the BMW a while ago, for free, and sold enough off the Envoy to keep the engine and buy a t56. The biggest expense thus far has been the front sump Canton oil pan.
FWIW - I found a nifty little article comparing cams on an otherwise factory 5.3l
Oil pump - I called Melling and spoke with one of their tech specialists. Given that the car will be tracked on occasion (high RPM) and have an oil cooler, he recommended a 10296. Done - just ordered one.
For chain - since the sprockets look good I decided to replace just the chain with GM12646386. I also ordered the LS2 damper GM12588670 to make good use of the two little wholes in the block.
For chain - since the sprockets look good I decided to replace just the chain with GM12646386. I also ordered the LS2 damper GM12588670 to make good use of the two little wholes in the block.
With that many miles the sprocket teeth will be worn down considerably. I would replace the chain and sprockets with a ls2 unit. It's cheap and the ls2 chain is beefier. Don't forget about the valve springs. At 150k I floated a valve and it made contact with a piston. When I tested the springs all of them had minimum pressure left in them. Replacing the valve train is cheap insurance on a 200k engine at the end of the day.
With that many miles the sprocket teeth will be worn down considerably. I would replace the chain and sprockets with a ls2 unit. It's cheap and the ls2 chain is beefier. Don't forget about the valve springs. At 150k I floated a valve and it made contact with a piston. When I tested the springs all of them had minimum pressure left in them. Replacing the valve train is cheap insurance on a 200k engine at the end of the day.
I just picked up a low mileage LS6 cam from a fellow forum member with matching springs and retainers. I'll try to borrow a spring checker from someone to check them before installation.
The chain I ordered should be the replacement "upgrade" for the LS2 chain. No? Both the chain and tensioner were ordered from RockAuto but I cross checked the parts with GMparts direct. https://www.google.com/search?q=ls2+...h2eWAnn&dpr=1#
Are you suggesting to replace the lifters or upgrade? The ls7 and ls1 lifters are the same performance wise aren't they? Only the ls1 lifters are nla.
Sorry for the late response.
I would consider the LS7 lifters a slight upgrade over the LS1 stuff. Plus, you already have the heads off and you're swapping the cam anyways, why not go ahead and replace them while it's easy? Pushrods are also a cheap upgrade and would be good insurance.
Everything I recommended is factory or GM stuff. The oil pump I mentioned is a ported and shimmed stock pump. I believe it's actually cheaper than the one you ordered.
I went ahead and sprung for some LS7 lifters from Colorado Speed. I dropped the short block off at the machine shop to have it cleaned, checked, and re-assembled. I have been out of the country and will be for the rest of the month. I am hoping when I get back I can start putting it back together!
What valvesprings did you pick?
You have the 243 heads right? Same casting as the LS6 got but withOUT the hollow valves and on the smaller engine likely needing more rpm. I would NOT use LS6 springs but rather something stiffer due to the combination of heavier valves and likely more rpm, your heads are better than the article and I believe the intake might be too. Expect to make more power but at a few hundred rpm higher.
Far as things like timing chains and oilpumps remember you are playing with a newer engine than the LS1s and many of the "improved" parts are standard production on the truck engines like the "LS6 oilpump" was standard in trucks I think 2001 and later. Of course new pats can be prudent at high mileage but don't get caught up in the "LS1" upgrades as LS1s were earlier production engines.
What valvesprings did you pick?
You have the 243 heads right? Same casting as the LS6 got but withOUT the hollow valves and on the smaller engine likely needing more rpm. I would NOT use LS6 springs but rather something stiffer due to the combination of heavier valves and likely more rpm, your heads are better than the article and I believe the intake might be too. Expect to make more power but at a few hundred rpm higher.
Far as things like timing chains and oilpumps remember you are playing with a newer engine than the LS1s and many of the "improved" parts are standard production on the truck engines like the "LS6 oilpump" was standard in trucks I think 2001 and later. Of course new pats can be prudent at high mileage but don't get caught up in the "LS1" upgrades as LS1s were earlier production engines.
The heads are not ls6 castings, I believe what Ron says below is correct that they are 706's. I plan on running the factory intake and heads which should give me more torque over the LS1 intake. As soon as i get the block back I am most likely going to take the heads and have a valve regrind. The LS6 valve springs should be plenty?
Originally Posted by RonSSNova
I believe the LM4 is just an alum LM7 and has 706 casting heads with the 1.89" intake valves.
I'd be curious as to what rods are in this. I'm betting not the better full gloating Gen IV rods. But then GM wasn't real consistent in this area.
Lastly, does it have the long or short head bolts?
Ron
I don't know which rods are in it. I stripped it down to a short block with the windage tray and dropped it off at the machine shop. I have been out of the country for the past few weeks on work and haven't contact with the shop. I'll ask when I pick it up. Don't remember on the head bolts. I have nothing to compare to so I don't know that i could tell the difference anyway.
The "truck intake makes more torque than the LS1 intake" is sort of a load of crap. That is spouted by the car guys because they have a hard time admitting the truck manifold is just better period. It benefited from being developed a couple years later with "lessons learned" and basically unlimited space.
http://www.hotrod.com/features/1507-...ifolds-tested/
Makes more torque at a slightly lower rpm and more HP at the same rpm as the LS1 intake. Like I said, better period, not the "torque piece" the car owners will tell you it is. If you run the numbers on it compared to the LS6 the LS6 HP advantage seems to come from letting the torque carry 100rpm extra, not actually making any more at high rpm.
Hell in that article the LS6 makes 2tq more at the same peak rpm as the truck but you don't see anyone calling it a part made for lowend torque.
What is a reasonable amount of time for a machine shop to have an engine?
I dropped off the short block almost 2 months ago to have it checked out and refreshed. I was out of country for Nov. but spoke with the machine shop and authorized them to do any work that was needed to get the block completed. I even paid a deposit to cover bearings and rings. I spoke with the owner as soon as I returned (11-30-15) and he had just torn the motor apart and hadn't inspected anything yet. Another week goes by and i called yesterday only to hear that he is just now checking the crank out and would let me know something.
This is my first experience with this shop (came highly recommended by a good friend) and my first experience having a short block built. I have had heads rebuilt by other shops and generally they return them within a week or week and a half.
Is two months normal for a short block rebuild/refresh? At the rate they are going it'll be after Christmas before I have any parts to play with.
09-13-2015, 11:27 AM
5.3 lm4 rebuild with newb questions 
