Question for the GM Vortec heads

[reklipz]

So, I was originally going to PM wed3k, but his inbox is full.

So, I'll ask the forum at large!

Hey all, quick question for you:

I'm looking for GM/Chevy 5.3 L Vortec for a buddy of mine. He was concerned with an aluminum block version, claiming that because it's aluminum, it wouldn't hold up as well to FI/boost as the iron versions. However, I'm pretty certain the aluminum blocks' cylinders are iron or steel sleeved. Is that correct?

Last, are there any major differences between the 3rd generation and 4th generation versions of these? I know the gen IV introduced AFM, but we're steering clear of that issue (so, LMF (iron) or LH9 (aluminum) for 4G).

Thanks!

--
Nate

Any input is appreciated. He plans to make some pretty big numbers here, if everything goes well.

[wed3k]

yea and i plan on keeping it that way. too many people were asking me questions about anything.

Whats big numbers? id personally get the 3rd gen 5.3l because the gen 4's need a lot more to convert (i have both)

the 6 bolt mains do hold quite a bit but anything over 600 id opt for the iron block. plus anything over 600, id probably switch to a forged rotating assembly.

get a head with the 2.00 intake valves like ls1 or 6.0l. the newer 5.3's came with 799's or 243 heads which are superb for overall performance.

[Jarrett]

With as cheap as CNC-ported 243 heads are from Patriot I'd go there for a 600hp build. An LS2 block is plenty strong and has a 4.000" bore from the factory. The LS1 block is stuck at 3.898" and can really only go to 3.905" maximum. If you're going to be boosting it, the factory 3.622"-stroke crankshaft is more than adequate. Forged pistons would be the only thing you lack.

Expect to spend about $1700 for an LS2 short block, $1300 for the heads and $500 for a set up of pistons. With the right camshaft and compression ratio you will be at 500whp before a power adder is even installed.

[reklipz]

I think he's shooting for around the 600 figure number. Initially, though, we're just swapping in the stock engine and getting everything running smoothly. Later on he plans to do the upgrades necessary for the boost, after we've figured out the temperaments from the yard.

The fourth generations also introduced variable valve timing, which to my understanding is tuned mostly for fuel economy, and isn't really worth playing with otherwise. Further, it's rather difficult to find a 4th generation motor at the yards around here, so I suppose those are out of the picture.

I scoured one of the yards today, and I came up with a single 5.3 L: a third generation LM7 w/ iron block. We're going to look at another yard tomorrow, but I'm going to guess we won't find an aluminum block there.

[Jarrett]

The LM4 and L33 are the 5.3L engines you need to look for if you're wanting a 5.3L base to build from.

[reklipz]

Thanks for the pointers fellas. This is the sheet I came up with last Friday:

https://docs.google.com/spreadsheets...it?usp=sharing

It should be fairly accurate. As well, it only includes the 5.3 L applications that don't have AFM/DoD, though VVT and FlexFuel are allowed.

the newer 5.3's came with 799's or 243 heads which are superb for overall performance.

By newer, you mean gen IV? I'm being lazy here, so I'll probably answer my own question in a bit.

Aluminum would be nice (LM4, L33 (hah, yeah right; we're avoiding this one anyway, due to the longer stroke and HO pistons), and LH9 (gen IV)), but we'll probably walk away with an LM7 or L59. That's no big deal as that's what we were planning on anyway. Finally, if pretty much any 6.0 L head is the 2.00 in valving, then we'll probably swap with these before we check out. ;P

[wed3k]

well, the 317's which are the early 6.0's have a big combustion chamber but the bore size is pretty far off. kinda like putting a h22a head on a f22. it'll work but i worry about preignition and the spark flamefront.

ill just give you the details of the 5.3 turbo that im building.

stock rotating assembly, deck, re-ring (obviously checking the ring gap), ls9 cam (125 off summit), arp head bolts, arp rod bolts, stock ls1 heads (853 or 241), trunion kit, hardened push rods.

itll idle like stock but be good for 500whp with a single 76mm. if you want 600whp then get a custom ground blower/turbo cam and maybe send out a set of ls1 heads to advanced induction. Ive used them 3 times already.

The texas speed and patriots are really affordable as well but advanced induction will let me do port work only and i finish everything in house. (use stock heads for ultimate sleeper status)

[reklipz]

So, how much front-end damage is too much; should I consider this motor? Someone has already taken the transmission from it, so half of the work is done already. The driver side motor mount is a little squished (looks like the rail is bent up/out; "counter-clockwise" a hair when looking from the front of the bay. This was the only candidate in the south yard.

[reklipz]

We picked up a freshly rebuilt 5.3 L Vortec; sub 10k miles on the rebuild; selling due to a total loss shortly after rebuilding. Block casting 12551358, 862 heads; complete long block. We haven't verified it's an LM7 (vs a 4.8 L) by looking at the pistons/crank yet, but the vehicle it came out of had the had the right VIN (8th character 'T'; LM7).

So, one thing that struck me as odd was these stampings on the sides of the cylinder heads. The shorter code (on the right side, by the cast "862"), seems the same, but the longer one on the other side is nearly identical, differing by two characters (90 vs 87 in the middle somewhere). Any ideas on these? Could these have been stamped by the shop when they rebuilt the engine/heads?





Also, as a sort of twist... I sold the guy my Honda Accord for him to beat around in while he finds a 383 to put in his own truck. Hopefully I'll get it back when he's done, but we'll see.

[Jarrett]

Those heads have a 1.89" intake valve and the older circular exhaust ports. In order to flow well they need to have the chambers reworked and larger 2.00" valve seats installed. In a boosted build they will be fine but they're probably the second least sought after next to the iron 6.0L heads.

[wed3k]

yea id probably scrap those heads then you can at least see which rotating assembly you have.

[reklipz]

There's a chance the heads will receive some work, or get swapped, but that will be at a later date. We're cleaning everything and prepping to make a harness for it all so we can get it running right when the subframe kit arrives.

[wed3k]

check those things for cracks, they crack near the center head bolt under the valve cover

[GenDBlade]

Vortec huh...you should go 8.1L. Hahaha

[reklipz]

I'm pretty sure we'd have a hell of a time fitting that in the the front end of an RX-8. But, that would be baller indeed.



That intake tubing on the left there: that's packed full of carbon and shitty sludge. I wonder what the rotor looks like.