I'm looking to put a replacement style GM truck engine in my '64 C10. Specifically, I am looking at their L31 type engines originally found in '96-00 Chevy full size trucks. Does anyone know what the differences are between GM #12530282 and #12530283? They seem to be identical EXCEPT that #12530283 has 4-bolt mains. Are there any other differences? #12530282 is designated for 1/2 ton trucks while #12530283 is listed for 3/4 and 1 ton trucks with the "heavy duty option". This is all according to Pace Performance. Can't decide which to go with if the 4-bolt mains is the only difference. Hell, its only $40 more... but I wanna check with you guys first! #12530282 http://paceperformance.com/i-648492...-van-savannahexpress-vans-under-8600-gvw.html #12530283 http://paceperformance.com/i-648492...00-chevy-gmc-full-size-trucks-3-4-ton-up.html
Both are 9.4 - 1. Same power and torque. Mild cam Intake lift- .414" Exhaust Lift- .428" Intake duration @.050"- 191 Exhaust Duration @ .050" - 196 Lobe Centerline- 111
Looks like the 12530283 has bigger exhaust valve stems also. 12530282 New 5.7L, 350 CID, RPO L31 '96-'02 crate motor long block Light duty, 2-bolt mains, induction hardened exhaust valve seats. 1999-2000 Chevrolet, GMC CK1 (L31) M30 (exc. NM8) 1996-98 Chevrolet, GMC CK1,2 (L31)(5.7R) M50, M30 (exc. NM8) 1996-2002 Chevrolet, GMC G1,2 (L31)(5.7R) M30 Engine-Specific Content: Crankshaft Hub, Front Cover, Oil Pan, and Valve Rocker Cover Notes: For 2001 G-van application, service engine block contains English threads. May require Valve Covers to be transferred from original engine for some applications. 12530283 New 5.7L, 350 CID, RPO L31 '96-'02 crate motor long block Heavy Duty, 4-bolt mains, 3/8" large-stem exhaust valves, hard exhaust valve seat inserts. 1996-2000 Chevrolet, GMC CK2,3 (L31) MT1 (exc. NM8, KL5) 1996-2000 Chevrolet, GMC CK2,3 (L31)(5.7R) MW3 (exc. NM8) 1996-2002 Chevrolet, GMC G2,3 (L31)(5.7R) MT1 1996-99 Chevrolet, GMC P3 (L31)(5.7R) MW3, MT1 (exc. NM8, KL5) Engine-Specific Content: Crankshaft Hub, Front Cover, Oil Pan, and Valve Rocker Covers Notes: For 2001 G-van applications, service engine block contains English threads. When used for 2001 and 2002 vehicles, must also use 2000 MY Starter/Trans/Eng mounting bolts
I would think about a LT1 type cam while you have it out, easy 30 plus HP plus it will sound a lot better at idle. GM 12551705 Melling; Melling # : MC1336 Part Description : Camshaft Opens : -18 BTC/39 BBC Closes : 39 ABC/-11 ATC Duration : 201/208 Opens : 10 BTC/69 BBC Closes : 80 ABC/27 ATC Duration : 270/276 CamLift : .297/.306 Gross Valve Lift : .446/.459 Center Line C/L : 117/117 Rocker Arm Ratio : 1.5/1.5 Valve Lash Clearance : .446/.459 Hoop
Heads are different on those two. I'd almost always opt for a HD application . & a Hotter cam for sure
The HD uses the 906 head, here are some comments; Vortec heads can be found in two castings; the -063 and -906. The -906 castings were used on the heavy-duty trucks and had a hardened exhaust seat. It was believed that these beefier seats inhibited flow and altered the compression chamber shape limiting the effectiveness. Recently this has proven to be false. There is no difference in flow between the two.
Awesome- so it sounds like the only real difference is 2-bolt or 4-bolt. Are the HD valves better? I guess #12530283 is the one to go with huh?
For 40.00 it seems like a no brainer. If you ever want to get some real power and high rpms out of it later (with mods) 4 bolt mains would be required.
If I undertand it correctly, The vortec engines heads use a specific expensive intake manifold because of the bolt pattern or angle... Besides that, Consider if it is complete it has a plastic intake which are prone to failure..... Maybe not what your askin, but I had a failure, and felt compelled to mention this....
No the heads are different Hd One has bigger stems and hard seat inserts. Handles heat better. There was some static that it hurt flow - mentioned above by hoop but really a non issue. The other has smaller valve stems and induction hardened seat area ( read spot hardened casting no insert)
I would stay away from the "bigger valve stems" they might well be sodium filled and are NOT a preformance valve at all, very heavy
This engine will see only daily driver/light truck duty. No racing or burnouts or anything like that. Just not sure which is better for me. On the one hand, the 4-bolt mains are always preferred, but on the other hand, if the valves are bigger and heavier, not sure how much it matters. Question: Are exhaust valve inserts better than an induction hardened seat?
Yes, the hardened seat is a separatepiece that is hardened steel. Induction hardened is just localized heating and quenching of the base cast iron. Not as hard as a real hardened seat insert, but better than nothing. The slighly larger stem diam is a very small difference, and the 4-bolt bottom end is a cheap upgrade, I would go with the HD version for the $40 difference.
The cam that comes with that engine is pretty small. Dropping in an LT1 or an LT4 cam would make a large difference in power, but be mindful of the lift limitation of the stock spring/seal/retainer. I have Vortecs on my OT car with a generic 300hp cam and 1.6 rockers. One of the great bennies is the ability to run regular fuel even at 9.6:1 CR.
Vortec heads do require a different intake, the bolts come in straight from the top and only have eight bolts. The factory fuel injection manifold uses a plastic plenum only, not sure what kind of failure you had but most coolant leaks were because of the plastic intake gaskets that were being over-torqued.
The Jalopy Journal
