L31 Vortec 5.7 Heads/Cam advice for my 1999 K2500 Suburban

[JayY]

Hey @JayMB,
Sorry to bring up your old thread, but I ran across this post because I'm in the exact same situation as you are. I'm 22 and have had a couple of newer vehicles. Eventually, I got tired of spending my hard earned money on a payment every month and wised up to invest in my own house. Dad had a GMT400 growing up and I had been looking for a big block truck for the mainly the same reasons you were. Dead nuts reliability, easy to find parts, and having a truck that was built to withstand 2x what trucks today will. (Don't get me started on my '06 and '16 Half Tons) After searching forever, I found a 1997 K2500 5.7 L31 4x4 with the 4L80E and the 9.5" 8 Lug 14 bolt with 3:73's. Only rust is in the cab corners but it's straight as can be. Picked it up with 127k original miles for $2,800 USD. Best decision I ever made, because I forgot how damn cool these old trucks are and how comfortable they are to drive. Immediately I replaced the muffler with duals, and for preventative maintenance, added a new radiator, 180 amp alternator, heater core, water pump, belt, hoses, Bilstein 4600 shocks, better brakes, and 33" Goodyear 10 Ply Duratracs for the mud and snow. This thing it the ultimate truck for a guy with no kids and is about to start building his own house. Crank windows, single cab, the old sealed beam headlights like you have in yours, it's just way too cool. Anyway, the reason I'm writing all this is to say you're not alone in your journey to restoring one of these, and I have the exact same intentions. I want to be able to drive this truck anywhere, anytime, still drive it to work, and haul a 24' gooseneck with a small load of lumber or a bobcat when needed as I am building my house. Not having a car payment really goes a long way, plus parts are cheap for these things, so I'm wanting to stick around the $10,000 number too. I'm going to end up re-painting it the original Laguna Green because I've yet to see another W/T 3/4 Ton with this color. I don't know if I'm going to do a 383 since the bottom end seems to be holding up well, but it might be in the cards, who knows? I plan to leave the stock heads and just do a mild low grunt towing cam, swapping for the newer injectors, and a nice Black Bear Tune. Of course, the trans will need attention as well for towing. Kind of lost on a good converter to use, but I know I want to install a TransGo HD kit and a trans temp gauge. I do want to regear in favor of a Full Floater 10.5 with 4:10's, which vehicle did you get yours out of? I always hated the difference in the width of the front and rear axle's on these trucks. Nice to know someone out there has similar interests and plans to keep these trucks alive. Best of luck and I look forward to hearing what all you've done to the truck.

Best regards,

Jay Y

 

[JayMB]

Hey man I'm gonna answer better in a few days because things are a little crazy for me right now but I think it's great that you and I have the same idea about a lot of things. And you're also a young guy like me too, that's cool.

I used an "aam1050" axle off a 2006 2500hd with a 6.0L gas engine, because I found one with super low miles on it. It's a 14 bolt full floater with discs. As far as I know, they come under all the 2001-2010 2500hd trucks that had 6.0 gas engines. You don't want one newer than 2010 because they have the stupid 180mm metric bolt pattern vs the 8 on 6.5 that everything else has (maybe you could swap old-syle hubs on the newer style axle, I don't know). Almost all of them '01-10 had a G80 "locker" limited slip and 4.10 gears (smaller gas engine needs the lower gears). The ones behind trucks with the 8.1 gasser or duramax diesel are aam1150s. Bigger ring gear (11.5") but almost all of them are 3.73's. They don't have that cool removable pinion support or the third bearing on the pinion on the far side of the ring. I was wrong previously in stating that gmt400's had SAE lugs - they are metric M14 and they're the same on the '01-10 trucks so all the lug nuts will all be the same. These alxes are 3" longer wms-wms (sorry I don't have the measurement handy) so both back wheels push out 1.5" over stock. You'll need to move the spring perches out about an inch and use the gmt400 shock brackets to make the newer axle fit. The e-brake cables can be made to work but I don't know which parts came from what in my pile, sorry.

 

[Redneck357]

Hi all,

I'm Jay. I'm new here. I bought a 1999 K2500 Suburban a while back and now I'd like to make it into a good towing/roadtrip rig for myself and my friends. I really like this generation of GM trucks. Prior to this I've only owned Squarebodies. I bought this one for EFI, Overdrive (4L80 - no 4L60's allowed here), lots of seats, and A/C. I'll do a build thread on it here when stuff gets serious but for now I just want to talk engine.

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I bought this truck for $1000 at an insurance auction. It's catalytic converters and drive shaft had been stolen, and it was listed as "possible engine damage" since it wouldn't start. I bought a parts truck for $400 and got a driveshaft, all the exhaust, and a new fuel tank + pump. Now it starts/runs/drives (fuel pump was shot).

The truck currently has a stock 5.7L L31 Vortec 350 with 260K KMs on it (162,500 Mi). It runs, clean oil, sounds fairly healthy (can't really tell if it ticks or anything because it has no exhaust at the moment).

I don't know the history of this truck, other than it was a fleet truck for a rural cable company for a large part of it's life. I feel like 255 HP / 330 TQ or whatever the Vortec 350's were rated for will be a little less than I want for it. I'd like to pull the engine out and get it redone as a 383. Here's what I got so far:

- stock 1999 5.7 Vortec L31
- 4.10 gears
- 4L80E being rebuilt with Jake's Performance B82 Billet converter (2200-2400 stall - basically an S10 converter)

I will be doing the 0411 swap and keeping the EFI. I have a marine intake that looks like a square-bore 4150 dual plane carb intake but has injector bungs in the runners. It's from a Mercruiser boat engine and it works with Vortec heads. I plan to use this with fuel rails and some 36-42 LB LS-engine-type injectors (either the 36LB supercharged 3800 V6 injectors that all the LS1 boys use, or the bigger 42LB ones found on 2010 or so 6.0L V8 truck engines with Flex Fuel). I'll get a pic of this intake shortly.

I want to use my fancy marine intake (pics to come later) and that leaves me with vortec heads. I hear that later Vortec heads (like, after 1998) are made in Mexico and have only 160CC runners, making them a bad choice. This, combined with the fact that these heads are well-known to crack - maybe I should get something else before I throw money at these making them support more lift and screw-in rocker studs. I like iron heads for truck motors. I'm thinking the EngineQuest EQ Vortec Head 350C. These can be had bare on ebay for $275 a side. My machinist will add springs and valves. They have revised water passages and thicker decks, plus screw-in studs from the factory. Anyone here use these?

What would you run for heads/cam on a L31 383?
I'm thinking iron heads and 9.3:1 compression.
4L80 & 4.10's put it just over 2000 RPM in 4th on the highway (65 MPH) with 33" tires.
Downshifting to 3rd to pass puts me at 2700 RPM.
Downshifting again to 2nd for towing heavy uphill takes me to 4000 RPM (roughly my peak power).
I would like max torque and decent fuel economy.

I'm thinking to go with the 395 HT383/Ramjet Cam from GM and basically build myself an HT383E.
GM advertises these as 323 HP @ 4200 and 444 TQ @ 3000.
Hotrod did an article where they got one up to 379 HP @ 4600 and 474 TQ @ 3700 with 1.6 rockers, an air-gap manifold and a bigger carb (not far off from my marine intake and throttle body).
https://www.hotrod.com/articles/gm-ht383-crate-small-block-tune-up/
Most importantly, they got the torque up to 450 LB/FT at 2500 RPM (roughly my converter stall speed).

I've been told that something like a Comp Cams Extreme 4x4 Cam might get me even more torque down low, but I'm not sure I want to thrash the valvetrain with super aggressive lobes on an engine that I want to tow across the country with. I'm happy to go full roller rockers and all that if it's a good idea. This engine was roller cam from the factory.

I need it to run on 87 octane and get decent fuel economy. I'm in Canada and our fuel options suck here. 91 octane is almost 20% more money than 87 so it doesn't really make sense for a truck.

I have EFI Live for tuning and I fear nothing electrical. I don't want to go LS engine because low-mile 6.0L truck engines (LQ4, etc) don't really exist here, and if they do - people want a fortune for them. Also I've always thought they don't quite have the torque down low that the old Vortecs did. I'd rather throw money at an all new forged 383 stroker and get more cubes than spend thousands on a stock engine I don't know the history on. It'll be 0411'ed anyways, so all an LS engine gets me is access to cheap aluminum heads - and I don't even like aluminum heads (for a truck).

Thanks for reading and thanks for your input,
- Jay

P.S. I built a 243 headed LS1 with a buddy for a Camaro that goes like hell. LS engines are awesome.. for stuff like cars. Or if you stroke them with 4" cranks. Or Forced induction. Or with a high stall converter and no plans to tow. For whatever reason I've always felt like they don't get going until 3500 RPM. I come from diesels, so this drives me insane. Some of your LS rides will smoke me all day long - so don't take my LS jabs as a dis. They were born to rev. I am not. Thanks again!

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Any updates on your build? I have been wanting to build my 1997 k3500 with a 5.7 and 4L80E for years but just haven’t been able to figure out which direction to go. I watch forums all the time to see if anyone with more know how has already built one for towing. My 10,000 lb travel trailer sure makes my motor grunt pulling up the hills here in Utah.

 

[Supercharged111]

Lots and lots of words in this thread, I just want to point out one thing if it hasn't been already. Those 36# L67 injectors are 36# at 3 bar. Run at the Vortec's 4 bar they flow 42#. Both trucks in my sig have them, they should be plenty for a healthy 383.

 

[JeremyNH]

Lots and lots of words in this thread, I just want to point out one thing if it hasn't been already. Those 36# L67 injectors are 36# at 3 bar. Run at the Vortec's 4 bar they flow 42#. Both trucks in my sig have them, they should be plenty for a healthy 383.

Bosh 0280158227 injectors fit the MI and have the same flow as L67 injectors but are cheaper. They're technically for Ford trucks but then so are the Denso 24# injectors now in my MI fueling my well running L31. I started a 390 stroker build (0.040 over, 3.8" stroke) last month and plan to use the Bosch injectors when I migrate my MI over. It will be a while though. Only have the block (89 LT1), pistons (KB164-40), and crank (Scat 4-350-3800-5700-L) for the moment. Have Howards splayed mains (picked up cheap) and the ARP stud kit for them as well. May not be needed for my power range but peace of mind on a long stroke and the fact that I was going to align hone anyway so only a partial cost adder to do it. CFO has me on a budget so I get parts as funds come available. I'll get the rods next month then save up for the machine shop. Then more saving for AFR 912 heads. Aiming for the latter part of next year.

 

[JayMB]

Any updates on your build? I have been wanting to build my 1997 k3500 with a 5.7 and 4L80E for years but just haven’t been able to figure out which direction to go. I watch forums all the time to see if anyone with more know how has already built one for towing. My 10,000 lb travel trailer sure makes my motor grunt pulling up the hills here in Utah.

Sorry for the delay in answering, my life has been a bit hectic lately.

Well, I still have the truck. It still has a 350 and a 4L80 that needs a rebuild. I bought a 2010 Chevy Colorado with a 3.7L inline-5 (yeah.. I know) with super low miles from an insurance auction, and retired my daily driver (a 2002 dodge caravan that was absolutely falling apart - I don't even have kids but it fit all my tools and I got it for $220. It worked for driving to work, which I didn't want to do to my nice squarebody in the winter).

Life got in the way..

I bought EQ Vortec heads for it for sub $300 US a side, I think they are ~$450 now (I'm pretty happy with how they look, but when I bought them they were still cast in New Zealand. I hear they are now chinese, and that there are Dart iron heads sold at summit that are arguably better, sold under the summit brand name - I'd google around if you're interested in those, they are mentioned on a lot of forums). I also bought a forged 4340 SCAT 4-350-3750-5700L crankshaft brand new in box for $400 US on ebay from a guy who bought the one-piece rear main seal version ("L" at the end of the part number) by mistake (I think those are ~$600 US if you shop around). Then I got a set of forged Scat 2-ICR5700-7/16A rods (with the ARP2000 series 7/16" bolts) basically on trade for something I didn't need, also new in box. And I paid $400 for a set of COMP cams "ultra pro magnum" (not even kidding that is what they call them) full roller rocker arms, but it was summit bucks day or something so I got like 15%-20% back.

I was gearing up to do a 383 stroker, like I said I wanted, slowly building up a parts pile as I found things on sale (not even going to lie I have probably a 4'x'4x4' foot pile of truck parts new in boxes in my spare room, it looks like there should be a pallet under it). Then, I heard that the *880 blocks (Vortec 350's) make bad stroker motors, because the cylinder walls don't come down as far into the crank case as the older *638 TBI blocks do (I also know that GM sold 6.2L vortec engines with 4" bore and 3.8" stroke to Mercury Marine to power boats, and they had *880 blocks.. so maybe they are hit & miss? who knows). I thought about it some more, and I really didn't want to take my currently running engine that has clean oil apart just for the block, especally if the block isn't even the best one to use for this. I'd rather have a complete "low" miles engine ready to go in my shed, since vortec engines are fetching prime dollar around here these days now that the cheap LS stuff has dried up. So then I went looking for a Dart SHP block.. and I should have bought the one I saw on ebay for $1500 when the Canadian dollar was at 84 cents.. (cause I am in Canada after all) but I didn't, because I'm stupid..

Then I got a different job where I make a lot more money than I used to (I was an unskilled laborer previously, so I wasn't making a ton) but I don't have anywhere near as much free time. I don't know if that was the right choice but in the short term it allowed me to buy a house (thank goodness I did when I did) that came with a modest 22'x26' garage with an 8' door and a 10' ceiling that was put up but never insulated or anything (it snows here and gets really cold for 5+ months of the year so shop space to work on your toys is definitely a thing I wanted real bad). For now I've been kind of focusing on that with my admittedly lacking free time. I'm hoping to be able to get back to doing more fun things about a year from now. Gas is $6.54 a gallon over here right now (for 87 / regular) so I mean I probably wouldn't be using my 3/4 ton suburban a ton for a bit anyways.

Sorry guys I wish I had cooler stories for you. If I get a dart block I'd go 4" bore x 3.75" stroke for 377 cubes or 6.2L. Probably not in the budget for a bit (time budget more than anything).

Best of luck on all your projects!