Ok guys, i have decided to rebuild one of my spare 599 blocks and need some input and questions answered.

I am going to install this engine into a 1991 suburban gasser.

I every other aspect covered except for the following:

1. is the 18.1 kit on e-bay worth a crap? its a Mahle brand.
2. Will it live with 20+ psi of boost?
3. I will use a mechanical IP, so what is the best one to obtain for max power?
4. What is the clearance deal with the 7 and 8 cylinders? I need to know what to tell my machinist.
5. Any other suggestion welcome.

I have sold my 5.9 cummins and have a nice chunk of change to do this project.

Thanks for the input guys.

Mahle is a good name from what I've heard.

20psi? stock will live with 20, 18:1 will swallow twice that and then some.

Whats your target HP? That will better tell us which pump you want.
If your going 220~250, 4911 should suffice.
If you want 250~270, you'll need to step up to the 833 head.
if you're aiming for 300, you'll have to shell out some bucks for the 4 plunger pump.

Refresh my memory, Which body is the 1991 burban, like the 1987's or the 1999's?
To put a 6.5 turbo with the factory turbo manifold in a older body like the 1987, you have to remove the A/C / Heater box or use a exhaust manifold like form banks for their turbo 6.2 kit.
If body is like 1999 then should all fit well.

IP infomation will have to come from one of our pump guys

Like the 87, last year of the old body style, with the 4 headlight grill.
I think the heater core still has to go.

Suburbans and 1 ton crew cabs kept the mid 80's body style until 1991.

Right, 'old body style' but 4 headlight grill where 88 or so and earlier had 2 headlights.

Here, like this one...
http://i16.ebayimg.com/03/i/04/2c/73/9b_1_b.JPG

Born - You didn't mention Intercooler. Don't bother with 20+ boost without one.

TDG - "20psi? stock will live with 20, 18:1 will swallow twice that and then some."

Stock won't live long at all...

Double it with 18 to 1 will net similar results, don't you think?

Your right, 20 is a bit on the high side for a stock engine, and turbo for that matter, I really didn't mean sustained boost pressure that high, but it sure did come out that way.

If your going for 20+, IC and turbo upgrade are a must!

Yes its the old body style without A/C. Thats why I picked it up so cheap here in AZ.

I want to use a gm 8 with a turbo master cranked to 20psi, thats all I should be able to get out of it if lucky. 18psi will probabbly be more realistic.

The only reason I want the 18.1 comp ratio is so I can crank my boost without a intercooler.

TDG, i have a 4911 pump, so I will probably use that one.

I'm not looking for a dragster, Just something I can run out in the hills and thought the 18.1 would help me on a lot of aspects such as cooling, head gasket problems ect.

Will be doing a lot of hill crawling for deer season as well as towing dutys.

Also, can anyone tell me about the clearance issues on #7 and 8 cyl.
I am fixing to take the block and heads to the machinist tuesday. Thanks for all the responce.
http://i16.ebayimg.com/03/i/04/2c/73/9b_1_b.JPG TDG....this looks like you took a actual picture of my new burb. You hit it right on the money.

BornReady, how many other 599 blocks u got laying around. I really need one to put my truck back in the game. I am finding it difficult to locate a used engine much less a block. Let me know if you wanna let one go.

Cranking Boost is why you need a charge-air cooler - even 8psi can get over 250deg very quickly.

Not sure how you've related 18:1cr to cranking Boost wihout one............

Splayed main caps. You can add an intercooler later, but this has to be done now.

Bagalac - Iirc, about .050 off top of piston will reduce c\r from 21 to 18.

Do a 'search' on grape, or compression ratio, fkr his calculated figures.

Second tho't, read QM's post from Feb '05 on 599 rebuild - mucho info in that thread.

It's long, but take your time, and make notes................

Piston clearances vary with piston manufacturer, but generally 7 and 8 should be about .001 looser than the rest to allow for their hotter running. Keep and intercooler in the back of your mind for later, because you will want it. You might also consider running a bigger turbo for increased bottom end torque. An hx35 from a cummins might be a good candidate, just limit turbo boost to about 20 to 22 psi. Make sure you have your block line honed to make sure the bottom end is up to the task and I would strongly consider using arp head studs. You will want a manual glow plug system, as 18:1 is harder to start when cold out, I even added an additional large glow plug and threaded it into the upper manifold and wired it to come on with the rest of the glow plugs. Use a 4911 pump and open it up wide open and you will have enough fuel to have problems with your egt's. Make sure your cooling system is up to the task, make sure to get a hd radiator from a 6.2, use a modified fan clutch and a high performance 180 thermostat. Push this combo hard and you will far exceed your cooling capacity! While you are at it, balancing might not be a bad idea and may as well do the gear drive timing and splayed main caps.:grd:

Thanks man. Thats what I wanted to know. Expecially about the 7 and 8 cyl's...I guess just follow mitchell on demands clearances....I was just wondering why.

Where do I get splayed main caps from.?

Also, Turbine, PM me with a little more info on your pistons if you dont mind. They look great. I'm stoked about this project.

I have 2 599 blocks and 8 6.2 blocks...is there a 6.2 head thats better than the 6.5 heads? Since I dont have to work tomarrow, I am going to tear them down(6.5's) tomarrow to see what condition they are in.

GMCTD, thanks for the reminder on thread searches.

Muchas Gracias.


Piston clearances vary with piston manufacturer, but generally 7 and 8 should be about .001 looser than the rest to allow for their hotter running. Keep and intercooler in the back of your mind for later, because you will want it. You might also consider running a bigger turbo for increased bottom end torque. An hx35 from a cummins might be a good candidate, just limit turbo boost to about 20 to 22 psi. Make sure you have your block line honed to make sure the bottom end is up to the task and I would strongly consider using arp head studs. You will want a manual glow plug system, as 18:1 is harder to start when cold out, I even added an additional large glow plug and threaded it into the upper manifold and wired it to come on with the rest of the glow plugs. Use a 4911 pump and open it up wide open and you will have enough fuel to have problems with your egt's. Make sure your cooling system is up to the task, make sure to get a hd radiator from a 6.2, use a modified fan clutch and a high performance 180 thermostat. Push this combo hard and you will far exceed your cooling capacity! While you are at it, balancing might not be a bad idea and may as well do the gear drive timing and splayed main caps.:grd:

splayed mains require machining to work, a main girdle doesn't. You have as many engines as hrjack. I'm envious!!

I read somewhere that on the 6.5 that it is a better idea to do the main girdle over splayed mains due to the machining (loosing) more block material. I think the reasoning is that they wanted to stabalize the mains while retaining as much block material as they could. What do you guy's think? Seems to make sense to me and something I have been considering for a while now, just a fairly big job while the motor is still in the truck.

Girdle will require engine align boring. The main caps must be checked for alignment and not distorted from the installation of the girdle. Align bore with girdle in place and torqued.

Really? I was under the impression that it was pretty much a "plug and play" type of instalation.

Nope, once you torque down the caps and install the plate, the block distortion becomes a whole new animal. THe engine block should even be bored, honed, decked and align honed while the block has torque plates on the head and the girdle installed. This while ensure correct tolerencing while doing pre-assembly. Its a lot to ask of a machinist to do but the only way to have componentes match up.

so what is more work and more money for a machinest, splayed mains or the girdle?

Wow! I had no idea, Thanks fo rthe info!

I am going to talk to the machinist tomarrow about the splaying or girdling. I have a pretty awesome one here. He has been building drag and race engines before I was Censored 'ing yellow. Keep ya'll posted.


Does anyone know if there is a 6.2 block that is better than the 599 block? And if it can be bored or stroked or whatever to be better? I have 3 "red" 6.2's, 4 "black" and one cucv 6.2.

I want the strongest possible even if I lose a few cubic inches. Or gain maybe?

I even have a 5.7 diesel I was thinkin about twin turboing for sled pulling and drag racing.:muahaha: Just Kidding!

From what i know from reading here so far (everyone here is awesome) the red blocks are the ones from 82 and are quite desireable becase of the high nickel content in them which makes them stronger. After that the nickel content was dropped to save money. Also a 6.2 from 91-93? that has the 599 casting is pretty strong too. Also if you want to sell some of those extra engines and blocks just pm me. Thanks

Can a red 6.2 be bored out to a 6.5? or should i just slap the 18.1' s in a 62 and turbo the hell out it?

Also, what heads are the th best to use?

I will have lots of engines and parts for sale after my project is done, gimme some time and I let yA'LL know. Plus, I need to still remove them from the vehicals and there will be a time issue there. Thanks

Also, Quantum.....where do you get the girdles from? can they be made?

I think to bore a 6.2L to 6.5L you have to remove .080" and only a 599 6.2L can go that far, iiirc you'll hit water before .080" on the older ones.

Only 300cc's difference - don't think you'd notice much gain between 6.2 and 6.5.

Use late '98-up heads with late diamond-shaped pre-cups to get all the factory revisions for cooling and such.

6.2 and 6.5 pistons are same weight, so GM could use same balancing on crank and rotating components.

All else is same.

IMHO: splayed mains move stress out to the rails AWAY from where they always crack- girdle "joins" caps together to share the stress, but they are still putting the stress into the weak point. Hey, go nuts, do both!

GM-8 at 18:1 will get off the line nice, but from direct personal experience, non-intercooled above about 14-15lbs boost and especially at higher RPM (and if towing) will be a smoke show, high EGT's. No experience with intercooling this combo, I would assume it would improve a chunk.

For a turbo, just like the the story of the 3 little bears- GM-8 too small, Penninsular too big, ________(fill in your favorite bigger than GM-8 wastegated turbo here) just right.

kennedy sells the splayed mains

6.2 and 6.5 pistons are same weight, so GM could use same balancing on crank and rotating components.

I question this statement. In order to determine for sure, I would have to pop a 6.2 piston off of a rod and weigh it. I just cut a 6.5 piston in half and when I clean it up I will post a picture to show the cross section of the piston. It has always been my understanding that the crown on a 6.5 is much thicker than a 6.2 to withstand the stresses of turbocharging. This coupled with a larger diameter leads me to believe that the 6.5 piston should weigh quite a bit more than a 6.2 piston. I could be wrong, but until someone chimes in that has actually weighed them, I will stand my ground.

The point I am trying to bring up is that a 6.2's weak link is the piston design, crown is not thick enough to withstand high boost and high egt's. I have cracked several sets of 6.2 pistons with only mild hot rodding. Last one was a 91 crate engine that was replaced under warranty with 30,000 miles. All eight pistons were cracked. On a brighter note, I was able to get the engine back and threw in a set of new pistons and sold it. I also know of a local hot rodder that has done a lot of experimenting with turboed 6.2's and he agree's that most of his engine failures were piston related, even with lowered compression.

Stay with the 6.5. Use a seasoned block, if it made it 100k with no cracks, it probably won't crack. Do something to stiffen up the bottom end, splay, girdle whatever, it can't hurt. There is a reason that Penninsular started using 18:1 pistons in their 6.5's, it was durability and it has proven itself. Marine engines see a different type of strain that our trucks, they are usually run hard at high rpms, but load doesn't vary a lot. Penninsular claims to have many 6.5's running with over 6000 hours on the clock.:cool:

I would like to support Kennedy and will be buying the splayed mains from him. I feel guilty I havent supported him, so on my 18.1 I will support him as much as possible...I think that is important. What about girdles? Hell I'll do them both!

As far as the 6.2 vs 6.5...I will use one of my 6.5 599's. My machinists said there would be no problem and was auctually excited to accomadate me.

Pistons will come from the deisel depot and this baby is starting to take its first steps.

Anyone have The ARP head bolt part #'s ?
keep the suggestions and comments coming.:ro)
BTW, this project may take me a month or two more. this Censored is exspensive!!!!!!!!

ARP headstudkit #130-4062 JK sells them but summits price is $100 less.

check with John Kennedy, my 18:1 pistons are from him not sure if he does them any more.

Use lots of sealer on the studs- I had some very slight leaking when I had mine rebuilt!

Thanks for the input. Looks like I will need a new ink cartridge for my printer soon from all the input. thanks, dslhead

check with John Kennedy, my 18:1 pistons are from him not sure if he does them any more.

Use lots of sealer on the studs- I had some very slight leaking when I had mine rebuilt!

this has been a good thread cause i am planning on doin the 18:1 rebuild this summer on that 94 block that i got. i hope the ideas and creativity keep coming.