jrtoffroad

Hey Guys,

I compete in Ultra4 offroad racing (King of The Hammers is the big race most guys know of) in my LS1 powered Jeep (#4580). Next season I'm stepping up to the unlimited class an am looking to add some big power via turbo charging. I'm hoping you guys can steer me in the right direction on turbo selection and probably a lot of other things....

My current engine is a stock bottom end LS1 with a TR 224/224 114 LSA cam, LS6 instake, ported LS1 heads with big valves. My plans right now are to forge and stud the bottom end with some dished pistons to lower to CR and then stud the heads (ls9 gaskets?). Cam can be changed if needed and I also have a set of stock 317 heads if its recommended I go that route.

The current engine put down 344RWHP (on 37" tires). I'd like to see about 750 CRANK HP (maybe 500 rear wheel with the big heavy drivetrain we run).

With that said, spool-up time is a big concern to me since I'm often on and off the throttle pulling out of corners or rock sections. I've been eyeing a T76 turbo with a .96AR, but am worried this might choke the engine at higher RPMS. I'd like to be able to spin this thing north of 6500.

Race fuel and E85 are both okay. I'd love to be able to adjust the boost down to run 93 on long endurance courses where ultimate power is less of an issue.

Thoughts?? Any help is appreciated!!!

jrtoffroad

Another thought, how reliable do you think the LS1 block will be at these power levels? Should I run a girdle? Are the later blocks better than the earlier ones? (believe mine is out of a 98 vette)

Tomhames

iTrader: (3)

We need pics.....

DavidBoren

Ick, '98 blocks are the worst of all of them for boost. My advice for 750hp at the flywheel, would be for you to buy a stock genIV 5.3 and put your heads/intake on it, with the T76 and a custom grind cam.

jrtoffroad

Bummer! If it's really likely going to be an issue, would a newer LS1 block be significantly better? Maybe run this one till it blows??

Rather not go with a 5.3 (even if it's a great option). Don't want less displacement and really want to stay with an aluminum block for weight.

I'd also consider an LS2 or LS3 block if they're much better suited to boost.

jrtoffroad

Here's one, I'll post more later:

[IMG][/IMG]

007FJ

iTrader: (28)

The displacement is nothing with a turbo application and there are 5.3 Aluminum blocks too.

A friend of mine had over 100k when he traded it (99 Vette) with a 10# Procharger set up on it for the 50k of that. That car had a bigger cam, kooks, bigger injectors and not much else (Never had the head bolts loosened or pan off). Stone cold reliable. He drove it to Wisconsin and traded it toward a 69 Vette that he had to have. That guy is still driving it. I think that yours can be reliable if you really want to run the 5.7 but you need to keep it below 600 RWHP and put on head studs, better rod bolts and make sure the ring gap isn't too tight. I am no expert but I know you need reliable as much as anything for KOH.

mkvamso

iTrader: (2)

He said he was going to forge the bottom end
Not sure why you would advise a 5.3 over a forged ls1

A 7675 will light off fairly quick still and definitely carry north of 6500
On a forged ls1 itll easily make 750

DavidBoren

A genIV 5.3 has thicker cylinder sleeves, as compared to any 3.9" bore ls1 block. And the genIV rotating assembly is notably stronger than the genIII counterparts.

If he went to the genIV rotating assembly, he has absolutely no reason to go with forged internals at his desired power levels. Some ARP hardware and be done.

A forged rotating assembly isn't going to fix the thin cylinder sleeves of any ls1 block.

CBM Motorsports

iTrader: (2)

Just to let you guys know, for the past 3 years in a row at the King of Hammers race, our engines have placed first (Randy Slawson driving). I believe 7 out of the 10 top finishers had our engines. So what I am saying, is we can help for sure. Feel free to call in or PM me for some options!

mkvamso

iTrader: (2)

How common is a sleeve breaking or cracking in an ls1 vs a rod bending

I dont believe an iron block has any advantage over an aluminum block on a sub 1000hp setup

jrtoffroad

Any input on this?

Is a later LS1 significantly better? What about an LS2 or LS3 block?

jrtoffroad

SO, I'm a little slow... can someone explain the difference between a 7675 and a T76? Are we talking the same thing?

They both have a 76mm compressor, but the 7675 has a 75mm compressor wheel and the T76 has?

Searching there seems to be a big price difference between the two, with the T7675 running upwards of 1500 and the T76 selling as low as say 650...??

THANKS!

Beanslsxnova

iTrader: (1)

The 7675 has a 76mm compressor and a 75mm turbine wheel. If your talking about an eBay t76 turbo most of those have a 76mm compressor and a 65mm turbine. The smaller 65mm tubine will spool faster but will limit power and choke the engine up top. It will work it's just not the most efficient option. I would opt for a 7675 with a small a/r housing. That combined with a custom can and a good tune will still spool fast and be able to carry Rpms a lot better

jrtoffroad

Thanks for the info. Good call, loos like the one I was looking at from CXRacing has a ~65mm turbine.

Would the added displacement of an LS3 warrant a bigger turbo, or would a 7675 feed it well? All this discussion about the early LS1 blocks has me wondering if I'd be better off grabbing an LS2 or LS3 block. Not sure I'll go this route, but Jegs & GMpartsdirect have some good prices on new blocks...

Beanslsxnova

iTrader: (1)

I would stick with the ls1 do the forged bottom end and and shoot for around 9:5 -10:1 compression. If your worried about more power take the money you would spend on a bigger motor and buy a good set of cylinder heads. Once you figure out what you final engine specs are gonna be call Jose at forced inductions have him spec you a turbo. Then once you have the motor and turbo sorted out have a custom cam cut match everything. Imo that's the only way to go

Martin Smallwood

iTrader: (2)

That's impressive CBM! I have a few Ultra 4 customers, KOTH guys and sand rail guys, but that record is very impressive.
The added displacement of a LS3 would work well with a 7675 in your application where you need quick spool times and not so much all out top end power, like is needed in a drag racing app.

I wouldn't personally go any smaller than a 75mm turbine wheel for your application. The 75mm has quick spool on its side and added under the curve torque production from the faster spool time, but it will run out of steam quickly up top, especially at higher boost.

You could go with a ball bearing Garrett unit such as a GT4508 which has a 80mm compressor wheel and a 87mm turbine wheel. This would breathe better up top than the 7675, and paired with a 1.01 AR housing it will still spool quickly. Granted the cam isn't too big to allow it. I can grind you a cam to match whatever you go with.

If you want to be able to run pump, stick with 9.5:1 compression. E85 could handle 10.5:1 if you went that route.

jrtoffroad

Little update to this thread.

I ended up building a 6.2L using an LSA block and crank. Rather than a turbo, I went with a F1R Procharger.

Car put down 682rwhp/565rwtq on 38" tires last Friday. Making 20psi at ~6k ft elevation. Might have been able to hit 700, but the tune is pretty conservative on the top end. Also think a larger collector on the 8 into 1 headers would help. Car is running E85 and has a static compression of ~9.5:1.

I'll post a link to the dyno later, or you can search for it on youtube under JRT Offroad.

chuntington101

Let's see some more pics of this thing! Sounds amazing.

What were the reasons for going provharger over turbo?

jrtoffroad

Quick update:

Ran my first race with the new car and lost a rear main seal, losing a bunch of oil and damaging a rod bearing (Engine still in car, full extent of damage not yet known).

The day before the race I pushed a valve cover gasket out during testing. This was replaced and I added an additional breather to ensure adequate flow, but I believe the damage had already been done to the rear main. It appears my roll-over check valves in my two catch cans were sticking.

So, the engine is about to get a full tear down. I plan to run total seal rings this time to help reduce blow-by (previous ring gaps were ~0.022in with JE pistons and rings). Also, I'm thinking about upping the breather size in the valve covers and valley cover to something closer to -10 rather then the -6 (3/8") stock size.

What's every ones thoughts? Do I NEED a vacuum pump, or will larger breathers work? What is every one running for ~20-25 psi? Is there a very high flow catch can available with a roll-over valve in it? I'm required to have a roll-over valve by Ultra4 rules.

Thanks!