Recipe for high RPM Chevy V8?

Say I wanted to mix and match various Chevy LS-based motors, parts, etc to build a V8 capable of high RPMs. The thought of a V8 up in the 7k or even 8k range (feasible?) sounds like fun to me (and would probably sound incredible to boot). I realize there are high RPM detractors out there, so, if you're one of those folks, no need to add the "ruins people's motors" comments. Just move along.

For those in the know, what pieces/parts make the most sense? This motor wouldn't be destined for a Challenge car, but budget is still a concern. I want to do this in GRM style.

Previous threads have mentioned using parts from the 4.8, 5.3, even the 6.0, but I'm not sure what the best actual recipe is. Please enlighten me!

Big bore, short stroke.

Wet sump recipe: 6.2 block, 4.8 crank, pistons with the same compression height-ish of the 6.0/6.2 pistons, and matching rods. Bolt on some ported l92/ls3 heads.... 25x dur@.050 cam in the .75x" lift solid roller.

Dry sump: Same as wet sump, but replace with a LS7 block and matching pistons.

But I probably would just hog out a set of L92 heads bolt on to a 6.0 shortblock with a hyd rlr cam with 25x dur@.050 and .67x" lift..... to be on the cheaper side.

In reply to Ranger50: .750-ish inches of lift at the valve? Seriously?

I would have thought a custom cam with something a little more sane in the lift department and some aftermarket h-beam rods in a 4.8 would do the trick if he's most excited about RPM's. But I don't pay a ton of attention to these sorts of things since I seem stuck firmly in the Ford camp of late.

Hmmm, if I'm not mistaken the old Ford 427 side oilers twisted to 7k and above.... at least that is what I remember reading about the Mk II GT-40

A previous thread on the 4.8L motor included this laundry list. How would this do?

Milled 243/799 heads (can't remember how much)  
Texas Speed Torquer V2  
PAC 1518 Beehive or PRC Dual Valve Springs  
ARP or Katech Rod Bolts  
Tune

This cam with the heads + upped compression should make hp up to 7000 rpm and redline around 7500 rpm (according to the peeps at Texas Speed).

Spinout007 chased this a little while ago and found some suppliers for some seriously high rpm capable top end parts. Might be worth an email.

A freshened stock LS2 motor will turn 8k rpm stock...for a short period of time. My Lemons crew built one for some circle trackers and they reportedly spun it between 7 and 8k for an hour. Then they blew.

If you're looking for long life, keep the rev's down.

MrJoshua wrote: Spinout007 chased this a little while ago and found some suppliers for some seriously high rpm capable top end parts. Might be worth an email.

Will do.

Xceler8x wrote: If you're looking for long life, keep the rev's down.

Why? Can V8s simply not sustain a life of high RPMs. Not asking that rhetorically. I don't know why they can't.

dyintorace wrote:

MrJoshua wrote: Spinout007 chased this a little while ago and found some suppliers for some seriously high rpm capable top end parts. Might be worth an email.

Will do.

Xceler8x wrote: If you're looking for long life, keep the rev's down.

Why? Can V8s simply not sustain a life of high RPMs. Not asking that rhetorically. I don't know why they can't.

Interesting reading. http://www.epi-eng.com/piston_engine_technology/comparison_of_cup_to_f1.htm

Ranger50 wrote: Big bore, short stroke. Wet sump recipe: 6.2 block, 4.8 crank, pistons with the same compression height-ish of the 6.0/6.2 pistons, and matching rods. Bolt on some ported l92/ls3 heads.... 25x dur@.050 cam in the .75x" lift solid roller. Dry sump: Same as wet sump, but replace with a LS7 block and matching pistons. But I probably would just hog out a set of L92 heads bolt on to a 6.0 shortblock with a hyd rlr cam with 25x dur@.050 and .67x" lift..... to be on the cheaper side.

the L92 heads have been discontinued by GM.. they do have a habit of stopping production on their best stuff just as they are becoming popular.. but that's ok, because some of the other heads have been shown to be almost as good at max lift and better thru the middle of the curve with a little bit of work.. i think the LS3 heads fall into this category.

there is no difference in the oiling systems of the blocks between wet sump of everything else and and dry sumps in the LS7- just the parts that bolt to it. there have been a few LS7's swapped in place of other lesser LS engines by using their oiling system parts.

an iron 6.0 block would be the cheapest way to get into one of the bigger bore blocks, and people have bored them out to the 4.125" of the LS7 block. i don't know how well they live at that bore, but it's been done..

m4ff3w wrote: Interesting reading. http://www.epi-eng.com/piston_engine_technology/comparison_of_cup_to_f1.htm

Cool link. In an attempt to contexualize the F1 engine mean piston speed at Wolfram Alpha, I learned that 4437 ft/min is "~~ 0.92 × speed at (or below) which Sammy Hagar cannot drive ( 55 mph )".

I don't know why they can't.

Tensile loads on the connecting rods cause the metal to fatigue and fail after a period of time. That's basically why.

Rods (and the weight of the piston, and the rate of acceleration due to crank throw, to a lesser extent) are the sticking point in super high rpms. Some motors have nearly unfixable valvetrain trouble at high rpms too, but the LS isnt one of them to my knowledge.

I have nothing to add but I know a crankshaft guy in Michigan that made a 180 degree crank for the ls engines. he had a customer that wanted his Corvette to sound like a ferarri .....

Kj

Can't find the link right now, but some time this summer Engine Masters (popular hotrodding) did an article about an AFR-headed LS2 407 that made 618 hp at 6800 rpm and still peaked torque at 3800.

That should be easy to duplicate with an LQ9 or LQ4 block.

Most of my V8 builds are low-rpm because I'm a big lover of massive cars, but I have no problem building RPMs for the street. Forged rods and pistons in an LS block can spin to 7000 pretty easily if you have the head flow to support it. If you're racing it, you have the sponsorship for the expensive parts. If you're streeting it, you will only see those top RPMs a small percentage of the time and it will last longer than you think.

A well build small block should hold up to the rpm's you want. I have had several sm blks in my life that were high mileage motors that I stuffed a cam in and had a lot of fun. Although people do blow motors,I have yet to blow one up. Just my 2 cents.

Oh, and sort of related, stock big block chevys hold up fairly well to high rpm. I was moving several states over and the truck I rented had some really low gears, I stood on it (3000+ from the sound) for hours on end just to get here. Chevy lower ends are durable.

377?

If you are happy with just 7,000 - an LS7 will do that bone stock.

People report that the stock LS6 (Z06, CTS-V) motors make power up until about 6500 so a lot of people shift around 7K.

My understanding is they are pretty much LS1's with a different cam, better heads (243's) that have better springs, pushrods and lighter valves. Also had a better intake. Most Corvettes and Camaros 2001 and up got them.

The plan for my LS1 in the 84 RX-7 is to get the LS6 cam (just bought a brand new one for $100 shipped with springs) heads ($400ish) and intake ($300) plus a ported LS6 oil pump, LS2 timing chain and I should be good to go making about 375rwhp in a 2500lb car. That's a pretty cheap way of getting most of the way there for a street car. More than that seems to get pretty expensive pretty quick.

More than that seems to get to expensive for me pretty quick. $800 cam and spring setups, FAST intake which runs around $1000. Hardened pushrods, rockers, valvestems, pistons etc etc. Wasnt worth it to me to spend all that when I probably can't put the power I'm going to make already.

We just picked up a cheap 4.8 (sub $200) thats probably destine for a lemons car. Its going to get the cast of stuff from my LS1 in a mix and match type deal.

Thanks folks. Some interesting thoughts so far.

Don't forget valve springs.

CTS-VR lifters are good to 8k and those were based on the LS2 engines when they ran in the World Challenge with the 1st gen CTS-V. So don't forget those.

I'm very interested in this thread as well as I'm planning on building an ls motor in the near future with high rpms. The vehicle recipient isn't confirmed yet, but it will be awesome.

I wouldn't hesitate to turn an LS6 with some decent valve springs to 7,000.

Dyinto-did you get a dyno graph with your 400whp FC? I would be really curious to know where the power band was in that car.

MrJoshua wrote: Dyinto-did you get a dyno graph with your 400whp FC? I would be really curious to know where the power band was in that car.

Why yes, yes I did.