J-Rod

The motor and the oiling system are up to the task. The issue with revs that high is valvetrain stability... Hyd. roller valvetrains are heavy...

LOnSLO

iTrader: (15)

Yes, but the shortblock will handle it no problem. You can get a hydraulic to 8000 with the right cam and springs.

WS-Sick

How high did the C5R's rev safely?

Gloveperson

iTrader: (9)

7800 keeps coming to my mind. Don't quote me on that though

restoman45

iTrader: (2)

dont forget, they are running those motors HARD for 24 hours straight!...i imagine for qualifying that they rev them higher. i bet 8500 would be no problem for that motor for 10k miles if it wasnt constantly being spun up to the moon...

Tony Montana

I asked about pushing this motor to some real rev limits and I got flamed to hell. I joined a "less abrasive" forum and got some answers and potential mods. If I can't get this motor to rev to at least 7500 revs I will not be considering it. And yes it will be daily, and I would drive it as if it were an E60 M5.

for those curious...: https://ls1tech.com/forums/generation-iv-internal-engine/236838-hmmm-so-i-just-heard-there-will-500hp-550hp-ls7.html

Sabre002

iTrader: (7)

Try more like 1500 miles you get testing, happy hour, qualifying and the race on one motor!!!


and Penske turns 1020RPM, 10grand durrng the race no problem!!! its that IRL **** they got.

And the motors are rebuilt after ever race if not a new motor just cause they can and will because the money is there no reason to go to the race with nothing less then new!!!

SSCamaro99_3

iTrader: (1)

I don't think they are turning them to 10,000 just yet. At Martinsville they may spike them near 9600, but on longer tracks 9200-9300 seems normal. At least from what I have seen.

Chicago Crew UnderBoss

iTrader: (1)

YEAH, like a complete new engine rebuild after every race and only runs a 360 cid motor at the max if not a bit smaller!!!! (and even some of those NASCAR MOTORS crap out on any give day during a race or practice sesson)!!!

chuntington101

asuming a 4inch stroke, 8Krpm would give you an mean piston speed of 27meter per second! i heard that F1 engine spin their pistons at 26mps so i recon you would be pushing it!

then again i also heard of a EVO engine builder using a 2.3 crank that took the pistons to similar speeds to the LS7 at 8000!

who knows.

thanks Chris.

Bink

Ummmm...... F1 currently 3 liters, spinning to 19,000+ RPM - on every shift (7spd mostly). I haven't done the math but I think their piston speed is a bit more.

CarsRFun

8500rpm good gawd

transamman400

iTrader: (1)

I think I read somewhere that the severity of wear on the valvetrain becomes substantially greater after 7500 RPMs and increases at an inclining rate...I probably wouldn't want to push it farther then that without investing in some near bullet-proof parts if I was daily driving something approaching those revs (or did it on a regular basis).

AdioSS

iTrader: (2)

You think wrong. I was told 10,200 last summer. They will probably be turning more this year.

And yes, it is VERY LIKELY that a titanium rod 4.125" bore, 4.000" stroke motor can turn 8500+ I know of at least one aluminum rod 4.125" bore 4.000" stroke LSX based motor that has done that.

Full-Force

iTrader: (11)

its about the piston speed at that point and Louis hit the nail on the head ...... anyway the car in question i just read today has some reliabilty issues

chuntington101

i tried to find out what the stroke for a F1 engine was, but had no luck what so ever! what i know about them though, is that the pistons more of vibrate in the bores as travel up and down them! also if you look at the diameter of a F1 piston (from a 3.0ltr V10 engine) you will see that they run very large bore and VERY short stroke. this is what lets them get the revs they get. and dont forget that they idle at about 8K!!!!

i also worked out what the mean speed for a few more engines, quiet interesting.

Suzuki Hayabusa. (with a 1.5ltr strocker crank and a rev limit of 11K) mean speed around 25ms-1
metro 6R4 3.0 V6 (very nice race engine that will rev to over 10K). around 25ms-1.

so i recon pushing over 26ms-1 will lead you into trouble. but if anyone KNOWS better then please tell me. shame though as i bet one of these things at 8K would sound very nice!

thanks Chris.

FaSS Blac

Guy's I'm no expert but I've built a few engines in my day and have learned that bob weight IS everything when building an engine. What alot of people fail to realize is NASCAR engines are big bore, short stroke engines. Chevys are around 4.125" bore, 3.33" stroke. Bob weight is around 1492g, with pistons at 400g, and rods at 525g minimum weight. The new LS7 has a 480g rod!!!! If you can find a 525g rod you can afford, you are doing real good!!! I noticed the LS7 write up said the pistons are cast aluminum. They didn't say hyperutectic, or forged, but cast. What this means is you will take your chances with a small nitrous hit or turbo/supercharging, but a casting WILL be lighter than a hyper or forged piston of the same size. Sooo, I'm guesstimating that the bigger 4.130" LS7 piston is the same weight as the much smaller hyper LS1 piston at 434g. with a long stroke, you don't need or should rev it sky high. There should be no need to go over 6,500 rpm with this engine. NASCAR can go to 9,500 rpm because of the short stroke and light bob weights used. By the way, an LT1 engine checks in at 1857g bob weight with a 606g rod, which is about the same as an LS1 rod. This is a light rod, at 5.7" and 6.098" respectively. BTW, I WEIGH ALL OF MY ENGINE PARTS BEFORE I BUILD AN ENGINE!!!!!!!!!!!

FaSS Blac

The Ferrari Tipo 049 engine has a bore of 3779" and a stroke of, (sit down!!!) 1.629"!!!!!!!!!!!!!!!!!!!!!! Do you guys see the correlation between big bore, small stroke now? You are NOT going to spin a 4.000" stroke engine to 18,000 rpm!!!! Or make over 800 HP with a 183 ci engine!!!!!!

jtsc23

On the right track here... The weight of the lifters can be controlled with some monster valve springs so that's not entirely the issue. Problem with the hydraulic lash adjuster is that at some point (~7500 crank rpm on type 5 valvetrains) the lash adjuster cannot respond fast enough to take lash out of the system. The internal check ball physically does not have time to return to it's seat. The rpm limit is of course dependent upon base circle diameter of the camshaft and the valve event durations. Large base circle diameter and smaller event durations give the check ball more time to recover. If the lash adjuster does not fully return each cycle, it will loose lash compensation each cycle in a ratcheting effect. End result is the lash adjuster "pumps down" making it unable to absorb lash and the valve slams closed on it's seat. Doesn't take long at 7500 rpm to break the valve then.

Race Car Driver

OK, I'll bite. Exactly what is an LS7 motor's specs? LS1 based, SBC based, . . . ?