Hey guys, I'm looking for tips on how to get my engine (an LM7 from a 2002 Chevy Tahoe) to rev extremely high. My goal is to have a naturally aspirated road racing engine, which I'll boost later(in a couple years, assuming it works well enough to survive that long). I've checked out different "dyno queen" builds but there doesn't seem to be much in the way of info on how to get it to rev higher. So far what I've got to go off of is my knowledge of motorcycle engines, which doesn't seem to be the most applicable thing ever. I'm aiming for a valvetrain capable of 10k RPMs, so i can take it to 8.5k with reasonable reliability. Has anyone tried getting that high and if so how did you manage it? So far the best info I've got is just to get the strongest springs possible and the stiffest pushrods I can find. Any tips on specific coatings for pistons, or which camshaft to use would be incredibly valuable, as well specific part recommendations. Thanks in advance for the help.

 

If you have the right gears and the right engine build, you do not need 10k RPM.
Look at present road racing LS engines to see what their setups are
Call Cam Motion and talk with them about what is feasible with LS engine valvetrains.
What sort of car is it going into? Which class of racing?
An LS engine revving out to 10k will not live long enough to see a full race.

 

The only thing you’ll use from that LM7 is the block. 8500 rpm requires lots of air. A dedicated induction setup with heavily worked heads fitted with Ti valves will be necessary to get enough air through the engine. You’ll want a dedicated forged rotating assembly designed for this application. Road racing is far different than drag racing, as it’s an endurance build made to spin big rpm for 20-30 minutes per session. Dry sump oiling will be mandatory with an LS turning left and right, with that kind of rpm. Cooling this engine will be doable with a custom made radiator setup. If I were you, I’d consult a top engine builder that’s heavily involved in the sport and ask questions. I don’t see you ever being able to convert this over to FI later, due to the dedicated type of build that road racing requires. From my past experience involved with Cup engines and big rpm builds I can assure you here that the LS platform will not go 10k rpm with the lifters in their current positions. The block will have to be re-designed in the lifter tunnel area for that to happen reliably. I’ve seen it done with an LS, so it’s possible, just cubic dollars. I said that because you mentioned a 10k rpm capable valvetrain. Forget that plan. Rpm limit the engine to 9k and plan your powerband around a 7800 to 8200 shift. You can get by with a shaft rocker setup that’s available off the shelf (we’ll probably not really…nothing is available these days) vs. having a custom made set built by Jesel or T&D that will add several thousand dollars to an already huge money build. Valvesprings will be completely dependent on what the final camshaft design is and will be a double setup with big pressure numbers. Pushrods will be 3/8’ minimum, likely 1/2” I’ve seen 9/16” pushrods used in endurance apps a lot. I have a couple sets in the shop and to get them to work in an LS build requires a lot of work. Doable with cathedral heads and almost impossible with square ports…almost.

 

That's why I don't plan on ever revving it out to 10k... As I said.

 

I've been looking at a set of solid roller lifters and 11/32 chromoly pushrods that I've also picked out a set LS3 heads to work with. The current valve springs I'm looking into are 409lbs/in, think that'll be enough or should I look for higher pressure? As for top engine builders... people in my area seem to be using almost exclusively Japanese engines, and most of the tracks near me don't even support the type of racing I'm building for, so posting here was my "runner-up" source of knowledge.

 

LS3 heads will NOT work with the small LM7 bore. Need at least 4.00" bore.
Do a little more homework....

 

The Wegner NASCAR LS2 spec engines ran ~8,000 + rpm and were pretty reliable race wise. Reading about them might provide some insight into what's required.

dynamometer-results-comparisons-tested-nascar-ls2 and 8,300 rpm

despite-controversy-nascar-spec-engine-a-viable-option-for-racers

nascar-new-motor-LS2 spec - 2007

Titanium valves are your friend if you want crazy rpm...have a spare set of Nascar LS2 spec heads if you're interested 😉

 

This is exactly the kind of stuff I'm looking for, thank you.