Hi, i am new to the forum and had a question. I searched transmission limits but i didnt get anything. I plan to eventually after i finish college, try to do a high rpm engine build. I like to think about it, the only part i dont know too much about is the transmission (and a lot of other things but not right now). How many horsepower/ RPMS can the stock transmission run before it blows?
From just looking at piston speeds and what the stock valvetrain can handle im seeing about 7100rpm is safe on the stock motor, and that is about 77fps on the pistons. But, if you use a 4.8 vortec crank, and bore the engine to a 4.125 (Max bore) you come out with a 347ci engine. 1 extra ci but when it hits the same piston speed as the stock setup it would be running at about 8500rpm. Which im sure would need some insane cam/head setup and basically the works. Its crazy, but every up and coming mechanical engineer needs something to dream about. Im sure that it may even be able to hit 9,000 rpms? Maybe this is the crazy "How to make a 9k rpm motor" everyone always trys to start a thread about. Any thoughts/answers from the new fam here at ls1tech?

 

I expect transmission limitations would be the least of your worries. The money you would have to put into the engine to get it to handle 9k would make it much more reasonable to make your power sooner. Another thing to consider is how much horsepower your parts can handle instead of rpm. Maybe consider a blower???

 

To stay on topic and not derail your hopes and dreams I'll give you the answers you seek with the best information i have collected over the years. The stock transmission doesn't like high rpms, so generally i would say its good for 6500 rpms and 450 rear wheel torque. If you happen to have the double and triple cone syncros out of a vette that can help you shift at 7 and higher reliably with an upgraded master cylinder such as the tick master cylinder. You will never get that bore size on an aluminum or iron block ls motor unless you have an ls7 and destroke it or re-sleeve the block. You can upgrade the internals of an ls1 2 or whatever your going to build to handle 8 to 9k rpms but the key is making everything light, which drives up price significantly. I would say your biggest limitation will not be the piston speed but the valve train required to run at those speeds. A solid roller would be pretty much required with all high end supporting parts. In the end your better off making power sooner like 7k and having more fun doing it instead of rebuilding it.

 

Never have understood this "jones" for RPM's, all it does is break parts. Get someone to give you a ride in a turbo'ed car and you'll understand quickly that torque is the answer and RPM has no part in the equation...

 

yeah its definitely insane, but 6500rpm and 450ftlb is a lie. ive seen a guy on one of these forums with a red gto running 8000rpms and making 500 to the tire on about 450lb+ torque. he was running like afr mongoose heads, valvetrain, cam, ported ls6 oil pump

 

rpm is more of an engineering boner like how people love high revving ferrarais

 

price is true, but ive seen people talk about their 4.125" bore ls1 motors with a 4" stroke running about 428ci or 7.0 on this very forum.
so a 4.125" bore with a 3.25" vortec crank equals 347.

Btw, i was more or less asking a question, but everyone is gonna hate me cause i said 9000rpms. Yes there really is no point, but whats the point of a corvette over a corolla when the highest speed limits in the usa are 70-80mph?

 

Yeah, that's pretty much what I said

 

LOL!

 

You'll have around 2k in the block alone. You cannot bore an ls1 at all. Esp not to 4.125.

You can have an ls1 block re sleeved to 4.125 but again, it will cost you around 2k to have that done.

 

Its not a lie and 8000 rpms on a t56. Gtos have tripple and double syncros again proves my point and some slight upgraded parts vs an fbody. Need to build them to last.

 

Those are not stock LS1 blocks tho, they are heavily modded with new sleeves. Also, I don't know if I'd be taking an OEM truck crank to your desired 9000rpm limit.

You can believe what you want, but you'll quickly learn that stock transmissions (especially something like the 4L60E) does not like rpms at all. The gto guy spinning his to 8000rpm is a) not stock or b) not going to last long.

 

I'm not sure i understand the logic here either. If you want an engine to turn 9k then look into an import motor that does that regularly...

The beauty of the ls engines to me is that they make tons of useable power under the curve and all under 6500 rpms so why rev higher? It just introduces the possibility of breaking stuff unless the drivetrain was designed for it in which case here it isn't.

You're not getting a stock ls1 block to 4.125" without sleeving it and even then the valve train wouldn't handle 8k+ rpm, never mind the fact the 4l60e and t56 won't handle it. If you look at motors that do that, porsches, ferrari, fords 5.0, they all have OHC and have insanely light weight components. They also don't make much power below 5k. I personally like the fact i don't have to spin to the moon to make the power some of those engines make at 8500 rpm

 

Yeah alright ive seen the light. lol. thanks for the answers