I was checking out the 4.8 and although it's less cubic inches it's got a 3.27 stroke and 6.278 rods which means a rod/stroke ratio of 1.92 which is VERY good. This is just a touch more than the 69 Z/28 302 (1.9 rod/stroke ratio). It should rev like crazy without too much stress on rotating assembly.

I'm just wondering with the stock rotating assembly, what kind of RPM's this motor could turn given the ideal cam and valve train. I know displacement is king but high revs, numerically high gears, and a manual transmission sounds fun.

 

Im no expert but i would think around 6500 RPM if you arent going to upgrade to ARP rod bolts and such.

 

Prepare for the onslaught of people who will come in to tell you are wasting your time.

You are right, displacement is king. Your combo sounds great on paper, but rod ratios are typically the things of engineers pipe dreams, in this forum. Many will tell you the right length rod is the one that reaches all the way from the crankshaft and connects to the piston pin.

For anything street driven, more displacement (5.3, 5.7, 6.0, etc.) will always make more power with the same hardware, at a lower RPM. That engine won't require all the high $$$ lightweight parts to build anything reliable that would see the rpm's you are looking for.

For what its worth, many people feel a 2001+ LS1 with stock internals is good for 6500 - 6800 rpms. For every three of them, there is one who'll tell you he spun his 97-00 LS1 to 7200+ every chance he got.

BTW - welcome to LS1tech!

 

An some who have blown them up in less then 50k with just boltons..... It's all a matter of how hard you beat on it. Most of the ls series engines share the same componets. not the same rotating assembly but, different variations of bore and stokes to give the 4.8, 5.3, 5.7, 6.0 displacements.

 

As long as the oiling is good it could probably handle 7500. Run it with the carbstyle victor jr intake. Mill the heads and tighten the quench. It might make 400rwhp

 

I have an 6.0 LS with a 3.622 stroke im spinning to 7200 with hardened pushrods, yella terra lightweight rockers, and stainless steel valves from the 2.5 stage cnc porting at texas speed.However the only reason i got the valves is because a timing gear failure and valves were bent etc not a fun time. However the failure wasnt from rpm so dont worry about that. i could probably push mine to 7400 but thatd be really pushing it, a 4.8 could probably do 7800 MAYBE 8 it you dont care how many runs you get but make sure to get a lightweight valvetrain and upgraded oil pump, saw a thread a while back where someone over revved by downshifting and the oil pump failed, so im guessing thats a weakness

 

With the right valvetrain, proper oil control, and upgraded rod bolts, you could push the stock rotating assembly to 7500rpms on a pretty consistent basis. Anything more than that and you are approaching the potential failure point of cast parts.

There are plenty of people pushing fully forged 4" stroke motors, with abysmal 1.5x rod ratios, over 8000rpms with LLSR cams. The rod ratio does not come into play so much as the quality of the components, things like grain structure in the metal mean a lot more than rod ratios.

Believe me, I will never build anything with a rod ratio of less than 1.60, because I think it is unnecessary and mechanically stupid to do so. But if you want more than 7500rpms, you really need to be using a fully forged rotating assembly.

 

This thread was from 2007 dude.