Does anyone know why the gsr rev limit is over 8g and the ls is under 7g. I'm in the process of building my b18b1 after frying piston rings. I need to know if I get forged internals and a vtec head can I push past 8500 rpm? What is the differance between the b18b1 and b18c1 bottom end as far pushing the revs.

 

i think the reason why is because of the rocker arms on vtecs and ls are different. The ls ones are a type of floating ones..as for vtecs they are bolted down and harder do any damage to them...im not too smart on these things but these are the things i noticed...and also on the vtec blocks, they have little oil squirters on the bottom of the pistons, so during high RPM's it helps cool down the pistons...

correct me if im wrong...

 

The stock valvetrain in a GS-R head limits safe opperation to around 8,400rpm. At or near this RPM range the valves start to float, due to the valvespring's inability to open and close the valves completely... a simple fix for this problem is to replace the valvesprings with stiffer aftermarket valvesprings. I am not sure what RPM the rotating assembly is safe up to, but I know that in stock form the valvetrain is more of the limiting factor in high revs.

 

simple answer, gsr's were designed to rev to 8k and still make power. ls' were not.

if you want to take an ls that high forged internals and a balanced crank would really help.

 

stock ls bottom ends can take 8k, but i dunno why and their rev limiter is set to 7300rpm btw...

 

Well since the LS engines don't have VTEC in their stock form, they are limited in top end power. The single cam lobes have to be able to keep a nice solid idle at low rpms, but still perform decent in the upper rpm ranges. Its a compromise between the two. They really only make power to about 6.5K rpms in stock form, but will still pull to fuel cut off fairly decent. Since the engine wasn't designed for top end power, the rocker arms and bottom ends werent' engineered for it either, why would they be.

You can upgrade the cams and valve springs on a stock LS motor. Just add ARP rod bolts for the bottom end and it will be ok to 8K rpms or where ever your power falls off, which will probably be lower. No use reving beyond where there is no power. The LS rocker arms max out at about 8.5K rpms, but few LS motors make power that high anyway.

With forged internals and a VTEC head, you can rev to 8.5 reliably on an LS block. There actually are some people who use the LS crank and rods in their GSR blocks to stroke it. They have no problems running that high with or without the oil squirters.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RS’R’ &raquo;</TD></TR><TR><TD CLASS="quote">stock ls bottom ends can take 8k, but i dunno why and their rev limiter is set to 7300rpm btw... </TD></TR></TABLE>

but for how long?

 

So it sounds like the head in the gsr is why it goes past 8g. Its built to do it unlike the ls. Also the ls doesnt make any power up there. So if I get a gsr head and forged internals am I going to make power above 8g or should I get the whole b18c1. You see so many ls/vtec I wonder what is better