I am doing research regarding an all motor build and I am trying to determine whether or not to build a NA all motor B18C or ls/vtec using a long rod or short rod. Now, I want to set this motor up for road racing, so the block will be sleeved either 85-87mm (not sure yet), 12:5:1 CR, now the question is which approach to take: stock LS crank with longer rods to achieve a better R/S even though I will lose some cc's or go with the GSR crank with a shorter rod? Any suggestions or comments would be much appreciated, thanks for your time!

 

right now im building this motor, almost the same setup...but it should be a great performer on the strip...

deck plated obviously LSvtec
GE sleeves
86 bore
13.0:1 compression custom Arias pistons
Cunningham custom rods (about a 1.6 R/S ratio i think the way we're doing it???)
Eagle 95mm crank

b16 head
P&Pd
full skunk2 valvetrain
skunk stage 2 cams
skunk IM

but i wouldnt run over 86 bore because if you do use it for daily driver you cant go over 86. also i wouldnt think that would do well on a road course..
but judging from your use i would run the gsr block with short stroke and quicker revving motor...u can make almost the same numbers and supposedly better high end? i think..but, there was a turbo magazine article about it awhile back.



[Modified by hybridvteceg, 2:24 AM 2/18/2003]

 

That sounds like a nice setup with lots of low/midrange torque....I wish Tubo Magazine would finish that article! The car will not be a daily driver at all -- strictly track. I am just trying to find the right combo with lots of low/midrange torque but also having some decent top end power up to 9000 RPM's --- frustrated

 

yeah they didnt finish yet, what a blower.. i didnt follow it up... but try 86 bore then so if u blow it you can goto 86.5 or 87mm...and run the short rod i think that would work fine...just use a gsr shortblock bored and sleeved...

 

you got it backwards man. the longer stroke the shorter rod and vice versa. the gsr crank will yieald a better r/s stroke ratio because of the shorter crank and more room for the rods.

honestly...you dont need a custom crank t make good power. 89MM crank with 85MM bore can yield 250+whp if built and tuned right

 

I thought that if you want to improve the R/S of the ls crank 89mm, then I would want to lengthen the rod? Just doing the math...I get 1:57 for the R/S using a 140mm rod length with a 89mm crank...anyone know ever try this? Also...what kind of setup have you seen lay down 250whp all motor? Thanks for the reply!!


[Modified by cleanEG, 10:18 PM 2/17/2003]

 

are you deck-plating??? because if you think your going run an LS crank (or bigger) with longer rods its not going to fit..unless you add a higher deck...

 

If you are going to run a road race car, use a gSR crank and rod combo.
This isnt a drag car.. so a bore of 86mm should be your max. you don’t necessarily need over 86mm bore. The gain of a longer rod and stroke isnt really going to benefit you in your application. Also even the deck plate isnt needed. The basic GSR and rod should be good enough to achieve the HP and setup you need for road racing.

Contact RS Machine for any other advice on building a race block… or call us as well. We can help you plan out a motor that suits your needs.

818-355-6156

 

Thanks all for you input and I have spoke to both GE and RS Machine and they were very helpful as well. Thanks again!

 

not a problem dude, hope you make what u want, let us know whats up when ur done..

 

I'd go with a bored B18C1 also. In fact my 85mm GSR block is at the machine shop just now. If you want to improve the r/s ratio of the b18a/b however you can use the longer eagle rods and raised pin pistons to do so. They're +.137" or 3.5ish mm. I think it comes out to an r/s ratio similar to a GSRs.