ok im kinda new to this b20 vtec stuff, but i want to know when building a b20vtec what makes the rod stroke ratio go all to hell. and if you speed balance the bottom end can you rev it safely to 8200k.thats if you strengthen the bottom end.right?

 

yeah you could...i rev'ed mine to 8.2k on a completely stock bottom B20...but if you wanna be more on the safer side (actually this should be a must) get APR rod bolts..not nessesary but if your not planning to resleeve then a sleeve-guard would help prevent cracking your sleeves at 'high rpm'...again not nessarary..but also a crank girdle...
oh as for rod ratio..kinda new at it but i think i get the meaning of it...
With a longer stroke..the piston/rod moves up and down farther due to the crank having a longer stroke...( i suck at explaning) well, the part where the big end of the rod connects to on the crank also moves farther side-ways as well as up and down...because it moves farther sideways..the rod has to angle more at the small end (where it is connect to the piston)..this increase in angling is not good (because it just is.. ) so the way you would solve this problem is to have a longer rod..a longer rod would reduce the angle at the small end if the amount of movement at the big end is the same... (blah...think of it like this..you are standing in front a person about 5 feet away from each other facing each other..and the other person steped 5 feet sideways you would have to turn turn your head about 45 degrees to look at em...but if he were 15 feet infront of you and he steped 5 feet sideways youd only have to turn your head about 5 degrees...increasing from 5 ft to 15 ft would be like increasing the rod lenth..) anyways the rod ratio is a ratio between the lenth of stroke and the lenth of your rod....... gesh bet this made me look like an idiot..oreoz...
i tap out anyone else wanna tackle this for me....


[Modified by 10K2HVN, 3:48 PM 1/28/2003]

 

r/s ratio is determined by rod length divided by stroke. The lower the r/s ratio then the more work the crank does to get power, higher the ratio more sidewall push when the engine operates. So compromised with something in between that keeps sidewall pressure to a minimum and crank usage to a minimum also. most people say 1.75...i dunno if its perfect, never tried it out, but lots of people think it is.

 

yep, you have done some searches right well done...

you can rev to 8200rpm safely, but HOW MANY TIMES?

things like balancing, stronger bolts/studs, quality oil, correct tuning, and good maintainance should help keep a b20 block reving to 8k...

if you replace the pistons and rods with forged items, you risks of damage is much reduced...

hth,

t..

 

so how critical is this sleeving or block gaurds, my freind has an lsvtec and has had if for about 40k miles and hadnt had any problems and he revs it to 8500k pretty regularly.also how much is a block guard and is it something i can install or do i need a machine shop to do it. i didnt mention im a honda tech in nc and the guys at work are like crvtec what? so you know i need all the help i can. if i was just working on my b16a thats differnt. so all the help you can give me is helpfull thanks.

 

are you going to be running a turbo or nitrous?

t..

 

no na only ,daily driver ,maybe little road racing. i was wandering to what makes the stress on the side walls so much more with a crvtec than just a straight b20.

 

OK, the answer is nothing.

except for RPM.

a stock b20 has a redline around 6700

a VTEC b20 would need to rev to 8200

this is because the cams will make power to there...

there is no physical difference between a b20 and a b20vtec except the head.

however, there is much more stress on a bottom end at 8000rpm than 6000rpm...

the need for block guards and sleeves is really for high output engines like 200whp++

so for a daily, tuned by a Honda tech, a stock block should be fine...

this is my humble opinion...

t..

 

so i want it to produce pretty good power i need to speed balance and put a blockgaurd in it?or would sleeving it be cheaper. this is something im gonna start this spring when i get my taxes back so i want to do it right. since it is my daily driver. what exactly did you do to your motor to make it stronger and what kina prices should i be lookin to spend.

 

blockguard?

or do you mean block girdle?

 

i believe he meant sleeve guard...and i meant crank girdle...

 

Rod stroke ratio really means nothing to most of you.
Its not bad enough to matter in most cases and as far as limiting rpm, it doesnt.
Most of you arent going to be revving past 9000 most of the time anyway.
Main girdle maybe helpful, but asfar as necessary its not really. To me, the
money you will spend installing one CORRECTLY will not really be worth it.
If you take the time to balance everything properly your mains will not show any
more wear than if you had the girdle.

Bottom line, you want a b20/b18 bottom end to take RPM, you balance it and
change the stock rod bolts. Rod stroke ratio means little to nothing

 

ditto...thats what tink and i were talkin about PM...