im gunning for 14-15 psi this year on my b20 tuned off my map now, 0 detonation but i know stock rods are weak so when is the breaking point (also run 94 all the time)

 

I've read account after account of B-series rods holding WAY over 300whp, of course it's all relative to the condition of the motor, but under 'normal' circumstances, I'd guess somewhere in the 350-400whp area if not more..?

 

Connecting rods rarely break due to high power.

Normally they break from excessive RPM.

Basically, there are two distinct types of loads that the rods endure....

Compressive loads, and Tensil loads.

A compressive load is applied to the rod when the cylinder fires and pushes down on the piston......this energy is trying to compress the rod between the crank and the piston pin. Effectively doubling the cylinder pressure wil double the compressive loads. As you can imagine, its pretty difficult to squash a rod this way.

A tensil load happens when the piston gets to the top of the cylinder and the rod has to keep it inside the engine. This tensil load wants to pull the rod apart.

The formula for calculating tensil load is F=MA. Meaning the Force applied is equal to the mass of the piston you are trying to stop, multiplied by the accleration of that mass. {in this case it is deceleration, but it works the same way}.

Assuming the piston stays the same size in a given engine combination, doubling the engine speed will QUADRUPLE the tensil loads on the rod. The Force goes up by the square of the change in engine speed!

So, if you leave the engine speed alone, and only increase the torque the engine makes, the rods should be fine. However in the pursuit of power people often raise the engine speed {since horsepower is a function of torque versus engine speed}........this is where the problems arise.

 

Thats what I always thought, it was RPM's not power thats throws rods. Informative

 

Yeah, I read an article on this last night. The rod's themselves are stressed by changing direction (ie piston going up, then down, etc) then they EVER are during a power stroke. Your rods should be able to hold a significant amount more power than they do stock, but revving your motor to the sky will be it's death. Stick with the stock revlimit, in most cases!

 

Great info!

 

I'm not 100% sure if its B-series rods (more than likely tho) , but my father is into Nascar. He's tellin me that nascar teams are usin "stock" honda rods in their 350 chevys and pushin 600+ HP in local pro-stock oval track racing and get at least a whole season on them. Just somethin to look into

 

This is true. I made up a Excel circular reference program using the gsr block specs and calculated the approimate tensile and compressive stress as a function of rpm. You can watch the position, velocity, acceleration and jerk vary with rpm referenced to tension and compression. The results were that the tensile loadings were higher compared to the compressive stresses, and as rpm rised you could see the loading change a couple order of magnitudes higher. I have done 425whp and 305 ft-lbs awhile back on stock internals, the red line was kept the same.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MyMario &raquo;</TD></TR><TR><TD CLASS="quote">I'm not 100% sure if its B-series rods (more than likely tho) , but my father is into Nascar. He's tellin me that nascar teams are usin "stock" honda rods in their 350 chevys and pushin 600+ HP in local pro-stock oval track racing and get at least a whole season on them. Just somethin to look into</TD></TR></TABLE>

You father meant 'stock honda rod bearings".

Theres actually part #s out there for using GSR Rod Bearings in Domestic Aftermartket Rods.

Suprdave

 

I swore he said RODS but like i said im not 100% so i'll check into this a little more and get back

 

I think around 300 realiable.

 

first off bringin this back from the dead.

interested in this because i am using stock rods. i know you will say just do some eagles its only 300, well its not. 300 + new bearings + machine shop costs and tearing apart the bottom end again. i need to apply the money towards tuning and already have wiseco's and stock rods in a B18C1. i would do eagles etc but being a single home owner dosent leave much in way of disposable funds.

would like to run around 350 whp and up to 400 if possible. would figure it be ok since rpm's seem to be the killer here.

any info/experience on this is appreciated. anyone ran 300 range for a period of time on a B with pistons only?

 

it can/has been done...
but in all reality man-power/reliability/money, you can only have 2.

also, i was kinda confused by your post, you have to tear the bottom end apart to install new pistons anyways and you have to take it to a machine shop to get honed already...

 

well the problem i have is this. i spun a bearing in a LS bottom in december. i had just fully redone the whole suspension a few weeks earlier. and shortly before that not by my choice became a single home owner and had been boosting for a year and half so was thinkin well motor is doin good ill dump the extra cash i have now in the suspension cause it was much needed then bang. so what i had left would only really cover enough to do pistons. and the GSR block i had sittin around had brand new bearings... rod, crank, and thrust from acura and a scratched cylinder wall/ bad oil burn. so i didnt do rods. long story short every dollar counts right now and gonna tune soon and have valves leakin pretty bad so i gotta spend around 2k already for valves, springs, tune, etc... so another 500, if could be avoided, would be really nice.

BTW i will be visitin an EXTREMELY experienced/reliable/reputable tuner for the tune so i think it'll prob be fine. just any reassurance is nice.

my searching turned up alot of speculation and SOME knowledge/experience but i like the discussion/debate of stock rods. power vs. rpm. rpm seems to be alot more of the issue. keepin the stock rev limit i think it is easily obtainable. but i dont know it all so...


Modified by agrn93ls at 12:18 AM 7/10/2007

 

more less i dont think anyone has found the power level limit of rods but there have been many posts of results of rpm/detonation limits of rods. not specifics but obviously the problem.

 

Ringlands will most likely go before your rods do.

 

talkin about with forged pistons.

 

o ok i got ya man...i would just do it for the peace of mind factor. elimating a weak point is always nice..
but in your post you said you need new valves, springs, etc...i have a set of stock valves, skunk2 dual valve springs and titanium retainers for a b series vtec head for sale, if your interested shoot me a pm

 

I am too doing the same thing using stock rods with forged pistons. In my case, I already had the pistons and ended up having a blown headgasket. My reasoning was all of the stock motors running around with 300 and 400whp. Even the blown engines are usually from ringlands and not rods. You are gonna hear everyone tell you to just run eagle rods to be safe. That is good advice, but I have yet to see a rod thrown that wasn't overrevved or run low on oil. My two cents. I hope it helps!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Professor X &raquo;</TD></TR><TR><TD CLASS="quote">I am too doing the same thing using stock rods with forged pistons. In my case, I already had the pistons and ended up having a blown headgasket. My reasoning was all of the stock motors running around with 300 and 400whp. Even the blown engines are usually from ringlands and not rods. You are gonna hear everyone tell you to just run eagle rods to be safe. That is good advice, but I have yet to see a rod thrown that wasn't overrevved or run low on oil. My two cents. I hope it helps! </TD></TR></TABLE>


also my mind set^^^^

my viewpoint mainly is tensile load vs compression load on the rods. compression load, what the cylinder pressure affects, surely could be quadrupled without affecting the rods. but tensile load, what rpm affects, i could see tearin apart a rod over time.......

that being said i would think stock rods and a really good tune i should be able to run 400+ on stock rev limit even though i will not do... but mid to high 300's i want. again using wiseco pistons and arp head studs.