Rating 3400 rods

[bob442]

what are stock rods good till? i know the 3400 valley is good till 400hp whos had rods actually take a whole motor with them? rather than just a rod making noise... only reason i'm asking is because i'l like to know how much strength and longevity i've taking out of my rods by polishing them and taking doen inperfections.

[geoffinbc]

You have removed the stress risers which will give them a longer fatigue life but it will not increase their yield strength. So basically they can run near their limit longer but still not exceed it beyond what a stock rod is capable of.

[bob442]

well, if i could ever imagine, my application is going to be at most 260-280 chp N/A 10.67:1 CR pistons.
heres the meat pics:
stock smallest width 3.148 modified 3.142

right to the left of my thumb is stock .38 modified .34

i beam thickness stock .894 modified .808

now, the width where the bolt goes through the cap not measuring the face of the rod journal, but the measurment just below, or to the 'side' is and was stock .674 modified .602, this is basically right where that 'lip' was shaved off

[Superdave]

7K RPM and roughly 400 crank HP. Detonation will turn them into pretzels quick though so you better watch your tune.


People have pushed the stock rods further in boosted applications but after the 400 HP mark you really should get some aftermarket H beams.

[bob442]

well, thats just it, i'm only worried now as i was talking to my foreman about this, and he races dirt modified, and has gone through alot of engines. i'm building this motor, i only want to build it once, but will these last and survive abuse? its hard to say how much HP i will hit, but i'm going with an over estamate compaired to what you guys have gotten with given combos. i've talked with Ben only a little bit, but the finial build is decided on:
3400 block and heads
10.67:1 pistons
long tube headers
ported and polished top end
DRTC
strip cam from WOTTECH
these rods and a ballanced rotating assembally
65mm TB
TCE lifter springs
ARP head and rod bolts
all new bearings
4200 trail blazer injecters

i dont know what i'm going to hit, i'm taking alot of time on the port work to make everything as perfect as possible.

No one has really practiced this on these motors so i guess i get to be the guinepig... and rarly does anyone talk about there failers on here. so....

I feel as if i made a ticking time bomb lol, i gotta settle on this somehow.

[MidnightriderZ24]

a set of $400 rods will save your entire investment. honestly these engines dont make enough power n/a to break a rod. rpm might kill them though.

[bob442]

a set of $400 rods will save your entire investment. honestly these engines dont make enough power n/a to break a rod. rpm might kill them though.

This is kinda where i'm at now, what i did was a great idea, and if it was a much smaller cam and stock CR, I think these would prove to hold some potantial in making power. But now that there lighter, it will most likely rev quicker and higher.

If I was going to invest some money in rods, I would like to know the weight difference in H beam to I beam rods. the I beams (atleast what i've found from reference photos) aren't that greatly shaped.
Being smooth like what i've done to my rods, but the H beams are a very nice looking piece. If they weighed the same or even less I'd spend the extra money. Only problem is i'll have to get bushings.
Then at that point i maise well go up in CR and so on and so on and this crazy power hungry cycle never ends. I just dont know what to do any more. i'm just about ready to scrap all my work and get a SCL67.
Being detoured from the rods really pisses me off, as i did my homework from all the knownlegde that the internet could provide me, took my time with sanding down the rods, there fucking perfect in size to one and other. But ONE IF one bends or breaks, the whole project goes through my $800 hood which would pretty much due me over.

[pocket-rocket]

But ONE IF one bends or breaks, the whole project goes through my $800 hood which would pretty much due me over.

This is why raising the performance bar on any vehicle can be dangerous if you don't watch what you are doing and do your homework. I'm willing to bet that you could reach your goal of 260-280 chp without a problem with them. The $400 rods would be $400 insurance. I mean, you're looking for roughly 100hp more than what your engine put out stock. Dave has passed that and is running ~350 chp on stock internals. That's a bit more than 100chp more than stock.

[bob442]

The $400 rods would be $400 insurance

When put like that it makes sence. i'm putting my heart and soul into this build with the headers turning port work, and trying to do all my homework too. i dont want anything to fail anywhere on the drive train on this build, simply i'm not cheaping out or taking chances. That is the goal of this build. later on, who know's maybe i'll go for a bigger cam or a N02 shot, as i'm building the motor to handle all this.

What is bearing is used for SBC rods that are modified to fit a 60*v6, i'll buy a set and turn them down on a lathe at work. and just order pistons to work with sbc rods... or get bushings...

EDIT, "looks like" 60*v6 bearings would work...

http://cgi.ebay.ca/SINGLE-SBC-6-200-CHEVY-H-BEAM-CONNECTING-ROD-V8-PH-/170602256293?pt=Motors_Car_Truck_Parts_Accessories&hash=item27b8afd7a5

[Joseph Upson]

Why can't you use small block chevy rod bearings? they're not too wide and although the pins are undercut at the ends I don't see where it will cause a problem. I used narrowed small journal chevy H-beam rods with the standard sbc bearings. I still have the 3.43" stroke forged crank that I don't have a use for that has radiused pins if you're interested. They do make chamfered sbc bearings that should clear the radius or you could just use the 3400 bearings. I decided to take advantage of the wider sbc bearings to support more load.

[MidnightriderZ24]

i spent a total of 375 for the rods (ebay), 85 on machining to the rods. piston pin size of the sbc was used. used 3400 bearings, but will change next season. it depends on what you want to do, i pushed 15 psi a few times and it held together (who knows how long). i only did that to a factory bottom end, now if i had at least a grand in pistons...

[Joseph Upson]

i spent a total of 375 for the rods (ebay), 85 on machining to the rods. piston pin size of the sbc was used. used 3400 bearings, but will change next season. it depends on what you want to do, i pushed 15 psi a few times and it held together (who knows how long). i only did that to a factory bottom end, now if i had at least a grand in pistons...

My rods look just like those from Ebay and I paid nearly the same only slightly more total because I also had some work done on the small end for better pin fit. I wasn't happy to find what appeared to be the same rods with better searching for about $80 less. They lied about the weight but in the end they still wound up being lighter than the stock 3900 rods.

[bob442]

breathing has regulated. just gotta find the H beam rod for around 400 with a weight less than 600g's

[bob442]

i found what i'm after, at 535g's, H-beam rated to 500hp, no over kill completely, yet. maybe i'll bump up my CR now lol http://lightningmotorsports.com/eagl.../i-329370.aspx

[Joseph Upson]

Be sure of what the stock rod weight is at the big end particularly and use that as a basis for the rod choice. You can end up with a pretty hefty balancing bill if they need to add mallory metal to balance the assembly. The rod will loose wt from narrowing but it can still be close and as I metioned earlier, people lie. My rods' advertised wt was a good bit less than the actual wt and I also asked personally before ordering and the wt given over the phone was still lighter than actual so that made two lies. The sbcr machined wt was about 609g, the stock 3.9 rods were 632g.

My assembly lost a good bit of weight from the crank pins, pistons and connecting rods. You may need to search out a good set of I-beam rods.