Info on mechining needed to put sbc rods in a 3.4l

[DANH]

I was hoping that some one here would help me. I need to find the info on what is needed to be done to a sbc rod to use in a 3.4l and i am asumming the cranks are the same for the 2.8,3.1 and 3.4 ,3.4dohc.

[geoffinbc]

No the cranks are not the same. The 2.8L has less stroke. But bearing dimensions are the same between all.

To use SBC rods you need to use early SBC rods for 2" journals and then you need to narrow the big end to fit the V6 journal and you need to bush the small end for the smaller V6 pin or use custom pistons with a bigger pin. Depending on your power level it is a complete waste of time and money in most cases.

[DANH]

I was looking at the fact that if somewear down the line if I were to turbo this 3.4 that I would not have to beef up the lower end.I know the 3.4 rods are pretty good but I do know that the sbc rods even better. So why not in so much as the lower end would be some what bullet proof.

[Joseph Upson]

I was looking at the fact that if somewear down the line if I were to turbo this 3.4 that I would not have to beef up the lower end.I know the 3.4 rods are pretty good but I do know that the sbc rods even better. So why not in so much as the lower end would be some what bullet proof.

Generally speaking you want to improve the weak points. The stock rods and crank from my knowledge have not been problematic, the pistons on the other hand have been, so you'd start there and if you plan to stress the engine enough to warrant it tackle the connecting rod upgrade. Cost of rods + cost of modifying + balancing, it can get expensive especially if you're not making enough power to justify it.

[DANH]

As you can see I know very little about 3.4l v6. Do not know the weak points of this engine. Does the 3.4lDOHC have the same problem with the pistons and I take it that the rods would hold up to 300+ at this point.

[bob442]

if you spend 2500-3000 on pistons heads, head work, mill work, ext. whats another 500-600 for insurance that your total investment does go through your hood.

And realistically, cases like Jbrogan's with a destroyed piston and bent rod, which came first? the chicken or the egg?

[pocket-rocket]

As you can see I know very little about 3.4l v6. Do not know the weak points of this engine. Does the 3.4lDOHC have the same problem with the pistons and I take it that the rods would hold up to 300+ at this point.

There is a guy with a DOHC turbo in a VERY nice Ferrari replica Fiero laying down 430 to the tires.

http://60degreev6.com/forum/showthre...hc....430-rwhp!

[DANH]

as far as the chicken and the egg .I would say the chicken came first. and for the piston rod thing if the rod let go first the piston would have more then likly stayed in the bore with some skirt damage and top damage put would be in one peace. with the rod action and the top from head damage if the piston would have let go it would be a mess with piston peaces being all over the place and it woud bend the rod.

[bob442]

it was stock pistons and rods, the piston was in pieces, and the rod was bent, but one if the rod bent and then took the piston with it? there wasnt anything left of the piston in the bore so.... lets say a bad tune bent the rod, and took everything down with it, its plausable, but so is the other way around. no way to tell unless you spent some time looking at all the pieces.

I'm going to run 11.5-1 CR, with a good sized cam, N/A, after talking with one person about a New motor built (SBC 350 making 350~ish HP) a rod broke and took the whole investment with it, this is for a dirt modified class with tight rules on all engine parts, basically the only thing after market was the intake and carb, and to a small extent the cam, anyways i'm investing the money in SBC rods. I'm ALSO going to bag the crap out of this thing every time i sit in it, tune it myself and i'm building the trans to take that abuse too.

If its a DD simple build, i wouldnt bother. plus if you decide to go F/I your going to want to swap the cam, and put in some sort of after market pistons. I'm told as it is that SBC rods are over kill, but i like it that way.

[MidnightriderZ24]

http://carphotos.cardomain.com/ride_images/1/2280/2021/5698510458_large.jpg

big ends must be narrowed from .940 to .854.

[bob442]

http://carphotos.cardomain.com/ride_...0458_large.jpg

big ends must be narrowed from .940 to .854.

You said that the 60* bearings fit? or did you machine down SBC bearings? i was thinking the easiest way would be to put them in the rod while/after there being machined. I personally would see it being to much over lap of .086", plus i would like to groove in "piston squirters", but i'm just asking, i think you mentioned in another thread that your machinest/builder said he's seen worse offset bearings when you used 60* bearings?

[MidnightriderZ24]

yeah, when i went to pick them up i asked why he didnt machine the tangs, he told me they would be perfectly fine the way they are, and that he has seen more offset perform. so im using factory bearings.

[dskopek]

I used SBC bearings cut down to the new size. Made a fixture to clamp the bearings in a lathe and recut the chamfer to match the crank. Used Scat H-beam rods, The crank or block will give up the ghost before i break one of these!!!!