17 replies to this topic

[UC308Hatch]

Hi guys, asking for a mate.

Does anyone make/sell a 6"conrod to suit a standard holden 308 crankshaft? (Standard non-floating gudgeon)

Cheers in advance👍👍


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[yel327]

I've never heard of one, but you may be able to do it using SJ Chev rods. Crank will have to be ground to SJ size and the sides of the rods narrowed to Holden V8 rod width - essentially the same operation that the guys used to do to do an offset ground stroker, except not offset ground. Eagle sell rods in SJ at 6" length.

[UC308Hatch]

Ok thanks yel327!


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[TerrA LX]

I think you will find with the cylinder spacing you may need to invert the rods to get the correct alignment with the piston to centre in the bore, as they do with the stroker motor.

[yel327]

Probably yes, same setup as an offset ground stroker but not offset ground.

[Litre8]

A 5.7" rod may be an easier option?

[mick_in_oz]

If you're keen Argo Engineering will make anything you want.

 

Why the desire for a 6" rod?

 

It's not always all its cracked up to be, and the way the cylinder head is done can have an effect on how much better or worse it ends up being.

[UC308Hatch]

Thanks guys for all of your replies. As I said in the beginning asking for a (computer phobe) mate, but I believe it was something to do with running a set of flat top 350 chev pistons (that he already has on his shelf) in a 308 he is building. Yes, Litre8 a 5.7" rod now seems to be the go...


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Edited by UC308Hatch, 30 March 2015 - 09:31 PM.

[TerrA LX]

Same deal with any chev rod.
Only If you find 5.7 Holden rods will there be no need for modification.

[yel327]

He could build an offset ground stroker using SJ 5.7" rods with the 350 pistons. Block needs decking to match the piston height though, how much depending on the crank's journal sizes now.

[UC308Hatch]

Thanks again guys for your help & info. It was really just a question to find out if 6" rods & the pistons he already had were viable option.
Based on your feedback & the aim of the exercise was a budget build for a cruiser, these pistons will stay on the shelf & 5.7" Holden rods & more suited pistons will now be purchased.

Thanks again👍👍


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Edited by UC308Hatch, 31 March 2015 - 11:48 AM.

[ozyozyozy]

A standard holden rod is under 5.7 inch.
If you want to use a 308 stroke crank, whether you use 5.7 or 6 the work is still the same.
Need to use a chev small journal rod, which also need to be narrowed, crank needs grinding, this can and does weaken a 308 crank, grinding to that the correct size.
It's common for a offset ground crank to crack coz of this.
Stroker cranks 3.48in are available to suit chev rod journals so a 5.7 rod is a straight fit with the correct chev piston(off the shelf)
I have heard that standard stroke 308's do like a 6 inch rod, very common in the group c days.
Coz the time and money involved very few people do this, cheaper just to use a harrop stroker crank, off the shelf rod and pistons, parts are more readily available.
Hope this helps

[Struggler]

FWIW you can use a narrowed large journal SBC conrod.

 

The big end on a LJ rod is 2.100" and standard 308 is 2.115" so a 0.015" cut on a standard crank will do it.

[mick_in_oz]

Its actually 2.125" for the Holden BE, I was gonna suggest the same thing.

 

Also had a thought of I wonder how close to the same the conrods are, maybe you could thin the LJ rod, and turn and hone the BE in the LJ rod and maybe get a standard Holden bearing in there, would save one additional headache of cutting down the bearing shell, the BE bore is 2.250" vs 2.225", so .025" or .0125" per side to come out, might be doable if the bearing shell tang is close enough... Got a friend thats good on the Lathe?

[TerrA LX]

So If my morning brain understands correctly what your say is that if I go 025" on a holden big end the size ends up 2.100?

Run a standard chev size bearing in the rod?

[mick_in_oz]

Yes, but the conrod big end needs to be narrowed to match the Holden rod, then the bearing shell also cut down to suit. All very typical in an offset ground 326 SJ rod stroker.