ARP Bolts + 125E Rods

[AlfaLofa]

I was contemplating using ARP con rod bolts with a set of 125E rods.

But then I saw this:

Which states that the ARP bolts are for use with steel rods.

Also the ARP recommended torque is 55 ft. lb. rather than the 44-46 suggested in the Miles Wilkin's book.

Can the 125E rods withstand the extra torque or is this an engine failure waiting to happen?

So - basically are the ARP bolts suitable for rods such as the 125E ???

[rgh0]

I have not built an engine for a long time with ARP bolts in 125E rods. However provided the bolts are dimensionally correct for the rods and the heads fit on the flat land area and thread size and length is correct then there should be no problem. From what I recall all these conditions were met when I last did it a few years ago now.

I would torque to the standard torque for a 125E rod not the higher torque recommended for a higher strength forged steel rod. The higher torque in a forged steel rod reflects the expected higher loads from higher revs that you cant use in a 125E rod. The higher torque should actually be OK in a 125E rod as the thread engagement length is long enough and the torque limit is normally set by the bolt not the female thread, But you don't need it so I would not change from the Lotus standard unless I had done the engineering (my first rule!)

cheers
Rohan

[StressCraxx]

Rohan is probably right, but I have tensioned the rod bolts both ways on my conn rods.

I used the bolt stretch gauge method for my 2737E rods in my Formula Ford. I was able to set them at 0.006" stretch. Max rpm is 6500 with the occasional missed shift

I used 45lbs/ft on the 125E rods in my Twink.

The important thing is the fastener stretch exceeds the expected cyclic loads and hopefully the unexpected ones too.

Regards,
Dan

[AHM]

So - basically are the ARP bolts suitable for rods such as the 125E which are not made of steel???

Mine are made of steel. What are yours made of then?

[el-saturn]

as far as i know both the 125 and 2737 rods are forged (=steel) - the 1st TC rods were casted! and a better bolt will always perform better -- no matter what material it?s put in - the better the material it?s in, the better the bolt will take the tension/load or it?s full tensile capacity AND if something fails you?ll always know in advance it wasn?t the ARP cheers sandy

[AlfaLofa]

Aha - I stand corrected !!

I made some wrong assumptions

[Jeff@Jae]

Great replacement bolts (that's all we use) and the torque is more about the fastener (bolt) than the rod. Use the ARP stated torque to get proper bolt stretch or better yet use a stretch gauge. Also use ARP Ultra Torque lube when using the ARP hardware. Great stuff and insures an even torque up. The ARP website explains this very well.