Main Cradle, And Head Bolts..

[nissan200sx.dk]

Hi..

I have a RB25DET s1 engine I'm building up. Are grade "12.9" bolts okay to use as head and main crank cradle bolts?

Ronni

[Adriano]

Hi..

I have a RB25DET s1 engine I'm building up. Are grade "12.9" bolts okay to use as head and main crank cradle bolts?

Ronni

Yes, but studs are better

[nissan200sx.dk]

I'm building a all std RB25.. But the bolts we have at work, so was just thinking it they are better then i would use them.

Thanks for reply

[45ULT]

i'd be careful with the headbolts especially, as they have to be a certain type as the torque settings account for the factory bolts stretching when torqued. I personally wouldn't risk it on something so important as the headgasket.

[grigor]

It's dangerous to swap bolt specs without knowing the spec of the original bolt.

The factory bolt torques or "turn of the bolt head" angles have been worked out to give the designed clamping force via bolt stretch.

By fitting bolts with a higher yield strength, and still using the same factory figures, you'd over clamp the joint.

Some examples;

Grade/Yield strength (MPa)

4.6/240

4.8/340

5.8/420

8.8/660

9.8/720

10.9/940

12.9/1100

As an approx guide, you multiply the bolt's grade numbers to get the bolt's yield eg (8x8=640) (4x6=240)

Say the factory spec was for an 8.8 bolt and you replace it with a 12.9, you almost double the clamping force if you use the same torque settings.

Edited July 7, 2007 by grigor

[Adriano]

i'd be careful with the headbolts especially, as they have to be a certain type as the torque settings account for the factory bolts stretching when torqued. I personally wouldn't risk it on something so important as the headgasket.

Agreed, sorry about the bump steer, i assumed you has some aftermarket head bolts and were checking they were ok.

[nissan200sx.dk]

Okay. But when using aftermarket bolts that are stonger wouldnt you get the same issues?

So bottom line is I shouldnt use 12.9 bolts for main cradle nor head?

[Adriano]

You torque aftermarket bolts to different torques, without the figures for those bolts, it would be anyones guess.

[nissan200sx.dk]

Hi.

I'm a little confused..

Only for main cradle now:

I know the tourque settings for theese 12.9 bolts. Can I use them instead of std bolts? Would it be stronger than std?

Head bolts:

Also know tourque settings for theese 12.9 bolts. Can I use them instead of the std head bolts? Would they be stronger?

Thanks for reply, and sorry for me being a bit slow. hehe

[nissan200sx.dk]

If you compare 12.9 specs with ARP2000 bolts they are both quiench and temper steel. Both have almost same Rockwell C hardness. The ARP2000 bolts have a little higher tensile strength 200000 - 220000 psi, the 12.9 bolts have 160000 psi. The 12.9 bolts have their thread rolled, not cut (Stronger)

So cant see why a 12.9 bolt wouldnt be better than std as main and head bolts. Have seen cars run with 12.9 bolts as head bolts.. The main std bolts of a RB engine, dont they come from a Datsun 1200?? So wouldnt a 12.9 bolt there be stronger also??

12.9 bolt info

[Fitzpatrick Speed Works]

as builder of many a a12 engine I can guarantee RB bolts are nothing even the same.

As mentioned as long as you match the category bolt you have to the clamping force required I think you will be sweet.

As a guide look on the ARP site to there bolt that most matches the one you are going to use and see their recommended torque settings

Dont forget to use a moly grease to tighten with.

Cheers

[T04GTR]

just use the factory ones. not china "12.9" grade ones

[nissan200sx.dk]

Hi.

Wont be using any "china" parts! The bolts are from work, were thay are used in "hydromats". Machine with alot of hydraulic pressure.. Low grade, or poor bolts simply wont hold up. So they are good quality.