I am doing one for a customer, and I am doing my own as well.

A quick note for Chris Dodgeman.

The problem is that when A12/14/15's were in production, a lot of Japanese fasteners were pretty crappy (not only Datsun). You could never be sure what you were getting---some of them you could easily get a file into, so they were not hardened very well at all. If you buy new ones from a dealer, it is still possible to get some of this old stock.

Having seen what happens when a rod bolt breaks at speed, like the block is all but cut in half, it is prudent to err on the side of safety.

Therefore, if you are building a big output engine, running on big compression, ARP or equivalent bolts are a wise investment.

Turbo or S/C engines seem to be a little less tough on rod bolts because the power is delivered at lower RPM (generally) so the loads on the bolt are much lower.

Stew. McK

Actually, my understanding of it, is that force fed engines can be a bit less hard on rod bolts because, when the piston comes down on the intake stroke there is some pressure helping it go down. The point at which a big end lets go is when the piston is about half way down and the crank is changing the direction of the big end from staight down to the side.It is this action which busts them. When the motor is sucking against pressure the load on the big end is less.
To this end , some motors have poor conrod/crankshaft geometry by design and aren't any good for big revs .

exactly a14force, hence the use of the a14 over the a15. better crankshaft geometry (less stroke than the a15) = better reving.

89mm
Your comments are good & i have taken them in. My own engines are street units with street-wise RPM limits & i have not encountered a Datsun A series that failed for that reason,.... yet.
The end result of a rod bolt failure at speed is not pretty,.. or cheap, so yes, good bolts are a cheap investment.

Quinn
I have heard this A15 versus A14 thing quite a few times, but my friend up the road runs a big bore A15 [1600cc] in his 1200 coupe racer. Its fuel inflicted & last weekend it posted a personal best around Oran Park.

He wins a lot more races than he is supposed to, & the A15 doesn't know that it is supposed to be inferior. At the present rate, he will wear the engine out before it blows up. I suspect that B310GX can vouch for this one.
This engine uses stock rod bolts, so i suppose he got lucky & got a set of good ones. I'l be checking mine with crack testing & Rockwell hardness tester before i use them from now on.

yes and no Chris, A15s are fine. But if you were someone who loved spending ####loads of coin on building( and rebuilding) your motor, often, so that it could do obscene rpms. Then an a15 wouldn't be as ideal as a shorter stroke motor.Horses for coarses, aye.
A mate of mine's a12 used to pull to 9500 quite happily( untill...you know what happened) When I began building my s/c project, EVERYONE I spoke to, ex rally guys current rally guys , and anyone with any real datto experience, told me to go for the a14.

Dodgeman and a14force are both right, the standerd bolts are very good in the a series and ive heard of people pulling large rpm with big compression and not busting them and if the motor was for road usage and i was going to keep the rmp to a sensible limit i wouldnt bother with ARP bolts, i'd just crack test the standard ones. BUT this motor is going to be 12-13:1 comp. and rev to at least 9thou so I dont realy want a bolt to give up. the same reason is why im building a a14 rather than a 15. I race against a guy with an a15 and hes real quick and still going after 3 seasons. But hes limited to 7200. and 10:1 comp. he has good torque and as i said is quick but EVERY one ive talked to has said go the a14 unless you can afford a $5000 forged crank from england because once you start getting big comp and high rpm you brake cranks.

Quote:
The maximum load on the bottom end occurs at the end of the exhaust/start of intake stroke. The piston is forced to change direction with no compressive resistance to slow the piston down as occurs on the compression stroke.

It is rare (but not unknown) for a rod bolt to fail from the loads at 90 degrees crank angle. The reason this is less likely to happen is the rod caps have two rod bolts in single shear. The forces required to break the 2 bolts in shear, are a lot higher than those required to stretch the bolts in unsupported tension.

Hey Feral any progress on the bolts?

ARP part number is 202-6002. They only come in six cylinder sets.