They will be going in a stock stroke ls1 with h beam rods. Are the 8740 bolts enough or will I be looking at a future failure?

 

What power level?

If its a H/C build NA then 8470 will work fine

Boosted, high nitrous then I would pay the extra $40-50 bucks for the arp 2000 bolts

 

Im running 2000. But I eventually plan on spraying it.

 

8740s are more than ok for a basic N/A engine making high 400s and keeping it under 7500rpm.

Anymore than that and you should invest in the better bolts.

 

I have 8740's in my LS3. It makes 650hp plus to the flywheel and I shift it at 7k all day long!! It may blow next time out but so for so good. Good luck with ur build. If not sure go with the 2000's.

 

RPM loads the bolts, not nitrous or boost.
The stock bolts do well, don't they?
The aftermarket rods have 7/16 bolts. The 8470 is better than stock.
The 2000 is only a little better than the 8470.

Ron

 

Thanks guys I just didnt want to go overboard and spend money where I didnt need to. Motor will definitely be seeing boost!

 

regardless of what bolts you use, I hope you're going to check for big end distortion. Be prepared to resize if necessary.

 

he's using H-beam rods, so I don't think he'll have to worry about that.

and as others have said, its RPMs that drive the need for bolts with a higher preload. I recommend checking the dynamic forces on the rod bolts against what preload you can achieve, verified with a bolt stretch gauge. 8740 should be good to around 7000 or so, based on the last time I checked (assuming reasonable conservatism and contingencies).

 

I've seen plenty of H-beam rods with out-of-round big ends, plus bolt manufacturers recommend at least a check of big end dimensions and round when swapping bolts.

I wouldn't bother with the 2000's, they're not much stronger, not enough to warrant spending more.
Lots of old BBC's were rebuilt with 3/8" stock thru-bolt rods and spun to 7K plus, swinging big ol' heavy pistons. Don't overthink it, but it's good to think everything through and determine where to spend your hard earned cash.

 

as stated above , RPM will stress rod bolt not the power level. because on a power stroke the rod will push against the crank and the rod bolt will not be stressed. But on the finish of the exhaust stroke the piston will be pulled down so the rod bolt will take all the stress.

 

 

Anytime you change rod bolts you change the clamping force and bore distortion of the big end so its critical to check the roundness if you switch bolts. Even with hbeam rods there will be change and always better to be safe and do it right the first time!!

 

I agree with those saying rpm is the concern but would add piston weight factors in. Which is the reason why you might go heavier duty rodbolts for a nitrous or boost build as those pistons might be heavier.

 

good point, I don't know for sure, but it seems that pistons for boost would actually be lighter because of the material removed from the top for the dish volume. maybe someone else can chime in on that.

 

Piston weight is always something to be considered as the extensive load increases with higher rpm. The piston crown and thickness can be altered but you also have to factor in ring placement as with any boosted application they will change in keeping the support above the top ring being enough to support the power adder.

 

For $40 bucks extra I would get the 2000's...

Same reason you get arp main studs, a lot of people don't need them for their 500-600 hp builds.. But they do it for peace of mind..

 

as long as you buy the rods with the bolts you want, you likely won't have any distortion as you would with adding higher strength bolts to factory rods.

 

Just like Rez said as that way they are honed to spec with the bolts.

 

You realize pistons are hollow from the bottom right?
You think maybe they leave the crown thicker if a piston will see the extra load of boost or nitrous?