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tinkwithanr
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I'm working on figuring out what direction I want to take my engine. I know that as stock, the rev limiting factor is the rocker arms. Assuming they are upgraded along with the valve springs, lets say billet arms with a 304 schick cam and schrick high pressure valve springs, what is the next weakest link in the engine? What rpm should the above be good to, 7500? 8000? 9000? Also, it can be assumed the fuel/intake system is up to the task of fueling whatever the engine is asking for.

And I do realize the drivability/usability/cost/is it worth it of raising the operational rpm of the engine, this is more just a question of what if.

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If your valve springs are stock, the rockers break at 6800- 7k.

If you uprate the springs, the connecting rod bolts start to get iffy

at 7500, altho (knock on wood) I run that high with them.

After that, the steel rockers become necessary.

If you uprate the rods (mostly for the bolts, the rods themselves are tough)

rumor is that 9k is survivable. If you lighten the crank.

I think it's the next weak spot, but that's beyond my fiscal rev limit!

t

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Guest Anonymous

i have been know to buzz up to 9000rpm (most just for defending) as the car doesn't make much power up there with a 328 cam. I run all day at 8000+RPM.

I have not had a rocker break or a pad wear in 5 seasons with 50+ hours of track time.

Pauter Rods and arp bolts, lightened crank, button clutch, skidmark arms, rocker locks, weber 50DCO SP carbs

Anthony

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If your valve springs are stock, the rockers break at 6800- 7k.

If you uprate the springs, the connecting rod bolts start to get iffy

at 7500, altho (knock on wood) I run that high with them.

After that, the steel rockers become necessary.

If you uprate the rods (mostly for the bolts, the rods themselves are tough)

rumor is that 9k is survivable. If you lighten the crank.

I think it's the next weak spot, but that's beyond my fiscal rev limit!

t

So suppose your were to get uprated rod hardware (ARP or the like), could you still run the stock rods? Or should you only match upgraded rods with upgraded hardware.

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the problem is that no- one makes that bolt, and there

isn't any room to fit a slightly- larger bolt. The hole's

already almost too big for the rod and cap thickness...

Byron says ARP will make you a bolt- but the first one was

something like $100,000. After that, they got more reasonable...

given that it's a 7500ish limitation, the few (like Anthony) who spin higher

usually just get better rods, since they already come with very good bolts.

t

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Guest Anonymous

For the money, if you are building a motor and have the option, I would upgrade to new rods or slot a set of longer s14 rods (144mm) and run updated bolts. This requires custom pistons but the longer rods and update ARP bolts run about 1/2 of a set of Pauters or comparable.

Never used the cheap ones Ireland sells (I think they are an offshore brand) so I can't comment and I have never really had the urge to try them.

As Toby said you are kind of limited with the stock rods given the design but they are certainly strong.

It is one thing to build a motor that can spin to infinity but if you can build a torquey mill that doesn't need to spin that high why bother? There are a lot of other things you need to do to safely spin at 8500 + and in the end it is a lot of work for limited gain.

Anthonyk

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