4.5 stroke how high Rpm

Some of you guys that run a 4.5 stroke crank how high do you wind them?


Thanks Tore

You wouldn't believe me if I told you...

I've been over 6500 with mine with no problems, and I know there are several that regularly go over 7000.

Depends on how good the heads and manifold are and how the engine is camed....as in how high does the engine want to go. The engine block oiling system is also a consideration. Many different answers.

I'm hoping my new one will zing like a small block!

Thought the longer the crank the lower the RPM had to be am I missing something

I shift mine at 71-7200 rpm.

Wherever it's gotta go........

I used to use the "Yukon Jack" rule.

7,500 if you're winning, 8,200 if you're losing........

511Fox wrote:Thought the longer the crank the lower the RPM had to be am I missing something

depends on the cam and cyl head package................

richter69 wrote:

511Fox wrote:Thought the longer the crank the lower the RPM had to be am I missing something

depends on the cam and cyl head package................

It really depends upon the weight of the reciprocating assembly as to what is considered OK. 90 feet per second is usually considered safe in a DRAG race engine if the reciprocating weight is under 1,100 grams; 75 feet per second piston speed in an endurance type engine.

I was commenting mainly on the applications ability to breath at a given rpm............and yes weight also plays a role.

and W's don't count


Randy

Mark O'Neal wrote:Wherever it's gotta go........

I used to use the "Yukon Jack" rule.

7,500 if you're winning, 8,200 if you're losing........

X2

I shift mine at 6800 go through the lights in the 1/8th at 7-7100. Turned it 7800 once by accident ( thank goodness for high side chips), but it was still pulling pretty good.

I roll through the traps at about 7200 with my 605. I would prefer to shift it at 6800 or 6900 and cross the finish line at 7,000 or less. Before I swapped to a 4.29 gear (from 4.56) it crossed at about 7,350. It goes faster with the lower RPM.

A couple of years ago, it saw 9,000 rpms for a fraction of a second due to a broken ring and pinion. The only problem was eight bent exhaust valves. The high side chip was out....grrrr.
Keith