Final Gear math and RPM

350 turbo with 2.52 x 2.56 = 645 = 6000 rpm
Glide 1.76 X 3.73 = 656
350 turbo with 2.75 first gear x 2.41 = 662
Glide 1.82 x 3.73= 679
Glide 1.76 x 3.90= 686
How can you...or can you do the math to get the RPM's for these ?...is it possible.
The only thing I know for a fact is our 350 "4valve relief, 450/450 hydraulic, stock crank, gm Z28 cast iron high rise, Holley 4412 stock, 1.5 rockers, stock rods, 1 to 1 pulley" in first gear We are turning 6000 rpm based on the tach after the race with a 2.56 ratio & 350 turbo.

All things equal and no tire spin, you should change close to 100 rpm/ point in gear change. So if you turning 6000 with a 6.45 then a 6.86 should give you right around 6400. Now if it makes you spin more, it could make you turn more rpms.

On a quick change we use the rule of thumb that says every ten numbers is equal to 100 rpm. This would apply here also except when you are looking for 700 to 1000 rpm change.

So I guess that leads to the land of the unknown and the million dollar question..."how many RPM can this type of motor handle" with another million variables...at least i got something to start with.

it also depends on the cam especially in the lower divisions and especially with a two barrel. Also the driver has a big effect on the rpm with a 2 barrel, if you have a stop and go driver you will need more gear. And if your cam is running out it dont matter how much gear you put in it, it wont gain rpm.

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Originally Posted by Graff Spee

On a quick change we use the rule of thumb that says every ten numbers is equal to 100 rpm. This would apply here also except when you are looking for 700 to 1000 rpm change.

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what or how would you do it for 700 to 1000 rpm change ?

Here is a web site with alot of info on different calculations
http://www.thedirtforum.com/toolbox.htm

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Originally Posted by 3dinter

what or how would you do it for 700 to 1000 rpm change ?

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You would have to sort of sneak up on it. When you try to jump that much just doing it all on paper you are missing out on the power curve and many other variables. You would not be close. If you sneak up you are ok. A couple hundred at a time till you get to the place you want.

Quote:

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Originally Posted by Graff Spee

You would have to sort of sneak up on it. When you try to jump that much just doing it all on paper you are missing out on the power curve and many other variables. You would not be close. If you sneak up you are ok. A couple hundred at a time till you get to the place you want.

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yep i agree, a couple hundred at a time now i think about it.

Quote:

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Originally Posted by Graff Spee

You would have to sort of sneak up on it. When you try to jump that much just doing it all on paper you are missing out on the power curve and many other variables. You would not be close. If you sneak up you are ok. A couple hundred at a time till you get to the place you want.

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I see alot of people talking about the 650 range, i would assume based over time thats what people are finding out what runs the best.....????