Thread: Dummy has a question

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ok Dummy here! I can't seem to sypher this one out. What is the average engine speed for a stock chevy 350 at a street speed of 65mph ?

Depends on the ratio of the ring and pinion in the diffferential and the ratio of top gear in the transmission. Also depends if the trans is manual or automatic. Manuals have a direct drive with no slip. Automatics can have a lockup converter so there is no slip or a conventional converter which will slip a certain percentage depending on design. On a fairly tight converter, I usually use a figure of around 3-5% slip when figuring mph @ a certain rpm.

Originally posted by gr8lite
ok Dummy here! I can't seem to sypher this one out. What is the average engine speed for a stock chevy 350 at a street speed of 65mph ?

hey dummy, no one else can either with the info. you gave. here is the calculator, you do it. hope you know i'm just joshing you .


http://home.tampabay.rr.com/1bking/c....htm#calc_disp

Thanks guys! I do understand gearing make the equation. However what do I need to be looking for in a average engine speed? I am trying to determine what gears I do indeed want to run. I am new to the V8 scene , so I don't know where they should be running. Thanks again to all!

Generally speaking, the lower the rpm's, the better the fuel mileage at cruise. Of course, like anything else, you can go too far to the extreme and the curve goes the other way. For instance, if you had the car geared to rpm the motor at, say, 1,200 rpm at cruise, then the motor wouldn't be making enough horsepower to pull the load and you'd be down on the loud pedal more to get it to pull, decreasing the mileage.

In my opinion, an engine speed of maybe 1,800 to 2,200 rpm's would be optimal for mileage/power if used with a short duration cam that would support making enough horsepower to pull the load at that rpm. Here's an example of such a cam, the very first one listed in Crane's lineup for a 350. Read the description in the upper right hand corner....
http://www.cranecams.com/?show=brows...tType=camshaft

That's the neat part of having an overdrive trans like the 700R4, you can have a very low first gear for launching the car and a nice, tall fourth gear for cruising. Here's a chart comparing a TH350 and 700R4, showing the effective final drive ratios.....
http://www.enjoythedrive.com/content/?id=7088
Note that the 3.06 first gear of the 700R4 combined with a 3.73 rear gear will be the same final drive as a TH350 2.52 first gear used with a 4.56 rear gear!!!!!!!

So, using the information given you by Mike, you can plug in some numbers and determine what you want to do. For instance, at 65 mph with a 28" tire, 3.73 ring and pinion and 700R4 with its .7 fourth gear, engine rpm's would be 2,037. If you allow 4% for converter slip, engine rpm's would be 2,118.

This information supports what I've been saying over and over on this board:
THE CAMSHAFT SHOULD BE THE LAST ITEM CHOSEN IN A BUILDUP.