Need someone to do a speed calculation for me.

[dmontzsta]

1964 LaveyCraft "true" Flatbottom.
390 Ford making 500hp spinning 6500rpm 11.50"x15 2 blade and 18 gears. what should the top speed be?
also, adding 125shot of NOS how many more mph should I see?
Thanks...I dont know how to do this math.

[Sangster]

It may not run Faster, but it will be Quicker..... :2purples:

[V-DRIVE VIDEO]

1964 LaveyCraft "true" Flatbottom.
390 Ford making 500hp spinning 6500rpm 11.50"x15 2 blade and 18 gears. what should the top speed be?
also, adding 125shot of NOS how many more mph should I see?
Thanks...I dont know how to do this math.
Donald, did you dyno that motor? It takes some doin to get five hunged horsies out of an old 390.
Jerry :confused: :idea: :D

[dmontzsta]

Donald, did you dyno that motor? It takes some doin to get five hunged horsies out of an old 390.
Jerry :confused: :idea: :D
NO, I know it does 500hp and dont try and tell me any different, I know engine very well and have been raised around buckets of parts, I know it lays a solid 500hp maybe more!
haha j/p Thought I would mess with you since you messed with me yesterday.
500 ponies will be with my blueprints I am laying out right now with my FE builder :D 500 + 125 of NOS.

[v-drive]

Damn! you had me goin.......vdrive

[dmontzsta]

Damn! you had me goin.......vdrive
sweet, it worked. :D

[ACCEPTENCE]

I was thinkin 390 and 500hp didn't matter in the speed calculation.
But I was wondering about the 500hp figure.
...and I was ready to flip out a crispy C-note to see the dyno sheet.
ya had me goin :D

[dmontzsta]

I was thinkin 390 and 500hp didn't matter in the speed calculation.
But I was wondering about the 500hp figure.
...and I was ready to flip out a crispy C-note to see the dyno sheet.
ya had me goin :D
damn that worked nice. I will take your c-note when I am done...if its still flipped out there for me? :D

[DUNDUN]

NO, I know it does 500hp and dont try and tell me any different, I know engine very well and have been raised around buckets of parts, I know it lays a solid 500hp maybe more!
Jeez!!! You had me going too. I read it more than once. You are good! :2purples: :D :D :D

[Kindsvater Flat]

108.9488985 with 0 prop slip.

[GofastRacer]

1964 LaveyCraft "true" Flatbottom.
390 Ford making 500hp spinning 6500rpm 11.50"x15 2 blade and 18 gears. what should the top speed be?
also, adding 125shot of NOS how many more mph should I see?
Thanks...I dont know how to do this math.
According to the formula, with 20% slippage that would be 87mph!..

[burtandnancy]

dmonstzsta, I'm sure Kinsvater used a formula like this:
rpm x pitch x ratio x .00094696 or
6500 x 15 x 1.18 x .000946697 = 108.94084 (or so)
with conservative slip for a GOOD flatbottom, you're just under a 100 mph
If you hold the button down long enough you may see upwards of 7000. If the motor lives, plug in the numbers...

[dmontzsta]

Thanks for sharing the formula, is that a safe formula to use from now on?
Also, thanks K Flat and GoFast. HalletFlatBottom, you have to watch out for me, I am in sales! :D

[burtandnancy]

Yes, its a safe formula, its pure math. Now slip factor, thats another matter. The best way is to find your exact slip is by time clock, GPS or radar. From that you then calculate the slip (but only for that speed). If your slip is 10% at 100 mph it may be 20% at 80 mph. A modern GPS speedo is inexpensive, accurate and causes no drag like a pitot tube. It may be a little slow during accelleration (just a few seconds) but from then on its dead nuts...

[V-DRIVE VIDEO]

According to the formula, with 20% slippage that would be 87mph!..
As heavy as that old true flat must be, I'm going to have to agree with Tow fast racer. :cool:

[dmontzsta]

As heavy as that old true flat must be, I'm going to have to agree with Tow fast racer. :cool:
What do you mean? I bet it does 100mph right now! wait...it is not a jet boat, or on ebay...nevermind. :D

[V-DRIVE VIDEO]

What do you mean? I bet it does 100mph right now! wait...it is not a jet boat, or on ebay...nevermind. :D
I know... they all go a hundred. :messedup: :D :D

[Morg]

Yes, its a safe formula, its pure math. Now slip factor, thats another matter. The best way is to find your exact slip is by time clock, GPS or radar. From that you then calculate the slip (but only for that speed). If your slip is 10% at 100 mph it may be 20% at 80 mph. A modern GPS speedo is inexpensive, accurate and causes no drag like a pitot tube. It may be a little slow during accelleration (just a few seconds) but from then on its dead nuts...
Word Up.
I found this method to be verry acurate on my old flat. Unfortunatly my slip factor was 27%.
I highly recomend a GPS. Between the GPS & the formula, you can track the efficiancy of your set up & how changes impact.
Morg.

[dmontzsta]

How do you find out slip?

[DetroitJim]

25% or more slip is realistic, I measured 28% slip with a Sanger true flat 4 seater running 80-85 mph.
DJ