Stroker Horsepower & Torque Numbers VS. Small Block V8's

[1bolt]

I agree with just plain cool to, I'd be the first to suggest a V8 crate motor swap for anyone looking for 300 or more HP. Still when we're comparing the stroker rebuild to a stock old pushrod V8 the V8 doesn't win in any catagory ease, power or cheapness and that's the thing people don't seem to realize and the reason for getting this thread going. Too many myths and outright BS out there.

[stroked'73]

Agreed wholeheartedly.

I come from the fullsize jeep angle, where we have the 360 to swap in quite easily. However, it's pretty shocking to compare a stock AMC 360 to a stroker in terms of numbers. And building an AMC 8 isn't as cheap as a SBC.
I guess the best way to convince the doubters is by politely and continually blowing the doors off their stock V8 rigs!!!!!!

[gradon]

I agree

[Jeep-Power]

Most guy's and gals don't consider the tire size when making their dyno runs. I may take some spare 30" rollers and see what kind of difference it makes. Gotta finish the rebuild first though.

My buddy with a 4 wheel dyno told me that the tire size won't matter on the dyno-- it is all figured in--

It would be real interesting to test at a dyno with some big(heavy) of road tires and some small (light) 26-27" tall tires.

to prove it true or not.

I thing the smaller tires would win out.
The dyno test rear wheel HP........bigger tires will have less HP at the wheel.
The reason i say this is that when i went for 27" stock tires to 33/11.50/15 not only did i noticed a big difference in lack of power but it took a lot more relastate to stop the jeep too!
They may be able to figure in for diameter.....but mass is a crap shoot...........Yeah I'm just talking out by butt here, as i have never done a dyno run in my jeep, diesel or my Cuda

Flash-

I was on a dyno today. I don't know if this helps-- but we made a few pulls in top gear (1:1) and then tried it in the next lowest gear to see if the HP numbers came up. They went down.

I posted this already in another section, here it is again:

on a Dynojet chassis dyno (readings were at the wheels):

117 HP at 3700 RPM

190 Ft Lbs of tourque from 1800RPM thru 2600 RPM


(Please remember that mine is NOT a stroker-- it's a 4.2 with a 4.0 head!)

[Flash]

Hmmm that is vary odd........not that i know a thing about a Dyno. But you would thing that the TQ and HP would have went up do to gear ratio creating more torque and HP...........Well it is basically the speed in which, or the time frame from start rpm too max rpm, that generates HP ### (Basically )

I would have thought that the ### would have go up.........Atleast a little????



Flash

[1bolt]

Here's what (little) I know on this subject. How quickly you rev is called "accelerated horse power" and is not tied in with wheel torque output (which HP is calculated from). Improved "accelerated hp" (from here on called AHP) will shorten your race times, but not show up on a typical total HP dyno plot.

Taller Gear ratio can shorten your 1/4 miles time via improved AHP but wont show up on a dyno... For the same exact reason. 33" drag slicks may shorten your 1/4 mile even with the same traction as a smaller tire (due to better "leverage" of the taller tire) but not show up on a dyno. Light weight forged alloy Weld drag racing wheels same thing. Less mass resisting the acceleration, or better mechanical advantage (leverage) will improve AHP and your ET. So a lighter weight crank, pistons, rods... Or ANYTHING that is lightened after the piston dish on back all the way to the contact patch. In addition anything that improves leverage from the same point...

Basically torque is a measument of how HARD you twist the rollers and AHP is a measure of how quickly you got to that twist.

[Flash]

Here's what (little) I know on this subject. How quickly you rev is called "accelerated horse power" and is not tied in with wheel torque output (which HP is calculated from). Improved "accelerated hp" (from here on called AHP) will shorten your race times, but not show up on a typical total HP dyno plot.

Taller Gear ratio can shorten your 1/4 miles time via improved AHP but wont show up on a dyno... For the same exact reason. 33" drag slicks may shorten your 1/4 mile even with the same traction as a smaller tire (due to better "leverage" of the taller tire) but not show up on a dyno. Light weight forged alloy Weld drag racing wheels same thing. Less mass resisting the acceleration, or better mechanical advantage (leverage) will improve AHP and your ET. So a lighter weight crank, pistons, rods... Or ANYTHING that is lightened after the piston dish on back all the way to the contact patch. In addition anything that improves leverage from the same point...

Basically torque is a measument of how HARD you twist the rollers and AHP is a measure of how quickly you got to that twist.

I agree with every thing but, the bigger tire giving you more leverage.....Taller tire would give you less leverage. now if you had a traction issue, the taller would be getter.

I have known for many a years, the light weight parts in a eng would NOT affect dyno ###......Eng or chassis Dynos.
Just hadn't added tire weight to the equation.
Do you have to input gear ratio into the Dyno???????? If not then i would still thing the dyno would.....should have a hight ### if the gears were lower ( example 4.10:1 to .4.88:1) or if you put the tranny in a lower gear then 1:1.............................................................
No?.....

Flash

[1bolt]

I think Dino had an experience with this, and someone questioned the accuracy of his Dyno numbers because he had to run in a gear other than 1:1 ratio. The long and short of it is, gearing is just torque multiplication, Its not creating free power, so if you're measuring the actual torque output of an engine, you must compensate for torque multiplication to arrive at a number thats meaningful. Fortunately its pretty simple to calculate what the 1:1 torque output is if the gear ratio is known.

I'm out of my element here and with new members like Alex who actually use and have access to engine and chassis Dyno's I'll let them correct me where I'm wrong.

The bigger tire has a larger contact area, and maybe leverage is the wrong choice of words... Or maybe I'm just wrong. If you put two different size wheels and tires on the same axle and spin that axle at the same speed: The one with a smaller outside diameter (say 13") will rotate a shorter distance at the contact patch, than a larger tire (say 33") the 33's tread will travel a longer distance at the same axle speed. If that's not exactly leverage, its certainly acceleration...

The older I get the less I know for certain, I'm getting to that point in life where even things I'm sure about I question <need an old Geezer smiley here>

[Cheromaniac]

I think Dino had an experience with this, and someone questioned the accuracy of his Dyno numbers because he had to run in a gear other than 1:1 ratio.

I simply ran my Jeep on the dyno in 3rd gear because that's the highest gear that I could use that would go all the way to the 5200rpm rev limiter. Fourth gear (1.00:1) would only have gone up to 4350rpm (116mph) where the top speed governor kicks in.

[ccpanel]

If anyone wants to contribute real stroker dyno numbers and has the sheet to back it please PM me and I will give you credit. (Wheel or Flywheel).

background;
http://www.jeepstrokers.com/forum/viewt ... f=8&t=1364

basics-
89 4.0 block
91 7120 head
various work done to both.
4.2 rods
hyper pistons
1981 crank
84 carb intake
91 HO OEM headers
2150 holly carb 1.13 version? forget. with 48? 51? jets
rebuilt OEM 1981 727 3spd auto trans-slipomatic
208 part time transfer case
3.31 gears
31-10.5-15 street tires
curb wieght at 4,000#

fully warmed up(75 minute drive @>60mph in the CA summer
3 runs within 15 minutes of each other
im just gonna average teh 3 stats till i scan the sheet
103' outside temp
29.84 baro
8% humid
6pm july 17 2014

first 2 runs at 153hp, 203 tq
third run 150hp 200tq

AF was averaging right around 12.hi(89-99) above 2400
wish i had numbers below 2400
fuel fattened up the higher RPM.
just looking at it now-I bet my idle circuit is a little too lean.

tq started dropping off after about 4200 but was above 190 from 2750-up


pretty nice..

what this tells me is i have a little timing/spark issue, probably a cam timing issue or not aggressive enough cam and teh trans is a real power robber.

im getting enough fuel(maybe not being burnt correctly) but i think EFI will help me too.