Hal's Great Stroker's Dyno Sheet

[Hal Copple]

i have had my stroked 396 CI Windsor on two different chassis dyno's, with ambiant temps about the same, ie, about 60 degrees. Both curves were very similar, varying only a few hp or # torque. I have Trick Flow/TW heads, a holley 750 HP Pro, sitting on an Edlebrock RPM intake. 32 degrees advance. The runs were with the aircleaner on, as the motor sits in the car.

So, here is my curve. Peak RWHP is about 360, peak RWTorque about 400#. What i learned from all this is that my motor falls off the power curve at about 5600-5800 rpm, so i don't need to shift over 6K rpm. I have my motor chipped at 6K, and try to shift just below that. Motorsports flat tappet/roller rocker cam.

Using say 20% drivetrain loss, i have about 430-450 hp at the flywheel, running with the alternator, water pump, etc.

Just thought i would toss out a probably representative moderatly stroked Windsor. By the way, the two times that were so identical, had about 50K miles between them!!

Ok, i'll post the dyno in the next post down below.

[Hal Copple]

here is a try:

[Hal Copple]

by the way, the lower curve was the first, baseline run, the later curve was when the operator noted the "jig" in the power curve, and put in the lightest "white" secondary vacuum spring, note that this 5 buck modification gave about 40+ hp increase in the mid range!!

All for about 5 minutes and five bucks. What Rice car driver would not just croak to get this much hp increase for so little cost and effort.

[BlueRooster]

Not too shabby Hal! I cant believe you are able to dyno your car. I am only 4 states north and my engine is frozen solid. There will be no dynoing going on for at least 2 months. When I chassis dyno'ed mine last year I hit 450 hp, 500 lbs of tq at 4500rpm. Just OK for a 520 though.

[gsharapa]

Hal,

Not too bad my friend!

[excelguru]

Hal,

ATS Performance on Two Notch road in Columbia hosts club dyno gatherings from time to time. I've long since forgoten the prices, but they seemed reasonable when I checked. We should look at getting the SC group together again for a day of dyno runs (and some good food of course!).

Those are great looking runs. I have my dyno sheet hidden around here someplace... unless my son chewed on it when he was teething...

[Turk]

I understood you loose aproximately 18% and 30% respectively on the chassis dyno with a manual transmission and an auto transmisson.

So, if you pull 400HP on the chassis dyno with a top loader, you must have an engine developing aproximately 472 HP at the flywheel.

Is this an accurate approximation for those of us who forgot to put our engines on a dyno before we piut them in our cars?

[svobud]

Originally posted by Turk


I undesrtood you loose aproximately 18% and 30% respectively on the chassis dyno with a manual transmission and an auto transmisson.

So, if you pull 400HP on the chassis dyno with a top loader, you must have an engine developing aproximately 472 HP at the flywheel.

Is this an accurate approximation for those of us who forgot to put our engines on a dyno before we piut them in our cars?

Depends on the Dyno brand .. and if you're using corrected or uncorrected numbers. But your % lose factors still look kinda high (IMO).

[jmkkingpin]

Those are nice results Hal ! Ilove the way you other guys Respond to Hals Numbers , my 520 did this and my 460 did that,who cares why cant you just be happy for Hal? It's not the size it's how you use it!!!

[Wayne Maybury]

Turk

I seem to remember that the average HP loss between the flywheel and the rear tires is supposed to be about 15 to 20% with a manual transmission, so 18% sounds about right.

Wayne

[BlueRooster]

I am very happy for Hal. It was just a response. If you read it again, I was actually giving him an offhand compliment. My 460 only pulled 450 at the rear wheel, his well used 396 did about as well.

Not that Hal needs anyone being happy for him, he's living the life of Riley down there!

[bmalone]

18% is the figure commonly used to account for loss--all else being equal.

Turk, I seem to remember people having a cow because you wondered whether 20% or more might not be the figure to use--this back some time ago when you had the ERA and engine for sale.

Hal, nice results--sounds great

[Bill Wells]

i have been to 3 chassis dyno shops. two of em said they typically use a percent loss figure of 17-21% for sticks when doing pulls in the 1:1 ratio ( 4th in a 4spd and 4th in a 5 spd) . the 3rd says he subscribes to a total hp loss, figuring 75-100 hp for side pipes etc regardless of the engine size or crank hp ratings . all admitted that most of their customers who have had engine dyno tests done are disappointed at a lower rwhp figure than they anticipated, and also said that most overstate their engine hp whether with fact or without. naw, who would do that ? hey, did i ever tell you about my 9 cubic inch 200 hp briggs and stratton ? LOL. B

[jdean]

I wonder if anyone has real "before" and "after" numbers they could share on dyno at the crank vs. chassis dyno numbers.

That way we could see if the 15-20% pans out, esp. with "Cobra" specifics like headers/sidepipes.

If you have them, let us know.

[wilf leek]

Hal - great to hear that the Great Stroker is still in fine fettle. Very interesting how it has not lost anything over all those miles, gives me renewed hope that mine might actually outlast me!

[kountzecobra]

Wilf, alot of things will outlast you according to your bride!

[Hal Copple]

hal here. goodness knows, i never interpreted any posts about more powerful motors as any kind of "one up's manship", but just good information. I thought i would put my sheet up so folks can see what useful information you can get from a little time on a dyno. Look what got me 40+ cheap HP!!

I have more rear wheel hp than a C5 has at the engine, and more at the motor than a Z-06 at the motor. Plus, i weigh about 700 pounds less than they do.

I personally think i am approaching the limit for a feasable, fully streetable, affordable, safe motor.

So please others post your own experiences. By the way, i have known several people who have had their motors on both engine, and chassis dynos, and they have gotten very varied results, very unpredictable. I honestly have a hunch that the more power your motor has at the crank, the greater percentage of "lost" or misplaced HP at the wheels. My friends' experiences seem to me to show that.

[Ant]

Hal,

I find your posts interesting, and as I have just got through the massive saga of deciding on which wheels, now have two sets of Trigos etc on the water, so I can now concentrate on the stroker engine decision.
I am not convinced that a 347 is the way to go for road and track due to the need to rev it around 7000+rpms and have potential valve train problems, so am thinking now more on 393 with an alloy Dart block so I can keep the weight similar to a light small block and get an easy 500+bhp, I read that 393 strokers can have big end bolt issues with high revs.

I am interested to know what revs you have been using with your stroker?

It would be a shame to think hey I need more grunt, a 347 may be nicer on the track for a better balanced car, but its going to be hard to get 500hp on pumpgas out of one! I am used to cars with well in excess of 500bhp but more BB stuff, some years ago I ran a circuit car with a F5000 302 Chev it had all the gear 6" Carillos etc but the valve train was the weak point, spinning around 8000rpm back then the valve gear did the let go, I have been told the quality of these components has improved a lot!

[clb]

Hi Hal,

nice results. amazing the difference made by such a minor and cheap change. just shows the value of knowledge gained by experience. you buy that man a beer?

and by the way - thanks for taking the time to load it up on the forum. does she drive nicely?

Hey Bill (Wells) - that Briggs & Stratton - does it have a mulcher too? ah man, one day I'm gonna build my own...

[DAVID GAGNARD]

Hal;

Glad you made this post,I have often wondered how much if any hp engines would drop by with mileage.... Yours is a well built engine with top shelf parts and I suspect that has a lot to do with your engine lasting the way it has with the use and mileage you put on it,congrats to you................

Wish I had dynoe'd my enigne when I built it..... Since then,there is a dyno within one mile of my house and I occasionally swing by there on saturdays and check out what's bolted on,mostly dirt late model chebby engines from 350 to 425 cu in....Have seen one "gain" 70 hp on the dyno with changes to the carb-timing-plugs,just little changes that were very inexpensive,but added hp that the owner would have never found,just like in Hal's case....

Next engine will be a race engine and will see the dyno for sure.........

David