Hal's Great Stroker's Dyno Sheet

[Hal Copple]

AJ, the magazine Muscle Mustang and Fast Fords has done lots of stroker motor articles, and in one issue a year ago, had a lot of pro motor builders comment on small block stroker issues, and virtually all of them commented that the 347 was just too much for reliabiltiy and durabiltity.

I think if one has the abiltity, an aluminum Windsor is the way to go, but i have heard that there are several different aluminum blocks out there, and some are supposedly better than others.

If one builds it so, a motor makes more power the higher it can rev, to the point that the RPM is just not very feasable, or very expensive, the extreme of that being the F1 18,000 motors.

It takes a lot of money to build a high rev motor, you can put in shaft rockers, all expensive internal parts, but sometimes just a small bump in displacement can get you that power cheaper and at a more useable, lower RPM.

All motors are some sort of compromise, and at some point, it gets hard to use a really high horsepower motor in a light unsophisticated car like a Cobra Replica. I guess one needs to closely examine what your desired parameters and finances are, and then put it in the car.

Mike Stenhouse, and SPF owner, has an RDI aluminum stroked Windsor, that makes about 540 hp or so, is pretty drivable, very reliable, but a large part of that is his gearing, very long-legged, to let his car use his power without wasted "thrust".

I think he can pull something like 90 mph out of second gear!

If you want to talk aluminum motors, i can put you in touch with him. He has had various internals (cams and such) in his motor, with lots of different dyno runs, and finally settled on a very streetable and very potent motor. He also has some pretty clear opinions on aluminum block differences, and worked with a NASCAR motor builder to arrive at his final build.

[scr11]

As for chassis dyno numbers vs engine dyno numbers, Mike Stenhouse did both. He lost exactly 21% on the Dynojet chassis dyno. And this was with stock SPF pipes.
(Mike - correct me if I'm wrong!)

Scott, SPF#1230

[Ant]

Hal,

Re: alloy block strokers
Due to a low budget, but patience to get the desired parts it all happens over time, I dont know whether alloy is a big advantage, but should make a noticeable difference on the circuit, as my local two circuits are quite big but have a few lower speed turns.
I would like to be able to contact Mike Stenhouse with the alloy engine and welcome any advice he may give!!!

I think 393 is the way to go for me, as I am not keen on big strokers, as it would probably go quite well designed for 6500max or less on a 3.27, 3.08 ratio.

[DaveSemko]

Enjoy Hal :-)

I guess I have a simple mind. My car starts when I need it to, stops when I need it too - gives me a thrill in between those two events. Oh yeah it looks OK too. What else do ya need?

[Mike Stenhouse]

Mike Stenhouse here. Answers to questions about aluminum engines and horsepower ratings. A bit long, but good questions deserve good answers.

I have an all-aluminum 351 Windsor with 4.125 bore by 4.000 stroke for 427 cubic inches. It was built by RDI, the FRPP distributor in Cornelius, NC, here in the heart of NASCAR country. Four bolt mains. Forged crank, rods, and pistons. Ported Victor Jr. heads. Hydraulic roller cam. Performer RPM manifold. Holley 750 carb. It was built as a dual purpose engine - equally at home on the track and the street. I drive it on both a lot. It is a gem.

I am running a Tremec TKO II transmission (0.82 fifth gear) and a 3.08 rear end with 275/60-15 Goodyears on the rear. This tall gearing gives me 52 mph in first, 85 in second, and 126 in third at the 6500 rpm redline. It will go 169 in fourth, but I won’t. I like to breath. Fifth is totally out of the question.

The advantages of aluminum are lighter weight and a resulting better weight distribution.
With the all-aluminum Windsor, my car weighs 2400 pounds ready to rock and roll. This is lighter than the new Mazda Miata, for goodness sake. And 55% of the weight is on the rear wheels. This thing hooks and goes like a rocket ship. Great fun. I have started giving out diapers to passengers on demo rides. It is also reasonably happy in traffic (when it cannot be avoided) and really loves back road blasting in fourth.

We ran my current engine on the engine dyno in an installed configuration (see below) - full side pipes and accessories. It made 480 net horsepower. Given the installation losses, this should be around 550 gross horsepower – adequate (as they say) for a 2400 pound car.

Aluminum has a number of other advantages. It be repaired easier than cast iron in case of (gasp) failure. The block can be welded. The cylinders use sleeves which can be removed and replaced, so it can be rebuilt forever without running out of bore. Bore damage can also be easily repaired. The RDI block is Siamesed, which allows a bore up to 4.185 inches. A 4.125 inch bore gives 427 cubic inches with a 4.000 inch stroke. The longer 4.100 and 4.200 strokes used with the 4.030 inch bore push the rings up on the piston and require a shorter piston to clear the crank. Both of these are reliability issues.

Aluminum is not a strong or as rigid as cast iron. An aluminum block must be designed from scratch as an aluminum block to compensate. Aluminum is 1/3 the weight of cast iron, but a good aluminum block is around 1/2 the weight of a cast iron block, so clearly it has more metal in it. The RDI block is designed from scratch as an aluminum block, which is why I used it. I have heard from engine builders that the Dart aluminum block is a derivative of their cast iron block. Whether this is still true or not, I don’t know. If anybody does, chime in. If it is, it would give me pause.

As to horsepower, there are three ratings that are commonly used.

Gross horsepower is engine dyno horsepower without accessories, with a bell mouth on the carb (no air cleaner), and with open headers. Gross horsepower was used by auto manufacturers up until about 1972.

Net horsepower is installed horsepower with accessories hooked up and functional, full air intake system in place, and full exhaust system in place. It is the standard used by the auto industry since about 1973. Typical installation losses for a clean installation run 15% to 18%. Cobra installations with headers, free flow side pipes, non-restrictive air cleaners, and minimal accessories can be as low as 12%. The 427 Cobras of the 1960's had the highly restrictive Snelling & Helling air cleaners and cast iron log exhaust manifolds with tiny mufflers. Installation losses were a staggering 40% or so.

Rear wheel horsepower is measured on a chassis dyno and takes into account drivetrain losses. The NASCAR guys who dyno the exact same setup on the engine dyno and chassis dyno tell me that the drivetrain loss (net horsepower to rear wheel horsepower) is about 10% to 11%.

Most crate engines and custom built engines are rated in gross horsepower since the engine builder has no control over installation losses and because their test facilities use bell mouths, no accessories, and open exhaust.

The loss from gross horsepower to rear whell horsepower can vary from 22% for a very clean installation to 50% for a very bad one.

Hope all this is helpful. If you got this far congratulations.

[ToyCollector]

Very well written Mike. Hey, with that talent, you should write for and publish a newsletter as a hobby.

As a former Second Strike recepient, I enjoyed your writings in the past.

[Cracker]

I second TC.

Having dynoed my 427 with accessories but with three different induction units I can shed some light on air cleaner’s effect on 427 ci motors using one carb. The results:

1) No air cleaner = 543 hp
2) Dual quad style w/ K&N filter = 532 hp 2% loss
3) Single Helling & Stellings = 521 hp 4% loss

So in my case, to my surprise the use of that little tiny air cleaner was not nearly what I thought it would be - so I use it.

Thanks again for your detailed info!

[Mike Stenhouse]

Tony,

I assume your Stelling & Helling had a K & N filter.

The standard foam units are really restrictive. We had an owner with a 427 FE report a 100 hp loss with the S&H foam on back to back dyno runs. He sent me the dyno runs, so I know it is true.

The old 427's with dual quads picked up a lot more horsepower from the second air cleaner than they did from the second carburetor.

Mike Stenhouse

[Cracker]

Michael,

I did not use the K&N or foam unit (it's still in the box) but another mesh type material. This may be why I didn't lose so much power but I'm still amazed at how little was lost either way with such a small and short assembly! I have plans for bigger and better induction systems!!! I'll convert the H&S thingie into a dog bowl - a small one.

[Ant]

Mike, Hal,

Thanks for the posts, and the information on the RDI alloy block, and your engine details!
I had a look on the RDI website and they claim a weight saving of 60Ib compared to a cast iron windsor block, which all helps, pending my budget!

With the 427 stroker you have certainly got a good cruising top gear with the TKO at 0.82, but I guess if you reduce the final drive ratio say to a 3.55 or 3.70 you will make the lower gear ratios closer together, and maybe not gain much more acceleration.