Lackluster Chassis Dyno Results
 

Prior to the last go round I had with the rear main on my car, I had taken it to get a baseline pull on a local chassis dyno. The results were a little milquetoast, but I kind of expected as such.

This pull was done with about 32 degrees total timing and all accessory belts in place and 91 octane. Basically driven off the street onto the dyno. The operator said to add about 18-20% to estimate crank output which would put it around 420hp and 510 ft/lbs torque. Decent torque, not so great HP. When I tore down the engine to replace the rear main I discovered a fairly substantial mismatch in intake ports so I'm sure that contributed to the results.

That said, I'm less worried about the actual numbers because I know they don't mean a lot with an automatic, but I am more surprised about how it peaked around 5k. I expected it to peak higher.

Unfortunately we didn't get a chance to play with the timing and do any more pulls because the Taylor wires and Pertronix weren't playing nice with their timing equipment. They did say they the A/F ratio was the best they'd ever seen on a Q-Jet so kudos to Ray Klemm. When I get some time I'll bring it back and do some more pulls now I've got the intake and ignition upgraded.

Mustang MD-750 dyno
4.25 Butler stroker kit
9.5:1 compression
236/242 114 roller
Port matched R69A heads
1.5 HS rockers
Ram Air Manifolds
2.5" exhaust
TSP 9.5" converter

https://forums.maxperformanceinc.com...1&d=1695837323

When you’re restricting the exhaust on a big engine like that expect to be down by about 30 horsepower. Your heads are stock and even though they’re a nice factory head they have their limits, cam is on the milder side for a 464 cube engine as well. I wouldn’t expect that it would be making power past 5k, looks right to me.

Some headers and a 3” exhaust would make it shine, but there’s nothing wrong with your setup as is.

So it made 480 hp at the crank. Sounds about right. Comparing it to a chassis Dyno which is about 20-25% off from measuring on a regular engine dyno.

What heads are these , D port or round port factory heads?

Also what stall speed is that converter set up to give you?

If that converter stalls at 3K and with the motors peak torque coming in at 3750 your going to have the worlds smallest power band!

Tell us a little more about the heads, especially if modified. Those numbers look pretty good to me overall. We have a Mustang Dyno at school and a Superflow engine dyno. 15%-18% drop from engine is typical with some automatic trans cars losing just over 20% with a lousy convertor. Pretty stout engine, really with low compression and pump gas.

I had the same thought about the exhaust. I like my RA manifolds, but it's tempting to see what a good set of headers would do.

It made 355 to the wheels so wouldn't that be about 425-ish to the crank?

Factory round port R96A. Port matched and bowl blended, but not ported. The converter flashes to 3k when you stomp on it, but stalls much lower (2k-ish?) in regular driving. Good point about the power band.

At the crank, I was 429hp/522 tq with RA manifolds, 439hp/518tq with headers, (which I still have a hard time believing, maybe I'm just in denial...). But really not too much different between RA manifolds and headers back-to-back on the dyno.. How does it feel when you drive it?

Oh, and I also have a Ray Klemm Qjet. Unbelievably great driveability. Great starts and so smooth. I haven't even done any tuning on it yet, mostly because I haven't felt he need to.

So even though you have 68 round ports with the RA chamber you still have what amounts to just bowl blended D port intakes in the heads.

In that case like the others have posted your Power numbers look like I would expect.

If you get a chance to get it on the dyno again I would try pulls with the timing at 34 and 36 just too see what’ that might get you.

When it comes to gasket matching the intake you want there to be a slight mismatch only on the push rod side of the intake runner .
This creates the needed pressure drop to allow the
Air to get around that bulge without as much of a change in air speed.

Jhein, that drop in torque is telling you that with headers you exh to intake ratio is too high.

If you valve springs can safely handle another .040” in lift( .570” ) I would add a set of 1.65 rockers on the intakes only.

Also if those springs your running on those E heads are the ones they ship with they have been known to have surge conditions at one or two points in rpm well below the peak rpm they can go to.
Remember if they are as shipped you have springs chosen and supplied to have the heads sell at a certain price point, not necessarily the best .

If nothing else our big 2.11”
Intake valves need a good spring, a good duel coil spring, not a outer coil spring and a crappy inner flat wire damper.

Plus full exaust?

GT

Must be, he said he drove it off the street and onto the dyno.

Sorry misunderstood thought it said you made 400 hp to wheels. So you’re correct around 425.

Yes - full 2.5" Pypes exhaust w/ Street pro mufflers.

Numbers are fine for that kinda smallish cam, through manifolds with 2.5 exhaust.
Little bigger cam and 2" headers and you have a 500HP+ engine at the crank. What is wrong with that ?
Sweet engine...........................and no leaks !

Sounds like a lot of fun to drive just like it is! I’m sure you catch the Mopar and Ford guys by surprise when they see a Qjet and cast iron manifolds under the hood. Love it.


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If I’m reading this correctly and If that’s the case and those are the heads that are on there now. Thats the power killer. Those heads maybe flow 190-210 cfm.
Rich’s 461 with out box Round port E-heads made 500 hp and numbers was back up at Norwalk. With the Crower 60919 cam hyd cam. They flow 270-280 cfm. But of course the manifold vs headers is a loss to. But hey as long as you’re happy with the performance and the way things turned out that’s all that counts. But down the road you can always go with set of E-heads.

PS: thats with Q’jet and RPM intake 1-7/8 headers.

It was very intentional to have a factory-looking setup and I knew that using those parts was going to create some limitations. I was honestly expecting anywhere from to 425-450hp with 500tq at the crank and I got that. You all know how it goes though, you get a taste and want a little more. I'd love 500hp, but that breaks the spirit of the build. Maybe I'll drop a set of aluminum heads or headers on it one day when I get bored with it as is.

Funny that cam is considered smallish - I was originally going to put a 232/236 in it.

Going to back to the point about the power band and converter, how can I tell if I should have the converter restalled to better fit the curve?

If the engine runs good and does what you want I would call it a success.... The dyno provides a number. I've seen numbers all over the place that relate to nothing on a chassis dyno. My brother's stock 2000 LS Firebird made 331 to the rear and went 12.9. It made 349 with headers and ran 12.7. That car felt fast!

Good perspective.

My '04 GTO automatic put down 375 to the rear wheels on a Mustang dyno and ran low 12s.

How do they seem to compare?