FE Torque Curve

[DanEC]

I had Keith Craft build my 428 stroker more for torque than raw horsepower. I witnessed the dyno pulls but didn't really sit down and closely study the dyno data until later. The recorder didn't start recording until 4200 rpm and based on everything, I always assumed that was well above the torque peak - which I figured was down somewhere in the 3600 rpm area.

I finally got curious enough to email Tony at Keith Craft and ask if they had any additional data in their file that recorded the max torque and peak rpm. He advised that the recorder starts recording when the motor hits the torque peak - indicating peak torque was at the 4100/4200 area.

I'm having a problem believing this motor's torque peak is at 4200 rpm especially with max power at 5300 rpm. What would you think?

[vector1]

1100 rpm split between horsepower and torque would seem reasonable.

[Dwight]

I have a stroked small block with about the same curve. Tons of low end tq.

I had mine on a chassic dyno and had the operator to start at 2000 rpms. I have about 300 at 2200 and top out at 422 at 4250.

Pulls like a rocket! But will spin to 7000 like a chainsaw.

Dwight

[AL427SBF]

The recorder didn't start recording until 4200 rpm ...
He advised that the recorder starts recording when the motor hits the torque peak ...

That kind of sux, build for torque sure - but at least measure performance from 2500 up, surprised KC thinks such a limited dyno band can be considered acceptable.

[Dwight]

I've been to Keith's shop several times and the last time we watched a 363 sb being dyno'ed. I ask the operator to make one pull at 2000 and he did. I have pics of the sheet but don't remember what it was. I do remember the last pull was 499.5 hp and I asked if he was going for 500. He said no! That's good enough.

Of course when the customer installs his own air filter, headers, side pipes, etc the numbers will change.

I think they prove the motor runs and it's close to the numbers they want and that's good enough.

Dwight

[DanEC]

Yeah - I'm sure if I had been paying a little more attention to the torque figures and asked the dyno guy to start the recorder earlier, he would have done anything to satisfy me. It wasn't until later that it really sunk in that for a fairly mild motor this thing was putting out a strong torque figure and I of course wondered what that peak just might be. I was guessing somewhere aroung 535 ft lbs or so until he told me the recorder starts as the torque peaked. So I guess 527 is it.

[AL427SBF]

I guess the way I look at it is - if you're going to have a dyno done, then get all the data from the pull. Who doesn't want to know how their motor performs throughout the RPM range. A dyno pull gives you that data, no reason not to record it - pretty lame on the operator's part imo - he should know better.

But, all of this a GOOD EDUCATION, you can bet I'll be telling my dyno guy exactly the RPM range I want recorded.

By the way, no question you have great torque there, KC gave you what you requested, on the next dyno run (whenever) something tells me you'll know exactly what the torque curve up to 4200 looks like

[ERA Chas]

Originally Posted by DanEC

I question several other things.
The heading 'A/F Ratio' is listing fuel pressure which is fine but the actual A/F Ratio would be valuable.
I think the BSFC is a bit high for these days but then I see the motor struggles to make more than 50% V/E.
Dan can you post some particulars in the motor's parts list? A 'torque' build should not have a lot of overlap or duration...

[WardL]

I'm looking at a dyno on my Roush. It starts recording at about 2,700 RPM where the torque curve is almost straight up to 440 ft-lbs at 3,000 RPM and slowly drifts up to 460 ft-lbs at 4,000 RPM. From there it slowly declines as the RPM goes up to 6,500 RPM. At 6,500 RPM the torque is down to 350 ft-lbs. The peak STD HP is 448 at 6,200 RPM. Based on my curve your torque may be very close to your 527 torque number around 3,000 RPM. I wasn't the owner when the dyno was run.

[blykins]

It's a reasonable set of numbers. Some dynos operate differently than others and a peak torque curve there is reasonable and realistic.

Keep in mind that you can't always pull an engine down that low, and most of the time it's not warranted, nor is it safe to do so. A wide open throttle pull at 2000-2500 can induce detonation and modern performance engines with larger heads and cams are not meant to have their guts pulled out at such a low rpm. You would see that kind of operation in a dump truck engine, which is meant to be fully loaded not too far off of idle....with compression ratios, dynamic compression ratios, piston design, ring gap, etc., to handle that kind of load and heat.

To make a long story short, I wouldn't advise asking a dyno operator to pull one down that far....

A reasonable starting point is 3500-4000. A dyno is more for determining issues with the engine, general A/F curves, and peak horsepower/torque numbers. You can't drive a dyno, and the poster that made the comment that everything changes once the engine is in the car, is correct. Different air cleaners, different headers, etc. make differences. While I'm ranting, I'll also point out that different ignition boxes (even of the same brand) will give different timing settings, so be sure and double check the timing once it's in the car and running.

[DanEC]

Thanks Brent. Yes, Keith's guys didn't much like my old school 427 dual point distributor and wouldn't run it on the dyno - using an MSD unit instead. So I had to re-time it in the car and check my total advance curve.

[DanEC]

Originally Posted by ERA Chas

I question several other things.
The heading 'A/F Ratio' is listing fuel pressure which is fine but the actual A/F Ratio would be valuable.
I think the BSFC is a bit high for these days but then I see the motor struggles to make more than 50% V/E.
Dan can you post some particulars in the motor's parts list? A 'torque' build should not have a lot of overlap or duration...

Chas - it's a 428 with 4.25 stroke crank. Has KC ported/polished/427 valve - 1961 390/401 HP heads, 63 low riser dual quad intake, 427 distributor, 600 Holleys. Compression is suppose to be 9.0. The cam is hydraulic 231/236 at .050 / .563/.575 lift / 112 deg lobe separation. I don't have the timing card handy to look up the overlap. I don't remember where I got this (maybe the dyno operator) but I understood that to actually be the A/F ratio but they were only metering air in one carb so it is half the effective A/F ratio is what I remember. At least that is what I understood (?). Here is the motor on the dyno.

[ERA Chas]

Originally Posted by blykins

A dyno is more for determining issues with the engine, general A/F curves, and peak horsepower/torque numbers.

Brent-what do you make of Dan's 50% VE?
Do you get numbers that low on your mild builds?
Thanks for posting the build Dan....

[patrickt]

What is the thing that is stuck in the front of the water pump? Or is that just an optical illusion of some sort....

[blykins]

Electric water pump drive...

Chas, some dynos don't record V/E, but I've seen 100%+ on some of my engines.

Could be something not hooked up on this particular engine....especially with A/F ratios reading low, etc.

[ERA Chas]

Originally Posted by blykins

Chas, some dynos don't record V/E, but I've seen 100%+ on some of my engines.

Could be something not hooked up on this particular engine....especially with A/F ratios reading low, etc.

I thought so-I've routinely seen +/-100%.
Would testing on only one carb cut A/F and V/E?

[blykins]

Not sure. You would think that the O2 sensors would be reading the results accurately, but I'm not sure.

I know that when we do dual carb engines, we lay the hood down on the distributor so that both carbs get a snoot full.

[vector1]

i would guess since they are only monitoring one carb, they half some of the data in the program, so double the a/f ratio, and v/e% and the air scfm.

[lovehamr]

Originally Posted by Dwight

Of course when the customer installs his own air filter, headers, side pipes, etc the numbers will change. Dwight

When I dyno'ed mine locally it made it's best runs with the air cleaner in place. The headers and intermediate pipes were from my car as well because the place where I got it done could hardly spell FE. I even had to make the mounts to hook my engine to the thing. Going to a place like KC would be "Candyland"!

[DanEC]

By the time I reached Keith's shop they had already run-in the engine and done a couple of test pulls. They may have stopped reading some data - I don't know. The runs I witnessed were primarily for my benefit.

I always did think the A/F mixture looked a little suspect even if it was supposed to be half the actual figure. It would be too lean. Never occurred to me that the figures were representative of fuel pressure - that actually does make sense. Chas may have that right.