First Pull on a Dyno

A local speed shop recently installed a dyno and I decided to go in and have a baseline pull. My first challenge was to get the car started at the shop; the weather in the Pacific Northwest is warming up and my lack of a high torque starter almost bit me today. The technician was ready to throw in the towel, but gave me a chance to work some magic. After several grunts from the starter, I got lucky and the car fired up.

I decided that for this effort, we would run it as is with no adjustments. The first pull was a little ugly; some black smoke but no apparent misses. The end result was 249.33 Horsepower and 285.53 Torque. I winced a little at the results, but the technician assurred me that the second pull would be better ("needed to blow out some carbon"). They fired her up and put the petal to the metal and cranked it up to 6200 RPMs. When the technician took his foot off the accelerator, the fan belt shot off the car! This time the results were better; 268.74 Horsepower and 291.22 Torque. Better but ..... Mike, one of technicians, suggested I bring it back on Monday for some carb and distributor tweaking. He thinks there's another 30 to 40 Horsepower waiting to be discovered ... will see!

A couple of observations: the Stewart Warner tach was reading 500 RPMs fast during the pulls so I guess I"ll have to explore alternatives, my alternator bracket needs to be replaced to allow sufficient range to properly tighten the belt and there is a high torque starter in my immediate future. More to follow ...

Bob

Bob,

Refresh us as to what engine combo you are running?

Kelly

Kelly,

It's a 351W (357) from Southern Automotive built in 1998 with Aluminum heads (Trickflow?), Edlebrock Performer Intake and a 1850 series 600CFM Holley with vacuum secondaries. It's got a pretty mild cam (stopped making power at 5500 RPMs). According to Bill Parham, compression ratio is 9.9 to 1.

Bob

i thought i needed a high torque starter too, until one of our members suggested trying a better ground, i used the cable supplied with the kit as a second ground straight from the battery to the starter along with the short ground from battery to frame and installed a heavy gauge cable for positive. no more starting problems!

Thanks Scott,

I'll check it out.
Bob

Bob:
Those numbers sound a bit low for your combo, although the age of the engine may have something to do with it. I have a nearly stock 351W, Performer RPM intake, iron Ford GT-40 heads, 750 Holley, very mild cam, 9.5:1 compression, and I put down 290 rwhp and 340 rwtq. This was after several timing and jet changes (it started out around where yours was). My car is way over-carb'd, and I think the numbers may even get slightly better when I step down to a 650.

I would think with the aluminum heads, you'd for sure be over the 315 rwhp mark.

What brand of dyno was it on? Dynojet? Mustang? Other?

Russ,

Dynojet was the brand of dyno ... Couple of updates; Mike the mechanic rejetted the carb and was preparing to check out the advance curve. As he checked the timing, he noticed a wobble in crank pulley. Assuming that the pulley was loose, he investigated ... and the pulley was tight. Seems as if the end of the crankshaft has broken (ouch!!!). Looks like the stroker kit I've wanted will come sooner rather than later.

I'm guessing that when the belt shot off during the last dyno pull may have been the moment of destruction. What I don't understand is how the motor can still run in it's current state. Oh well .... The shop told me that they can turn the motor around in about two weeks. More to follow ...

Bob (dazed and confused!)

(dazed and confused!) Ouch is right - That's the way I would feel! I don't know if it's worth a second opinion or not. If you were planning a replacement/rebuild in the very new future, maybe not.

Good luck.

I had a mustang with a procharger, and after 15k miles with the blower the harmonic balancer came apart from the belt tension. Two thousand miles later the front of the crank fell off in my driveway, the only thing holding the pulley in place was the blower belt.
From what we were able to determine the sudden vibration from the balancer coming apart cracked the crank and it just weakened over time. We put a stock crank back in the car and an ATI balancer and never had a problem again. In short make sure you use a quality balancer because the current one could be the source of your problem.

Justin

Justin,

Thanks for the tip; no more broken cranks for me! Now that the initial shock of the broken crank has worn off, I've been wondering why the shop chose to spin the motor up to 6200 RPM. As I look at the Dyno sheet, the motor stopped making any additional power at around 5500 RPMs but they continued to push it. With 20/20 hindsight, I wonder if my crankshaft would still be intact if the motor had been limited to 5800 RPMs? Do you folks think that's a reasonable question to ask the shop ... or am I guilty of whining ... inquiring minds want to know!

Bob

Bob,

The purpose of the dyno is to find out where the engine quits making its power and then set your shift points accordinly (sp). Any well built engine should be able to spin 6200 with no problems unless it has an inherit fault just waiting to happen.

Kelly

I agree with Kelly, turning a small block 6200rpm even with a stock crank is nothing. If it happened at 6K it was going to happen anyway.
I would not burn a bridge by pointing a finger at them.

Thanks Guys,

I needed a sanity check!

Bob

After a number of frustrating delays, I got my car back with it's newly installed 392 stroker. I took it out for a test ride and it sure goes!!!. Next week, Mike the mechanic is going to tune it on the dyno. I did get to see the old crankshaft and it was a mess. As it turned out, the crank wasn't broken .... just destroyed. The crankshaft dampener tore up the end of the crankshaft. According to Mike, the bolts affixing the dampener to the snout of the crank were too long and allowed the loosened dampener to chew it up. Oh well ...

My initial driving impression is that this motor has gobs of torque and once the carb is set up properly (too rich) and the motor loosens up a bit, it will be scary fast. I am concerned about the adequacy of the cooling system; the temperature climbed to 210 in traffic after just a few minutes. I have the skinny SPAL fan in addition to the standard pusher fans and I'm wondering if it will keep the temperatures down ... I see an impending winter project ...

I'll have all the engine specs next week and will post them for anyone interested in them.

Bob

Bob,
Sounds great. Those Winsors are some good engines. They can make a lot of horsepower. Good Luck

What temp thermostat is in your car? Also, you may want to try 25% coolant and 75% water along with some Redline "water wetter" or Royal Purple "ICE".

I have a 425in Windsor with 11.25:1 comp and no coolong problems at all, with the Spal fan.

Tell us a little more about the motor; heads, cam, intake, carb etc.