What should I expect during dyno run?

[TKing]

What should I expect be adjusted/tuned on an engine dyno? A local speed shop rebuilt my FMS 392 motor (milled, new bearings, polished crank and so forth) and will dyno it next week. I never had an engine dynoed . Should I expect the engine to be run for some time period to wear in components before adjustments are made?

My purpose for the dyno is less about max performance and more about proper setting of jets, timing, valves and fixing problems before I reinstall the engine. I will be there when it’s done and don’t want to be a complete idiot when I asked questions. What should I expect from the engine man?

Thanks,
Tom

[blykins]

The engine should be started and if the cam isn't a roller cam, it should be broken in for the specified time period. The engine will then need to be ran with a small load on it for some time and then shut off. A couple of 30 minute runs then 30 minute rests to heat cycle the engine is ideal.

After some warmup runs, then they should make pulls on it with a full load. At that time, timing should be played with, jets, idle air bleeds, distributor stop bushings/springs, vacuum secondary springs, etc. should be tested and swapped if necessary.

I had my 428 dyno'd at Performance Engineering in Cinci, OH. They made around 12 pulls and kept pulling more horsepower out of the engine each time. We stayed until around 6:30 that evening and were tweaking the whole time.

I would take the air cleaner that you're going to use and the headers as well. That way when you get it in the car, you'll only have to make minor adjustments on the carb.

[DAVID GAGNARD]

I agree with all of the above...........My race motor is down now to be freshened up and when I dyno it, I still treat it like a new motor....I go thru the break-in process, even though I'm running a roller cam, after a 20 minute run, we shut it down for about 20 minutes or so and pull the plugs and check them, reset the idle and carb and basically check for anything loose (valve covers/water pump bolts,etc.)....

Then the fun starts, we start the pulls to max out at 5000 rpms and each pull there after increase it by 500 rpms till I hit the max (7000rpms for my motor).... Since it's not the first time, I do have a baseline for jetting and timing, afterwards we adjust the timing by 2 degrees each way to see how it acts.....

Nows the time to try anything you have in mind, I've tried different carbs and different carb spacers, found what works best with my combo........

I also agree, dyno the motor with the your headers and at the very end, I add my air filter for a pull or two.....

BTW: with my 14" diameter, 3" tall paper filter, I only lost 3 hp and the same in torque!!!!!!!!!!!

David

[xlr8or]

Anything but a loud bang would be good.

[TKing]

Thanks for the information. I'm looking for forward to the session and hopefully a much better running engine.

Tom

[hoppy]

You should expect to be pinching your cheeks really hard when the RPMs get past 5500.

[BlueRooster]

Expect less horsepower than what you bought, and you should be happy.

[DAVID GAGNARD]

Expect less horsepower than what you bought, and you should be happy

Ain't that the truth................last time on the dyno, the operater asked me what I hoped for, told him 500 hp would be nice, but, realistically I'd be happy with 450 hp......he asked about the internals of the motor, compression, cam,etc.... and then said I would leave a happy camper, and I did, the motor made 472hp.....

He's been in the engine building/dyno business for about 15 years now and said he can't count the number of 600hp "street" motors he has dynoed that barely made 400 hp......too many people reading too many magazine articles and throwing some parts together and expecting mega hp numbers........

Just for the fun of it, you MUST go stand next to your motor on the last pull.......it will get your attention real fast.........

David