[chuckies76ta]

Hi Folks: What's the consensus. Vacuum pump use on dyno.
Do we use it right from the start, or do a couple of pulls without it, then connect it after rings are seated?

Ok, I see I posted this in June, Sorry for the duplicate. Could not delete.


Thanks

[steve25]

Unless you will be breaking in a flat tappet cam I would run it right from the start.

Get the motor confirmed to be sound and do 5 pulls with it running and average those out and then do 5 pulls without it , then average those out , and on all ten pulls try your best to keep the oil temp seen within 20 degrees .

[chuckies76ta]

Thanks Steve. It's a Solid Roller Cam,. 505 Cu In. IA2 block. It goes on the dyno tomorrow. Pretty excited.

Thanks

[slowbird]

Originally Posted by steve25

Unless you will be breaking in a flat tappet cam I would run it right from the start.

Get the motor confirmed to be sound and do 5 pulls with it running and average those out and then do 5 pulls without it , then average those out , and on all ten pulls try your best to keep the oil temp seen within 20 degrees .

Why would you do 5 pulls with and 5 pulls without?

[John Langer]

Rings usually seat within 5 pulls. We run the timing a little low and hot lap it till it stops increasing in power then tune from there. We can generally make around 20-25 pulls in a day.

[chuckies76ta]

Thanks John.

Charles

[chuckies76ta]

We won't do any pulls without the vacuum pump working as we don't have a PCV system installed. My main concern is during initial startup when it's a crucial time for the rings to seat.

Thanks
Charles

[steve25]

So your absolutely sure the numbers are not a fluke!

[ponjohn]

What are the engine specs?

[slowbird]

Originally Posted by steve25

So your absolutely sure the numbers are not a fluke!

At $500 to $1000 a day for dynoing, 10 pulls is a huge waste of time.

[Steve C.]

John finally dyno'd my 505 with the new cam two weeks ago at Westside Performance in Houston, cost was $650 for the day. He arrived at 9:00 AM and by 11:30 they had made 13 pulls. Went to lunch, came back and made three more. A total of 16 pulls. No equipment testing, like intake manifold changes, carbs or carb spacers. Engine break-in, lash changes and jet changes only. This was not John's first rodeo at set up, it didn't take him long to set up the engine on the dyno cart, plus he had a mechanic friend helping.... not me


.

[blueghoast]

Well what did it make? We want to know?

GT.

[Steve C.]

I don't want to muck up Charles thread too much, but I guess he got his answer regarding the vacuum pump. So in short....

Depending on the pull, it's now a 625-630 HP engine. The best number was 635 HP. Peak torque at 4400/4500 rpm and peak power at 5700/5800 rpm. Start of the recorded numbers at 4100 rpm the torque was 627/628 ft.lbs. It carried over 600 ft.lbs torque from 4100 rpm up thru 5400/5500 rpm. The new cam has the same .050" duration but less .200" duration and less lobe lift. The goal was to reduce the cam profile intensity in order to significantly reduce my valve spring pressure. Tim at Bullet Racing Cams was expecting about a 20-25 horsepower loss at peak power, it was a bit more. Other factors, but my lower net valve lift is not taking advantage of the cylinder heads. Peak power with the previous cam was at 6000 rpm, I won't notice much difference in that arena for a street car. So I'm OK with it.

[chuckies76ta]

Steve: Don't worry about posting, it's all good.

Charles

[chuckies76ta]

Originally Posted by slowbird

At $500 to $1000 a day for dynoing, 10 pulls is a huge waste of time.

The dyno is never a waste of time. It's pretty much a must on a new build.



Charles

[slowbird]

Originally Posted by chuckies76ta

The dyno is never a waste of time. It's pretty much a must on a new build.



Charles

Completely agree! I said wasting 10 pulls on just the vacuum pump is a waste of time.

[chuckies76ta]

Originally Posted by slowbird

Completely agree! I said wasting 10 pulls on just the vacuum pump is a waste of time.

Ok, Sorry, Misunderstood.


Charles

[steve25]

The most accepted way of dyno testing for a accurate change in engine power is to make 5 pulls, then you toss out the best and the worst pull and then average the remaining 3.

If you don't see the value in that for accuracy sake then your beyond help!!

[slowbird]

Originally Posted by steve25

The most accepted way of dyno testing for a accurate change in engine power is to make 5 pulls, then you toss out the best and the worst pull and then average the remaining 3.

If you don't see the value in that for accuracy sake then your beyond help!!

Just how many days you planning to spend on the dyno? You want people to do that with every chance? I average about 20-25 pulls in a day, my guys and me are pretty efficient at it. Most other people that aren't experienced might get 10-15 pulls in a day. At that rate they'll be on the dyno for a week or two using your method. Id hate to see that dyno bill.
If the dyno operator is good and the dyno is maintained properly then it should be repeatable (within a horsepower or so) that is plenty good to see what a chance does. This isn't NASCAR or ProStock where we are looking for 1/2 a horsepower.
Sorry but your method just isn't practical for 99.9% of people dynoing

[Skip Fix]

My 455 in the TA, 500 IA and 470 /409 we made between22 -25 pulls in a day. 455 was on a Stuska dyno other Superflow.