Thread: Dyno Guys

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I'm 2 days away from having my short block together for the el camino. I'm getting really antsy to see what she'll do at full strength.

For a little sneak peak, could someone with a good version of desktop dyno tell me what you need to know in order to give me a fairly accurate hp/tq rating. Thanks a bunch.

motor type, cubic inches, cylinder head type, valve sizes, port work?, exhaust type, header size, with/without mufflers, cam lifter type, cam lift, duration, intake type, carb type and size, compression ratio. That would be the basics for a start.

George

Motor Type: Small block Chevy
Cubic Inches: 377 CID
Cylinder Head: '441 Casting Iron heads 76cc Combustion Chambers
Valves: 2.02/1.60
Exhaust: 3 inch 'X' pipe
Headers: Yes, not sure on size though.
Mufflers: Yes, 40 series flowmaster
Cam: Solid Roller, ".567/".567 int/exh 242/242@.050
Intake: Edelbrock Torker II Intake
Carb Type: Not sure, possibly looking at 750cfm holly double pumper or demon
Compression Ratio: estimated @ 10:1

The pistons are Probe forged flat top. The rods are forged 'H' beam. The crank is Scat cast steel. Block is 4 bolt 400 SBC. Cam is Chet Herbert Performance. Valve train is Renegade Racing. Cam is on a 110 degree lobe center.

I appreciate anyone who will take the time to help me out here. If you need anymore information, just ask. I will provide

Originally Posted by Hopper111

Motor Type: Small block Chevy
Cubic Inches: 377 CID
Cylinder Head: '441 Casting Iron heads 76cc Combustion Chambers
Valves: 2.02/1.60
Exhaust: 3 inch 'X' pipe
Headers: Yes, not sure on size though.
Mufflers: Yes, 40 series flowmaster
Cam: Solid Roller, ".567/".567 int/exh 242/242@.050
Intake: Edelbrock Torker II Intake
Carb Type: Not sure, possibly looking at 750cfm holly double pumper or demon
Compression Ratio: estimated @ 10:1

The pistons are Probe forged flat top. The rods are forged 'H' beam. The crank is Scat cast steel. Block is 4 bolt 400 SBC. Cam is Chet Herbert Performance. Valve train is Renegade Racing. Cam is on a 110 degree lobe center.

I appreciate anyone who will take the time to help me out here. If you need anymore information, just ask. I will provide

sounds to me like its gonna be quite the monster

Hopper, here's what I got. I had to make a few assumptions (intake centerline =106*, large tube headers, 4" bore, 3.75" stroke = small bore 383?).

381HP @5000, 479lbft @ 2000-2500

Seems a solid roller might be overkill for low revs Could probably get as good performance out of a good hydraulic...

Your heads are holding you back. With that much cam, you need a set of good breathing aluminum heads like AFR or Brodix to make your combination work to its full potential.

I'm sorry, i did not specify bore and stroke. It's a 4.155 bore x 3.5 stroke

Destroked 400 SBC. The cam is a 110* lobe center.

What would the numbers be if i swapped over to a good set of AFR or Brodix heads?

I used destop dyno 2000 and got very different results for some reason.
I also had to try to fit your specs into the program parameters(that leave a bit to be desired). I used 4.155 bore, 3.5 stroke, solid roller .567 lift, 296 int dur, 302 exh dur, 106 lobe centers, 87 deg valve overlap, large tube headers w/ mufflers, "low performance, pocket ported" heads with 2.02, 1.60 valves. 10.1 comp. etc, etc.

here is what I got...

rpm hp tq

2000 106 279
3000 186 326
4000 307 403
5000 423 444
5500 457 436
6000 477 418
6500 483 390
7000 470 353
7500 454 318

Big difference...I went back and checked to see if I missed something obvious. Didn't see anything. Then again I'm known for not being able to see the milk in the fridge! For what I put in, that's what DD2000 spit out. For the motors sake, I sure how my numbers are closer!!!

Hope this brightens your day a bit.

Can someone else out there give it a run to get a third opinion...it shouldn't be that different! I'm probably the one screwing it up here...sniffed too much race gas...or was it glue...what's my name again?

For the record, I do agree that your heads would represent your most obvious bottleneck in the power department. I suspect a reasonable amount of power would be gained from a nice set of aluminum castings. Plus the aluminum would help for keeping detonation at bay. I have a 383 sbc with 12.5:1 comp and fully ported big valve 461 fuelie heads and although they won't flow as well as the newer good stuff, I like running the vintage stuff and it runs pretty hard at the track considering the heads are older than I am!

My motor isn't that different than yours, aside from the small displacement difference, the biggest difference is the comperssion. I run a solid flat tappet .570 lift older custom cam. Team G intake, modified 750DP carb, 1 7/8 headers, full 3" exhaust with mufflers. Even has an old gear drive timing for effect. Never dynoed it, but in a 3400lb 69 Firebird with 255/60/15 worn out radial t/a actual STREET tires (no traction whatsoever) having to baby it off the line(1.95 60ft.) and it had no problem finishing at a consistent 114-115mph, 12.2sec fighting for traction HARD for the first 1/8th.

My heads should flow a bit better, my higher compression is certainly helping me a good bit, maybe 5-10% or so. Your cam is probably a better profile than my 10 year old solid flat tappet stick. I'd ballpark guess that my motor shouldn't be more than 10-15% or so stronger than yours.

George

I just used the same perameters as before and just changed the head type to flow around 280 intake or so, and I came up with a power boost of...

hp 483 to 527 at 6500
tq 444 to 477 at 5000

As usual, this is FAR from acurate, just ballpark at best!

George

We're running people's combos in Desktop Dynos? Ooh, ooh! Run mine.

Motor Type: Small block Chevy
Cubic Inches: CID 353
Bore/Stroke: 4.02/3.48
Cylinder Head: L31 Vortec Heads
Valves: 1.94/1.5
Exhaust: 2.5-2.25" H-pipe
Headers: Yes, 1 5/8ths primaries and 2.5" collectors.
Mufflers: Yes, Turbo style, 2.25" in and out
Cam: Hydraulic Flat, .447"/.454" int/exh 212/218@.050 110LSA 106 Centerline Comp XE256H
Intake: Edelbrock Performer Vortec
Carb Type: Qjet, 750CFM
Compression Ratio: 9.25:1

Originally Posted by 76GMC1500

We're running people's combos in Desktop Dynos? Ooh, ooh! Run mine.

Motor Type: Small block Chevy
Cubic Inches: CID 353
Bore/Stroke: 4.02/3.48
Cylinder Head: L31 Vortec Heads
Valves: 1.94/1.5
Exhaust: 2.5-2.25" H-pipe
Headers: Yes, 1 5/8ths primaries and 2.5" collectors.
Mufflers: Yes, Turbo style, 2.25" in and out
Cam: Hydraulic Flat, .447"/.454" int/exh 212/218@.050 110LSA 106 Centerline Comp XE256H
Intake: Edelbrock Performer Vortec
Carb Type: Qjet, 750CFM
Compression Ratio: 9.25:1

304 HP @ 4k, 384 Ft/LBS @3.5k Desktop dyno 2000 figures

Cool, thanks. The time sheets seem to confirm those numbers.

I get 339 hp at 5,000 rpm, 443 lb-ft torque at 2,500 rpm .............

Kitz

Originally Posted by Hopper111

Motor Type: Small block Chevy
Cubic Inches: 377 CID
Cylinder Head: '441 Casting Iron heads 76cc Combustion Chambers
Valves: 2.02/1.60
Exhaust: 3 inch 'X' pipe
Headers: Yes, not sure on size though.
Mufflers: Yes, 40 series flowmaster
Cam: Solid Roller, ".567/".567 int/exh 242/242@.050
Intake: Edelbrock Torker II Intake
Carb Type: Not sure, possibly looking at 750cfm holly double pumper or demon
Compression Ratio: estimated @ 10:1

The pistons are Probe forged flat top. The rods are forged 'H' beam. The crank is Scat cast steel. Block is 4 bolt 400 SBC. Cam is Chet Herbert Performance. Valve train is Renegade Racing. Cam is on a 110 degree lobe center.

I appreciate anyone who will take the time to help me out here. If you need anymore information, just ask. I will provide

First of all you don't have enough compression to run that cam.
Second your heads are to small.
Again if you want to run the 377 you will have to gear the $hit out of it to get it to work and run a really loose stall.
Ask any one who runs a dirt mod. and they will tell you a 377 is great for a "dry slick" track because it will take a lot of the low end torque away.
Then ask them for a "tacky" track what they would run and they will say a 383/406.

cool, thanks guys. i was counting that with my choked up cast iron heads i'd make somewhere between 450-500 hp. This has been a ride. For $2500 I've managed to put together a complete engine and valve train minus the head castings to put the valve train into that is capable of 500+ HP and a healthy shot of nitrous. Not bad in my book. Granted, to make this puppy into a fire breather monster, you'd need to put some money into a good pair of cylinder head castings. However, I have everything needed to assemble the cylinder heads/valvetrain. Not bad. Just wish i was still into the racing scene and still needed this motor

I gave the specs to those particular cylinder heads because they are the only pair that I have. The thought crossed my mind to use them, but i knew that they wouldn't breathe well enough for that cam and the chambers would be too big to really let that cam rip. I just thought that if the motor made decent numbers with those old heads, it would make great numbers with a good pair of heads.

Also thinking of selling this motor to pay for my books and tuition for my college classes. What would be a fair price for this motor? (I have everything except carburetor, distributor, and cylinder heads. The valve train and shortblock are complete)