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383 sbc first dyno experience

General engine tech -- Drag Racing to Circle Track

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steve cowan
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383 sbc first dyno experience

Post by steve cowan »

Finally got to dyno-
383 sbc
Dart little M sportsman block
Scat rotating with 5.7" H- beam
JE pistons 1.2mm,1.5mm,3mm
Set oil ring at 4 pounds.
11.45:1 comp
Comp 240 - 256 @ 0.050"
406" lobes
680"- 590" net lift 1.7-1.5 rockers.
105 ICL 109 LSA.
Engine has 15 " manifold vacuum at idle.
Dart cast iron 165cc heads
Ported to 186cc 2.10" avg csa
1.94"-1.5" valves.
PSI Springs
Ported 300-25
850 hp carb.
Total of 20 pulls for the day.
Most power without vac pump
Timing 32 degrees to peak torque 34 degrees after to 7000rpm.
More timing lost power.
MS 109 was the only fuel used.
There are no fuel flow readings as sensor packed it in.
I Ported heads and intake and done valve job myself.
I assembled engine.
Very happy with results and it achieved more than I expected.
I will try to answer any questions if they come but be mindful I am just a hobby guy.
When I receive more information from shop I will post up,
Thanks.
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20220511_200408.jpg
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steve c
KnightEngines
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Re: 383 sbc first dyno experience

Post by KnightEngines »

Holds the power nice up top!
Good job, makes more than the sum of it's parts suggests it should.
LRE dyno is honest, she'll be quick.

Need to figure out why the vac pump dropped power tho, that's unusual, I'd normally expect 5-10hp gain on a motor like that.
408 Nova
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Re: 383 sbc first dyno experience

Post by 408 Nova »

steve cowan wrote: Fri May 13, 2022 12:45 am Finally got to dyno-
383 sbc
Dart little M sportsman block
Scat rotating with 5.7" H- beam
JE pistons 1.2mm,1.5mm,3mm
Set oil ring at 4 pounds.
11.45:1 comp
Comp 240 - 256 @ 0.050"
406" lobes
680"- 590" net lift 1.7-1.5 rockers.
105 ICL 109 LSA.
Engine has 15 " manifold vacuum at idle.
Dart cast iron 165cc heads
Ported to 186cc 2.10" avg csa
1.94"-1.5" valves.
PSI Springs
Ported 300-25
850 hp carb.
Total of 20 pulls for the day.
Most power without vac pump
Timing 32 degrees to peak torque 34 degrees after to 7000rpm.
More timing lost power.
MS 109 was the only fuel used.
There are no fuel flow readings as sensor packed it in.
I Ported heads and intake and done valve job myself.
I assembled engine.
Very happy with results and it achieved more than I expected.
I will try to answer any questions if they come but be mindful I am just a hobby guy.
When I receive more information from shop I will post up,
Thanks.20220511_200331.jpg20220511_200405.jpg20220511_200408.jpg
Very nice work!
6.50camaro
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Re: 383 sbc first dyno experience

Post by 6.50camaro »

Steve,
Is the 16 degree spread on the @.050 valve timing because of the 1.7 intake rocker ? Did you check the .050 timing at the retainer on the intake to see how much the high ratio rocker added ? just curious for my own reasons. Dan
P.S. very nice results by the way.
skinny z
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Re: 383 sbc first dyno experience

Post by skinny z »

Well done Steve.
What's it going in?
Kevin
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Re: 383 sbc first dyno experience

Post by Elroy »

=D> =D> =D>
steve cowan
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Re: 383 sbc first dyno experience

Post by steve cowan »

KnightEngines wrote: Fri May 13, 2022 3:29 am Holds the power nice up top!
Good job, makes more than the sum of it's parts suggests it should.
LRE dyno is honest, she'll be quick.

Need to figure out why the vac pump dropped power tho, that's unusual, I'd normally expect 5-10hp gain on a motor like that.
Thanks Tony appreciate your help over last few years,
Everyone said 15-20hp with vac pump and I was not sure as I had read some engines don't respond to vacuum.
Is it because the motor sealed up really well??
It was worth 5 hp at 11"
At 17" it lost 10hp .
So we set it at 11",even with the light oil ring this engine could be run with no vacuum pump and most of the pulls were with no pump.first 15 anyway.
steve c
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Re: 383 sbc first dyno experience

Post by steve cowan »

6.50camaro wrote: Fri May 13, 2022 8:58 am Steve,
Is the 16 degree spread on the @.050 valve timing because of the 1.7 intake rocker ? Did you check the .050 timing at the retainer on the intake to see how much the high ratio rocker added ? just curious for my own reasons. Dan
P.S. very nice results by the way.
Thanks Dan,
The higher ratio added around 4deg ,speeding valve up is a plus on the intake side as you know as long as you have control of the valve,I am looking for as much lift as I can get,my intake port flows 90% max at 400" lift and does not gain huge amounts after that but I would take more lift if possible.
steve c
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Re: 383 sbc first dyno experience

Post by steve cowan »

skinny z wrote: Fri May 13, 2022 9:02 am Well done Steve.
What's it going in?
Thanks Kevin,
Car is 1973 Holden .
Ran 11.13@119 mph last year with same heads on a 010 short block.
Turbo 400 trans 8" 5600 converter.
9 inch rear 4.1s
255/60/50 MT radials
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steve c
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Re: 383 sbc first dyno experience

Post by PRH »

Nice job!!

It hangs on up top quite well with as short as the intake lobe is.
Somewhat handy with a die grinder.
steve cowan
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Re: 383 sbc first dyno experience

Post by steve cowan »

I appreciate all the responses,
When you do the calculations it peaks higher than what I thought possible.
I will be track testing in a week or 2 depending on weather.
My goal is to tune the car around the engine and I am confident it will happen sooner rather than later.
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Re: 383 sbc first dyno experience

Post by skinny z »

steve cowan wrote: Fri May 13, 2022 5:49 pm
My goal is to tune the car around the engine and I am confident it will happen sooner rather than later.
This is the same approach I intend to follow once the 357 is between the fenders.(Yes, it's finally in the works).
The biggest decision at the moment is how far one way (strip/street) or the other (street/strip) I'll go.

Following with interest.
Kevin
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Re: 383 sbc first dyno experience

Post by steve cowan »

To insight a bit of discussion I am curious on why peaks fell where they did and why it carries up top to 7000rpm.
The only headers I could use were my 1 3/4" 4 into 1 headers
Could not use the 13" extensions as they hit dyno frame.
So shelf header with 3" collector at 6" long with a curved extension to clear frame.
The 300-25 intake is to suit my Dart 180 shp heads so port match is far from perfect, testing carb spacers certainly changed my perspective on Google theory as well.
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Re: 383 sbc first dyno experience

Post by steve cowan »

skinny z wrote: Fri May 13, 2022 5:56 pm
steve cowan wrote: Fri May 13, 2022 5:49 pm
My goal is to tune the car around the engine and I am confident it will happen sooner rather than later.
This is the same approach I intend to follow once the 357 is between the fenders.(Yes, it's finally in the works).
The biggest decision at the moment is how far one way (strip/street) or the other (street/strip) I'll go.

Following with interest.
My opinion is have a plan and try and stick with it.
Let's say you have a genuine 500hp 350ish cube engine in your car it will run well in street trim.
I am confident to say that if I did NOT dyno I would not to be able to get close with 12 months of track testing.
Is engine dyno expensive "yes" in the short term but it opens your eyes.
For the time and effort these dyno shop guys put in I doubt they make much money as in hr rate of pay.
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Re: 383 sbc first dyno experience

Post by F-BIRD'88 »

The top end power hangs on because of the extra exhaust duration.. In the car, you can gear the hell out of it and buzz it thru the traps at high rpm,. thus take advantage of the gears torque multiplication , on launch to leave hard.... Like a Super Stock car..
This one likes to rev...😁
The generous carb and generous ported intake,. adds..

The high Intake RR adds area within the short intake duration. and gets the valve away up off the seat fir best flow with a small valve situation on a sbc...
The intake on a sbc likes lift and area.. The exhaust likes"time" to get the exhaust out.. events "when it opens, when it closes. vs lift... ,at high rpm...

Nice job..
Last edited by F-BIRD'88 on Fri May 13, 2022 8:09 pm, edited 2 times in total.
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