383 sbc first dyno experience

[skinny z]

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.

That fact is not lost on me. And something I've considered. (But the logistics are a nightmare).

[steve cowan]

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 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...

Thanks for your response.
So do you think there is a relationship with duration split and power after peak?
Here is the cam card
383 cube 4.030" bore 3.75" stroke

20220514_101143.jpg

Click on picture to better view

[steve cowan]

Intake lobe for a 1.6 rocker
Exhaust using 1.5 rocker
As stated I ran a 1.7 rocker.

[bob460]

Did you play around with lash?

What did the heads flow?......before and after porting.

[steve cowan]

Did you play around with lash?

What did the heads flow?......before and after porting.

Bob,
We played with tighter lash on around the 15th pull it picked up through the curve and not 1 or 2hp.
Hot lash now is 10"-12"
As cast heads flowed 210-138 around that .
At 700" @ 28" intake is 274cfm
At 700" @ 28" exhaust is 227cfm
With manifold bolted on intake port flows 305" at 700" at 45 inches.
The last 12 months playing on flow bench I have stopped looking at numbers especially on exhaust and flowing at the highest depression I can and listen to the port.
It has been said before by others way smarter than me -
The cfm will be there if the size and shape are close to correct.

[1980RS]

Looks like a 10 sec engine to me. Nice job.

[steve cowan]

Looks like a 10 sec engine to me. Nice job.

Thanks Bob.
At my weight 3650 with me
Moroso slide says 10.6s@126mph
Larry's pipemax says 10.70 @ 125 mph at approx 580hp

[steve cowan]

I would be interested in opinions on tighter lash and a torque increase is a automatic green light for a bigger cam??
There is a good chance over time I want to keep valve sizes as is and shoot for 600hp at same rpm.
Is this possible? And how would you approach this.
Lift,duration, change valve job,I might be able to get a little more area in ports but getting thin in places but I do have sonic tester.
Opinions welcome.

[HQM383]

Intake lobe for a 1.6 rocker
Exhaust using 1.5 rocker
As stated I ran a 1.7 rocker.

So around .690” lift on the intake. 30* overlap @.050”. Int close 49* @.050” ABDC. That kind of intake area, overlap, intake velocity with port and valve sizes and enough exhaust timing for cylinder fill and closing intake early would go a long way to holding torque.

Installed at 109* ICL?

[steve cowan]

Intake lobe for a 1.6 rocker
Exhaust using 1.5 rocker
As stated I ran a 1.7 rocker.

So around .690” lift on the intake. 30* overlap @.050”. Int close 49* @.050” ABDC. That kind of intake area, overlap, intake velocity with port and valve sizes and enough exhaust timing for cylinder fill and closing intake early would go a long way to holding torque.

Installed at 109* ICL?

Jamie,
105 ICL,
I wanted to test ICL on dyno but boys said it will only rock the curve up or down and probably not show power increases??
Because my car heavy the suggestion was to test at the track

[HQM383]

Intake lobe for a 1.6 rocker
Exhaust using 1.5 rocker
As stated I ran a 1.7 rocker.

So around .690” lift on the intake. 30* overlap @.050”. Int close 49* @.050” ABDC. That kind of intake area, overlap, intake velocity with port and valve sizes and enough exhaust timing for cylinder fill and closing intake early would go a long way to holding torque.

Installed at 109* ICL?

Jamie,
105 ICL,
I wanted to test ICL on dyno but boys said it will only rock the curve up or down and probably not show power increases??
Because my car heavy the suggestion was to test at the track

105* ICL, there it is in post 1. I should have checked.

Did you get a VE figure?

[steve cowan]

So around .690” lift on the intake. 30* overlap @.050”. Int close 49* @.050” ABDC. That kind of intake area, overlap, intake velocity with port and valve sizes and enough exhaust timing for cylinder fill and closing intake early would go a long way to holding torque.

Installed at 109* ICL?

Jamie,
105 ICL,
I wanted to test ICL on dyno but boys said it will only rock the curve up or down and probably not show power increases??
Because my car heavy the suggestion was to test at the track

105* ICL, there it is in post 1. I should have checked.

Did you get a VE figure?

The guys were dyno with a stout LS engine this weekend, I will call them during the week for more information and video

[1980RS]

Looks like a 10 sec engine to me. Nice job.

Thanks Bob.
At my weight 3650 with me
Moroso slide says 10.6s@126mph
Larry's pipemax says 10.70 @ 125 mph at approx 580hp

That sounds right to me. One thing I will note was that on a test with the 300-36 dual plane vs the 300-25 strip dominator I thought the 300-36 was better ET wise and mine was with no porting and only 1 mph difference. I also know last fall that my Air Gap with the divider cut all the way down really worked good, so there's a couple of more options at the track if you don't hit your goal.

[Arthur]

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.

Nice work
Would you elaborate on your spacer journey -

[steve cowan]

Looks like a 10 sec engine to me. Nice job.

Thanks Bob.
At my weight 3650 with me
Moroso slide says 10.6s@126mph
Larry's pipemax says 10.70 @ 125 mph at approx 580hp

That sounds right to me. One thing I will note was that on a test with the 300-36 dual plane vs the 300-25 strip dominator I thought the 300-36 was better ET wise and mine was with no porting and only 1 mph difference. I also know last fall that my Air Gap with the divider cut all the way down really worked good, so there's a couple of more options at the track if you don't hit your goal.

Good information there Bob ,
So there are 2 schools of thought with the small intake port/valve combination -
So as rpm increases so does port velocity but the limit is around 0.55 mach - 690ft/sec
For this engine to peak at around 6500-6600rpm and hang on is the port shaped well to handle the speed??
Or is the ported intake manifold a baidaid
Runner opening at intake is 3.13" and 2.25" at the flange this is with radius taken into account.
Pushrod pinch is 2.05" throat is 2.27" includes stem factored in
Thoughts ??