383 sbc first dyno experience

[Bob Hollinshead]

Good stuff Steve and Thanks for sharing. Very nice work! Still trying to wrap my head around the valve sizing though LOL. I just come here to learn.... as a hobbyist. I think most people looking for the most power out of that combo at that rpm range would be using a head with a 2.05 or 2.08 valve. Your MCSA is supporting the power you're making. A bigger valve should flow more air if the bowl/throat/chamber supported the larger valve....but does something just work better with the smaller valve? It must be flowing a full curtain of air well past the the lift point of 25%/VALVE DIA. Having the bowl shape concentric with the valve stem must help? I know some porters are blowing the bowls out to 105% of valve diameter chasing super high lift flow numbers and making good power. Just boggles my mind Haha

[steve cowan]

Good stuff Steve and Thanks for sharing. Very nice work! Still trying to wrap my head around the valve sizing though LOL. I just come here to learn.... as a hobbyist. I think most people looking for the most power out of that combo at that rpm range would be using a head with a 2.05 or 2.08 valve. Your MCSA is supporting the power you're making. A bigger valve should flow more air if the bowl/throat/chamber supported the larger valve....but does something just work better with the smaller valve? It must be flowing a full curtain of air well past the the lift point of 25%/VALVE DIA. Having the bowl shape concentric with the valve stem must help? I know some porters are blowing the bowls out to 105% of valve diameter chasing super high lift flow numbers and making good power. Just boggles my mind Haha

For that combo there probably is some luck as well as I don't fully understand what is going on.
3 things that are probably not correct in Google land-
Mis-matched spacer
Mis- matched 300-25 intake manifold, I did that intake to fit my Dart 180 SHP heads.
The combustion chamber not going to the bore wall.
I have more questions than answers unfortunately.
I agree with you on the bigger valve if bowl etc is sized for application. But how big will the front halve of intake port be.
I know it nearly impossible on a 23 deg head but I think we should work towards as constant a CSA through the port but hard to achieve.
My pinch is 2.05"
Throat is 2.27"
Avg csa is around 2.10"
Bob,
Do you have any opinions on how you would improve the cylinder heads without increasing valve sizes, remember I am nearly at max at the pinch

[steve cowan]

When I done my calculations before dyno I was sure it would peak at 6300rpm.
The dyno guys say it is the intake helping the head carry ?
I would like to hear anyone who has has good experience with a undersized valve/bore and made more power than expected.
If you look at the port mould the SSR is not layed way back,I tried to shape it instead of laying way down to get the big number, maybe the shape works well for turning the fuel?
I really wish dyno shop had there fuel flow meters working correctly, would be interesting.

[steve cowan]

New 255/60/15 R series radials.
Still turning tyres off the hit as shown in the 60ft

Are you liking the new tires?
I'm assuming those are the Mickey Thompson ET Street R Radial Tires 3553.
I'm in the market for 255/50/16's myself but M/T only offers the SS version in a 16".

I ordered another set of 255/60/15 R series this week.
Been told up to 12 months wait

[skinny z]

New 255/60/15 R series radials.
Still turning tyres off the hit as shown in the 60ft

Are you liking the new tires?
I'm assuming those are the Mickey Thompson ET Street R Radial Tires 3553.
I'm in the market for 255/50/16's myself but M/T only offers the SS version in a 16".

I ordered another set of 255/60/15 R series this week.
Been told up to 12 months wait

12 months!
Man, I thought two months for pistons was bad.

[Bob Hollinshead]

Steve did you do any flow tests without a valve? What back cut on the valve?

[Bob Hollinshead]

Are you liking the new tires?
I'm assuming those are the Mickey Thompson ET Street R Radial Tires 3553.
I'm in the market for 255/50/16's myself but M/T only offers the SS version in a 16".

I ordered another set of 255/60/15 R series this week.
Been told up to 12 months wait

12 months!
Man, I thought two months for pistons was bad.

Build back better

[steve cowan]

Steve did you do any flow tests without a valve? What back cut on the valve?

When I first started with my bench I flowed without valve but was soon told to stop doing it
The valve is the restriction so let's work around that.
Do you have a bench or access to a bench?

[steve cowan]

Sorry,forgot about backcuts.
No backcuts on valves, I have done some bench testing but that's all.
I still find the subject confusing and it's probably the most argued subject.

[Bob Hollinshead]

Thanks for sharing info, I don't have a bench but have wanted to build one.

[Arthur]

Good stuff Steve and Thanks for sharing. Very nice work! Still trying to wrap my head around the valve sizing though LOL. I just come here to learn.... as a hobbyist. I think most people looking for the most power out of that combo at that rpm range would be using a head with a 2.05 or 2.08 valve. Your MCSA is supporting the power you're making. A bigger valve should flow more air if the bowl/throat/chamber supported the larger valve....but does something just work better with the smaller valve? It must be flowing a full curtain of air well past the the lift point of 25%/VALVE DIA. Having the bowl shape concentric with the valve stem must help? I know some porters are blowing the bowls out to 105% of valve diameter chasing super high lift flow numbers and making good power. Just boggles my mind Haha

For that combo there probably is some luck as well as I don't fully understand what is going on.
3 things that are probably not correct in Google land-
Mis-matched spacer
Mis- matched 300-25 intake manifold, I did that intake to fit my Dart 180 SHP heads.
The combustion chamber not going to the bore wall.
I have more questions than answers unfortunately.
I agree with you on the bigger valve if bowl etc is sized for application. But how big will the front halve of intake port be.
I know it nearly impossible on a 23 deg head but I think we should work towards as constant a CSA through the port but hard to achieve.
My pinch is 2.05"
Throat is 2.27"
Avg csa is around 2.10"
Bob,
Do you have any opinions on how you would improve the cylinder heads without increasing valve sizes, remember I am nearly at max at the pinch

What method do you use to measure cross sectional areas - specifically port dimensions.

[steve cowan]

Good stuff Steve and Thanks for sharing. Very nice work! Still trying to wrap my head around the valve sizing though LOL. I just come here to learn.... as a hobbyist. I think most people looking for the most power out of that combo at that rpm range would be using a head with a 2.05 or 2.08 valve. Your MCSA is supporting the power you're making. A bigger valve should flow more air if the bowl/throat/chamber supported the larger valve....but does something just work better with the smaller valve? It must be flowing a full curtain of air well past the the lift point of 25%/VALVE DIA. Having the bowl shape concentric with the valve stem must help? I know some porters are blowing the bowls out to 105% of valve diameter chasing super high lift flow numbers and making good power. Just boggles my mind Haha

For that combo there probably is some luck as well as I don't fully understand what is going on.
3 things that are probably not correct in Google land-
Mis-matched spacer
Mis- matched 300-25 intake manifold, I did that intake to fit my Dart 180 SHP heads.
The combustion chamber not going to the bore wall.
I have more questions than answers unfortunately.
I agree with you on the bigger valve if bowl etc is sized for application. But how big will the front halve of intake port be.
I know it nearly impossible on a 23 deg head but I think we should work towards as constant a CSA through the port but hard to achieve.
My pinch is 2.05"
Throat is 2.27"
Avg csa is around 2.10"
Bob,
Do you have any opinions on how you would improve the cylinder heads without increasing valve sizes, remember I am nearly at max at the pinch

What method do you use to measure cross sectional areas - specifically port dimensions.

Once I am getting close to where I think it should be I usually do a port mould then cut it in sections and put on graph paper.

[skinny z]

Once I am getting close to where I think it should be I usually do a port mould then cut it in sections and put on graph paper.

Short of pouring a mold, can a guy get in there with a pair of inside dividers and get a measurement that way?

[steve cowan]

Once I am getting close to where I think it should be I usually do a port mould then cut it in sections and put on graph paper.

Short of pouring a mold, can a guy get in there with a pair of inside dividers and get a measurement that way?

Yes,inside divider or telescope snap gauges but I think where people get lost is calculations on corner radius. Larry has mentioned he has made templates that he uses.
Experienced guys use divider and alot is the shape .
Even on a 23 degree head you should be able to see a fair amount of the valve.
Measuring inside ports and intake manifolds is difficult and time consuming.

[skinny z]

Once I am getting close to where I think it should be I usually do a port mould then cut it in sections and put on graph paper.

Short of pouring a mold, can a guy get in there with a pair of inside dividers and get a measurement that way?

Yes,inside divider or telescope snap gauges but I think where people get lost is calculations on corner radius. Larry has mentioned he has made templates that he uses.
Experienced guys use divider and alot is the shape .
Even on a 23 degree head you should be able to see a fair amount of the valve.
Measuring inside ports and intake manifolds is difficult and time consuming.

Yeah. I had considered the corners being problematic.
That said, working in a manufacturing machine shop has it's tool advantages. Maybe QA has the right gizmo for the job. We measure everything.
Once I get into it, I'd like to have covered all the bases covered regarding these heads as I'll be posing a couple of questions about their potential.
Thanks Steve.