600 HP 350 SBC?

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Re: 600 HP 350 SBC?

Post by GARY C »

Stan Weiss wrote: Sat Aug 17, 2019 4:48 pm Gary,
The math that Chad and I posted has to do with the relationship between cfm, csa and average velocity in fps. It does not matter if that CSA is in the head or the port. To be honest at this point I am not sure what you are looking for.

Stan
I am just curious and asking questions, I understand the relationship of the math I am just not exactly sure what I should be shooting for.
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Re: 600 HP 350 SBC?

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KnightEngines wrote: Sat Aug 17, 2019 8:59 pm Gary, open the valve till its flowing 280cfm, probe at that lift.

Fast is good, just not too fast.
That would be about .550 lift, I have not tried that, I thought the goal was to look at max lift so I have only done that so far.

I will see what it is doing there as well as with the intake which will probably reduce cfm to 280ish at peak lift.
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Re: 600 HP 350 SBC?

Post by GARY C »

Rick Jones wrote: Sat Aug 17, 2019 6:03 pm
GARY C wrote: Sat Aug 17, 2019 4:01 pm
I have always wondered why all engine discussion and math equations exclude the intake?
The rest of the inlet air column must not matter. But not being as smart as everyone else, I've always calculated the
required average area and mean air velocity of the entire inlet air column from plenum, or atmosphere, to the valve.
It seems like that would be more important than just the head info alone but I wouldn't even know where to start or what to do with that info once I had it. :)
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Re: 600 HP 350 SBC?

Post by SpeierRacingHeads »

Anyone remember Larry Meaux saying the cross section is "X" but should always be measured with a pitot?

CORNER RADI will influence airspeed.

If your a head porter and your setting cross section with a formula, your big.

Set it with velocity and stuff is smaller, faster, and makes more power.
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Re: 600 HP 350 SBC?

Post by Carnut1 »

SpeierRacingHeads wrote: Sat Aug 17, 2019 11:20 pm Anyone remember Larry Meaux saying the cross section is "X" but should always be measured with a pitot?

CORNER RADI will influence airspeed.

If your a head porter and your setting cross section with a formula, your big.

Set it with velocity and stuff is smaller, faster, and makes more power.
Great post Chad.
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Re: 600 HP 350 SBC?

Post by KnightEngines »

GARY C wrote: Sat Aug 17, 2019 9:38 pm
KnightEngines wrote: Sat Aug 17, 2019 8:59 pm Gary, open the valve till its flowing 280cfm, probe at that lift.

Fast is good, just not too fast.
That would be about .550 lift, I have not tried that, I thought the goal was to look at max lift so I have only done that so far.

I will see what it is doing there as well as with the intake which will probably reduce cfm to 280ish at peak lift.
As Chad correctly suggests you need to probe to get correct cross section, calculated is just a starting point.
But you also need to probe at a relevant flow capacity, no point in probing a head when it's moving 350cfm if the engine is only going to consume 280, you'll get a false idea of velocity, it'll be much higher than the engine will see. At 600hp the engine will be consuming less than 280cfm, so best to set your velocities at a flow that the engine will see.
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Re: 600 HP 350 SBC?

Post by steve cowan »

As Chad correctly suggests you need to probe to get correct cross section, calculated is just a starting point.
But you also need to probe at a relevant flow capacity, no point in probing a head when it's moving 350cfm if the engine is only going to consume 280, you'll get a false idea of velocity, it'll be much higher than the engine will see. At 600hp the engine will be consuming less than 280cfm, so best to set your velocities at a flow that the engine will see.
[/quote
Hey Tony,
After you have set your intake manifold to the CSA and or taper you want to use,do you bother checking airspeeds again or just look for a minimum flow loss with manifold bolted to the cylinder head.
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Re: 600 HP 350 SBC?

Post by KnightEngines »

Depending on just how optimised the combo needs to be (ie, labour is not that cheap, how much time can the customer justify me spending on it).
For most street/strip stuff I just match port, set cross section & tidy runner entries, don't usually flow head with intake on.
This is one of those area's where the skilled DIY guy has an advantage, your own time is free!
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Re: 600 HP 350 SBC?

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KnightEngines wrote: Sun Aug 18, 2019 8:14 pm
GARY C wrote: Sat Aug 17, 2019 9:38 pm
KnightEngines wrote: Sat Aug 17, 2019 8:59 pm Gary, open the valve till its flowing 280cfm, probe at that lift.

Fast is good, just not too fast.
That would be about .550 lift, I have not tried that, I thought the goal was to look at max lift so I have only done that so far.

I will see what it is doing there as well as with the intake which will probably reduce cfm to 280ish at peak lift.
As Chad correctly suggests you need to probe to get correct cross section, calculated is just a starting point.
But you also need to probe at a relevant flow capacity, no point in probing a head when it's moving 350cfm if the engine is only going to consume 280, you'll get a false idea of velocity, it'll be much higher than the engine will see. At 600hp the engine will be consuming less than 280cfm, so best to set your velocities at a flow that the engine will see.
Thanks for the additional info, I will do some testing in that range to see what I have.
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Re: 600 HP 350 SBC?

Post by FC-Pilot »

Slightly off topic, but I want to say thank you to Chad and Tony for sharing the info that you did in the last few pages. It has turned a light on in a dark room for cylinder head testing for me. It did not give me all the answers I needed, but gave me the direction I needed to start finding the answers for myself. Thanks for taking the time to share what you know.

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Re: 600 HP 350 SBC?

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FC-Pilot wrote: Mon Aug 19, 2019 8:55 pm Slightly off topic, but I want to say thank you to Chad and Tony for sharing the info that you did in the last few pages. It has turned a light on in a dark room for cylinder head testing for me. It did not give me all the answers I needed, but gave me the direction I needed to start finding the answers for myself. Thanks for taking the time to share what you know.

Paul
Yes they have been the few, as well as Darin Morgan that have been willing to put any specific numbers out there to look at as well as correspond on these kind of open discussions.
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Re: 600 HP 350 SBC?

Post by Warp Speed »

KnightEngines wrote: Sun Aug 18, 2019 8:14 pm
GARY C wrote: Sat Aug 17, 2019 9:38 pm
KnightEngines wrote: Sat Aug 17, 2019 8:59 pm Gary, open the valve till its flowing 280cfm, probe at that lift.

Fast is good, just not too fast.
That would be about .550 lift, I have not tried that, I thought the goal was to look at max lift so I have only done that so far.

I will see what it is doing there as well as with the intake which will probably reduce cfm to 280ish at peak lift.
As Chad correctly suggests you need to probe to get correct cross section, calculated is just a starting point.
But you also need to probe at a relevant flow capacity, no point in probing a head when it's moving 350cfm if the engine is only going to consume 280, you'll get a false idea of velocity, it'll be much higher than the engine will see. At 600hp the engine will be consuming less than 280cfm, so best to set your velocities at a flow that the engine will see.
How much is a 600hp engine actually using per cylinder?
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Re: 600 HP 350 SBC?

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Warp Speed wrote: Tue Aug 20, 2019 5:02 am
KnightEngines wrote: Sun Aug 18, 2019 8:14 pm
GARY C wrote: Sat Aug 17, 2019 9:38 pm

That would be about .550 lift, I have not tried that, I thought the goal was to look at max lift so I have only done that so far.

I will see what it is doing there as well as with the intake which will probably reduce cfm to 280ish at peak lift.
As Chad correctly suggests you need to probe to get correct cross section, calculated is just a starting point.
But you also need to probe at a relevant flow capacity, no point in probing a head when it's moving 350cfm if the engine is only going to consume 280, you'll get a false idea of velocity, it'll be much higher than the engine will see. At 600hp the engine will be consuming less than 280cfm, so best to set your velocities at a flow that the engine will see.
How much is a 600hp engine actually using per cylinder?
Oddly enough if I use Darin's math for my engine and RPM it shows a piston demand of 300 cfm at 76 degrees for what ever that is worth... Seems there are lots of numbers, theory's and ideas. you would think by now a 350 would be simple but as my OP questioned, Why isn't 600 hp rolling out of most shops?
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Re: 600 HP 350 SBC?

Post by KnightEngines »

Warp Speed wrote: Tue Aug 20, 2019 5:02 am
KnightEngines wrote: Sun Aug 18, 2019 8:14 pm
GARY C wrote: Sat Aug 17, 2019 9:38 pm

That would be about .550 lift, I have not tried that, I thought the goal was to look at max lift so I have only done that so far.

I will see what it is doing there as well as with the intake which will probably reduce cfm to 280ish at peak lift.
As Chad correctly suggests you need to probe to get correct cross section, calculated is just a starting point.
But you also need to probe at a relevant flow capacity, no point in probing a head when it's moving 350cfm if the engine is only going to consume 280, you'll get a false idea of velocity, it'll be much higher than the engine will see. At 600hp the engine will be consuming less than 280cfm, so best to set your velocities at a flow that the engine will see.
How much is a 600hp engine actually using per cylinder?
Real world actual cfm - no idea!
Will vary quite a bit with trapped VE%, combustion efficiency etc.
But I do know that 275cfm at peak valve lift on my bench can make 600hp on pump fuel with relatively simple components (no dry sump or high vac or gas porting or thin rings, regular .440 odd lobes, single 4150 carb etc).
Heads that flow more with a slightly larger cross section tend to hold power longer after peak but give up a little average between peak tq & hp.
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Re: 600 HP 350 SBC?

Post by KnightEngines »

If I get a chance in the next couple of days I'll post up another build I did a few months ago.
It was a 383 holden, pump fuel, flat tappet street engine, it's a good one to illustrate larger heads holding power longer, this one wore aftermarket alloy heads that imo were a bit big.
I missed on the cam a little, unfamiliar heads that I haven't used before is my excuse.
It made 490lb at 4600, 507lb at 5100, 575hp at 6300 and 558hp at 7100.
If I'd got the cam right it woulda made 585-590.
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