Ported Chevy 083 heads, the tpi project

[Curtis Mc]

very interesting results

Meaning? You thought they would be further apart, closer, more flow, less flow?

Great effort, kudos on finding out what's what and close to the casting limits in some cases.

[Carnut1]

very interesting results

Meaning? You thought they would be further apart, closer, more flow, less flow?

Great effort, kudos on finding out what's what and close to the casting limits in some cases.

Yes, I was expecting much more from the slp modified runners. Now that may just mean the obstruction is somewhere else. I need to take some more airspeed #s. Thanks, Charlie

[cv67]

Wonder if sheer runner length and csa limits hold you back from more?
The joys of trying to make a fat lady dance haha.

[randy331]

After a bunch of work with no real gains I decided to look closely at this chamber.

The chamber side of the valve is much more likely to lead you down the wrong path, than the port side of the valve.

Randy

[Carnut1]

After a bunch of work with no real gains I decided to look closely at this chamber.

The chamber side of the valve is much more likely to lead you down the wrong path, than the port side of the valve.

Randy

I took a long look at that as well. I know the system flows more with a bigger port but is that wise? Having fast air in the runners and a lazy port may not be a great combo. What I think would work well is have each section close to flow and csa so the airspeed is similar. I haven't done any long runner applications so I don't know. Thanks, Charlie

[LoganD]

After a bunch of work with no real gains I decided to look closely at this chamber.

The chamber side of the valve is much more likely to lead you down the wrong path, than the port side of the valve.

Randy

I took a long look at that as well. I know the system flows more with a bigger port but is that wise? Having fast air in the runners and a lazy port may not be a great combo. What I think would work well is have each section close to flow and csa so the airspeed is similar. I haven't done any long runner applications so I don't know. Thanks, Charlie

I've done a lot of long runner development, what you are saying is right. You don't want large airspeed changes in a given runner/port section. Your fastest air should ALWAYS be in the head, at least from an average velocity standpoint. This will produce a responsive engine with good transition response between middling load to high load. This isn't always the easiest thing to see in a static flow bench test.

[randy331]

After a bunch of work with no real gains I decided to look closely at this chamber.

The chamber side of the valve is much more likely to lead you down the wrong path, than the port side of the valve.

Randy

I took a long look at that as well. I know the system flows more with a bigger port but is that wise? Having fast air in the runners and a lazy port may not be a great combo. What I think would work well is have each section close to flow and csa so the airspeed is similar. I haven't done any long runner applications so I don't know. Thanks, Charlie

Sorry, meant to say the flow bench will lead you down the wrong path on the chamber side, much easier than the port side.
Chasing flowz on the chamber side is likely to take you backwards.

Randy

[Carnut1]

The chamber side of the valve is much more likely to lead you down the wrong path, than the port side of the valve.

Randy

I took a long look at that as well. I know the system flows more with a bigger port but is that wise? Having fast air in the runners and a lazy port may not be a great combo. What I think would work well is have each section close to flow and csa so the airspeed is similar. I haven't done any long runner applications so I don't know. Thanks, Charlie

I've done a lot of long runner development, what you are saying is right. You don't want large airspeed changes in a given runner/port section. Your fastest air should ALWAYS be in the head, at least from an average velocity standpoint. This will produce a responsive engine with good transition response between middling load to high load. This isn't always the easiest thing to see in a static flow bench test.

Thank you!

[Carnut1]

The chamber side of the valve is much more likely to lead you down the wrong path, than the port side of the valve.

Randy

I took a long look at that as well. I know the system flows more with a bigger port but is that wise? Having fast air in the runners and a lazy port may not be a great combo. What I think would work well is have each section close to flow and csa so the airspeed is similar. I haven't done any long runner applications so I don't know. Thanks, Charlie

Sorry, meant to say the flow bench will lead you down the wrong path on the chamber side, much easier than the port side.
Chasing flowz on the chamber side is likely to take you backwards.

Randy

So Randy, I will admit I did not expect such a large flow gain by some chamber deshrouding. Do you think the shrouded chamber had the ability to make more power with less flow? If you do what do you think some of the reasons that would happen? Thanks, Charlie

[LoganD]

I took a long look at that as well. I know the system flows more with a bigger port but is that wise? Having fast air in the runners and a lazy port may not be a great combo. What I think would work well is have each section close to flow and csa so the airspeed is similar. I haven't done any long runner applications so I don't know. Thanks, Charlie

Sorry, meant to say the flow bench will lead you down the wrong path on the chamber side, much easier than the port side.
Chasing flowz on the chamber side is likely to take you backwards.

Randy

So Randy, I will admit I did not expect such a large flow gain by some chamber deshrouding. Do you think the shrouded chamber had the ability to make more power with less flow? If you do what do you think some of the reasons that would happen? Thanks, Charlie

That's easy, a shrouded valve will cause more charge motion, generally in the form of tumble. This will help BSFC and knock resistance. Most modern tumble port 4-valve heads deliberately shroud the area of the intake valve near the cylinder wall to cause a low pressure condition that forces tumble.

[slo-svt]

That's easy, a shrouded valve will cause more charge motion, generally in the form of tumble. This will help BSFC and knock resistance. Most modern tumble port 4-valve heads deliberately shroud the area of the intake valve near the cylinder wall to cause a low pressure condition that forces tumble.

Logan what does the D stand for? David?

[Carnut1]

Sorry, meant to say the flow bench will lead you down the wrong path on the chamber side, much easier than the port side.
Chasing flowz on the chamber side is likely to take you backwards.

Randy

So Randy, I will admit I did not expect such a large flow gain by some chamber deshrouding. Do you think the shrouded chamber had the ability to make more power with less flow? If you do what do you think some of the reasons that would happen? Thanks, Charlie

That's easy, a shrouded valve will cause more charge motion, generally in the form of tumble. This will help BSFC and knock resistance. Most modern tumble port 4-valve heads deliberately shroud the area of the intake valve near the cylinder wall to cause a low pressure condition that forces tumble.

I have seen that, now often on ST pros will state they will rather have higher flow than swirl or tumble. As far as a wedge chamber from what I have tested (flowbench with swirl meter) they actually have too much swirl and a step back would be better. Thanks, Charlie

[F-BIRD'88]

The amount of swirl/tumble produced at the chamber shrouded near the in valve is relative to engine rpm.
A engine running at part throttle at 1600 rpm in OD needs a lot more induced tumble/ swirl than if running at 5000 rpm ++++. What works and gains at low rpm (the stock motor) can be way too much effect at high rpm on a racey engine. It is relative to the job the engine is intended for. And its rpm range.

[F-BIRD'88]

You would want to dyno test compare the result of your chamber mods to see if the increased flow gets you increased dyno power or torque.

Interesting budget hot rodded sbc head on a capable hot street/strip 355 or 383 (sans the tpi system.)

But the modded tpi should make lots of mid torque.

These tpi heads in Carnut modded form are a great alternative to vortecs or old 60's camelbacks for street strip on a budget and the oem look.

The 081 305 TPI motor cast head is another potential candidate. The smaller chamber "081" allows for even more creative die grinder carving. Lots of both these around as many were swapped out for aftermarket heads in the TPI motor power search frenze of the 80's and 90's.
The twinned center exhaust egr passages need to be blocked to stop center ex port cross talk and cooler running at WOT with headers.

[naukkis79]

Most modern tumble port 4-valve heads deliberately shroud the area of the intake valve near the cylinder wall to cause a low pressure condition that forces tumble.

If done like Cosworth 60's patent tumble is made with port bias - port is at different angle than valve and at high lifts flow detach from SSR and makes SSR side of valve low pressure area, which with upper valve part flow directed downward with chamber creates tumbling motion in cylinder. More valve lift than what is needed for max port flow increases tumble even more so its usual to lift valves much more than what is needed for max flow. Modern eco-heads have skijump in port floor to detach flow from SSR without high valve lifts.

There is no low pressure area where chamber shrouds valve, only restricted flow.