Don Terrill’s Speed-Talk

naukkis79 wrote: ↑Tue Mar 19, 2019 2:18 pm

LoganD wrote: ↑Tue Mar 19, 2019 12:55 pm 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.

I didn't say the chamber was shrouding it, but you are right they use low valve angles (flat combustion chamber) with a port that is angled steeply near the valve. When the valve opens it is shrouded by the cylinder wall, and the air wants to head towards the exhaust side because of the port shape. This causes a low pressure area near the cylinder wall underneath the open valve, inducing tumble. We actually have extremely high tolerancing on the valve/seat/guide in modern 4-valve heads because we put the valve so close to the cylinder wall. We sacrifice quite a lot of potential flow here, but it allows us to run 1.4 bar boost pressure on pump fuel with no knock.

LoganD wrote: ↑Tue Mar 19, 2019 12:55 pm 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.

Mr. vizard,,, I was not aware that was you///// and then I saw Rochester.

,i used to be in West Bloomfield,,,not far from you/ it was common knowledge then you lived in the basic area but I heard you had left south to be with nascar. I mainly lurk here and read your posts sometimes but didn't know you had changed to logan

slo-svt wrote: ↑Tue Mar 19, 2019 1:12 pm

LoganD wrote: ↑Tue Mar 19, 2019 12:55 pm 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?

Sumtingwong wrote: ↑Tue Mar 19, 2019 2:43 pm

LoganD wrote: ↑Tue Mar 19, 2019 12:55 pm 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.

Mr. vizard,,, I was not aware that was you///// and then I saw Rochester.

,i used to be in West Bloomfield,,,not far from you/ it was common knowledge then you lived in the basic area but I heard you had left south to be with nascar. I mainly lurk here and read your posts sometimes but didn't know you had changed to logan

Just to be clear, my name is not David. I do not know David Vizard personally.

LoganD wrote: ↑Tue Mar 19, 2019 2:47 pm Just to be clear, my name is not David. I do not know David Vizard personally.

. sorry there I hope I didn't spoil your anonymity I should go back to reading It sems every time I post things go awry.

LoganD wrote: ↑Tue Mar 19, 2019 2:47 pm

slo-svt wrote: ↑Tue Mar 19, 2019 1:12 pm

LoganD wrote: ↑Tue Mar 19, 2019 12:55 pm 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?

Sumtingwong wrote: ↑Tue Mar 19, 2019 2:43 pm

LoganD wrote: ↑Tue Mar 19, 2019 12:55 pm 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.

Mr. vizard,,, I was not aware that was you///// and then I saw Rochester.

,i used to be in West Bloomfield,,,not far from you/ it was common knowledge then you lived in the basic area but I heard you had left south to be with nascar. I mainly lurk here and read your posts sometimes but didn't know you had changed to logan

Just to be clear, my name is not David. I do not know David Vizard personally.

I know David Vizard personally, I would like to state up to this point this thread has been interesting and fun. I have only one blocked guy from ST and it is not because I don't like him or his views are different than mine. I am pretty sure he cannot post on my threads so I will be blocking guys who are not positive. I don't care who you really are and I am not accusing anyone. I have had a bunch of threads shut down and it sucks. I personally like different viewpoints and I do have a lot to learn. So please guys, Thanks Charlie

Wong, I will state that for a street project like this charge motion will be important for torque. This slug may only get to 6000 rpm! Thanks, Charlie

This set of ported heads need a customer/forever home now.

What size engine? Is he going to dyno it? I what be shocked if it peaked past 5300 with the TPI runner length. Beautiful port work! I have not forgot to pour a head. will get to it soon.

Kenny M wrote: ↑Tue Mar 19, 2019 11:39 pm What size engine? Is he going to dyno it? I what be shocked if it peaked past 5300 with the TPI runner length. Beautiful port work! I have not forgot to pour a head. will get to it soon.

Hot street 355, 350+hp was asked for. I would like to beat that, yes dyno at end of project. Thanks,Charlie

Carnut1 wrote: ↑Wed Mar 20, 2019 12:08 pm Hot street 355, 350+hp was asked for. I would like to beat that, yes dyno at end of project. Thanks,Charlie

You should be able to beat that.
Make 1.1 LBs/ cube at 3500-4000 and it should hang on to enough TQ till 5500 to make over 350 HP.

I had a 355 with 882 heads, dual plane intake, 9-1 comp, and a rv cam make 380tq and 365hp. Your project seems more serious than what I had.

I say,... raise the bar some!

Randy

randy331 wrote: ↑Wed Mar 20, 2019 12:34 pm

Carnut1 wrote: ↑Wed Mar 20, 2019 12:08 pm Hot street 355, 350+hp was asked for. I would like to beat that, yes dyno at end of project. Thanks,Charlie

You should be able to beat that.
Make 1.1 LBs/ cube at 3500-4000 and it should hang on to enough TQ till 5500 to make over 350 HP.

I had a 355 with 882 heads, dual plane intake, 9-1 comp, and a rv cam make 380tq and 365hp. Your project seems more serious than what I had.

I say,... raise the bar some!

Randy

Well, he asked for 350. HaHa

Interesting thread. I had (have, as the engine is on a cart in the garage) a set of '217' heads on a 327 with a mild 214/218 cam. It ran pretty well considering that short block was flat worn out (40+year old OE GM build that was way beyond it's useful life - cylinder ridges and all). 217s are the same as 083s. Mine had 2.02 / 1.60 valves and nothing done other than a bowl blend, and a rather poor valve job from a shop that didn't do quality work (long story).

Sumtingwong wrote: ↑Tue Mar 19, 2019 2:43 pm

LoganD wrote: ↑Tue Mar 19, 2019 12:55 pm 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.

Mr. vizard,,, I was not aware that was you///// and then I saw Rochester.

,i used to be in West Bloomfield,,,not far from you/ it was common knowledge then you lived in the basic area but I heard you had left south to be with nascar. I mainly lurk here and read your posts sometimes but didn't know you had changed to logan

Why is everyone here so paranoid? Lmfao. This is getting comical.

At this point the base is flowing 235 cfm @.5" lift through head. The cross ram design has an s shape and changes from round to square to rectangular. The highest speed air is at the manifold to head transition. Thanks, Charlie

Are u flowzin the base+ head with a generous radius (putty) at the base inlet? Great thread.