more intake flow with smaller and recessed intake valve

[Sir Yun]

hi,

just checking if somebody has found this as well .

it's an A-series Siamese port so zero valve angle , 90 degree port with a ssr half an inch high.

modified a closed chamber to an open chamber design and roughed in a seat to fit a 32 mm valve that is not shrouded much . some flow gains but not great and noisy ,so needs work. Just as an idea I put in a 29 mm valve and flow-tested again . it now gains about 8-12 cfm vs the stock version throughout about the entire lift range ( ca 20%)., quite bit more than the bigger valve . This mid lift gain has been described before for this head but using the same size valves and recessing
looking at the exit geometry of the seat area it makes sense that the smaller valve has a better geometry at low to mid lift

seat is a 60-45-30 (but not much more than a break a thou or two wide) and the valves had no back cut (yet).

anyone had something similar on a different head ?

cheers JR

[Cubic_Cleveland]

If I understand you correctly, the top 30 cut is only a few thou wide? If so, you will definitely pick up flow and flow quality sinking the valve like you intend and having a much larger top cut. Do a search on here for discharge coefficient, posts by Darren Morgan, Erland Cox, and others should help you out and point you in the right direction.

[cjperformance]

X2 as above and Go into the Advanced engine tech forum here and find the ' pressure recovery in the combustion chamber ' thread aswell.

[Sir Yun]

Thanx I re read that thread. it's probably something along those lines. back then I even made an adaptor to sit the head on the manifold to do readings with a pitot but never got around to using it. I should get that running

This is cooking my noodle. I retested the whole lot and I changed a few minor things (position on test bore was a tad off) and now the 29 mm valve is just slightly better than the 32mm, but still better.

[lada ok]

" Do a search on here for discharge coefficient " .... and ....

" pressure recovery in the combustion chamber "

what a load of meaningless SH ..

So you change the dis / co ... did that flow more or less ? .... no ! you made a real change ... the valve
pressure recovery ? how do you measure that ? if you want to recover energy, you have to buy or trade it vel < > pres PE < > KIN HOT < > COLD
how can you accurately measure such a tiny tiny difference called " pressure recovery " when pistons are pumping and sonic pressure waves are smashing and bashing their way past valves &c Forget that theoretical rubbish, you carry on doing it the right way

now ! back to your trials, doesn't surprise me in the least that a smaller valve flows better, perhaps better relationship between port / bowl / chamber masking
I know that the 1600cc Ford Kent engines with the Heron head as used in Formula ford went way better by counter sinking the intake valve 0.100 " +/- and developing a small radiused chamber , and a fair bit of cheating went on as well, like canting the intake valves about 4 +/- deg, just enough to not notice it
'

[wyrmrider]

sinking the valves also cuts down on backflow several threads on this

[cjperformance]

" Do a search on here for discharge coefficient " .... and ....

" pressure recovery in the combustion chamber "

what a load of meaningless SH ..

So you change the dis / co ... did that flow more or less ? .... no ! you made a real change ... the valve
pressure recovery ? how do you measure that ? if you want to recover energy, you have to buy or trade it vel < > pres PE < > KIN HOT < > COLD
how can you accurately measure such a tiny tiny difference called " pressure recovery " when pistons are pumping and sonic pressure waves are smashing and bashing their way past valves &c Forget that theoretical rubbish, you carry on doing it the right way

now ! back to your trials, doesn't surprise me in the least that a smaller valve flows better, perhaps better relationship between port / bowl / chamber masking
I know that the 1600cc Ford Kent engines with the Heron head as used in Formula ford went way better by counter sinking the intake valve 0.100 " +/- and developing a small radiused chamber , and a fair bit of cheating went on as well, like canting the intake valves about 4 +/- deg, just enough to not notice it
'

re the ford kent heads you mention, does this not describe a modification that aided pressure recovery etc??

[cjperformance]

Thanx I re read that thread. it's probably something along those lines. back then I even made an adaptor to sit the head on the manifold to do readings with a pitot but never got around to using it. I should get that running

This is cooking my noodle. I retested the whole lot and I changed a few minor things (position on test bore was a tad off) and now the 29 mm valve is just slightly better than the 32mm, but still better.

I am not at all familiar with the heads from these engines but would be interested to see a before and after pic of the chamber if possible? Cheers

[Cubic_Cleveland]

" Do a search on here for discharge coefficient " .... and ....

" pressure recovery in the combustion chamber "

what a load of meaningless SH ..

So you change the dis / co ... did that flow more or less ? .... no ! you made a real change ... the valve
pressure recovery ? how do you measure that ? if you want to recover energy, you have to buy or trade it vel < > pres PE < > KIN HOT < > COLD
how can you accurately measure such a tiny tiny difference called " pressure recovery " when pistons are pumping and sonic pressure waves are smashing and bashing their way past valves &c Forget that theoretical rubbish, you carry on doing it the right way

now ! back to your trials, doesn't surprise me in the least that a smaller valve flows better, perhaps better relationship between port / bowl / chamber masking
I know that the 1600cc Ford Kent engines with the Heron head as used in Formula ford went way better by counter sinking the intake valve 0.100 " +/- and developing a small radiused chamber , and a fair bit of cheating went on as well, like canting the intake valves about 4 +/- deg, just enough to not notice it
'

I don't quite understand what your babbling, but if something helps make power I try to find out why, not just "forget that theory crapola". I miss-spoke, and cj said what I was trying to, although discharge coefficient is some good reading on big valves not always being better.

Have fun in the Stone Age destined to repeat the same mistakes over and over Lada. How's those 2013 Ferrari F1 engine tear down pictures going??

[cjperformance]

" Do a search on here for discharge coefficient " .... and ....

" pressure recovery in the combustion chamber "

what a load of meaningless SH ..

So you change the dis / co ... did that flow more or less ? .... no ! you made a real change ... the valve
pressure recovery ? how do you measure that ? if you want to recover energy, you have to buy or trade it vel < > pres PE < > KIN HOT < > COLD
how can you accurately measure such a tiny tiny difference called " pressure recovery " when pistons are pumping and sonic pressure waves are smashing and bashing their way past valves &c Forget that theoretical rubbish, you carry on doing it the right way

now ! back to your trials, doesn't surprise me in the least that a smaller valve flows better, perhaps better relationship between port / bowl / chamber masking
I know that the 1600cc Ford Kent engines with the Heron head as used in Formula ford went way better by counter sinking the intake valve 0.100 " +/- and developing a small radiused chamber , and a fair bit of cheating went on as well, like canting the intake valves about 4 +/- deg, just enough to not notice it
'

I don't quite understand what your babbling, but if something helps make power I try to find out why, not just "forget that theory crapola". I miss-spoke, and cj said what I was trying to, although discharge coefficient is some good reading on big valves not always being better.

Have fun in the Stone Age destined to repeat the same mistakes over and over Lada. How's those 2013 Ferrari F1 engine tear down pictures going??

[miniv8]

How big is the bore?

[Sir Yun]

the port is a shared siamese config.
bore size is 64.5 mm but i will use 100 over pistons.
i tried adding a nice convex dam on the plugside to see if you make the transition better.. zero difference.
then I did a bare port flow with stem and found out that the port hits a wall at 73 cfm .

then i basically took a bunch of putty and filled in bottom of the shared section so that there is a smooth upward curve to the ssr for both ports
and bare port flow jumped to 96 cfm..

so i will try first to get the basic csa 's in the ballpark then continue the seat work

[Sir Yun]

well. strike the gains. I F#4ed up and forgot the put in the sparkplug that'll teach me to tinker this late when it is bloody hot. still stalls like a mother at 75.

[billet]

Too funny, while I think everyone has had way more of those type of days then many would admit

[cjperformance]

well. strike the gains. I F#4ed up and forgot the put in the sparkplug that'll teach me to tinker this late when it is bloody hot. still stalls like a mother at 75.

Classic