to fast over SSR

[Walter R. Malik]

% of valve diameter is what most are referring. For a given valve size you can do the seats a hundred different ways that could give you different throat % if using a valve seat reference. Typical conventional seats has the seat OD the same as valve OD so it wouldn't matter. Throat % of valve od makes sense to use since that indicates how much room you have to make your valve seat and bottom cuts in any manner you want.

I had not heard/seen anyone mention throat to valve seat % before reading it in this thread.

Rick

I have been using actual seat O.D. for over 30 years to measure the true percentage difference and, as I said ... anyone can use whatever dimension they want to use.

EVERY single head from any O.E.M. manufacturer, (MILLIONS of heads), has the seating area considerably inboard of the valve head diameter. Now they certainly aren't race heads but, I definitely would consider them CONVENTIONAL, especially when trying to make comparisons.

Again, use whatever dimension YOU want.

[zums]

Just work slow and make a flow test ( keep good notes and take photos ) after every .030" you remove to get a good grip on how things are trending.
Keep a close eye on your Intake flow numbers @ .200" and .550" , you would be doing well to have 140 cfm or better@ .200"@ 28".
Clay can be your great friend as you can add it in at places to see how fast flow numbers change / go down and by doing such you can then judge with good certainty what parts of the port will thru rework provide the most flow gain for the least amount of port enlargement.

Steve, those heads have real good Exh numbers at .100" and .200" for a 1.50" valve with also coming close to the ports peak flow at around .400"!
Let us know before you go head long into reworking the Exh ports.

Whenever port a head 98% of the time I am doing a valve job to some extent just to get the main seat out to with in .010" to .005" of valve OD so valve ODis what I judge the Throat percentage off of.

Where is the piston @.2 valve lift, why would you want 140 cfm @ that lift
Tom

[Rick360]

Just work slow and make a flow test ( keep good notes and take photos ) after every .030" you remove to get a good grip on how things are trending.
Keep a close eye on your Intake flow numbers @ .200" and .550" , you would be doing well to have 140 cfm or better@ .200"@ 28".
Clay can be your great friend as you can add it in at places to see how fast flow numbers change / go down and by doing such you can then judge with good certainty what parts of the port will thru rework provide the most flow gain for the least amount of port enlargement.

Steve, those heads have real good Exh numbers at .100" and .200" for a 1.50" valve with also coming close to the ports peak flow at around .400"!
Let us know before you go head long into reworking the Exh ports.

Whenever port a head 98% of the time I am doing a valve job to some extent just to get the main seat out to with in .010" to .005" of valve OD so valve ODis what I judge the Throat percentage off of.

Where is the piston @.2 valve lift, why would you want 140 cfm @ that lift
Tom

My 18º dart heads with a 2.15 valve only flow 134cfm. I guess they are junk. Only 870hp 434ci.

Steve-don't worry about the low lift flow and don't EVER give up flow (even a little bit) in mid or high lift to gain flow at .200" lift.

Rick

[Walter R. Malik]

Steve-don't worry about the low lift flow and don't EVER give up flow (even a little bit) in mid or high lift to gain flow at .200" lift.

Rick

That statement is painted with an awfully wide brush ... with an N.H.R.A. "stocker" with a combination where only .382" to .390" intake valve lift is allowed; pretty much all the flow you can get anywhere above .075" is useful.

[Rick360]

Steve-don't worry about the low lift flow and don't EVER give up flow (even a little bit) in mid or high lift to gain flow at .200" lift.

Rick

That statement is painted with a pretty wide brush ... with an N.H.R.A. "stocker" which only is allowed .382" to .390" intake valve lift, pretty much all you can get anywhere above .075" is useful.

Maybe a bit broad, I haven't built one. Maybe the right number for a Stock class sbc would be <.150". Likely other engines/combo's I am not familiar with that may not apply perfectly, but in general, low lift flow (may be different lift value for different engines) is either unimportant or detrimental to power production.

Rick

[mag2555]

How is it that so many builders find it hard to see the big link between good flow numbers @.200" or so and how much VE the motor makes due to scavenging with a well tuned Exh system?

[CGT]

How is it that so many builders find it hard to see the big link between good flow numbers @.200" or so and how much VE the motor makes due to scavenging with a well tuned Exh system?

Maybe it would clear it up for you to display your highest ve achieved with this process?

[steve cowan]

Hi Chad,
i am 18 pages into reading project SN again,there is some great information provided by you guys on cam timing,valve events,seat angles etc,really appreciate that thread
for sure,can you give me an update on where it ended up,i understand there was some ring seal stuff going on and i understand you a deep in the LS3 stuff at the moment,just curious that's all

[mag2555]

Well on the flip side of the issue you comment on CGT maybe you can provide evidence as to why it would not?
Let's see now about this.
1) both valves open at overlap.
2) The tune of the Exh system is yanking on the Intake column back thru the Intake valve with many times the 1" depression that a cylinder ever see's across it, but there's no benefit to this to you in a NA motor?

You can think your way, but thanks a bunch , I'LL just keep looking at things like this my way!

[68corvette]

Maximum potential VE increase depends on compression ratio.
The higher the CR, the lower the calculated increase potential is.
Increase potential is simple to calculate by calculating swept volume percentual volume ratio compared to cylinders displacement volume.

[CGT]

Well on the flip side of the issue you comment on CGT maybe you can provide evidence as to why it would not?
Let's see now about this.
1) both valves open at overlap.
2) The tune of the Exh system is yanking on the Intake column back thru the Intake valve with many times the 1" depression that a cylinder ever see's across it, but there's no benefit to this to you in a NA motor?

You can think your way, but thanks a bunch , I'LL just keep looking at things like this my way!

Oh I get it now.

[mag2555]

Agreed 68corrvette , the size of the chamber that the Exh has to suck down first before it sucks on the Intake port is a factor, but percentage wise on race motors its not that big a spread because even though the chamber may be bigger in a 14.5 comp 632 cid motor as compared to the same compression 540 cid motor , the bigger motor is making a somewhat bigger depression in the Exh system also.

And by the way, on a flat out race motor I am not saying that you should for go high lift flow for the sake of low lift flow but there is a balance to things one you lock down the power band that the motor will need to proform its best in!

[CGT]

Hi Chad,
i am 18 pages into reading project SN again,there is some great information provided by you guys on cam timing,valve events,seat angles etc,really appreciate that thread
for sure,can you give me an update on where it ended up,i understand there was some ring seal stuff going on and i understand you a deep in the LS3 stuff at the moment,just curious that's all

SN is back together, ring seal issue fixed . Just waiting on some more comfortable weather to be in the dyno room. I'm still planning on base lining with the bullet cam, then trying the Comp. Pm me if there is anything your interested to know....and yeah, I think their is a lot of info in that thread that is overlooked by many.

[randy331]

How is it that so many builders find it hard to see the big link between good flow numbers @.200" or so and how much VE the motor makes due to scavenging with a well tuned Exh system?

I'd say it's because most of us aren't up to your level of understanding of the ICE.

Randy

[steve cowan]

hi guys,
during the week i made a template of one of the stock SSR,i used this a reference for when i took the SSR down from 1.130'' down to 1.050''.
i retested this morning,test correction and leakage accounted for,CFM is down a couple after 0.500'' lift,is this a issue?? velocity is more realistic and stable,the port sounds quieter and smoother now,please let me know what you guys think looking at my test data,all velocity was taken half inch prior to the SSR apex,velocity at port opening at all test pressures was approx 250-260 ft/sec.

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pay no attention to velocity,was done at full lift and different depressions

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010.JPG

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hopefully my diagrams are easy follow,seems the fastest velocity now is just past the PRP area,would this require to be slightly wider in that area??
done final measurements and cc the intake port,the PRP was measured at the narrowest area around the bulge.
AVG PORT CSA = floor + roof divided by 2 = 5.51'' no radius factored in
intake port CC = 178 cc
1.94'' intake valve - throat is @ 89.5% = 1.73''
PRP = 1.01'' x 1.77'' = 1.81'' no radius factored in,
any feed back appriciated.
PS - not taking radius into the equation is it a big deal??????????