Head Flow Charts

[Paul Wright]

I think World is leaving the spark plug out when they test!
I am pretty sure my numbers are accurate and the equipment is calibrated regularly. I noticed that Brezezinski reports similar numbers to mine in stock form though they advertise 225-230 cfm for their max ported version ($2,295 assembled!)

I figure another 10 cfm is not out of the question but that means opening up the chamber and thinning the push rod wall. I'm not sure I want to go that far. World may be reporting potential flow if blue printed, not "as recieved". Variations in testing techniques and other factors may influence the results, but I feel confident in my numbers.

I wouldn't be too dissappointed in the numbers. 214 CFM can support up to 440HP.
I don't think the engine will make that much but these heads are more than capable of around 400 hp. I'll copy the ports to the rest and maybe do some fine tuning. I can retest later. I might be able to get another 3-5 cfm. I'll need to cc the chambers and see how much I can unshroud the valves without putting the SCR in the toilet.

I didn't have any time left to test the camels. That will have to be another day also, but my measurements show most camel humps have the same cross section dimensions as the S/R's. While there may be some castings that have slightly better cross sections and certainly casting variations, but unless the push rod is moved you are constrained on width.

Brezezinski reports stock unported:
'492 heads flow 206 cfm Intake and 141 cfm exhaust.
Bowtie #14011034 heads flow 212 CFM Intake and 140 CFM exhaust.
Vortec '062 218 cfm intake and 150 cfm exhaust.

So Kev's ported heads are somewhere between stock Bowtie's and Vortecs. 214 cfm Intake @.525" & 149 cfm Exh. @ .600"

Here's the cross section difference between the Sportsman and the S/R.
The sizes are "as measured" though I'm guessing the offset is about .050" towards the pushrod side. By moving the pushrod slightly the dog leg straightens out a bit.
The port is higher as well. Notice the Sportsman cross section area* is increased significantly over "stock". (*note: Cross section was calculated with Solidworks Cad program which took into account the .125" radius)

This picture is not the port opening! It's the minimum cross section area inside the port at the pushrod bend. Flow velocity hinges on the minimum area. Peak torque rpm hinges on flow velocity. According to my calculations, Peak torque will be no higher than 3,200 rpm, depending on intake manifold, exhaust system and cam timing. This will help give us an idea on what stall speed you'll want for best acceleration.

[Tom Griffin]

I think swapping the S/R's for AFR's would help even more!


I was initially dissapointed in my AFR 190's, I had them flowed by two local engine builders and results were much lower than AFR posted on their website a couple of years ago.

Straight out of the box..
Intake
100 62 cfm
200 116
300 166
400 211
500 244
600 backflow (not sure what this means)

Exhaust
100 47 cfm
200 95
300 126
400 147
500 164
600 170
700 176

Tg

[Paul Wright]

Here are the graphs of the results I got before and after.
There's a kink that I think is the result of shrouding of the valve over .450" lift. I went back in and relieved the chamber slightly and that seemed to help. I was afraid to open them up further because of compression loss.
Clearly adding a big cam or 1.6 rockers to unported stock head has little or no performance benefit. Port matching helped mid lift flow but oddly no where else. Opening up the port to 1205 gasket size didn't help, in fact there was a slight loss in flow.
While this testing answered some questions it opens some new questions.
I'm wondering if smaller, less shrouded 1.94 valves might flow better with this chamber. Vortecs have 1.94's and they flow really good.
Since S/R's and camels have the same cross section, chamber and valve sizes they should flow the same...or do they? I'll have to go back and try round two.

[Paul Wright]

Here's the Intake Graph with the Stock S/R (similar flow as a "camel hump") for reference. One thing I noticed was the kink at .525" lift. If you only took data at .100" increments as magazines often do, this anomaly would not show up. The other surprise is Kev's ported S/R's flow better (247 cfm) than these stock Sportsmans (236 cfm).
That won't be the case when I get done with these. I know they won't be as good as Dave's AFR's but there will be an marked improvement.

[Paul Wright]

Here's the exhaust graph.

[Paul Wright]

Here's all the stock iron head intake flow data I have so far. These are actual tested numbers not magazine or vendor numbers.
The Vortec does best out of all of them at lifts under .460" which coincidently is the max lift on stock Vortec's.
Notice the 182's do much better at mid lift than the S/R's. Kev procured his S/R's from Ebay and they may have been factory rejects being resold (Bill Mitchell sells the rejects). I don't know that for a fact but the casting was real rough. Much rougher than ones I've bought direct. Certainly the flow is less than they advertise.

Next up is to make some measurements and then start grinding. Stay tuned!

[Paul Wright]

A good 3 angle with flow better than a mediocre 5 angle. Paul, thoughts?
People always ask me "what's best", but in truth the best one is the one that works best for that particular head combination. It's sort of like asking fisherman "what fishing lure is best?". Super Secret Valve grinds are as common as can't miss fishing lures. In fact there are virtually unlimited cutter combinations for the Serdi seat machine. They can custom make any seat profile you want. If you talk to ten head porters you'll probably get ten opinions. One thing they'll all agree on is the valve seat interface is definitely an area that can make a difference in flow.

Some of the things I tried were different brands of valves and different back cut angles. I was surprised by some tests that looked like they'd work, but only made the flow worse. You can gain peak lift flow at the expense of low lift flow or gain low lift but lose peak lift or you can screw it up everywhere. It's real tedious to test seats scientifically. Machining a head over and over isn't a reliable way. Probably the best way is with a flow box with removable seats. That way you can swap valves and seats quickly so it's consistant.

Here's just one test sequence I ran that tested a particular angle combo on the exhaust.
If you just consider peak flow then test A is better. However, B flows much better at low to mid lift. Keep in mind that exiting exhaust pressure is highest when the valve is just lifting off the seat. Pressure is lower at peak lift and the valve spends little time at max lift so big gains at lower lifts are more beneficial than small losses at peak lift values.... (unless, of course, you are just into bragging).

[DriveWFO]

What a great thread! This has to be a stickey with all this good information. You do raise another interesting question, tho. If the stock vortecs are about "flowed out" at about 0.450, what benefit if any is there to the Scoggin Dickey mods that get them up to 0.525 lift? ...or am I reading your graphs totally wrong (the most likely explanation!:D )

Dave

Going a little beyond that point will let the valve operate in it's "max flow" range twice (once while opening, again while closing). Here's a graph comparing my 062 Vortec castings, stock VS. my competition valve job. This is with the stock 1.94/1.50 valves. Aftermarket valves would more than likely yield even better results.