Let's see how much m20 heads suck.

[ForcedFirebird]

Pretty sure the valve angle is 22*

Finally had a chance to repeatably measure this for a consensus. 22° +/- .3°

Question- Is there a sizable difference between doing a standard 30-45-60 cut with 30deg back-cut valves vs. whatever angles you've come up with?

Short answer, yes.

[4x4_e30]

I got 22deg as well. I have the head reverse engineered to the best of my caliper measuring ability, put a degree finder/ dial indicator on the cam and got a rough profile. Pipemax gives me a target duration at .050" of cam lift, so I was/ still am kind of in the dark as to what that equates to in valve lift. Rocker ratio's are still perplexing me, CAT cams specs show 1.61:1 at max lift, but my measurements on the stock cam/ valve arrangement put me closer to 1.45:1, and my model gives me 1.55:1 ratio.. I pretty much concluded this was all a huge waste of time, and I'll just go with the cam that has the highest lift with least amount of duration.


My computer isn't fast enough to get the mesh settings I'd like so the flow numbers are meaningless, looks cool though.


As far as seat angles go, I went with a Goodson FT-45063U1 cutter per advice from Rama, that is 25 45 60 with a 1.5mm seat width then going to do a 75 deg bottom cut to meet the throat. I got the RHD engineering 44.5mm intake valves, machine shop is putting the bigger seats in next week (SPI SB1812-10) throat will be 39.5mm. I'm leaning towards shaping the roof of the port like the TK head(s), then the rest will be ported to match my target CSA, biggest SSR possible, with a slight taper to the manifold. Hopefully I'll get to >200cfm by the time I grind through my 2 practice heads.

All I need now is someone with a calibrated flow bench to send my orifice plates to...

[e30RS]

Those are impressive number anywhere near 220.

[decay]

i know i'm late to this thread, but if you had any before/after bench numbers specific to the 731 head getting the valve upgrade, i would be interested. see sig for why.

[ForcedFirebird]

i know i'm late to this thread, but if you had any before/after bench numbers specific to the 731 head getting the valve upgrade, i would be interested. see sig for why.

See post #120 ;)

[decay]

See post #120 ;)

i saw that, which is what made me ask the question- 885 valves in a 731 head is where i'm likely to wind up- do you have a baseline on an unmodified 731?

[ForcedFirebird]

Found some more on the intake using a stock valve. Ignore the name of the head, got sick of lugging and bolting full heads on the bench, so chopped one up into single cylinders for research purposes. ~185-ish at .400 has been pretty consistent with the valve angles I've been using, tried something new and got another 5cfm. The first test is a random selected stock port for the database. The second two tests were done back-to-back with the additional found angle (that actually helps).

When time permits, will test the same port with a Supertech valve with the 6mm stem, as well as a standard +1mm valve, then again with the Supertech +1. As mentioned earlier in the thread, simply cutting the seats for a larger valve hurts flow, the angles have to change for larger valves to work proper.

i saw that, which is what made me ask the question- 885 valves in a 731 head is where i'm likely to wind up- do you have a baseline on an unmodified 731?

731 mods will be soon. The 885 valves are a little large for the 731 seats, so have a plan for that. Member here ordered a modified 731 head. :)

[ForcedFirebird]

+1mm valve, mild porting, 3 angle valve job. Pretty sure there's more still in there (again random stock port drawn from the database)....

[digger]

thats starting to get very good that cracked one you gave me went 200@400 and 216@ 500 +2mm different bench of course so they are probably as transferrable as the ole dyno. Amazing how little material needs to be removed.

proper cam, CR and ITB's thats easily 270+whp kick some 4V ass. Got a cam lobe thats 14.5mm lift in the works

[ForcedFirebird]

Yeah, well, typically clients like me to be all hush-hush, but don't think this guys cares....



up-cycling cracked m20 heads :)


Yes, very little material, and because of that, doesn't take much to botch it, either.

...and yeah, benches are like dynos, but these Flow Quik benches seem to be very close to SuperFlow and the pass around plates help get your calibration spot on. Have though about adding additional pitot tubes etc to get analog readings to verify, but as long as the FQ is calibrated often, it's been working just fine.

[hasa]

Hey I want to ride on this topic as here are all the "flow" guys hanging around. Ignore if seems being inappropriate.

How much does the throttle shaft and butterfly disturb flow compared to straight tube? My motivation to this is that I have 40mm roller barrel ITB-setup on the shelf (basically a straight through tube at WOT). Trying to figure out if it would flow enough for a M20 stroker, when combined with a properly ported head like above (+200cfm).

[ForcedFirebird]

Hey I want to ride on this topic as here are all the "flow" guys hanging around. Ignore if seems being inappropriate.

How much does the throttle shaft and butterfly disturb flow compared to straight tube? My motivation to this is that I have 40mm roller barrel ITB-setup on the shelf (basically a straight through tube at WOT). Trying to figure out if it would flow enough for a M20 stroker, when combined with a properly ported head like above (+200cfm).

Pretty negligible in the grand scheme of things (the throttle plate/shaft). I have seen people do all kinds of things like cutting the shaft in half and leaving the threads for the plate, knife edging the plate etc, but I can say holding a ~.080" piece of metal in front of the bench during a flow test doesn't show much - and leaves room for accidents like sucking a throttle shaft screw into a chamber. Typically when flowing a package, the TB will get mounted and throttle plate pinned open to simulate actual conditions.

40mm ITB's is a great size for an m20 - even 42mm (which might be similar cross section to roller 40mm at WOT).

Have some more numbers from last night. Ended up staying quite late, then the software crashed and lose the last few tests, so called it a night. (bad habit of not saving enough). I am having trouble removing the trough at ~.3-.4. Low/high lift seem to have the biggest gains. Hoping to see stock 24v 400 casting numbers, but still in the low 21x's. Have a feeling the CSA is about to get too large at this point and gains to be reversed.

EDIT: You can see how little work was done with the die grinder in the last pis posted. The floor doesn't show any work and the coloration difference is actually a closed valve.

[digger]

Pretty negligible in the grand scheme of things (the throttle plate/shaft). I have seen people do all kinds of things like cutting the shaft in half and leaving the threads for the plate, knife edging the plate etc, but I can say holding a ~.080" piece of metal in front of the bench during a flow test doesn't show much - and leaves room for accidents like sucking a throttle shaft screw into a chamber. Typically when flowing a package, the TB will get mounted and throttle plate pinned open to simulate actual conditions.

40mm ITB's is a great size for an m20 - even 42mm (which might be similar cross section to roller 40mm at WOT).

Have some more numbers from last night. Ended up staying quite late, then the software crashed and lose the last few tests, so called it a night. (bad habit of not saving enough). I am having trouble removing the trough at ~.3-.4. Low/high lift seem to have the biggest gains. Hoping to see stock 24v 400 casting numbers, but still in the low 21x's. Have a feeling the CSA is about to get too large at this point and gains to be reversed.

EDIT: You can see how little work was done with the
die grinder in the last pis posted. The floor doesn't show any work and the coloration difference is actually a closed valve.

I doubt you could ever get 24v numbers (240@500 )for flow especially on lift point to point comparison. but a 2v will make equal power with less flow anyway

as for the shaft it comes back to the power level. I’m not sure a static flow bench is the right tool to evaluate it as it doesn’t consider what the engine needs/ wants or can utilise

[ForcedFirebird]

Yeah, looked up some 24v we flowed, and not even going to touch stock lol. Maybe see m54 numbers. I forgot how much the 24v can flow with +1 valves and light work.

[digger]

Yeah, looked up some 24v we flowed, and not even going to touch stock lol. Maybe see m54 numbers. I forgot how much the 24v can flow with +1 valves and light work.

yeah m54 at peak youre already there iirc, through middle unlikely

done an N52 ?