A race bmw 316, m10, s14, m20, turbo, na, its been the lot!

[Graham]

Re: A race bmw 316, 240bhp Atmo M10 now going s14 power!

had another go at the flow bench today, with a very interesting result, the heads flowing practically the same as before its not the end of the world because i'd previously only opened up one port and i havnt really lost anything worth worrying about

its up 1 cfm in some places and down 2 in several others but in some matches the previous test, the only thing it did as i predicted was to loose at 0.050 lift, although at 0.100 it was slightly up which i wasnt expecting, in theory it should of lost at low lifts and gained at high, i can only conclude that the areas of the head i've been working on are no longer holding it back, it looks like either the std valve shape is wrong for big flow or its time to get some carefull and fancy seat cutting done

because im dammed sure theres more flow in there somewhere, 140 cfm isnt bad thats 20cfm up on about the best a conventionally modded pinto or std yb can muster but certainly isnt as good as it could be

[Graham]

Re: A race bmw 316, 240bhp Atmo M10 now going s14 power!

actually i think i've found something, the long side of the thread were it meets the enlarged port has something of a bump it, its hard to see but its there and is probably preventing air flowing nicely round the long side of the port, on a pinto which has little air flowing round the long side it would have little effect, but i know this head does flow a lot around the long side so the effects going to be greater,

only one way to find out, more grinding and meassuring..........

[caprimentle]

Re: A race bmw 316, 240bhp Atmo M10 now going s14 power!

the heads flowing practically the same as before

when you say the same as before, are you saying its now basically the same as a standard evo spec head now

[Graham]

Re: A race bmw 316, 240bhp Atmo M10 now going s14 power!

yeah its flowing the same as an evo spec head, the extra work hasnt given any more flow, that said it hasnt hurt it either, im confident i'll get some more flow from it

[Group4_Mark2]

Re: A race bmw 316, 240bhp Atmo M10 now going s14 power!

It would be great if you could take a silicone mould of the inlet port and then make a casting out of plaster. .That way you could experiment with the plaster cast rather than the real head and then when you find that elusive flow just transfer it to the real head. It must be nerve wracking grinding on your good head in case you go too far.

[Roadsport]

Re: A race bmw 316, 240bhp Atmo M10 now going s14 power!

Good thing its an alli head though. You can fill it back up to a some extent if you get somethig wrong.

[Graham]

Re: A race bmw 316, 240bhp Atmo M10 now going s14 power!

right had yet another go at the head last night, i removed the bump from the port, thinned down the valve seats and added a 30 degree back cut to the inlet valve,

i was pretty sure i'd made an improvement but doubtful i had made much difference.

and the flowbench proved me right, it started out good, with a 6cfm gain over the previous test at 0.050 but by 0.200 the gain was nothing and match the previous peak flow of 138cfm, still 2 cfm down on previous best.



frustrated i had a cuppa and put my thinking cap on, nothing was making much difference, the port which i'd tried part filling in various places, short side seats, i conclued either the port was too high or the wrong angle to suit the valve angle, velocity probes showed most flow happened in the top of the port, i then stuck some plastocene in the top of the port at the manifold end, and suddenly i had a flow change, it dropped suggesting i needed to remove material there, a bit of grinding and i had some more flow, over the next couple of hours i keep going back removing more and flow kept going up, as i removed more, i found it benificial to take some out in a few other places as well, the result was a LOT more alloy dust all over daves bench!









end result 158cfm thats more like it the heads probably capable of more even on std valves but i've got a figure im happy with... for now......

[caprimentle]

Re: A race bmw 316, 240bhp Atmo M10 now going s14 power!

feck me thats huge! how on earth you gonna get your manifold to fit

[Graham]

Re: A race bmw 316, 240bhp Atmo M10 now going s14 power!

of course there always room for improvement,

having nicked the flow figs for modified xe heads off cnc heads website i've got a comparison,



blue line is my s14 head others are std and large valve cnc xe's

[caprimentle]

Re: A race bmw 316, 240bhp Atmo M10 now going s14 power!

are your flow figures just done literally on one valves port with one valve open and not both ports feeding both valves with both valves open then, as surely just even with just one valve open, not opening up the other side of the port to match would affect the flow as they do share the same entry port.

[Graham]

Re: A race bmw 316, 240bhp Atmo M10 now going s14 power!

it doesnt make any difference whether you flow one or both valves, dave walker told me that, he learned it from wilcox tried it himself and proved wilcox right and i've since tried it and proved them both right!

[caprimentle]

Re: A race bmw 316, 240bhp Atmo M10 now going s14 power!

i'm amazed, you wouldn't think it would as it shares the same primary port. thats quite interesting that.

[Graham]

Re: A race bmw 316, 240bhp Atmo M10 now going s14 power!

its probably because the primary port is more than twice the area of the secondary

[caprimentle]

Re: A race bmw 316, 240bhp Atmo M10 now going s14 power!

true point, its amazing this nearly flows as well as a cnc machined modern head, very impressive result with like you say hopefull more to come.

as most of the air flows along the top of the port then i take it your going to have to make quite an upswept inlet manifold or otherwise all your hard would could be undone.

[Graham]

Re: A race bmw 316, 240bhp Atmo M10 now going s14 power!

cnc machining doesnt nec make a head flow more air it just makes it easy to get all the ports exactly the same and exactly the same on every head.

the airflow is pretty even across the port now showing the ports about right,

dont think manifolding willl be a problem