I'd ordered some .30 - .36 shims from CB on my last order, I figured that with the crank grind/polish I might have to take up some slack.
Forgetting of course that I have new mains too to take up that slack.
Ssoooo, 1st measurement, 45microns or 1.8thou (.0018"). Bugger. More clearance needed.
I rekn peak power of this motor at 4500rpm or so (baby cam with pocketed heads) so I need 4.5thou endplay (.0045"). Rev it to 6000, 6thou play, etc.
Not that I have any scientific basis for these ideas though.
Since CBs shims aren't much use to me I had to rummage through my stash under a few benches, but I got there in the end.
I ended up with 112microns or 4.5thou! Huh! How flukey is that!
Little penlight, masking tape, an offcut of brake airline, a manometer of dubious accuracy, and a big vacuum cleaner makes............
a velocity probe for mapping out high and low speed airflow thru a port, so I can maybe make them a bit better. Or worse maybe.
Well, if it works anyway.
This should keep me occupied and happily ignoring important stuff that needs to be done for hours, days, weeks possibly.
Until I eventually just save up and buy a set of CB Panchitos and plonk them down on a bog-stock 1600 motor and call it job done, which will happen, well, when I've saved up enough money!
OK, finished velocity-mapping (with yet more dubious accuracy.......) the ports on my stock replacement Empi heads.
The black stripey sections are the lowest airspeed bits, and the red-coloured bits are where the airspeed is higher than anywhere else. As expected, the airspeed is highest on the inside of the ports curve, not the outside wall. The difference is way more than double the airspeed.
I only checked it up to about .300" valve lift, as after that you'll probably have a cam, and rockers, and .......... Panchitos!!!
If you take too much off the red bits there's a chance of a hole out the head (big air leak, so measure it), if you take some of the black bits off you won't add much if anything. I usually just blend the seats to the ports under the valves (pockets), then clean them up a bit with good 3-angles on a high-flow intake valve. For the exhaust I pocket the seats, then round off the short turn (where the inside curve meets the seat) into a nice gentle radius and ignore the rest. Go easy though, taking only 2mm or so off the red bits adds nearly 10% to the total port volume, which is a lot........
It's really, really hard to find this stuff in pics almost anywhere, because most sensible people just buy Panchitos ( Oops! Did I say that again?), but if you like doing this stuff just coz you enjoy the process of getting dirty in the shed then here you go.......
Hope it helps someone if they see the pics.
PS: I hope nobody minds.
Hahaha! Never again! I can still remember how much my hands hurt, but they did work very well.
Then I progressed to these little carbide burrs in a drill, much faster and easier, but very bulky and heavy/unwieldy and they catch and shudder badly (drill speed isn't high enough), so you hafta be careful.
Next was the Dremel. Brilliant things, excellent job, heaps of really cool fittings too.......but........they burn out really fast. When all the smoke gets out they stop turning, go figure, huh? I used 3 dremels on my last bike 4 cylinder head.
And this is what I'll be using here, it's basically a bloody big 400W Dremel with an extended nose (to reach into the ports).
It uses all the Dremel fittings, can take a 3mm shaft tool or the bigger 6mm shaft carbide burrs (thats the aluminium ones lined up), $125 online. If you get one you are MUCH better off getting the variable speed model.
I also have valve seat cutters, but little experience with them (I always used to use stones for that) so I will do a heap of practise on them first so I don't need to spend extra time getting them fixed if I stuff it up.
With these heads I'm just doing a basic clean-up and getting the chamber CC's right for my compression. I'm not getting fussy about HP or torque as it all takes a heap of time for the work, and coz I want to go cruising in this little car RIGHT NOW!!!!
So if you clearance around the valves in the chamber out to an 87 or 88mm bore, like I did, then you gain another 5% at least in flow. Huh! Cool. Easy trick for more cfm.
But then the 85.5mm cylinders for a 1600 create a fat ledge at the head that stuffs the flow up, unless you clearance the cylinders too.
Worked fine on a 88mm bore using 44mm intake valves in the past (oh, and also for 1.94" valves on a 253, I think from memory?, etc), theoretically should work OK on a 1600 with less than 1/2 the HP I think.
We'll see hey?