Thank you ever so much guys for your kind words
and your encouragements.
Highly appreciated !!!
With your kind permission, a few questions & comments?
Absolutely!..Thanks for showing an interest in my little project.
I'm quite sure no-one knows more about supercharging old bikes than you Jeff.
Thanks for publishing your absolutely brilliant site: Supercharger Installation on Older Motorcycles
A fountain of info to be gathered there.
This is bored to the H-D 45 cylinder size, 70mm?
The SCTA class will be 500, not 650, since your actual displacement of 600cc is discounted by 1/3 for side-valve cylinders and heads. IIRC you must exceed 750cc to qualify for the 650 class (i.e., be illegal for 500).
Yep, but I'm running at the BUB Motorcycle Speed Trails, that does not go by the SCTA-rules
but goes by the A.M.A. rules (..and F.I.M. rules) that gives NO 'allowance' for side-valve engines.(
BTW AMA/FIM do NOT even consider the Indian engine to be a 'side-valve' at all (!!!)...
I checked that with the Tech. Inspector. Something to do with the very short lengths of Indian ...erh...non
I find that a little weird as the specific definition of "push-rod" in the rule-book reads:
"..with camshafts located below the cylinder head deck, push rods that open valves
with the use of individual lifters
...". No mention of length.
I would assume that the push-rod-class was set up to distinguish these engines from overhead valve engines,
but Hey!..it's their party and if I wonna join it, I'll go by their rules.
An idea would be to clearify by using the definition from 'Utah Salt Flats Racing Association"
"...Pushrod: “must have pushrod operated valves with camshaft located
at least one crankshaft (stroke) length below the OEM cylinder deck
or utilize OEM pushrod length at least twice the crankshaft stroke
....so anyway; it has to run in the 'Vintage' class; that is; engine manufactured before prior to 1956,
must retain O.E.M. heads and cases.(Rule '12.J.').
Are you using the same drive ratio for the Aisin as used on the automobile engine? IIRC that's about 1.25:1 (25% overdrive).
IMHO this isn't fast enough, and won't develop boost until far up the RPM scale.
I'll start of with something around 1 : 1,5 and probably move up to somewhere close to 1 : 2.
I'm in contact with a guy in Australia that has just finished his blown Triumph 650
using the same blower as mine. He runs close to 1:2 and develops around 6psi. at around 10000 RPM's blower speed.
Works just fine.
Now, I've looked into several sources of calculation pressure, drive ratio etc. etc.
both using the calculations on your site and from the old book
by Maurice Brierly "Supercharging Cars and Motor Cycles" and other places.
I bumped into a few problems; I needed to know the comp.ratio and the valve-overlap.:
...apparently no-one had ever measured the compression ratio on the 741 engine
so I did a low-tech measurement; glued a transparent plastic to the 'under'side of
one of the heads (with a head-gasket attached).
Stuck in a syringe and measured the quantity of water I could pump in:
...then calculated the comp. ration (in case of being bored to 600cc) to 1 : 6.
Now that's low
Same thing with the valve overlap. No where could I find any info,
so did a real
low-tech test. Sat up the cam'wheels' (cams are behind the wheels)
and held down the (non
)-push-rods with rubber bands.
...turned the wheels and by holding each of two fingers
on top of the in- and out-let (non
tried to feel the period where there was an actual overlap (both rods moved by cams)
Surprise: there was none...or it was negligible, to the point where my "test" couldn't detect it.
In all the literature on blowing (old) engines I've plowed through,
I'm told that 'low comp. ratio' and 'small overlap' is a good thing on a blown engine.
So this has got'a be good
I'd expect some fuel drop-out
in the plenum because of the large cross-sectional area.
Yep. I'm aware of this potential problem, but in order to get a proper
volume of the intake/plenum that's what I ended up with. There
is no practical provision for making it narrower (and therefore longer).
We'll see how it works out.
BTW: a 1940 military engine is 740, since the last 2 digits are the year.
Naaaa! I could be wrong, but I'm quite sure
all these engine are designated 741
irrespectively of the year of manufacture. Never seen an engine designated, let's say: 740 0r 742.
Did Rivera equip the carburetor for methanol as to needle & seat size?
Nope. The carb was a gift from a friend. Unknown former application.
I'll set it up myself. The rule of thumb seams to be to enlarge the jet to around
double size (double area of cross-section, so to speak) compared to running gas,
when running methanol.
I have a couple of books on SU carbs and some calculations relating to the subject
including haw to size down needle-profile etc. I'll give it a go.
One other problem when using the Rivera SU (compared to the car-application SU carbs)
is this thing here
a bi-metal mechanism that moves the jet 'down' when cold (to make the mixture richer on cold-start)
...here you can see it inside the float-bowl:
I'll have to '"kill" that thingy so it doesn't interfere with the mixture, what with running
alcohol that will make things cool down there.
That's a huge carburetor, which means that spring tension and needle
profile will be critical to get good atomization.
Yeah, I know, but that's the carburettor I had available,
and looking at it very un-scientifically, it kind'a looked "right" ;
almost the same cross-section on carb-outlet andblower intake
...and it being a CV-carb it will hopefully "self-adjust"(*) to the requirements
of the engine.
The carb/blower intake on the photos above (cut-off blower intake and cut-off carb. manifold...welded together)
will be replaced by this adaptor we made up a couple of days ago,
to go between carb and blower:
Is the cam timing doped out yet?
No. I do not plan to do anything in that department (..but I could be wrong is not doing so).
Remember; this is a low-tech attempt to spice up things...not to go for the ultimate power-gain
at the cost of loosing reliability.
On a side-note: I've installed a blower on my Honda GL1000
(60 cubic inch Magnacharger and double barrel Weber carb,)
with no other modification, including valve timing, and it goes like flipping stink.
Again; thank you guys
and thanks 'panic' for taking an interests and offering advise.
Please keep 'em coming.