AVL inlet cam is about.280" lobe lift. Rocker ratio is about 1.2. I say "about" because probably no 2 cams or rockers are the same.
Std Bullet cams and "S cams" are about. 312" lobe lift.
The AVL cams are the ones with the larger base circle.
If you want more low-mid rpm torque, then advance the cams with the Hictchcock 3-way pinion. Also, do the compression increase and set the squish. Do the tappets and cam spindles as reliability mods. I would also get the Wossner 87mm flat top piston, and put that in.
Don't do iron barrel performance cams for low-mid power. They are for upper rpm power. Don't do a bigger carb for low-mid power. Make a longer header and longer inlet stack for low-mid rpm power.
ACE, thanks, great info/advice. The basic principles take me back to V-8 tuning - advancing cams and utilizing long-runner tunnel-rams (/mopar cross-rams) for increased torque... and the opposite for high-speed power.
As delivered, the AVL seems a bit odd really - too big port, too small carb / header. Wonder if even back then RE had in mind the possibility of varying tuning as per market preferences. The big port would flow enough for 40hp and higher revs for places that wanted that, but the whole thing could be tuned down to run well below 2,000rpms, at 90mpg, where Indians largely like to keep 'em.
535 Wossner piston is out of stock at Royal Motorcycles, don't know what other sources there may be, but anyway their pricing at near $300 was way out of proportion for this project - believe it or not, I'll probably have less than half that much in the entire rebuild, with decent quality stuff. Didn't import bearings but the Indian NRB's are supposed to be decent (better than OE anyway), which is what I've got on the rod/crank. The 84.75mm piston (510cc), made here by SAM (OE-quality), cost me about $12 complete in Delhi!!! At any rate re-bore is done, piston fitted (.0025" clearance) and modded (2.5mm crown cut) as of last week, so think I'll stick with this for now.
To clarify, I don't necessarily need
more low end torque, I just didn't want to hurt it in pursuing the midrange / all-round performance.
I couldn't find the "3-way pinion" in the timing section at Hitchcock's. What is it exactly? If the stock cams have 40 teeth(?), then
advancing/retarding, with cams running at half-speed to crank, means 4-1/2 degrees per tooth?
Should both be advanced or could there be particular benefits in doing only one or the other?
Leaving aside aftermarket cams, is there performance to be gained by using standard CI units, being that the lift is apparently higher (my shortened cylinder could help compensate for the smaller base circle, I assume)? But would this extra lift additionally strain the marginal strength limitations of the thin AVL followers? You're so right about the manufacturing variations and as they say "the proof is in the pudding". I've ridden a number of stock AVL's from this fleet - a couple of them, despite having great compression and every indication of being pretty fresh felt like I was riding a 350 - in fact on one solo test ride I could hardly get ahead of a 350AVL that had two adults aboard. Switching carbs with that of a stronger-running bike had no helpful effect. I remember another "identical" bike that seemed a lot more powerful than all the others - on-throttle, the rear tire would struggle for grip on dry asphalt. The engine also vibrated somewhat more than the others. And I wondered, being that none of these bikes were modified, what was making the difference... Maybe it had the unintentional 1.3:1 rocker arms, or high-lift cams, or a lighter crank, or maybe the factory ran out of hot-tubes / silencer baffles - or maybe all the above???
I'd like to hear more about velocity stacks. Any calculators out there for optimizing lengths? UCE 500 has a pretty long runner directly from the "toolbox" filter to carb, which might be pretty effective, whereas the AVL's have that apparently useless intermediate "resonator box" which is what on the older models housed the filter itself. I mean, I'd like to know how long the stack / runner actually ought to be, depending on diameter, cylinder displacement, and proposed ideal rpm range. If some extra length is going to net me noticeable power where I want it (vs. something mounted direct on the carb), then maybe I should try to adapt the UCE's rubber tube and keep the filter in the toolbox (which I'd otherwise hoped to reclaim for, well, tools - or else lunch). Anyone out there actually experienced noticeable effects, or is this going to be pretty nuanced (my Honda 150 has probably ten-inch long stack right from the airbox, supposedly is tuned for torque, but still doesn't produce any oomph till 5,500rpm)?
Same goes for the header/pipe & muffler (silencer), of which from what I understand smallish diameter but unrestricted path is what we want for torque. I could see the point of extra length, too. But how large/long is actually ideal - any calculators out there? As mentioned above, my header is 1-3/16 ID from port to maybe end of the bend, opening to 1.5" in the straight section.
Re: carbs my thinking is that the orig. 28mm was really put there for cost reduction / fitment issues (tight around the tank mounts for typical CV diaphragm-chambers), and acceptable only because Indians typically like to run Enfields at very low revs - but that otherwise, strictly speaking, it's pretty undersized for the application. My 150 Honda came with a 28mm, and the donor bike for the proposed 32mm was a 220cc, its sibling being a 200cc with a 33mm from this same company (UCAL/Mikuni). CV's are a bit tolerant of oversizing but I don't think I'm in any danger of that, and I doubt my low-end or fuel economy would be affected (till riding hard). The UCE500's have 33's and are pretty grunty / efficient.
That said, anyone have a clue as to initial jetting on this? It's currently got a #115 main and a #15 pilot, as set up for a 220cc single; Would I have to be going to larger or smaller jets here (twice the displacement, more fuel demand, but presumably also bigger cylinder pulling more air through the same size venturi, thus more vacuum sucking more fuel up from the bowl - lower vacuum requires larger jets, right (?), which is why my 150 with the 28mm had a big #132 jet, whereas a Bullet 350 with a 28mm uses a #95???)? I've got a fairly wide range of jets on hand from 95 to 132 for the main, in pilots I think I've only got #20/15's. Any thoughts/experience here?
Still trying to decide about the tappet/guide upgrade...
The CI's stems are 9.5mm, the AVL's only 7mm, which does seem small considering the loads/speeds they're being subjected to. Fleet owner confirms he's never seen a failure in this whole decade in the context of (highly grueling) tours, but occasionally on privately owned and less carefully maintained bikes; Again credits the difference to his extremely frequent oil changes, which kinda makes sense: additive breakdown = more friction on lobes/tappets = greater side loads = greater stresses on that thin stem = more likelihood of breakage. Other possibility is partly RE's typical quality control - possibly some will never break, while others break early on / unpredictably?
Just having a hard time understanding how the AVL-upgrade engineers could've made such a "mistake". Could they have been assuming normal material strengths that in reality were never realized in Indian production? I'm assuming they were trying in thinning them to make the valvetrain lighter... And that gets me thinking of the problem these have already got with valve float - the CI tappets are definitely a LOT heavier, and I don't really want to get into aftermarket valvesprings and such.
Thinking more about it, also not very confident about the level of lathework possible locally - huge machine I've got available must have about a 2-foot swing and huge chuck, not very suited to small-diameter parts - I'd really rather be using a collet to hold the guides for this level of precision, and to save the threaded portion, from which I'd have to hold it - but have yet to find a collet-equipped lathe in this land. The OD is going to be critical as it's a press-fit piece (threads are only there to give the extractor/puller something to grip). Also a little concerned about any need of modded pushrods, as they wouldn't exactly be available roadside in the event of some failure whilst touring.
The CI/AVL tappets themselves measure almost exactly the same length, so pushrod length should not be much issue - but main trouble is that the CI's don't have the little socket built into the top of the tappet stem, which on the AVL's is what locates the pushrods. Guess I could make a little cap above the lifter stem as the CI's used, but with the socket on the top face? But likely won't find toolbits here locally for making that radiused recess, and probably there are material contstraints (tool steel or?). Tappet stems themselves presumably being hardened, don't think I could machine those sockets into the tappets directly AVL-style; And barring these options, we're speaking of hybrid pushrods (old-style lower ends with AVL top ends?) which may or may not be a pain to fabricate. Or am I just supposed to use the CI pushrods (are the tops the same, workable on AVL rockers?), whereby my CI-style "socket" is on the lower end of the pushrod, and would match up to the cap atop the lifter? In this case, does the stock length rod work? And if so with which - the AVL or CI cams?
Sorry, I must be exhausting you all...
And if I go further I'm going to get confused myself...
-Eric