Topic: The World Wide Web of Performance Mods

[BomberMann650]

The YouTube Algorithm floated this video to the top of my screen.
Another of the many eastern hemisphere engine parts fabrication videos out there.

So this individual has himself a small 2v camshaft, a couple lathe chucks, a grinding wheel and...
and a Need for Speed.

By the end, you can see that he reduced the base circle of the camshafts.  Then handily (literally hand) refinished the ramps.
So the internet debates the big base vs small base performance characteristics. 
Tappet rocker follower setups, can they achieve more lift or not?  The internet is divided.  Pushrod guys exit the chat.  The schools of cam measurements discredit each other, while shim under bucket types think the added reach on the valve stem will net gains.
Then the metallurgist chimes in and it all goes to heck.

So, fact or fiction? 

[Terry in Australia]

Those South East Asian guys are fantastic, I like watching "Le Dan" building 4 cylinder engines out of old singles, converting 4 strokes to 2 strokes, etc etc. Reducing the base circle to increase lift is as old as time, I have a dozen CB750 cams here, some OEM and some aftermarket, with several base circle sizes. Reducing base circle sizes also reduced the need to hog out the cam cradles in CB750's or the cam covers in Kawasaki Z1's for "high lift" cams. I love that guys work, he probably made all the tools that he used, including his lathe and grinder.  

[BomberMann650]

I would try it, if I also had a 2v single to experiment on.  Repeatability across 8 lobes with all manual equipment could quickly fall into the realm of diminishing returns

[Terry in Australia]

You’d need a cam grinder to do it properly, the one that he made is excellent, when I bought my RC51 I couldn’t find any aftermarket hot cams for it, but saw that some other RC51 guys were getting their stock cams reground to reduce the base circles, and were very happy with the results.

[scottly]

One of the guys from my old neighborhood did a cam for a Briggs & Straton on a bench grinder by hand. The same guy once made an expansion chamber for a Cox model airplane engine. Both attempts were somewhat successful, but the actual power increases weren't that great. You had to give the guy credit for trying.  

[Terry in Australia]

My cousin is the best motorcycle mechanic/untrained engineer I've ever seen. When he had his shop he did a huge business fixing bikes, chainsaws, pumps, generators, even cars, that no-one else in a 500 mile radius would touch. I've seen him weld/regrind a cam's profile for ancient British, American and European engines and put them back together to work better than they did when new. He retired a couple of years ago but works one day a week to help a guy who fixes Euro-trash cars like Mercedes, BMW, Alfa's, Fiat's, Porsches, etc, that dealers won't touch if they're over 10-15 years old. I wish I had half his skills.  

[BomberMann650]

Stories like this make me sad about the local cam shop - which has a old commercial repeater grinder to make cams.  Yet they don't know how to make the guide plates for their grinder.  So when you call in, if there's not a tool on their shelf for it, they can't make it.  Even if you had a complete cam card to hand them.
They stay busy enough working on chevy parts.

[grcamna2]

I respect individuals & businesses they manage when they do their best with what they have and 'raise the bar' bit by bit to accommodate their customers,rather than telling them 'sorry,we don't do that'.
A fine example of that is forum member here 'godffery' and all the different services he offers to his customers.

[BomberMann650]

Considering performance - rocker arm ratios

Popular pushrod engine mod.  Does it apply to tappet followers?

Armed with a tig welder and grind stones, can someone achieve additional lift by moving the contact patch of the paddle?

[grcamna2]

Considering performance - rocker arm ratios

Popular pushrod engine mod.  Does it apply to tappet followers?

Armed with a tig welder and grind stones, can someone achieve additional lift by moving the contact patch of the paddle?

I'd like to see someone do a bit of research and do something on a small scale,with the proper machine tools and some experience gained along the way.I know MegaCycle charges their $$$ for camshaft & rocker modifications/improvements.
A person can give it a real Go and perfect their skills. 

[BomberMann650]

Considering performance - rocker arm ratios

Popular pushrod engine mod.  Does it apply to tappet followers?

Armed with a tig welder and grind stones, can someone achieve additional lift by moving the contact patch of the paddle?

I'd like to see someone do a bit of research and do something on a small scale,with the proper machine tools and some experience gained along the way.I know MegaCycle charges their $$$ for camshaft & rocker modifications/improvements.
A person can give it a real Go and perfect their skills. 

I gave it the ol college try.

I was able to snag the oem cam specs from a post here.  Verified that as a control. 
Stock 550 intake lift is indeed .272"
The rocker arms, that was interesting to measure.  But I got the numbers and essentially, they're 1:1 - some discrepancy in either my measurements or factory production, they could range 1.01x - not a significant figure according to my chemistry teacher.  I digress.
A little sharpie blue, a scribe, and a hot date with the belt grinder later, I was able to move the peak of the paddles radius inboard.  Using the wear pattern on the used part as a reference, i scribed a line 3mm inboard.  As described in the video.  I was aiming for 2-1/2mm but may have overshot.  Very small target for a quick hand grind.

Tl:dr - the calcuated ratio ended up around 1.16:1 and netted a pretty handsome increase in lift vs stock.  From 272 to up about 315.
I cannot report on any effect in cam timing open/close - and the dwell at full open seemed a little brief.
It would be a helluva way to cheat the rulebook in the vintage production class.  Setting up more tooling to do this repeatedly would be necessary on anything with more than 2 valves and a single cylinder.

I'm also thinking it may be simpler to cut then weld the rocker arm follower back on.  The thickness of the cutoff wheel (or bandsaw blade) would suffice for this small amount of change in ratio,. And would preserve all the radiused face on the part.  They are a ferrous casting, so dc pulse tig should be able to manage.
The cut n weld method may also enable me to do one more mod to the valve end of the rocker.  The tappet adjusters from harleys street 500 have a rotating head.  I could maybe budge the padde upward to offer some additional clearance for the ball and socket joint.

Fwiw, I scheme these things up because I'm bored and have more tools than i do money.

[Terry in Australia]

Are you going to get the rockers re- hard faced after grinding off the old hard facing, Cowman? I don't think they'll last very long otherwise.

[BomberMann650]

Are you going to get the rockers re- hard faced after grinding off the old hard facing, Cowman? I don't think they'll last very long otherwise.

That's one more consideration for simply cutting the whole thing off.

The welder supply store does sell hard facing rod.

[Terry in Australia]

I wonder why I’ve never seen re-profiled rockers for CB750’s sold by all the usual suspects? Does re-profiling them make them weaker, or have some other affect? On the face of it (pun intended) re-profiled rockers seem to be a better option than a lumpier cam?

[BomberMann650]

I wonder why I’ve never seen re-profiled rockers for CB750’s sold by all the usual suspects? Does re-profiling them make them weaker, or have some other affect? On the face of it (pun intended) re-profiled rockers seem to be a better option than a lumpier cam?

This mod may effect the open and close timing of the valves.  An adjustable cam sprocket may be able to compensate.
Either way, not a drop-in stock setting job.

And yeah, if I could zero in on a more modest 1.11:1 ratio, it would take a 650 cam up to race cam lift.  Wether the overlap would allow such tom-foolery idk.

I'm obligated to say this is stupid and incredibly dangerous and nobody should do it.

[BomberMann650]

I will be the first to admit, this belongs in *The ABOMINATION thread*.

The more I thought about what I was doing, the sketchier it sounded.

I'll put the welder down now 😬

[grcamna2]

You keep going Man;you're 'perfecting' the task at hand. 

[dave500]

id leave the lift alone via rocker ratio unless its a new forging,also the increased angle pressure on the guides and valve stems im not keen on,id stick with modifying the cam lobe profile.

[BomberMann650]

You keep going Man;you're 'perfecting' the task at hand. 

It's not that it welded badly (i feckin love this tig machine)
Its just that the effort/risk/reward in doing so doesn't add up.  The heat affected zone is the big worry there.
Cutoff blade thickness was .070" - converting from bananas thats ~1.78mm - not a major ratio changer.
Would rather turn the attention back to grinding and resurfacing.
Making a rocker grinder tool won't be too hard, now that i've rewatched some yourube university footage.

The chin rub now is selecting a rod for refacing the rockers.  The local shop is a dealer for an alloy rod outfit.
Not knowing what honda used (someone please chime in if they know)
On the menu is a nickel-chromium-cobalt-molybdenum hot noodle stew.  Though simple ER-CoCr rod without nickel & moly is a standard automotive hard facing rod.  Would the nickel-moly be kinder to the stock camshaft?

[BomberMann650]

id leave the lift alone via rocker ratio unless its a new forging,also the increased angle pressure on the guides and valve stems im not keen on,id stick with modifying the cam lobe profile.

Why not both 🤷‍♂️

Will be test fitting a valve stem follower in the near future.  A little part should be arriving from Milwaukee soon.
Seemed smart as i was eyeballing the dp-335 and megacycle 126-20 race cams anyway. 

Which, i'd have to live on ramen noodles to afford right now.

[BomberMann650]

.. I like watching "Le Dan" building 4 cylinder engines out of old singles, converting 4 strokes to 2 strokes, etc etc.

Terry, you gotta see this

[dave500]

is there one of it running?radials use a master rod.

[Terry in Australia]

.. I like watching "Le Dan" building 4 cylinder engines out of old singles, converting 4 strokes to 2 strokes, etc etc.

Terry, you gotta see this

Thanks mate, I have seen that one, I was hoping he'd have it running by the time the vid ended, but I haven't seen it running yet? He's pretty good though, I like his videas too. Good weld on that rocker arm too, what brand of TIG welder are you using?

[BomberMann650]

.. I like watching "Le Dan" building 4 cylinder engines out of old singles, converting 4 strokes to 2 strokes, etc etc.

Terry, you gotta see this

Thanks mate, I have seen that one, I was hoping he'd have it running by the time the vid ended, but I haven't seen it running yet? He's pretty good though, I like his videas too. Good weld on that rocker arm too, what brand of TIG welder are you using?

It's a fairly new video so hopefully they're able to follow it up soon.

Ordered a primeweld 225x as I was finishing up gtaw class.  They're a good deal.

[Terry in Australia]

.. I like watching "Le Dan" building 4 cylinder engines out of old singles, converting 4 strokes to 2 strokes, etc etc.

Terry, you gotta see this

Thanks mate, I have seen that one, I was hoping he'd have it running by the time the vid ended, but I haven't seen it running yet? He's pretty good though, I like his videas too. Good weld on that rocker arm too, what brand of TIG welder are you using?

It's a fairly new video so hopefully they're able to follow it up soon.

Ordered a primeweld 225x as I was finishing up gtaw class.  They're a good deal.

Thanks mate, I'll check out that welder, I need a good one.