HMB Cams

[blackcat]

I don’t know whether to blame John or the forum generally.  I just ordered a P3 from Stein Dinse.  $460.00 shipped.  It’s going to go on the special part of the shelf that has the PHM’s.

I wish I could put this cam in my 1000S but NG.

[Turin]

My LeMans SE has a Norris RR3 cam (megacycle X8) . It's streetable and makes big power. I like this cam for the big valve motor.

[TOMB]

I'm suspicious in the specifications of what bikes that it fits it says it fits a convert if that's the only can they're making that will not work and a convert the picture shown has a tach-drive, but doesn't have a tach Plus on the convert where the tach-drive is shown on the in the picture that would be removed and the front of the camshaft would be broached to install a keyway to the pump in the transmission and the front cover not likely there's going to be sold a lot for a convert but just by my take on it unless they make it totally separate cam for the convert which I think would be very cost-prohibitive just my two cents

TOMB

[blackcat]

My LeMans SE has a Norris RR3 cam (megacycle X8) . It's streetable and makes big power. I like this cam for the big valve motor.

I have the World engine in the 1000S, but they heads have been flowed by Mike Rich. It's not something I'm going to do until the clutch needs to be replaced and the bike doesn't have a distributor so it needs a cam without the gears.

[moto-uno]

  Holy crap guys , has anybody reread their remarks before posting them ?  Peter

[Frenchfrog]

I'm suspicious in the specifications of what bikes that it fits it says it fits a convert if that's the only can they're making that will not work and a convert the picture shown has a tach-drive, but doesn't have a tach Plus on the convert where the tach-drive is shown on the in the picture that would be removed and the front of the camshaft would be broached to install a keyway to the pump in the transmission and the front cover not likely there's going to be sold a lot for a convert but just by my take on it unless they make it totally separate cam for the convert which I think would be very cost-prohibitive just my two cents

TOMB

They do not  supply new cams but regrind your old one as long as it is suitable. Therefor, they could fit a Convert if you supply a Convert cam.Likewise in Black cat's case they would regrind the cam you send them so ther is no worry that they cannot supply the right one. In any case I don't thing it would be that much of a big deal to cut off or turn down the geared portion of say a P3 cam from Agostini if there is a clearance issue.

[moto]

Removing and refitting the camshaft is presented on "Mike's Machines" Youtube channel. It's not hard. Mike explains it all calmly and clearly while doing the work on a motor still installed in the frame. Here's his particular video on removing the cam, part of a series showing steps before and after that:

https://www.youtube.com/watch?v=IfLy9eX7K9I&t=64s

One thing that appeals to me about a cam swap versus a motor swap is its simplicity and reversibility.

Moto

[moto]

Can anyone report their own experience with installing a B10, P3, or similar cam in an 850 engine with VHB 30 carburetors, and no other changes? Did this kill the low end response? Cause detonation problems? Make for a nicer street engine?

Moto

[Frenchfrog]

I've got a P3 in a mid valve le mans roundhead with 36 mm carbs...runs really strong everywhere.I've experienced no loss of power low down ...if anything the P3 is better there too.

[Scout63]

I've got a P3 in a mid valve le mans roundhead with 36 mm carbs...runs really strong everywhere.I've experienced no loss of power low down ...if anything the P3 is better there too.

Frenchfrog - did you have any issues with piston to valve clearance or cam to rod bearing clearance?  Did you install different valve springs?  Different followers?  Did you match the intake to the carbs?  Thanks

[Frenchfrog]

No issues what so ever.New followers.I fitted heavier springs but afterwards heard that that is only necessary if your revving the engine out...(I'm rarely above 6,000 )that could be BS but came from a good ,reliable source.I spent time clearanceing the whole lot, especially the valves ,valve guide to spring keepers and piston to valves.I also blended the heads to the delrin 36 mm manifolds.I think all of this is important.
Now , when it comes to detonation/pinging I have had issues but that only happened when the temperatures rose above 30 C and I was running far too lean on my idle jets  initially. By fattening up those yo 60's and increasing the atomizer to a 268 she runs good at high temperatures now without air filters and Mistral silencers with the DB killers in. I'm certain I could get improvements in the carburation but that kind of fine tuning is a bit beyond me without an air /fuel ratio set up or dyno runs, neither of which are at hand at the moment.

[Frenchfrog]

I must add that we only started to have to use 98 octane with 5 % ethanol recently and this probably makes the detonation worse.I really don't think it has much if anything to do with the cam itself.

[Scout63]

No issues what so ever.New followers.I fitted heavier springs but afterwards heard that that is only necessary if your revving the engine out...(I'm rarely above 6,000 )that could be BS but came from a good ,reliable source.I spent time clearanceing the whole lot, especially the valves ,valve guide to spring keepers and piston to valves.I also blended the heads to the delrin 36 mm manifolds.I think all of this is important.
Now , when it comes to detonation/pinging I have had issues but that only happened when the temperatures rose above 30 C and I was running far too lean on my idle jets  initially. By fattening up those yo 60's and increasing the atomizer to a 268 she runs good at high temperatures now without air filters and Mistral silencers with the DB killers in. I'm certain I could get improvements in the carburation but that kind of fine tuning is a bit beyond me without an air /fuel ratio set up or dyno runs, neither of which are at hand at the moment.

Fantastic info  - thanks.  Not only did I just buy the P3 while reading this thread, this morning I bought a '79 SP to put it in.  I should never read the forum when I have cash.

[moto-uno]

  What better thing could you spend your money on ? :) . I loved every mod I made to my LeMans2 over the years,
and I did a few ( remarked on this forum earlier ) . Still puts a smile on my face every time I ride it .  Peter

[czakky82]

So I’m likely to try the HMB cam as it’s somewhat unchartered territory and is only about $100 more than a p3. I plan on doing springs, followers, etc. I’ll keep the VHBs for now.

[Frenchfrog]

Good on ya ...but it is a regrind whereas the P3 doesn't need you to give a good core...

[moto-uno]

 ^  And you have something to sell if you get other ideas ! Peter

[moto]

I think getting the HMB is a good move. It's offered specifically for 30mm carbs, unlike the P3 (so far as I know). All those recommending the P3, I think, have gone to 36mm carbs and other modifications too. If you figure on trying to keep the VHB carbs, it seems like HMB should be the better option.

It would be great to measure the HMB cam's lobes and compare those to the P3's, assuming anyone has measurements for P3's.

I happen to have a similar T3 not far away that could be used for before and after comparisons....

Moto

[Scout63]

I will be installing the P3 in my next build starting this Fall and will report on the process.  I plan on having the heads ported and matched to 36 PHM's.  Although I've assembled and timed a big block and a small block successfully, I've never gone into non-stock territory.  I like the note I saw somewhere about building a motor "from the bottom up."  I hope that someone else is doing a build at the same time.

[Rough Edge racing]

I must add that we only started to have to use 98 octane with 5 % ethanol recently and this probably makes the detonation worse.I really don't think it has much if anything to do with the cam itself.

Did you use a degree wheel to check the  lobe centers and or duration? if the cam is installed with to much advance it will increase lower and mid rpm cylinder pressure and could cause detonation....You are in Europe? 98 octane is about equal to 93 US octane..

[Frenchfrog]

Interesting...I did degree it. With a standard chain drive it's not easy to change though unless you are a complete tooth out and that's almost certainly not the case.I've got a moto spezial belt cam drive kit which I've used in the past and that has a very fine degree of adjustments.. It's going to go back in at some point.

[Michael Moore]

I will be installing the P3 in my next build starting this Fall and will report on the process.  I plan on having the heads ported and matched to 36 PHM's.  Although I've assembled and timed a big block and a small block successfully, I've never gone into non-stock territory.  I like the note I saw somewhere about building a motor "from the bottom up."  I hope that someone else is doing a build at the same time.

I've just had about $2500 of tools and parts ordered/delivered for my 1979 1000SP, so hopefully mine will start going together in the not too distant future.  I be doing lots of "dry build" checking - cam timing, squish clearances, etc etc so it will be a fairly slow process (not counting my usual "slow to make progress" lack of speed).  The chassis is very rough, so that will take a lot of time to sort out.

cheers,
Michael

[Simon_London]

In general I really rate HMB quality, functionality and service. I believe they are the best accessory and tuning shop for Guzzis available. Just look at the parts they supply that no one else does. They really know how to make old Guzzis fast without become unreliable or unpleasant. 

[Jens_L]

I had a P3 cam installed in an 850 LM engine, which I decided to overhaul because it had not run in a decade. The engine had some other work done to it as well ( Higher CR, Squish band optimization), But I suspect it had been 'overdone' (it had the tendency to detonate). I decided to invest some of my hard earned Euros and do the engine right. Will assemble this winter/ next Spring and have collected:

   - HMB 8.1 Camshaft;
   - original 36 and 40mm carbs for experimenting;
   - Lightened/balanced flywheel
   - Twin spark heads
   - ...

Won't be able to compare performance of the cams anymore but I can say
I have bought many parts of Michael from HMB and as it is my first time opening up a Guzzi engine, I have asked him numerous (probably some stupid) questions and he has always replied straight to the point. Machined Pieces are really high quality too ( I have measured the entire engine with (holtest-; laserscan- and just regular) micrometers, just because I'm a little bit of a perfectionist, and parts were almost always right where you'd want them to be). I have also seen boxes with HMB- tape lying around at Guzzi garages/specialist, so I'm probably not the only one that has confidence in the guy.

I wonder if there would be some interest if I'd started a thread sharing my findings concerning the 'overhaul story'?

[Mayor_of_BBQ]

I wonder if there would be some interest if I'd started a thread sharing my findings concerning the 'overhaul story'?

Yes please! start a thread on it in the Bike Builds & Rebuilds section (under general category)!

[Frenchfrog]

Go for it Jens...
I for one would be very interested in reading your findings as my engine is similar.I've not gotten entirely to the bottom of my engines pinking issue but it seems to happen in the summer when the heat is excessive.I'm going to invest in an Air /fuel ratio meter soon so as to have a more accurate idea of where the mixture is at...if that doesn't work it will be duel plugging next in all likely hood.Your findings and especially in carburation would be a real help too.

[henwilv]

I’m sure out and out objective performance is the goal of anybody tuning an old Guzzi. It’s just fun! You wouldn’t want to know how much I’ve spent transforming my old Yamaha R5 from 30hp to a whopping 55hp! But I dare you to not ride it and either swear off motorcycles or laugh hysterically!
Plus I just like the old bike!

And that is the only rationale you need to turn a perfectly good motorcycle into a money pit - Go for it, I say, enthusiastically!!

[Kredge75]

So I’m likely to try the HMB cam as it’s somewhat unchartered territory and is only about $100 more than a p3. I plan on doing springs, followers, etc. I’ll keep the VHBs for now.

So how did everything work out? Did you end up with different carbs?

[mtiberio]

FWIW, I built a land speed racer last year using a 949cc convert donor motor. I put 41mm Malossi carbs on it mated to quicky welded straight back manifolds, and no porting. Yes. when you looked down the intake with the slide up, you saw a series of unblended steps (carb to manifold, weld of manifold tube to the plate, manifold plate to head). The motor had convert small valves, stock springs, and some 88mm pistons (unknown origin) which had an Eldo/T-3 style dome which I figure with the bigger bore netted 10.5:1. It had helical timing gears in aluminum, with vernier holes in the cam gear. Using a degree wheel and a dial indicator, I timed the Web 86a (mild) Cam to 106 degrees Intake Lobe Center (ILC) (stock timing measured out to 100 ILC). This motor pushed me to 141.010 MPH at an SCTA event at El Mirage. My old pro-twins bike with Manfred heads, 992cc and a much hotter cam only managed to push me to 141.673.

My point? None really. The above build was a "junk yard dog" using parts I had on the shelf. It does show the importance of cam timing and big carbs above a lot of other stuff. Once at Daytona while pitted with Dr John and Manfred, I crashed and destroyed my bike but not my motor, but decided not to transplant my motor into a donor bike because the "intakes were not blended". Manfred pulled me aside and told me, "here is a secret, it is not that important", which would agree with what Rough Edge said. Why wouldn't this be common knowledge? Manfred made a bunch of $ porting heads for people.

Don't get me wrong, I am not telling you to spend less on your bike. I have spent tons, foolishly. It's fun. Just don't assume because you have all the go fast parts that you are fast, conversely it doesn't cost that much to go fast. Attention in a few key areas is whats important. Factory engineers are damn good and they have bunches of dyno time to test. For most of us, our motor tuning is like a blind man throwing buckets of water at someone yelling "fire".

The junk yard dog with a GoPro camera down its throat (note reversion near end of run.)
I went 138 here: https://youtu.be/PHHKQNEizxY?t=140

Need some big carbs, cheap?: https://www.ebay.com/itm/124150503531

Don't worry about the torque, you'll have plenty

[czakky82]

That’s awesome Mtiberio!
My take away from that is what happens in our “minds eye” is likely not what’s important to go fast.
Thanks for that!

@Kredge, I did end up using an HMB8.1 cam in a different bike though. I bought a V7 Sport project that was a total rebuild. I’ve basically got it tuned in completely at this point. The V7 has more willingness to rev either because of the short stroke motor or cam, I’m not sure. It likely has more power than the T3 but not by much and it’s all a little bit higher in the revs. The T3 being out of breath after 6500rpm the V7 would likely rev to atleast 7500, but power is flat after 7000 or so. Both are probably strangled by carbs.
Lawnmower cam (stock T3) vs 8.1? 8.1 for sure! That being said if I had a stock T3/850t I wouldn’t change it. If a guy was going to hot rod his small valve I’d play with higher compression, displacement, carbs and at that point a real spicy cam would need to have valve to piston measured, etc.

This being a drop in cam and me needing cam followers and springs, etc. I don’t regret my choice. So I don’t have a back to back comparison.

On the quality of HMB, I’ll say I’m very satisfied. I bought other parts from them and they are doing some really cool things for these old lumps for reasonable prices. Shipping may be hit or miss according to some. For me it was good.

Does that sum it up?