B10 CAM INSTALL

[Don G]

I have installed a B10 cam in one of my 700 Roundfin engines, it is a re-ground cam from Colt Cams, I have checked the LSA and it comes out as correct, I checked the separation angle according to Webb cams info, zero lash @.050 lift, my question is what clearance is used to check opening and closing point of the valves? Or do you not care about this as the cam is set correct to the center line? I could not get the degree wheel to jive with the opening and closing specs from Guzzi other than the centerline specs.
 I had installed this cam this spring, the LSA was set to spec, the engine seemed to run hot and didn't seem to have the power that a fresh engine should produce, the jetting seemed correct as well as the ignition timing, new advance weights etc. I figured that perhaps the cam timing was out as when I got this engine the previous person that worked on it had the cam gear out of synch. these early engines have a fine pitch gear form and 5 dowel holes in the cam gear, it wouldn't be hard to go astray! What do the educated tuners think?  Thanks DonG

[rodekyll]

For those of us who are NOT educated tuners but want to play along, please 'splain us LSA.  Thanks.

All I have to offer is valve lash.  I just installed a B10 last week and set to 0.006 and 0.008.  I've got timing gears, but only the one hole for the index pin.

[Don G]

LSA stands for lobe separation angle, its like the centerline between both intake and exhaust lobes(106*). This 700 has 750 cylinders and later Ambo heads as well as 30mm VHB carbs. as well as a freer flowing mufflers.  DonG

[rodekyll]

Thanks for that.  I never would have guessed.

[guzzisteve]

OK, Loop engines for valve timing I think are 0.5mm rocker clearance and later engines are 1.5mm. This is what I used in the past and it came out correct w/cam spec. Got a sheet from Raceco for the 390 cam too, got to find it.

[Don G]

Thanks Steve, the 700-750 manual states .0195 clearance for checking timing, I was not sure of the clearance for the B10 cam. Funny thing is I tried zero lash, 1/2 mm or .0195. and 1mm or.040, still didn't really work out. I will have to start playing the dowel in a different hole game because it is not quite correct as of now. DonG

[Don G]

Here is a little theory for the people who ask why do I have to be at top dead center to adjust my valves? www.austincc.edu/wkibbe/camtheory.htm A little light on a dark subject.  DonG

[guzzisteve]

Found the Raceco sheet, it didn't say anything about set-up lash. While I was looking stuff up(to see if I remembered correctly) I checked when it changed, with the 850T it went larger.

[pressureangle]

Truly, you should have specs directly from the manufacturer- but you can whittle your way down to it if you have intake opening and closing specs (because intake is by far more important than exhaust)
Beginning with zero lash, record the open/close. Then recheck both @ .050" tappet lift. That should surround the specified timing points, and if you have equal differences on both sides of the lobe- that is, if adding clearance reduces crankshaft degrees by the same amount on both ramps you can pretty much assume you're safe. To do it right, find the clearance at which the O/C specs match exactly the paper specifications and then try to discover if it's a reasonable number. All American manufacturers I can think of call out numbers at .050" and/or zero. Once you have your numbers @ a specific clearance, you can call Web, Megacycle, et al and get their opinions on the clearance number.

[Don G]

Well I finally got the cam specs from Colt Cams on their B10 regrinds, as follows:
Int/Ex-251*@.050"
.348 lift
105.5 lobe separation angle
IO-20*BTDC  IC-51*ABDC
EO-51*BBDC  EC-20*ATDC
Waiting on further word if there is a clearance involved when checking, am assuming that these specs are for checking timing before the top end is on. I hope this info will help some one else.    DonG

[guzzisteve]

That's weird, I was thinking about you this AM, wondering if a hole lined up for your cam.

[Don G]

Weird shite happens! I was speaking with Geoff at Colt Cams today and got the low down on his specs. Basically checks are done @.050"zero lash, best done before the heads are on. Anyway he was telling me that he is going out of the Gasoline engine cam business and strictly doing Diesel only, so that makes one less avenue for cam work. 
Going to sit down tonight and go through the procedure again as my readings on the exhaust side are a bit wonky. Geoff claims that as long as you are +or- 3* on the cam centerline you are good to go. At the moment I am at .25* advanced on the lobe center separation.......   DonG

[Don G]

I did some tinkering last night, degreed the cam, here is what I came up with:
Intake-
net lift 0.373
IO-16*BTDC
IC-58*ABDC
+180*= 254*DURATION
254/2=127
          -16=111* INTAKE CENTER LINE
Exhaust-
net lift 0.366
EO-49*BBDC
EC-31*ATDC
+180*=260*DURATION
260/2=130
         -31=99* EXHAUST CENTERLINE
LOBE CENTER SEPARATION-
111+99=210*/2=105*

THE SUPPLIED SPECS.-
IN/EX -251* DURATION
0.348" LIFT
105.5* SEPARATION
IO-20*BTDC 
IC- 51*ABDC

EO-51*BBDC
EC-20* ATDC
All checks done @.050" zero lash
The question of the day is although the intake readings are somewhat close to spec. why is the exhaust so far out to lunch? I am going to try and get the intake closer to the specs. or is that possible? Am running the real early fine pitch timing gears with the 5 dowel pin holes.    DonG

[John A]

It may be that the master the cam is ground from is worn. I installed a MegaCycle cam and came up with some discrepancies like yours and finally called them and that's what they said as well as telling me the venerable P3 cam suffered from that as well and that's why they didn't have that grind.They said the best you can do is install it within +_ a couple degrees of intake centerline and let the rest " hang and rattle".  So I put it at 2 degrees advanced on the intake centerline of the left side using chain and sprocket with an offset bushing/ dowel. I made up a bunch of different bushings and then by trial and error fitted them until I got my two degrees. With a Valtech tensioner, I got sore fingers. That engine runs really well and it's been on the road for more than 100K miles.

[Don G]

I persevered and finally got it closer to the ball park, In don't have the exact figures in front of me at the moment but the opening point on the intake is @ 20* like it is supposed to be, I found that the lash on the exhaust had to be 1.5mm with the crank @122* in running direction and the exhaust lobe against the lifter, I  picked the closest hole in the cam gear that lined up with the cam dowel. She should run like it should now. Thanks for the tips! DonG

[rodekyll]

Gee.  And I just slapped mine in   I have no idea how many arc-sines of diameter I am from the horizon event.  I was not on the centerstand when I torqued the crank nut.  I hope none of the extra drama was necessary on mine.   

[Don G]

Just cuz it work don't mean its right either!  DonG

[rodekyll]

That's kinda what I was thinking.  I'll know later today when I fire it up.

[John A]

Just cuz it work don't mean its right either!  DonG

I was working on an automatic transmission with an old guy and I observed that when we set something, don't remember what, it wasn't what the manual said to set it at. I do remember what he said. " the damn thing didn't read the manual" whatever it was, it worked well

[John A]

That's kinda what I was thinking.  I'll know later today when I fire it up.

Fire that thing off !!!, I want to know!

[John A]

how's it going out there, David? that thing will probly make a half a revolution and fire off. maybe a couple revs while the timing sensor finds itself but I think you'll be happy with that cam.

[rodekyll]

I'm chasing an intermittent outage at the brake light.  I have the tank off for the event, so I can't start the engine.  I'm bored with it for the day.  I might replumb the circuit tomorrow.  I've already spent more time looking for the problem than it would take to rewire it.  It's always something.

[Don G]

Got my engine back into the chassis and fired up last night, fired right up and idled nicely, exhaust has a nice rap to it. Wont be able to road-test for about 5 or so months yet DonG

[rodekyll]

Is the idle noticably different?  How?  What about idle speed?

[Don G]

Idle sounds a bit choppier, idle speed did not change sounds nice on the over run  have to road test it in the spring, old man winter is here.  DonG

[pressureangle]

Intake closing is by far the most important timing event. Set that as close to spec as you can, verify valve-to-piston clearance, and roll with it. You can't change it.

Personally, I'd return the cam or ask for a partial refund. It's simply not high quality.

[Rough Edge racing]

Intake closing is by far the most important timing event. Set that as close to spec as you can, verify valve-to-piston clearance, and roll with it. You can't change it.

Personally, I'd return the cam or ask for a partial refund. It's simply not high quality.

 Yes.....many cam grinders and tuners prefer to  use intake lobe centerline degrees when making comparisons.... A cam with long opening  and closing ramps may have a late intake closing on paper.. But to the engine the intake closing is earlier because the valve flows very little on the ramps..

[Don G]

Well this is what I actually ended up with:
IO-20*
IC-51*
EO-51*
EC-20* 105.25* lobe separation angle
This is spec. from Colt Cams:
IO-20*
IC-51*
EO-51*
EC-20*
lobe separation angle-105.5*

Likely close enough for the girls I go out with....    DonG

[Don G]

OOOpppS! I screwed up I got :
IO-20*
IC-54*
EO-52*
EC-25*
105.25 LSA

[pressureangle]

OOOpppS! I screwed up I got :
IO-20*
IC-54*
EO-52*
EC-25*
105.25 LSA

It works.

That short LSA will make you very happy on the road. I have a Web 86b in my LM1000 with 105* LSA and it pulls from almost idle. Almost the same cam but .447" lift with fast ramps.