Montjuic valve timing

A

AndyB_11

Full member
Location
Bedford
Morning all,

I?m currently trying to set the valve timing on my Montjuic engine before checking and ordering new shims and while I know from using the search facility on here that the standard Alpino book and setting marks are wrong for S1 cams can anyone advise roughly how many teeth away from standard I should be looking at?

I?ve set the engine at TDC on the right hand side and positioned the cams so the lobes on that side are roughly pointing towards each other as suggested in a post from some years back and each sprocket is approximately 3 teeth away from having the marks line up. Does this sound right? I?ve not connected the chain up and turned the engine over yet and it?s such a difference from standard that I though it best to ask before turning it over even if I do it slowly and stop if I feel any resistance.

Another question is does anyone know the approximate clearance between standard valves and 10.2:1 pistons because I?ve got some plastigauge shim I can use to check it and the tappets have in excess of 0.5mm of clearance after changing the head for a decent one  :)
 
Right then,

Since my earlier post I?ve messed about a bit more and the lobes are now closer to being horizontal and pointing at each other with about 2 teeth variation from the datum marks on sprockets and bearing blocks so I?ve set the camchain tension and rotated the engine a few times with no ominous clicks or signs of contact between valves and pistons so that?s a good start.

I?ve got to say that it?s a pain trying to get the cams in the correct position relative to each other with the piston at TDC and I was having a minor epic getting the link back in the chain even with the adjuster removed until I decided  to use some circlip pliers to squeeze the two ends close enough to fit the link. Even with the adjuster fully wound out I was only getting 8mm of movement on the chain at the slackest point but it?s done now so I?m feeling better about repeating the performance when I fit new shims.
 
AndyB_11 said:
Morning all,

I?m currently trying to set the valve timing on my Montjuic engine before checking and ordering new shims and while I know from using the search facility on here that the standard Alpino book and setting marks are wrong for S1 cams can anyone advise roughly how many teeth away from standard I should be looking at?

:)
Click to expand...
News to me , unless I'm missing something.
If you have 'factory' issued S1 cams then the line on the cam wheels should line up with line on top of the cam bearing cap.

Andy
 
I?ll have another look and try them as per the alignment marks later but I was going by comments made by Piet about getting the lobes lined up at TDC as per the post below.

https://www.laverdaforum.com/forum/index.php/topic,80936.0.html

It?s probably me misinterpreting the information because I?ve looked at a chart for open/closed timing and according to my trusty degree disc they?re not right at the moment. I?ve given up for the day because I?ve been waiting for a set of cranked feeler gauges to arrive and they were delayed from Thursday to today but that?s Amazon for you.
 
Vague memories indicate that closing the cam chain is a pain in the backside because the valve springs will be slightly under pressure in the right position.

Paul
 
I?ve got a set of circlip pliers that you turn a knurled adjuster to tighten then hold the jaws in position so I made a pair of pins that were a decent fit in the ends of the chain and wound it in. It took me a lot of swearing before I arrived at that method but it?s under 1mm of pull needed so idiots persevere don?t they  :)

Surgical forceps are a good idea because they clamp together so if I feel the need to buy new toys they?re now on the list and I wish I?d thought of the cable tie idea but I?ll be using it to put slack in the chain when I inevitably split it to fit shims.

I?m going to mess with the timing a bit more today and check exactly where the valves are opening/closing then work to the figures given in the table here

https://www.laverdaforum.com/forum/index.php/topic,87809.0.html

Once I?ve got a setting I?ll stamp the cam sprockets at TDC and that?ll be my datums. I might try moving things a bit to see what it does but that?s a while away yet. 
 
I just used a pair of pointy pliers - worked for me, but I like the suggestion of the cable tie as it?s a cheap and easy option.
 
I have just rebuilt a 500 with S1 cams and hi comp pistons, the cams need seeing up as per the Alpino service manual,  with the marks lining up to the lobes, each sprocket tooth is equal to 10.58 degrees, my exhaust cam was 1 tooth out when I first put it together, which to say didn't make for very good starting at all is an understatement. My pistons are about the same compression as yours and there is no issue thus far with clearance.
I'd make sure you have a good quality thin magnetic picking up tool, before you start joining the cam chain, makes retrieving the chain back out of the sump so much easier
 
AndyB_11 said:
I?m going to mess with the timing a bit more today and check exactly where the valves are opening/closing then work to the figures given in the table here
Click to expand...

Not sure actual valve opening/closing figures for cam timing are accurate, due to many factors that i won't go into here. Apparently 99.9% of cams are symmetrical so the method for ascertaining cam timing is at maximum lift (ie halfway between to open/close figures). That's how I dialled my SFC 5/C cam and how we dialled Yoshimura cams on Kwaka 9s back in the day.
 
Lyndoneil said:
I have just rebuilt a 500 with S1 cams and hi comp pistons, the cams need seeing up as per the Alpino service manual,  with the marks lining up to the lobes, each sprocket tooth is equal to 10.58 degrees, my exhaust cam was 1 tooth out when I first put it together, which to say didn't make for very good starting at all is an understatement. My pistons are about the same compression as yours and there is no issue thus far with clearance.
I'd make sure you have a good quality thin magnetic picking up tool, before you start joining the cam chain, makes retrieving the chain back out of the sump so much easier
Click to expand...

That?s good to know.

I do have a very strong, thin, telescopic magnetic pick up that I needed to use a couple of days ago after the chain slipped out of my fingers and went for a walk down the inlet side of the tunnel. I?ve also got a flexible mechanical pick up for anything caught up where the magnet struggles and a borescope with a magnetic pick up attachment in case I drop anything tiny and it goes completely missing  :o

Did you use the original M9 nuts on the cylinder studs or source new ones? I?ve been struggling to get any replacements for the originals on mine and they?re a bit tired and as it stands they?re back on but I?d sooner replace them if I can.
 
Piranha Brother 2 said:
Not sure actual valve opening/closing figures for cam timing are accurate, due to many factors that i won't go into here. Apparently 99.9% of cams are symmetrical so the method for ascertaining cam timing is at maximum lift (ie halfway between to open/close figures). That's how I dialled my SFC 5/C cam and how we dialled Yoshimura cams on Kwaka 9s back in the day.
Click to expand...

I?ve got plenty of DTIs and a small Myford lathe so I can turn them over by hand and put a dot opposite the high point on the cams. That should make checking things a lot easier because once the clearances are right I don?t want those cams out again  :)
 
I used the original cylinder nuts, I would be very careful tightening the cam block nuts, 2 of my studs had stripped their threads and been previously helicoiled, one is just about holding, the other I had to have drilled out  and fixed in a different way with a bolt instead of the stud and nut.
The bolt head had to be lowered to fit in the rocker box and the stud holes are very close the the bearing positions so there is not a lot of room for repeated repairs,  if it happens again the head will need welding and redrilling
I brought a digital torque adaptor so that I could see what I was tightening too, as I did not have faith in my mechanical torque wrenches at those settings
 
Hello Andy, dont know if it helps, when we built my engine, we even went to the extent of slotting the cam sprockets to enable the valve timing to be played with, complete waste of time I think

Not related to this issue but after exploding the first build of the engine (long story) I found that the cam sprockets had moved when the engine locked up, not surprising really, it was a spectacular blow up. After reviewing the damage, we agreed that this was the result of the blow up - not the cause. However, just to be safe, we set up the valve timing (pretty much as standard) then used small locking bushes to fill the slots, that way they cant move. Never had any problems.

I run Atlas valves as they are slighty larger, I had new valve seats inserted and cut with three angles as is modern practice, my barrel base was skimmed to bump comression, Ross pistons. So all of these factors make using standard shims a little difficult hence making them. We did use plastercine to ensure clearance and found that was fine, 1.8mm on the inlet and 1.52mm on the exhaust (obviously measured cold) we did this with my engine man, proper race engineer

Just something else I found after blowing my head gasket twice in the same position during Dyno runs, measure the height of the barrel spigot at opposing postions on each cylinder and check they are level, even and will suit the recess on the head. Mine had a high spigot on one cylinder so was never going to seal effectively, the attachement shows the result. We (engine man) machined the barrel spigot and the problem was resolved. I think I saw a similar problem on a Jota recently, that was chuffing through a head stud, Keith had seen the same issue before so its always worth checking

Sounds like you have it all in hand
 

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When I stripped the top end I went through everything to see what had been done previously and I did check the spigot in case the head had been skimmed then checked the replacement head to ensure it was going to fit before pulling it down. When I say everything that?s not exactly true because I?ve not removed the cam sprocket bolts so they sprockets might well have been slotted before ingot hold of the bike. They are on a list of items to be changed when it reaches final build stage but I?ve been using them to move the cams a few times when the chain is off so decided to take them out, replace them and torque new bolts up right at the end. I?ve broken cam sprocket bolts on a different bike and the engine was wrecked so I?d sooner avoid a repeat.

Regarding the cylinder head and bearing cap studs, it?s a crazy idea having the same size hex on both M8 and M9 nuts so the M8 ones on mine have a dot from a yellow paint marker on them which should reduce the chance of me trying to over tighten one of them. On the original head 5 of the M8 studs had been helicoiled which is never a good sign  :o
 
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