Monty race engine

Fitz

Fitz

Senior member
Location
Cheshire UK
Does anyone have any interesting information on valve timing for 500 race engines, I have a copy of a sheet that i found showing valve timing for most models but it only states standard timing for 350 and 500 twins

My engine has new race cams and my engine man is working to the figures shown on the sheet, it has meant slotting the cam wheels to adjust the standard timing using the fixed hole centres

I am also using one of Phils backing plates and a Boyer Ignition system, any information about ignition timing is also very welcome

Thanks guys
Dave Fitz'
 
Hello Andy, the latest from my engine man is as follows:-

"I have been doing the inlet cam first and just need to check with you the actual cams supplied. I understand these to be S1 cams. The figures on the inlet for these are 24 deg BTDC and 43 deg ABDC opening and closing (247 total) . I have had to machine radial slots in the inlet cam wheel to achieve the opening figure of 24 deg bang on but the closing figure is 78 deg or a total of 283 open period.

This is as near as dammit the megacycle figures of  38/62 or a total of 280. What is unsettling is that when set on the original holes and timing marks I got 40 on the opening which with the total open period would have given me 63 and as can be seen  Megacycle 38/62 and 40/63 seems a bit of a coincidence so can we clarify which cams I have . Also can you check with Austin as to what valve to piston clearance we should have. We have clearance as the inlet has turned over but I could do with an actual figure"

So at the minute I am waiting for an answer Austen but I have asked him a lot of questions and to his eternal credit he hasn't told me to sod off (yet)

I sent the information you suggested to my guy and asked Phil Todd if he could help but Phil tells me his expertise is not really with the 500's

So if you can help with any information regarding valve and ignition timing, the more the merrier

Thanks for your interest
 
The engine builders name was mentioned a few times re Bob Dixsons Barcelona race bike threads a while back.Might be worth doing a search for his info and giving him a call
 
Hi Dave,
If your cams are S1 they will be stamped S1?
If your man has found a closing figure of 78 degrees with opening of 24 then I would run with it,Sounds like good opening period.Is your man working to maximum lift (ML) when setting figures?
It will interesting to see what  the closing figure is on the exhaust when opening at 39.
I ended up setting my inlet on a dyno by running several runs and moving the cam each time to find the best position for power.Actually came in with the cam opening later by 6 degrees,but that is my motor running 30mm inlet vales and 78 mm pistons.Ran out of time do the same with exhaust.One of the reason for doing this way because I was unsure of the figures being quoted!
Igintion system I currently run Sachse - plug and play - curve 4
Surely your man will to a dry build and check valve to piston clearance.When I checked mine I found readings of 3.0mm to 4.5 mm - massive!!!!.
The first build of a race engine is just the start of the development curve!

Andy
 
Fitz said:
I have had to machine radial slots in the inlet cam wheel to achieve the opening figure of ...
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G'day Dave

Can't see how radial slots would be of any use. Slots need to be ay 90? to radial - circumferential? I presume that's what your engine bloke means.

No info on 500s specifically, but in general, trying to set valve timing with opening and closing specs is difficult and fraught with potential innacuracies. It's much easier and more accurate to do it at centre lobe.

Cam
 
That's the 2nd time I have heard of 108 degrees and optimum cam timing and that's on 2 differant types of machines.I read a blog by a bloke in Melbourne called Brad Black,spent a lot of time fiddling with Ducatis and Dino's.
http://www.bikeboy.org/performance.html
He usually sets cams up at 107 on both 4 valve and 2 valve Ducats.
And then we hear this Pip bloke,a pro engine guy uses the same figure.The F1 cams in my 180 are supposed to be set at 100,and that's what Red set them at.So I wounder what effect going to 107 would have,that's 1/2 a tooth,anyone been there on 180 triples.
 
  Moved the F1 timing back and forward a bit and they seem to work best at 100 degree lobe centres ( factory timing )


    Keith
 
Paul Marx said:
Didn't Pip Higham do dragsters?
Paul
Click to expand...

Yes - He was pretty good at building quick motors to say the least.


So I wounder what effect going to 107 would have, that's 1/2 a tooth, anyone been there on 180 triples.
 
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1/2 a tooth is 12 crankshaft degrees - 720?/30 teeth - Regards - Phil



 
For what it's worth when i was doing Kawasaki 500 twins for our F3, we used megacycle race cams and set them up at the recommended 106/108 lobe centers. 80 odd horse at the wheel on alky was acceptable.
The small 4V per cylinder motors are quite sensitive to lobe center settings. The kawa is a very similar layout and head shape to the monty from what I can see so i'd expect similar LC's to be a good starting place.
Never attempt to get your lobe centers by looking for the point of max lift...Lobe centers, by definition are the center of the opening period. Cams are not always ground symmetrical, either on purpose or due to grinder setup issues.
 
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