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M20 cams for methonol/ petrol

Hi All.
Have been given the BSA part # for the above cams.

Petrol Inlet 65-2442, Exhaust 65-2446.

Methonol Inlet 65-2448 , Exhaust 65-2450.

Carbie and jetting for Methonol Amal 289/022R.
Slide 29/6.
Main Jet 1100 SB.
I have no needle #.
Iam after some methanol cams.
Hope this helps some one
Cheers Drew.

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Re: M20 cams for methonol/ petrol

From memory 2442 and 2446 are Clubmans cams (In & EX 500 engines)...2446 was also used on both the inlet and exhaust for scrambles engines..

2448 and 2450 are Gold Star touring cams and I'm unsure as to why these would be specified for Methanol....

If you are planning to rev the engine to 7000- 7500rpm I would have thought a 289 carb to be on the small side (assuming you are going to run a normally aspirated engine...)

For my own M20 project the RPM limits above are the ones I am going for based on previous experience...I'll be running mine at a 94mm stroke and 90mm bore for 600cc...IMO you need to think about how you are going to modify (strengthen) the bottom end if you intend to run to those revs or beyond...

I'm using a 'one off' inlet cam and a 2446 exhaust...

Without knowing the class limitations you are running under regarding external modification or the speed you are hoping to attain it's difficult to ascertain what you might need in terms of engine specs.

My advice, for what it's worth, would be to determine what you are aiming for and the class limitations, then work out the engine spec. and then start spending money on parts...

I spent a long time and did a lot of research to determine my engines' spec. and still haven't fully finalised the cylinder head details though the rest of the engine is ready for assembly...Ian

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Re: M20 cams for methonol/ petrol

Thank You O Wise One.
Thinking of Sellicks Beach [South Australia] when they run it again.
This one is a bit of a long running project.
I put the call out to the rest of the world to race against me and others at the next Sellicks Beach Races, that includes you Ian.
Its a great two days and a real hoot.
Cheers Drew

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Re: M20 cams for methonol/ petrol

On the subject of piston speed I made the following calculations...

M20 (94mm stroke) 18.8 mtrs/sec @ 6000 RPM
21.93 mtrs/sec @ 7000 RPM

M21 (112mm stroke) 22.4 mtrs/sec @6000 RPM
26.13 mtrs/sec @ 7000 RPM

B31/33 (88mm stroke) 17.6 mtrs/sec @ 6000 RPM
20.5 mtrs/sec @ 7000 RPM

I read a long while back that 22 mtrs/sec was a reasonable (rule of thumb) upper limit for piston speed but I'm not sure how relevant that is currently.. It's interesting to note where the figures above are in relation to that..Ian

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Re: M20 cams for methonol/ petrol

It seems 22-25 mtrs/sec is still a current figure for a competition engine...

Taking the upper figure that equates to a rev limit of...

M21 (112mm stroke) 6750 RPM
M20 (94mm stroke) 8000 RPM
B31/33 (88mm stroke) 8500 RPM

I've run B33s up to 7000 rpm on standard conrods and a bit beyond that on an after market rod (maximum power [dyno tested] 40 bhp with the standard rod in that set up.)
I've replaced the long and flexible standard rod in my M20 project, which I expect to have a rev limit of approx. 7250 rpm, with a Carrillo rod...Ian

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