camshaft settings

[win]

I need some advice please, I have a Midget 1275 12CC engine, in my S11, I acquired this engine over 20 years ago, it had the head off, sump, timing chain and timing cover missing, but the cam was fitted. It is now fitted with HIF 38 carb and a 4 into 1 manifold, 1 5/8" exhaust.
It has a standard cam (I believe) fitted with a 5 deg offset key to advance the cam timing, it was too retarded with a standard key, my timing is still 1.5 deg retarded.


I am considering advancing the sprocket one tooth, 9 deg and using the offset key to retard the camshaft by 5 deg this should give me 4 deg advance, which I believe is beneficial to my engine.
Does this sound correct, my only tuning knowledge comes from information from this great forum, and David Vizard.

With the new setup I have done various checks.

The peak cam lift on number 1 inlet occurs at 101 deg ATDC.

Using the mechanical method to check the split overlap gap this is inlet ,062" exhaust .029", which = 4.5 cam advance.
This check is very sensitive, various between 4 and 5 deg.

Checking the opening and closing angle of valves with gap set at .029".
inlet opens 7 deg BTDC closes 24 deg. ABDC
Exhaust opens 50 deg BBDC closes 3 BTDC.

Does all this sound correct, I am only looking to get the best out of what I have, thanks in advance.

Kind regards Win

[philthehill]

Win
Checking your numbers against those in the Vizard book for the 1275cc Midget camshaft they do not match and by some degrees.
I suspect that the camshaft has been re-ground at some point. If the camshaft was standard ex factory you would get the correct reading (plus or minus 1 - 2 degrees) using the factory markings on the crank and camshaft gears.
Personally If I could not get the factory figures and not knowing the pedigree of the camshaft I would ditch the camshaft and fit a known standard camshaft.
Are you using a degree timing disc attached to the front of the crankshaft and a dial gauge? The two items are most invaluable when setting the camshaft.

[win]

Thanks for the reply Phil, I am using the timing disc, courtesy from Declan, and a dial indicator, I will hunt for a cam shaft, and reply with out come.
Regards Win

IMG_20220113_153435935.jpg (3.43 MiB) Viewed 986 times

[philthehill]

Win
Whilst you have the rocker system in pieces - a tip is remove the 3/8" side of the rocker shaft locking plate on No: 2 pillar and replace with a plain washer.
This allows you to remove the rocker shaft locating peg, rocker shaft and rockers without disturbing the head gasket.
BL fitted a similar locking plate to their later engines but without thinking it through - they secured the locking plate under the 3/8" stud nut
Phil

[win]

Phil
Thanks for the tip to make removing the rocker shaft easier.
I am looking at new camshafts, will the Evolution 002 at Mini spares be suitable for my engine, only comes in slot drive, unfortunately I have just bought a new star drive pump, but I have the followers.
Thanks again.
Kind regards Win

[philthehill]

http://www.minispares.com/product/Class ... o%20search
The above camshaft appears to be ideal for your application.
As regards the oil pump I would replace the oil pump with the appropriate oil pump suitable for the slot drive or if you have an old slot drive pump you could try changing the oil pump drive shaft and having just looked at a slot drive oil pump it seems easy to do. I have changed oil pump drive shafts in the past to get the right oil pump / camshaft combination. Loctite the rotor to the drive shaft if there is no key as it is not unknown for the shaft to come loose from the rotor.
http://www.minispares.com/product/Class ... o%20search

[win]

Just fitted new Evolution 002 cam, with new followers and pump.
Set No 1 inlet on peak of cam, valve timing shows 107 deg ATDC, just as makers settings state.
Checked cam overlap clearance, inlet 0.006" larger than exhaust, so that looks very OK to me.
Checked No 1 inlet opening with no tappet clearance, this is 109 deg ATDC.

So is there any advantage in advancing it, as mentioned in Vizards book, or does that only apply to the original cam.

Kind regards Win

[philthehill]

I would suggest that you set the camshaft timing as per the manufactures settings. Personally I would not deviate from those settings as they would have been determined by extensive testing.

[win]

Thank you, I am much obliged for all your advice and help, I will advise when I am up and running.
Regards Win

[win]

Now up and running and on the road, all appears fine, I have not pushed it yet, treating it gently, for now, a big thank you for all the help.

Looking forward to the start of a new era on Thursday, it may be a leap too far for some of us, if I dont make it thanks for the memories.

Regards Win