Standard 1098 camshaft variable timing settings

[Merlin 2]

Hi all

I have a standard 1098 engine and a set of the adjustable timing gears. What I would like to know is the degree of maximum opening for the inlet valve on the standard camshaft so that I can adjust the timing gear.

By the way I had the variable gear on another engine that was sitting doing nothing so I thought it was a shame not to use it.

[Merlin 2]

I seem to think I have read on a sprite website forum that they were talking about 110 degrees ATDC. Don't think I can assume that the sprite and the Morris share the same camshaft.

The best bit is I bought the Vernier timing gears from David Manners at Birmingham so sent them an e-mail to ask if they knew - not a clue and they are the ones selling them.

If i can't find out I will have to stick the standard duplex gears on and put the Vernier set back on my 1275 as I know the setting for the 1275.

[oliver90owner]

OK, I will bite and perhaps start the ball rolling. I'm not really into these engines but I would have thought that opening and duration are more important than degrees at full lift?

[philthehill]

The 1098cc Minor and 1098cc Midget/Sprite have the same camshaft Pt No: AEA630.

The valve timing data for the 1098cc camshaft can be found in the Minor Wksp Man General Data section.

Inlet valve opens........ 5 degrees before TDC. Closes........ 45 degrees ABDC.

Exhaust valve opens........51 degrees BBDC. Closes........21 degrees ATDC.

Use 0.021" valve rocker clearance (for checking purposes only).

Valve lift............0.312".

Using the above data the exact timing can be set using the vernier timing chain set up..

I would suggest though that unless the camshaft has been reground/modified there is little point in fitting the vernier set up to a standard 1098cc engine - setting the camshaft timing using the standard marks on the crankshaft sprocket and camshaft sprocket is more than sufficient/adequate.
Fitting the Duplex set up to a standard 1098cc engine is in my opinion a better way forward.
I would save the vernier set up for a modified engine fitted with a performance camshaft where you need to precisely set the cam timing/valve lift details.
Unfortunately the picture below cannot be rotated to give the correct portrait view as the web site keeps putting the picture upside down

[MikeNash]

Mr Merlin,
May I suggest you read this old thread https://www.mmoc.org.uk/MessageBoard/vi ... ng#p573883
wherein I measured valve timings on a couple of 1098 engines? You'll see that regardless of the timings and lifts declared by BMC what you actually get can be a good deal different.
Regards, MikeN.

[philthehill]

Mike
The link appears to be not working.

I would suggest that the BMC stated setting are good for a new engine but production methods and tolerances back then were not as tight as they are now. Also a well used engine may be different in that the valve train including the camshaft and valve seats will have been subject to wear.

The 'A' Series seems to benefit from up to 3 degrees valve advance over the factory settings.

Whilst it is good to have the valve timing perfect those settings are only the beginning and maximising the cam timing can only be determined by use of a rolling road/dynometer or extensive road testing.
Therefore I still believe that the factory markings/settings are good enough to be used for a standard 1098cc Minor engine otherwise a lot of effort and time is expended for very little gain. And to get the valve timing right the use of two dial gauges and a timing disc is a prerequisite (see picture above).

Phil

[MikeNash]

Well Phil, it worked for me just now! However, the link took me into the centre of the thread and you need to scroll upward to get to the important bits. Regards, MikeN.

[Merlin 2]

Hi all

thanks for getting back to me. Using the figures above and the fact that the part number is the same as the sprite that means maximum opening should be at 110 degrees ATDC.

I know you all think its complete overkill putting the Vernier setup on a standard 1098 and that the wear on the engine means the settings will be out and that to get any benefit i need to get it on a rolling road but I have a vernier set of gears and if I don't use them on the 1098 then they will just sit on a spare engine not being used at all. The only saving grace would be to let them sit on the spare as it is a 1275 and some day I might get round to re-building the 1275 and put it in the car.

Once again thanks for all your help and letting me know the figures I needed