Help!!! Am I a tooth out?

[IslipMinor]

will always be true on any normal camshaft

Only IF the timing about TDC is symmetrical! If the timing is asymmetrical, as with all BMC OE cams, there is a simple arithmetic explanation that supports the needs to make an adjustment, but not the other way round - unless you have something else?

If you put 'equal lift on overlap' into Google there are a number of puzzled owners of Mini and TR's who cannot get it to work on cams with asymmetrical timing, and it's not surprising as it never will! Make the simple correction to TDC of half the asymmetricity and away you go.

[philthehill]

In the course of checking/setting the cam timing I always use a 360 degree timing disk attached to the crankshaft pulley and two dial gauges. One gauge in conjunction with the timing disk to determine piston/crankshaft TDC exactly; and one gauge to determine the lift of the cam follower at the degrees specified by the manufacture. Unless you do it this way total accuracy cannot be guaranteed and engine performance may be effected. The use of a adjustable timing cam sprocket enables the cam to be set to manufactures specification. Also with the adjustable set up you can advance or retard the cam timing to suit the engine. I am not an advocate of using offset woodruff keys to obtain correct timing because to me it is not good engineering practice and there is a built in weakness at the root where the woodruff key offsets.

[IslipMinor]

Phil,

Other than I only have one dial gauge, that is exactly what I did to set up the cam originally. Using the 'equal on overlap' today suggests it may be 1-2° retarded, but this is based on the timing marks, so first need to validate the timing marks before rushing off making changes to the cam timing!

For a standard set up, the 'equal on overlap' is very easy, a quick bit of arithmetic to offset the TDC if required, but other than that just the usual spanners and feeler gauges.

[philthehill]

Richard
Exactly
That is why I wanted to see the cam sprocket/timing marks to confirm that the woodruff key slot is in the right place.
If there is nothing obvious causing the problem go right back to basics and start from there.

[Shawn]

Thanks to all who helped out with this one. I finally (sort of) worked it out. The mixture was way too lean.

A bit of background:
The engine that I swapped in is intended to be a stopgap, while my original one gets rebuilt. I checked out my two spare engines and chose the one which had no appreciable wear in the (standard) bores, nice snug piston fit and seemingly good bearings. When I couldn't get it to run well, I pulled the distributor (and electronic Hitachi) and swapped an original back in. The problem persisted. The carb (a single HS2) and manifold were the best of my spares and had been running perfectly well in the previous engine. It seems to be working fine, but I did clean out the dashpot and filled the damper with new ATF.

So in desperation, I set the carb to baseline mixture (12 flats), it was still way too lean. Then went back to base and tuned with a Colortune, idled fine but still way too lean. So I gave up and just turned the mixture way rich, and the problem seemed solved. Now, I'm blowing black smoke and fouling plugs, but the engine is running well and pulling like a train. A compression test shows about 120psi on all four (dry, hot & w.o.t.).

Can an engine require a richer mixture because of poor compression? The engine that I removed was worse than the one I fitted and it didn't need it.

Should I be looking harder for a vacum leak? I've checked hoses and done the brake cleaner spray test on the inlet manifold, not finding anything.

[MarkyB]

Check how much wear there is where the throttle shaft runs in the carb, they wear here, and probably worse on the end you can't see.
Are you using the lifting pin to check the mixture as you go, one flat at a time is the best way to get it right.
ATF is a bit thin, try engine oil as per the book.

[bmcecosse]

The compressions are desperately low.....I suggest test the gauge on another engine, just in case.... You shouldn't need a rich mixture. Is there a spring in the carb - above the piston? And yes - try engine oil in the carb.

[Ufudu]

I must thank BMC for his "equal lift on overlap" test.

I was idly browsing the forum, saw BMC's test method & gave it a try this morning.

Valve - rocker gap readings - about 40 thou apart! Off with the timing cover and guess what? One tooth out (cam was advanced) according to the timing marks.

Can't say I would have noticed since I only drove it for a few hours in February before starting the "restomaintenance" activity!

Fixed that and now no 1 reads 33 and 30 thou (give or take a few thou)!

So that's sorted. Many thanks again for sharing your many years of experience Roy!

One question I do have though: I purchased a new Crankshaft pulley lock washer from ESM:[frame][/frame]

BUT, I don't see how it locks onto the crankshaft, it has no tab?

[bmcecosse]

It simply is knocked in to the flats on the pulley - and then bent over a flat on the starter dog...... Not very good - but does seem to do the job. I put a few spots of Loctite on the threads (after degreasing) ...

[Ufudu]

Thanks for the quick response; By "flats on the pulley" you mean? There are two depressions on the pulley face, do you knock it into that? I presume it goes in concave side forward

Apologies for the "doff" questions!

[bmcecosse]

Yes - although the ones I have seen are flat. Is the bore a good fit on the crankshaft nose?

[Ufudu]

Yes, it is a good fit on the shoulder of the starting nut.

Thanks for your help, I will give it a "bash"

[bmcecosse]

Ah yes - the shoulder !