timing with a B cam grind

[Clem Clement]

I have a bud who just put a B cam grind in his Model A. Does he need the B timing cover? With the A timing cover the spark advance is ineffective.

[Chuck Sea/Tac]

What do you mean the A cover is ineffective?
The timing cover is for the different distributor, not the camshaft.

[oldbike99]

No, the cover does not need to be changed. I would suggest that you carefully go over the timing procedure, which has been covered many times on this forum (do a search) and you will find the solution.

[Patrick L.]

The model B timing cover is for the model B distributor. Valve timing difference in the model B cam has nothing to do with ignition advance. Most A cams are reground [ or newly made] to model b specs [ or close to it]. Is your bud going to use an A or B distributor ?
So I would answer your question by saying no if he is using an A distributor.

[1931 flamingo]

"spark advance is ineffective"

When the cam was installed are the "dimples" on the cam gear and crank correct??
If you'd installed a B dist then the front cover would have to be changed to time it correctly.
Something else is going on. JMO
Paul in CT

[Bob C]

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I assume you are asking about valve cam and not distributor cam.

Bob

[Patrick L.]

Originally Posted by Bob C

I assume you are asking about valve cam and not distributor cam.

Bob

Thats a good point, I was was certainly thinking camshaft due to the way the post was written.

[redmodelt]

I was thinking cam shaft but in reality it could be taken ether way esp as he is asking about timing.

[Tom Wesenberg]

Distributor B cam gives more dwell (time the points are closed), but it's still timed at top dead center. So, it's the same timing as a stock A distributor cam.

[Clem Clement]

I'm so confused. He sez he has a 340 grind on the cam. He times the car by hand several degrees ahead of the normal spot. He now has a fine idle but the car is not together so he doesn't know how it will work under load.

[Marco Tahtaras]

Originally Posted by Clem Clement

I'm so confused. He sez he has a 340 grind on the cam. He times the car by hand several degrees ahead of the normal spot. He now has a fine idle but the car is not together so he doesn't know how it will work under load.

Hi Clem,

It sounds like he has a new cam from Bill Stipe???

If he is running a Model A distributor then it needs to be timed like a Model A with it at TDC with the lever fully retarded. If he can't get a decent idle at that point he needs to determine why.

Keep in mind that the Model A distributor when fully advanced provides 40 degrees advance or 40 degrees BTDC. This is workable (when used properly) at the low factory compression ratio of 4.22:1. If he has added a high compression head then in most cases the full 40 degrees advance (fully advanced at the lever) is not usable without potential damage.

The FULL story is needed for appropriate advise beyond what I've offered thus far.