distributor advance problem

M

Masot

Member
Hi guys.

I have a problem with the advance on my 8BA flathead.

Mallory Chevy distributor with pectronic.

start 800 Rpm 10º BTDC.

When accelerating the engine advance 20º ATDC

Why does it work backwards?

Start ok, running ok, not hot, everything ok...



Thanks
 
I have no idea what your problem can be. I have converted a couple of early chev distributors, never had a problem.
Where is your vacuum connected to?
Try testing it with the vacuum plugged and see what you get.
 
Are you sure you are reading the advance properly? I get confused just thinking about it.

One possible explanation is that you converted a marine reverse-rotation distributor? Then the advance would work the opposite way. But then I don't think it would run very well, but I have no experience with that.

The Pertronix is another complicating factor. Maybe unconvert it and see what happens? (I'd do that on general principles.)
 
Last edited:
69a said:
I have no idea what your problem can be. I have converted a couple of early chev distributors, never had a problem.
Where is your vacuum connected to?
Try testing it with the vacuum plugged and see what you get.
Click to expand...

mechanical distributor, not vacuum
 
One additional thought. How did you obtain the advance numbers? If it was with an advance timing light, I have had problems with them going bad after a short period of time and giving false readings. Perhaps you could borrow another and double check the curve?
 
If using a standard timing light, will the mark on the crankshaft pulley "move" clockwise as the RPM increases? If it does then there is an issue with the advance mechanism inside the distributor. Wrong components installed at factory. Clockwise components mixed with anticlockwise ones (Ford Chev.)
You say in original post "Mallory, Chevy". Who did the modification?
 
If it's a Mallory, the advance plates have different part numbers for CC vs CCW units. The part number should be visible if you remove the cap. That part number would be indicative.
 
Hi. I'm not sure exactly what your problem is, I'm just guessing. Number 6 cylinder is halfway through the firing order. The rotor in the distributor only spins at half the RPM as the engine. So if you rotate the engine one complete revolution, you will get the "first piston" will be number 1.
 
I'm not an expert on actually what the initial timing deg. should be, but I've always set my distributor, at idle, so the pointer on the front cover aligns with the mark on the pulley. My SBS HEI has 22 degrees advance, at 2500 RPM.
Let us know exactly what you are trying to do, you say it will run and idle, so number 1 must be in the correct position. Check that all the leads are going to their correct cylinder, as it is easy to get a couple of them crossed, especially 6 and 7.
 
Piston one and piston six coincide at TDC.

Now my distributor works TDC with piston six.

It seems that the problem is in the Cam advance.

I guess I have to adjust the cam, I need a tutorial on how to do it without removing the cylinder heads.

Someone who can tell me how to fix this in a simple way

Thanks
 
You can't adjust the cam.
Follow the lead from number 1 cylinder to the distributor cap. Put a mark on the distributor body below number 1 position. Remove the cap and rotate the engine until the rotor is lined up with the mark you put on the side AND the timing marks on the front pulley line up. You now have the engine at TDC with number 1 on the compression (firing) position.
What problem are you trying to sort?
 
Masot said:
Piston one and piston six coincide at TDC.

Now my distributor works TDC with piston six.

It seems that the problem is in the Cam advance.

I guess I have to adjust the cam, I need a tutorial on how to do it without removing the cylinder heads.

Someone who can tell me how to fix this in a simple way

Thanks
Click to expand...

As it pertains to adjusting the cam there is no simple way to do any cam timing without removing a head. The process is rather involved.
 
Yes, I have, distributor position piston one.
Engine won't start, carburettor pops.
Only works on piston six...
 
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