Ignition Timing adjstemnt For H-iCompression

Bob Bidonde

Bob Bidonde

Well-known member
I have a 6:1 cylinder head on my engine, so I can only use the first 3 notches on the spark lever. The 3rd notch is for 30+ MPH speeds to avoid spark knock. I need to be able to retard the spark somewhat to fully appreciate the hi-compression head. My thought is to time the ignition at TDC of compression of Cylinder 1 with spark lever down 4 notches. This should give me 4 notches of lever travel up to retard the spark to occur at about 13 crankshaft degrees max.
What are your thoughts about my plan?
 
I have a 6.0 head also, and I set the timing with the lever down a couple of clicks. I run at highway speeds with the lever down at about 9.30 position, sometimes at 9:00 before spark knocking. Everyone’s linkage maybe different but yours sounds odd that you can only run 3 clicks down ? At least to me. I notice when my points close up I can run the lever down more, usually find the point gap .016 or so. New points I set the gap at .022 and when they wear in set them .020
 
I time my engine similar to the way you suggest. I have a Nu-Rex auto advancer and I time this way to prevent it from advancing too far or I hear it ping.
 
Bob, you are different than us since you are the only one driving, -but I tend to go the other way and I use the spark lever to set maximum spark advance when the lever is all the way downward. Start the engine about the 9 o'clock position and then do a full advance (-or less) as the terrain dictates. That way you never worry about over-advancing.
 
I'm with Brent. I don't set it to a number of clicks, since that varies from car to car, with a lot of cars not even having the detents to click anymore.

I set it to full advance all of the way down. I start it with the lever fully up, and usually run it at full advance or just above, unless knocking and terrain say otherwise. I also don't adjust the advance at stop lights or make other changes once it's warmed up.
 
This is interesting since I have noticed that I can only use a very little amount of the travel on my spark setting. Glad to see this discussion because I was wondering if I was imaging things, or if I had something broken.

Question; will shell premium change things? If so, how?
 
When I fitted a 6:1 head, I was aware that I would have to limit the spark advance so, after setting the timing in the usual way, I used a scale at the front pulley to help e set a stop. I made up a bracket that I screwed to the side of the distributor. It had a screw on it that operated like a throttle stop, only it prevented the arm on the top plate from going any further. IT WAS A PITA. I had to move the lever as the engine gained revs in fist gear, then retard it when I changed into second, advance again as the revs rose and repeat for third gear. I think I did only about 3 miles like that before I decided to do things properly.
I had a B distributor laying about so I took it to an ignition specialist and asked him to check whether it could be adapted. The answer was NO so I asked them to put together a distributor with max 22° advance by 1,800 engine rpm (from memory). When I came to collect the device, I was told they had fitted a vacuum advance as well. Wow!
Once I had it fitted and timed, the car now drives like a modern one. That was money VERY well spent.
My advice: while it is all very well to do things yourself (I understand the warm glow of telling people that you did it), there are some things that are better left to an expert. I get an even better warm glow when I drive that car now because it is such a joy to drive.
 
Synchro, so what distributor did they actually use. DND the no on a B distributor makes no sense as As have been using B distributors with no problem for a very long time.
 
If you are going to be serious about getting your timing correct with a 6 to 1 head you should consider finding true top dead center, marking your crank pulley and using some form of degree marker like the nurex item and a timing light. Total timing should be around 24-25 degrees or maybe even a little less. Once you set your total timing adjust your lever to wherever you want it to be. Pulled all the way down, 9 o'clock whatever. Retard for start, adjust for speed, what ever rings your bell.
 
Each engine is different. The only way to correctly set the ignition timing, in my opinion, is to search for the knee. Modern engines have a computer and a load of sensors to adjust the timing for the conditions. Even if you have a centrifugal advance and/or a vacuum advance, you still need to find the knee. After you find the knee you can measure the advance with a timing light and degree wheel. But setting the advance to some arbitrary number, even if it works good for some engine, does not guarantee that it will work for your engine.
 
nkaminar, I don't disagree with what you say. Every car engine combination is slightly different. You call it finding the knee I would call it the sweet spot. Clearly you find this easy to do. I have been doing the same thing for as long as I can remember. I think we both have mechanical backgrounds and a lot of A/engine experience. But I don't think those abilities exist with all A owners, in fact for many this may be a foreign concept. So what do those folks do. Look in a book?, find a friend? That is where timing lights and degrees come into play. Sure there are no one set of numbers that work for all combinations but it is a way to at least get in the ballpark and have a reference point we can discuss or argue about!
 
Richard Knight said:
Synchro, so what distributor did they actually use. DND the no on a B distributor makes no sense as As have been using B distributors with no problem for a very long time.
Click to expand...

I think they decided that it was not worth the hassle to use the B distributor - too much thinking to work out where and how to set the initial timing so that max advance came at 22°. I also suspect the weights were worn so that a smooth, reliable advance was not going to happen.
The distributor they adapted was from a Nissan. The only numbers I could find on it are:
T3T 127B1 8901
22100 33615

I think it is highly likely that if those numbers don't mean anything to you that they are from a Nissan Model that was not sold in the US.
 
I run a Burtz head and cam on a stock block. I timed it with the dimple on the cam gear. Using 87 octane non-ethanol fuel with one “glug” of Marvel Mystery Oil per tank, the knee or sweet spot is almost full advance. Also the engine will not start when retarded more than about 10 o’clock. So it seems to like lots of advance.
 
Richard, You are right that the nuances of Model A mechanicals are foreign to a lot of people. What is second nature to us is rocket science to them. But I will keep trying to educate the newbes. Us oldtimers all went through a learning curve even if we cannot remember doing that. I am still learning stuff and recently figured out what the Ford engineers were thinking when they designed the front brakes. Live and learn. Learn by doing.
 
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