Dwell #'s

71mtnscout

71mtnscout

Member
Ok, I need a refresher! My dwell meter got crunched and doesnt work, so I borrowed a buds. His meter doesnt have a 4cyl scale, so I have to use the 8cyl scale. Is 8cyl 1/2 of the 4cyl setting? I know the 152 with the delco dizzy likes 72* or so, so do I set it at 36* on the 8cyl scale? I did this and it seems to run ok after I reset the timing and then re-adjust the carb. I havent had a chance to take her out on a road test yet to see if its good.
 
71mtnscout said:
ok, I need a refresher! My dwell meter got crunched and doesnt work, so I borrowed a buds. His meter doesnt have a 4cyl scale, so I have to use the 8cyl scale. Is 8cyl 1/2 of the 4cyl setting? I know the 152 with the delco dizzy likes 72* or so, so do I set it at 36* on the 8cyl scale? I did this and it seems to run ok after I reset the timing and then re-adjust the carb. I havent had a chance to take her out on a road test yet to see if its good.
Click to expand...

On all the analog/old skool dwell meters I have, to directly read dwell on a 4 cylinder distributor, you double the 8 cylinder scale reading. So...using the 8 cylinder scale, set the dwell to 36 degrees which is within spec for only a delco distributor.

Most eight cylinder scales only read up to 45 degrees as no eight cylinder distributor would ever use a dwell spec greater than 45 degrees.

Engine analyzer oscilloscopes do usually include a four cylinder scale on the screen, the tick marks are clearly denoted in a range between 0 degrees and 90 degrees.
 
Thanks michael thats what I thought, just couldnt remember. Havent used a dwell meter in probably 15 years or so. Goin on a test run.
 
Runs much better, tried to performance tune it tonight, but the dizzy is 180 out and the oil tube is hitting the valve cover before I get it to the "edge" of advance. It is better than it was though.
 
If it's running that well, it can't be "180" out of synch. It's only one tooth retarded from correct position.
 
I dont think that its out of sync. The dizzy was stabbed 180 out from what I normally see. The window is almost pointing to the valve cover. It times just fine, I just cant move the dizzy far enough to get to the max advance due to its orientation. I will pull the dizzy this weekend and re-orient it so that I can get more movement before anything hits something.
 
It takes less than 60 seconds to properly re-locate a distributor onna I-4!

And in the case of the delco unit on an I-4 motor, the defining factor is locating the oiler tube and vacuum advance in the correct orientation to allow maximum rotation of the distributor body for timing lock-down. That in turn positions the cap window in an accessible location for inserting the tool for adjusting dwell when needed.
 
michael mayben said:
it takes less than 60 seconds to properly re-locate a distributor onna I-4!

And in the case of the delco unit on an I-4 motor, the defining factor is locating the oiler tube and vacuum advance in the correct orientation to allow maximum rotation of the distributor body for timing lock-down. That in turn positions the cap window in an accessible location for inserting the tool for adjusting dwell when needed.
Click to expand...

Yup, yup, will be doing that this weekend and do a real power tune on her. She drove amazingly better to work and back today. This is the first 80 that I left the 152 in and I dont plan on changing it out. Well maybe for a hotrod 152 one day.
 
Ok, got the dizzy re-oriented correctly and tried to power tune it, but cannot get it to ping. I can advance it till it starts to falter, then cut it back just a touch so it smooths out, but no ping?
 
Power tuning must be accomplished while engine is enduring wot or at lease while it is under significant loading and cylinder pressure.

Ping (detonation) in a function of timing and high relative combustion pressures and temperatures. These threshholds are only achieved under high power conditions. At your altitude you May not get it to ping easily infact it May start to lay down and not had enough heat to ping. I have been building boat engines for use on bigbear lake for many years and you can run a bunch of timing on crappy gas and not ping but loose mph. I lay on the floor next to the engine from a standing start to max mph to hear it and usualy won't before it lays down.

I've got 36 degrees of total timing on my 152 when the centrifugal advance maxes out at around 3300 rpm. No ping at wot at sea level.
 
Robert's analysis is spot on! It's all about your altitude!

Along with on-board fuel octane rating. And octane can vary tremendously with each load of fuel, no matter what grade is dumped in.

I base all my tuning info for these engines on the use of whatever passes for "regular" fuel in my local market...at an average elevation of 700ft.
 
Ahhhhh, well it runs alot better than it did before the power-tune attempt. I will keep the dizzy a little loose for now and see if a few minor timing adjustments will net a litle more ponies. Working on the front wheel bearings right now....need parts.
 
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