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404 ignition timing with strobe

7526 Views 6 Replies 6 Participants Last post by  hammogger
Hi. In the book it says that the ignition timing for a 404.1 at 800rpm (I think it said 800) should be 15 to 25 BTDC!
Does anyone know what the accurate (exact) timing should be?
Thanks,
Matt
Hi. In the book it says that the ignition timing for a 404.1 at 800rpm (I think it said 800) should be 15 to 25 BTDC!
Does anyone know what the accurate (exact) timing should be?
Thanks,
Matt
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· Registered
85' U1300L Holset Turbo VA A/C, 66' Propane 404.1 rock mog, 1975 416 Doka, G500, Volvo C303
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5,794 Posts
Time it where it runs best. Most mog gas engines are a little particular, some run anywhere. It really depends on your engine.
 

· Registered
1967 404 Unimog (Belgian), 2010 Ford Fusion Hybrid
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255 Posts
15-25 BTDC sounds rather far advanced to me.

With a Pertronix mine runs well around 12 BTDC. If you're running points I think you'll be less advanced than that. I seem to recall hearing that adding the Pertronix allowed more timing advance.

I can't remember what I used when I had points.
 

· Registered
1988 U1300L RW-1
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504 Posts
One m180 in a 404: 18 btdc, mechanical distributor, Pertronix

Another m180 in a 404: 22 btdc, vacuum distributor, points

And another: 14 btdc, mechanical distributor, Pertronix

The motor that is timed at 22 came to me that way. It runs so well I have never been inclined to change the timing. I seem to remember a note I found from the previous owner that said he had liked where it ran at 27(???) but put it back to 22 because it ran noticeably warmer.

I wonder where all the variations come from? Several different cams were apparently used, a couple of compression ratios used, add variations in timing chain wear and engine wear...many variables.

All of these motors run on 85 octane fuel, never any pinging, and timing values on the two that I changed were arrived at using the 'best running' method (highest top speed achieved in a given distance).

Crazy that you have to put so much energy into timing the thing, but it does end up being rewarding! FWIW, I started at 12 btdc and advanced until power went flat and backed up to the last setting.
 

· Registered
'62 404 Bundeswehr Radio Truck, '61 Bundeswehr 404 Doka
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438 Posts
The variations are probably due to varying advance mechanisms. These things are all 40+ years old now, so who knows if the advance in the distributor has ever been serviced?
 

· Registered
'88 U-1300L, '70 406, '78 406, '78 416 project, '82 406, '57 404, '65 404, '70 404, '68 Haflinger.
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1,852 Posts
IMHO there is no exact normal timing, just a factory starting point. The biggest variable is the gasoline you got last time you filled up. Might I suggest you forget the timing light and simply advance the timing until every day driving indicates the timing is too far advanced and performance starts to drop off, then back it off a little? You might be surprised at how well very early timing works. Remember, with mechanical spark advance the timing is going to run up at least 35 or 40 deg BTDC at highest rpm. It's that high rpm setting that means the most to us 404 drivers who want the most get-along on the highways.

Bob

Hi. Thanks for all the replys. I think I'll just have to play with it and see!

All the best,
Matt
 
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