Timing a type 4 (TIV)

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Timing a type 4 (TIV)

Post by 71_georgia_beetle on Wed Oct 22, 2008 3:18 pm

OK, I think I found out a few things about the iffy running of my new westy. All the exhaust valves were set around .008. I adjusted all the valves to .006 and the engine runs fairly quiet now.

Here is where I'm having trouble. To dwell or not to dwell. The dwell is suppose to be +/-2 of 50 (or +/-2 of 25 on my 8cyl dwell meter) but it is currently at 10 more than specked. I can adjust it but some say time it with a light not dwell. If I am reading the book correctly, my 74 "AW" engine should be timed 10 ATDC. This means with the engine to temperature, vacuum hoses on, that my timing mark should be between the 12 mark and the 8 mark to the RIGHT of the zero on the shroud scale. Correct? The timing was set at 12 BTDC, 12 mark to the LEFT of the scale. All of the timing 's were using the 0 static timing mark on the scale. Before, the engine was set at 12BTDC and the engine RPM was over 1000 rpm (so says my tach) and the audible tone was high as well. I have since changed it to 10 ATDC and this has brought down the RPM to 800-850 and the audible sound considerable lower.

My main question is 10ATDC, using the static 0 on the scale, is this correct?
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Re: Timing a type 4 (TIV)

Post by Treehive on Thu Oct 23, 2008 1:14 pm

I am anxiously awaiting the answer to this question as well. It's good to have another Type IV bus out there.
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Re: Timing a type 4 (TIV)

Post by zabo on Thu Oct 23, 2008 1:31 pm

i timed at 7.5 degrees BTDC
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Re: Timing a type 4 (TIV)

Post by 71_georgia_beetle on Thu Oct 23, 2008 4:16 pm

OK here is the official answer. My set up is fucking junk. Single progressive carb with a mechanically advanced 009. If you follow the idiot book which was written for a dual carb set up with a vacuum advanced dist of 10 ATDC the idle sounds great but the bus runs like shit. 2nd and 3rd are sluggish and she will "kangaroo" in second on a slight grade.

The answer with my set up is 28 full advance which is 12 BTDC idle. I reset the dwell, timing, adjusted the idle and she runs great. I also added half a can of octane boost and the dieseling (spark knock) has ceased.

I am in the market now for a set of dual carbs, manifolds and linkage.

For Teddy: 28 full advance is where your TDC mark on the pulley will line up with the 28 mark on the scale, to the left of zero when you time it with near full throttle. There is actually an indicator at 28. 12 BTDC (to the left of zero) is where the TDC mark on the pulley will show on the scale with the engine at idle. Not being a smartass, just putting it in english.
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