Boost prep distributor
10-20-16, 12:13 PM
#1
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Boost prep distributor
I hate to ask questions but I just can't seem to find a answer and the person who I had bought this distributor has horrid customer service skills. I'm building a 13b blow through with a Nikki carb. I have a locked mechanical distributor. But what in wondering is do you still use the vacuum lines for the advance or do you lock them so the distributor fails to do any advance or retard. If this question has been answered in sorry I just didn't see anything.
10-20-16, 05:32 PM
#2
You don't want a locked distributor. You want one that still can advance but only by 10 degrees through mechanical action only.
Don't hook up the vacuum lines because the diaphragms would experience boost which they were not designed for and may react badly.
It is best to shorten the length of the slots the advance weights travel in, so they can only move half the distance of stock. The **** is 5mm so factor that into your new slot length calculation.
I've found that filling the end of one slot with weld and then hand filing and shaping it to be um... was it 7.2mm in length? That is down from a 9.8mm of original length. This new shorter length gives you 10 degrees of mechanical advance compared to the original 20 degrees. However that varies by year. You need to know the model number stamped on the outside of the dizzy body. Your numbers to look for are:
N201
N231
N249
N304
Avoid N304 as is it has a curved slot and advances more than the other numbers due to its length. It was a little cheat Mazda did for the GSL-SE so they could set it to 5 degrees ATDC and still end up with 24 degrees total mechanical advance by 4000 RPM. You don't want to have anything to do with this dizzy and boost.
Even the N249 has a slightly longer length slot than the N231 and N201. The N249 allowed for 24 degrees full advance while starting at 0 degrees TDC.
The other two models are the easiest to modify. They only advance 20 degrees.
Did I just confuse you with the memory dump? Hopefully not.
Don't hook up the vacuum lines because the diaphragms would experience boost which they were not designed for and may react badly.
It is best to shorten the length of the slots the advance weights travel in, so they can only move half the distance of stock. The **** is 5mm so factor that into your new slot length calculation.
I've found that filling the end of one slot with weld and then hand filing and shaping it to be um... was it 7.2mm in length? That is down from a 9.8mm of original length. This new shorter length gives you 10 degrees of mechanical advance compared to the original 20 degrees. However that varies by year. You need to know the model number stamped on the outside of the dizzy body. Your numbers to look for are:
N201
N231
N249
N304
Avoid N304 as is it has a curved slot and advances more than the other numbers due to its length. It was a little cheat Mazda did for the GSL-SE so they could set it to 5 degrees ATDC and still end up with 24 degrees total mechanical advance by 4000 RPM. You don't want to have anything to do with this dizzy and boost.
Even the N249 has a slightly longer length slot than the N231 and N201. The N249 allowed for 24 degrees full advance while starting at 0 degrees TDC.
The other two models are the easiest to modify. They only advance 20 degrees.
Did I just confuse you with the memory dump? Hopefully not.
