Ignition timing help request

[bowjangles]

My 1975 13-B (from a REPU) has a '81-'85 RX7 breakerless distributor in it. The pulley has two timing marks on it.
Can anyone advise me how to adjust the timing in this situation- i.e. how many degrees for Leading and Trailing? With, or without, vacuum attached? Thanks

[chibikougan]

Yes it is in that Factory Service Manual I have given you the link to 11 times.


http://foxed.ca/index.php?page=rx7manual

[bowjangles]

Mtr. K: Perhaps you didn't understand the question- Let me explain in a different way:

Does one use the timing settings data for the '75 13 B engine ,or for a vehicle with the '81-85 RX 7 distributor? The manual you referred me to (11 times?) claims that they are different. Is that not correct?
FYI:Perhaps you could be a little more tolerant of those neophytes who haven't reached your level of expertise. After all, the Forum is there for all levels of interest and knowledge. Lets increase the interest in the forum, not smother it with degrading statements by respondents.. Help don't insult!

[chibikougan]

Originally Posted by bowjangles

Mtr. K: Perhaps you didn't understand the question- Let me explain in a different way:

Does one use the timing settings data for the '75 13 B engine ,or for a vehicle with the '81-85 RX 7 distributor? The manual you referred me to (11 times?) claims that they are different. Is that not correct?
FYI:Perhaps you could be a little more tolerant of those neophytes who haven't reached your level of expertise. After all, the Forum is there for all levels of interest and knowledge. Lets increase the interest in the forum, not smother it with degrading statements by respondents.. Help don't insult!

I don't understand how me stating a fact is an insult or degrading. I gave you a helpful tool that answers your questions. If you can figure out how to use this tool it will help you much more in the long run.

I try to link this manual to everyone who joins in the intro section just like I did you.


I am also no expert I just reference the data needed when needed.


Good Luck.

[tom93r1]

First you need to determine what pulley you have on there. Different engines and different years had a few different timing marks so until you know for sure what marks are on your pulley you won't be able to time it correctly. And once you have that figured out, it probably doesn't matter if you time it according to GSL-se instructions or REPU instructions. Neither will be the same as your setup but both are a good starting point. Once you have it set to one of those two specs then you can fiddle with it until it feels right.

[bowjangles]

Thanks for your help TOM:

I will certainly do what you suggested, but don't have a clue how to determine what kind of a pulley I have on the 13-B.??
I do know that it only has two marks on it, and the '74 REPU manual sez to time the Leading at 0 degrees and the Trailing at 15 degrees. However,

The distributor on the car is from a '81-'85 RX7 and for that car, the manual calls for Leading at 5 degrees and Trailing at 20 degrees.
So, which settings do I use? Also, when I do decide which settings to use, this is done with vacuum hose disconnected at the distributor and plugged, correct?

Lastly, when you say "fiddle with it" does this mean just turn the distributor 'till engine runs it's best and forget about the numbers?

[RETed]

I have to ask...

Do you understand the basics about ignition timing?

Since we're talking about an OLD vehicle, I would assume that emissions is not a concern.
If this assumption is correct, the timing marks - and what they represent - don't really mean anything; they are there as a guideline and make it easier to get the engine started.

Like everyone else said, you really need to verify TOP DEAD CENTER.
There is a quick and dirty method to do this by sticking something into the spark plug hole (after removing the spark plug) and seeing where the object would protrude into the engine the LEAST - shallowest.
Once you get an idea where TDC is...reference this with the pulley marks.

BTW, the later models usually have marks at 5-degrees *A*TDC and 20-degrees *A*TDC.
The *A* part is important, cause it means AFTER; if you confuse this with *BTDC* - we're talking a difference of 10-degrees total!

First step, adjust distributor until you feel the engine idles best...
Since we're not worried about emissions, use the pulley marks as a guide and go from there.
Typically, most engines will run a little better with a little more ignition timing advance than stock.
More advance at idle will cause the idle to bump up a bit, so there is a balance between idle quality and how much fuel it's going to drink - i.e. gas mileage.
Just adjust for what is best for you...

Now, as for absolute advance at full load - what you call pulling-the-vacuum-hose - start at 20-degrees and go up from there.
20-degrees is a good, safe starting point.
Most rotaries will make good power somewhere around 25 - 30 degrees of total advance.
I've seen some motors make power all the way up to 35-degrees, but EGT's tend to get mighty hot up there - you're sacrificing engine life for power.
If you don't know what you are doing at this point, I would HIGHLY RECOMMEND you find someone who does...


-Ted

[bowjangles]

Thanks for the excellent primer on timing, Ted. This should be made available to all who ask for help in this matter.

[rxtasy3]

i think it's more knowing what pulley u have for what amount of timing each mark represents than what distributor is being used.