This putting the race car back to "in the day" specs is kind of a pain. I have an old TI distributor that i've tested thanks to advice from board members. it's fine. The distributor does not have a vacunm advance. Now i'm looking at the advance weight springs and they look pretty weak. This is a race car and I want all the advance in at 3000 RPM ( I think) I called around to find someone with a SUN machine in the Denver area and they either don't know what i'm talking about or they don't have them anymore. i've contacted race engine shops etc. Do i just put a standard spring in and not worry about it or??? I really don't want to mail this off to someone. i'm trying to get ready for a race.I thought about putting the springs in from the MSD distributor that was in the car but they seem to not match up with the spring post height. Any ideas. Jerry
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Re: TI distributor advance curve
Are you racing this car or driving it on the street ?
Bill -
Re: TI distributor advance curve
Strictly racing. This is an old road race car. the distributor i'm putting back is is an old L 88 pure mechanical distributor. I normally run about 38 degrees total advance. at 3000RPMComment
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Re: TI distributor advance curve
If it is a L-88 distributor, the centrifugal curve is not that aggressive. Maybe someone with a CSM can check if you give the year and dist. no. In particular ,you want to know the max advance, so you can get your initial timing in the correct range, and I suggest you disassemble the dist. to be sure the advance limit bushing is in good shape.
I ran a '67 L-88 TI system on my '63 L-76 for several years, but before I installed the dist. I replaced the weights, springs, and VAC with the '64 SHP/FI parts that had all the centrifugal in at 2350 engine revs.
I kept all the original parts and reinstalled them after the system went TU on me the second time and I figured out how to make the single point system work to 7000 revs. In 1988 I sold the system to David Burroughs, who at that time owned the '67 L-88 that the system came from, and he installed it back on that L-88.
Once you get it installed you can check the curve with a dial back timing light. Mr. Gasket and somebody else markets a kit of three spring sets and weights available through the usual hot rod parts sources. The weights are junk, but the springs can be used to tailor a moderately aggressive curve.
DukeComment
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Re: TI distributor advance curve
Ok , I have looked the distributor over and i see the button under the advace plate that restricts the total advance. I'm assuming it's a stock unit. How much total advance will it allow and do I need a different "button" to allow more advance. I can check the curve with my degreed damper and my backdial timing like. I'd like 38 full advance. how much advance at 1200 RPM idle can I stand? or should I have. It seems with the advance limited that I will need to run more advance at idle than I'd like to get 38 degrees at 300RPM. Is that correct??Comment
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Re: TI distributor advance curve
what is the part number on the dist tag?Bill Clupper #618Comment
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Re: TI distributor advance curve
Yeah, that's what's needed. Clup has a spec listing for all Delco distributors. If the tag isn't there, and you know the year L-88 it came from maybe some good samaritan can check the appropriate year CSM.
It's probably in the range of 26-28 degrees, which means you need 12-10 initial to achieve 38 maximum. Once the total dist. advance or at least a ballpark number is known, you can set the initial at some nominal value then rev up the engine until the advance stops and adjust the dist. to achieve 38.
A set of light springs is good for the above procedure to minimize the revs you have to achieve while holding the timing light. Some distributors are as high as 5100 and most guys don't like sticking their heads into the engine compartement with the engine screaming.
DukeComment
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Re: TI distributor advance curve
Clem, you are a wealth of knowledge! I just checked and the "button" . It has a C clip under it to hold it on but it appears to be a hard black plastic. What should I replace it with and where do i get it?Comment
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Re: TI distributor advance curve
some of the after market advance kits have a steel or brass replacement. NEVER use the weights supplied in any after market advance kit because they are not hardened and cause all kinds if problems. i will look tomorrow to see if i have any bushings.Comment
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Re: TI distributor advance curve
this kit looks like it may have a brass bushing. http://www.streetperformance.com/par...619-31042.htmlComment
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Re: TI distributor advance curve
Thank you. I agree the kit you found on the web site looks like brass. i'll find out. I appreciate your looking through your stuff. thanks. JerryComment
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Re: TI distributor advance curve
Jerry, I have been reading your discussion and have a few questions and comments. In reading I am not sure if the distributor has provision for a vac canister or not. You were asked for the P/N on ID band. I have to assume it does not have one since you have not indicated the P/N. So, maybe we can figure it out. If indeed you have an L-88 distributor (67-69), you would have P/N #1111240, 295 or 927 depending on year-they all used vac canister #373, which is a "plugged"/no vac unit. The other possibility is a #1111263, which many say was an L-88 unit; but it is not, because it does not have any provision for a vac canister-the "General" never put a no vac provision dist on an L-88, or any other OEM model of this era-only the P/Ns above were used. The #263 was available only as "over-the-counter" through the Performance catalog in the late 60's, early 70's. It, like the 3 L-88 units is mechanical advance only, and was available for early BB with partial lower groove or fully grooved for SB & later BB. It was also available as a CCW or CW rotation-all using the same P/N-go figure.
I have the specs for every P/N Delco distributor (at least during the era we are talking about) and have a very good working Sun Distributor Tester. In my distributor business, I set all distributors I work on to factory specs. I have the advance mapping for each P/N above and they all are slightly different in the middle RPM range (but not much), but all are 0-2 degrees at 500 RPM and max out at 12-15 degrees at 3000 RPM (distributor speed-half engine speed). If we can more closely ID your unit, I can give you the specific mapping-but you are going to need a Sun Machine-I have modified my machine to be able to not only test TI distributors, but also the GM amp at the same time on the same machine. I have given you the idle and the max specs, which could be tested in the car in a number of different manners, as Duke has indicated-it's just more difficult and time consuming to do it correctly.
I have a brass sleeve/button for replacing the factory rubber piece that Clem mentioned, but it is readily available at any Performance Shop in an advance weight kit. Weather or not you use the weights and springs is no matter-it's about $10 bucks and faster than me to send one to you.
If you can not ID the distributor you have, anyone with a Sun machine can customize or set the advance to the specs you wish/desire. With additional info i.e., C/R, RPM range, intended use and altitude, etc. the Sun tech could recommend an advance curve mapping that would maximize performance.
Happy to help in any way. I realize you don't want to send your distributor out, but I am in Albuquerque if you want to come down.
MichaelZ505Comment
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