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Tips
Tips

Distributor repositioning question

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Hi Hondo,

I wonder if that was related tot the mod Jeff did? Both of the distributors I'm familiar with (the one on my 4A and the one on my 8), the vacuum advance moves the breaker plate, and does indeed have some limitation on the movement, but the mechanical advance works on the shaft, and shouldn't be affected by the position of the plate.

But it does bring up an important point, Ed should check that using all of the thumbwheel advance isn't interfering with getting the full vacuum advance.

-Darrell
 
really not sure all I know is I had my thum wheel almost all the way in one direction, advanced direction then when I used a timing light and reved the engine the timing mark on the damper would not advance to 30 degrees BTDC, so I centered the thumb wheel, adjusted the timeing by moving the distributor and when I reved the engine that time I got full advance, now I am running pertronix also, could be a coincidence.

if you rev your engine and get full advance then no issue

not sure

Hondo
 
poolboy,

Jeff told me that he put the thumbscrew nearly to the end of the advance range, and to leave it there. This information came to me late. Before I receive it, I had dialed the thumbscrew to the middle range when I did my static timing. But upon receiving Jeff's information, I dialed the thumbscrew back to the end of the advance range (which on my unit is a little difficult to do because of some binding... thus my use of "wrestling"). Bottom line: I checked the timing next with an advance timing light and it was right on 12 degrees BTDC -- the best I can do without removing the distributor and repositioning it, which I am not prepared or able to do at this time. (Jeff recommends 12-15 degrees BTDC.)The car runs great with the current setup, and so I will leave things alone until I see or hear signs that something else needs to be done.

Relatively warm day in the Valley today.... I'm going for a long ride.
 
When I read the "Tips" manual, it alludes to setting the timing as far advanced as possible without getting "pinking". So the initial setting is really just a starting point, isn't it? The actual "best" setting would be determined by driving...or is it?

John
 
CJD said:
When I read the "Tips" manual, it alludes to setting the timing as far advanced as possible without getting "pinking". So the initial setting is really just a starting point, isn't it? The actual "best" setting would be determined by driving...or is it?
Click to expand...

Best possible by ordinary mortals, yes. Personally, I like to back off by about 2 degrees, as a little extra insurance against having knock I cannot hear.

I'm pretty sure this was caused by knock, that I didn't hear:

BrokenTR3piston.jpg
 
Randall,

Are you saying that when you get the timing about "right," that you then retard ("back off") by 2 degrees?

What do you think of Jeff's instructions to me that I should set the timing at 12 to 15 degrees BTDC at idle without vacuum, and that "14 degrees is best." And that I should leave the micrometer thumbscrew at nearly the end of the advance range? These are pretty precise instructions, not just a starting point.
 
LexTR3 said:
Are you saying that when you get the timing about "right," that you then retard ("back off") by 2 degrees?
Click to expand...
What I do is warm the engine thoroughly, then advance the timing until I can just force it to ping slightly by using full throttle around 1500 rpm (normally I would never use full throttle at such low rpm). This procedure is documented in the owner's manual. Then from that point I back off about 2 degrees, so it never pings under any circumstances.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]
What do you think of Jeff's instructions to me that I should set the timing at 12 to 15 degrees BTDC at idle without vacuum, and that "14 degrees is best." And that I should leave the micrometer thumbscrew at nearly the end of the advance range? These are pretty precise instructions, not just a starting point. [/QUOTE]

Well, you've paid Jeff to modify your distributor, so it seems kind of foolish to ignore the advice (that you also paid for). If following his advice nets you performance that you like, then why not?

For the thumbscrew argument, I can't see where it could have any effect at all on the centrifugal advance. As noted, the centrifugal advance moves the point cam, not the point plate. It might have some small effect on vacuum advance, but not enough to worry about, IMO. The entire vacuum advance plays only a small role anyway (and was eliminated on later Triumphs to reduce NOx emissions).
 
Randall,

From what I am reading from you and others, it seems clear that the thumbscrew adjustment and vacuum advance is useful for only minor adjustments.

I drove north of here yesterday to visit a friend who works in a shop that restores Triumphs (and other high end sports cars). He took a look at my distributor and said that the way it is positioned -- not hitting the head yet -- should allow me to further rotate it.

I told him that I had loosened the pinch clamp but the distributor had hit some sort of obstacle and wouldn't rotate any further. He said that I should also loosen the bolts holding the clamp to the pedestal, and that would allow me some additional rotation room. I'll try this today.

He was very surprised when I told him that the advance has been reset from 4 degrees BTDC to 12 to 15 degrees BTDC. When I told him that I have been able only to reach about 11 or 12 degrees BTDC, he said that a couple of degrees retarded won't hurt anything (which is what I think you have said also).
 
Randall,

Once more you are right on the money. It was you who first suggested loosening the distributor clamp bolts as well as the pinch bolt in order to further rotate the distributor. And my friend yesterday said the same thing.

Today I loosened the bolts slightly, loosened the pinch bolt, and voila, the distributor rotated easily the rest of the way to give me more advance.

Thank you again for your informed advice. Remember: I was the first to say that you ought to write a book (manual).
 
I agree with Ed about the book! I've only been on the website for a few months and I've seen Randall solve an uncanny number of issues!
 
LexTR3 said:
Remember: I was the first to say that you ought to write a book (manual).
Click to expand...

Well, first on this forum, perhaps :laugh:

Seriously, I just don't seem to be able to write even decent tech articles. Answering questions is easy for me, something I can do in my spare time (waiting for the bits to go round). But somehow when it comes to writing an article (let alone a book), I get all bogged down in details and can't put together a coherent narrative.

So, I'll leave the articles and books to others (what a shame that the author of the excellent articles on the Buckeye Triumphs site has moved on). Someday if I run out of better things to do (not bleeding likely!), I might plagiarize Dan Master's TR6 electricals book into a TR3 version, but don't hold your breath :smile:
 
I just reinstalled my new engine in the Tr3 on Sunday of last week, I did the start up last night at about 6:00. The timing was off because of the same thing Lex is dealing with. It took about 15 minutes to pull the pedaistal and reposition the dist. No big deal. Just getting the slot to line up with the oil pump took a couple of try's with a long screw driver to turn the oil pump.
 
I just found this thread and thoufght I'd interject a few comments based on what I read.

The verrnier adjuster's increments ARE 4 crank degrees per mark, but it takes roughly one full turn of the wheel to move 1 degree. You can make big adjustemnts here (up to 10 degrees) BUT you'r changing the breaker plate position away from optimal. The more adjustments you make here, the further you're moving the ignition rotor away from the cap terminal when the points fire. Adding a Pertronix makes the problem worse due to an improperly phased module (rotated clockwise from where the points were positioned.

When I rebuild a distributor, I correct machining mistakes from the factory. In some cases they are BIG mistakes and the distributor will inherently have to be positioned further CW from original to compensate. In TR6s, its almost every one!!!

Now to timing recommendations. If I say 10-14 BTDC or 12-15 BTDC, I always recommend starting at the high setting. If it pings under load, decrease the setting until pinging goes away, then 2 more degrees for a margin of safety. You can also advance it more until it pings if my setting doesn't make it ping. I've seen timing marks so far off that 40 BTDC at idle is correct!

If you start at the bottom number and just leave it there, you're potentially leaving a LOT of performance on the table. For all I know, your timing marks are wrong and 10 is actually 4, or something like that. Will it hurt anything to run retarded? Maybe. Your fuel mixture will be more rich for sure, but not a huge amount. Your fuel economy will certainly be lower, and throttle response will be significantly lower. You could be leaving 5-10 rear wheel horsepower on the table. Significant? Yes!!!

When I rebuild a distributor the timing setting is for idle - anywhere below 1000 rpms. It doesn't matter if you're at 500 or 950. Its all the same.

As for the gear position that was first posted, its the number one problem I see with engine rebuilds. They're either 180-out of one tooth off in at least 25% of all engine rebuilds - even among the absolute best engine builders in the country. Just be thankful its easy to change and you're not working on a Jag, where you have to pull the engine and oil pan to make the correction!!!

I hope someone can find this info useful? My mind is fully corrupted with this jibberish. :smile:
 
I am so glad that you touched on the "phasing" situation, Jeff.
I remember you writing about it in the past and was one of the reasons I brought it up...that and the fact that I once misused the vernier adjustment and found myself in that out of phase situation.
An email to you and your reply got both me and the distributor properly oriented once again.
As for the accuracy of the timing marks on the damper I'm glad you brought that up, too. I've seen it estimated that with a chain driven cam, the marks can be a degree or more off per 20k miles on the components, indicating a more advanced timing than reality.
Because of that I rely on intake manifold vacuum as a more reliable indicator.
Thanks for weighing in.
https://automotivemileposts.com/garage/v2n8.html
 
Thanks, Jeff,

As the initiator of this long thread, I appreciate your comments about the pitfalls of engine rebuilds. Clearly that's what caused me trouble and got me started on this line of questioning because the position of the distributor in my rebuilt engine restricted the amount of advance I was able to achieve. Fortunately, with Randall's suggestion, I was able to get a few more degrees and reach 15 degrees BTDC, and backed it off to 14 degrees BTDC, without having to pull the distributor.
 
"Without having to pull the distributor" you say ? You could remove it 100 times but unless you alter the "gear position" it's going back the way it came out.
 
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