TR6 Ignition timing on '72 TR6

[rlester]

I just added a pertronix ignition module to eliminate the points on my 1972 TR6. When I went to set the dynamic timing I set it 4 degrees after TDC with the distributor vacuum hose removed. After replacing the vacuum hose, the timing went to about 10-12 degrees ATDC. My low end acceleration is pretty jerky now.

Did I set the timing correctly?

 

[Tinster]

I think you have made an error.

My 1969 TR6 timing is 12 degrees before Top Dead
Center and runs very smoothly at idle and thru the
gears.

Better wait for the experts. The vac lines on or off still confuses me. With the lines attached I read 12 degrees
BTDC.

dale

 

[TR3driver]

Nope. If you are going to use the 4 ATDC figure, the vacuum retard should be connected and operating while you check the timing. With the retard disconnected, the timing should move to the 'static' value given in the book (around 10 BTDC, don't have the exact number handy).

Yes, I know the books say to disconnect the vacuum line, but they are referring to the vacuum advance line, found only on non-US spec 72 TR6. The 4 ATDC figure applies only if the retard is connected and working (not, for example, disabled by the TVS on the radiator or upper hose).

Smog regulations at the time required them to publish the 4 ATDC figure; but IMO it's better to ignore it and set the timing to the 'static' value with the retard disconnected.

 

[rlester]

Thanks

I will do that. You are a real lifesaver.

 

[Brosky]

As Randall and Dale have said, disconnect and plug the vacuum line so there are no leaks and then set the timing at 12 BTDC to start.

And welcome to the forum!

 

[poolboy]

Also keep in mind that an engine with age may not find the timing marks as relevent as when fairly new.
Although it is a good starting point.
The Haynes Manual addresses this issue in Chapter 4/ Ignition System, Section 10/ Ignition timing and in particular paragraphs 7 & 8.
Wear develops in timing chain gears, the chain itself, dizzy drive gear, the dizzy itself. All that plus carbonization and quality of fuel.."all contribute to make the recommended settings no more than nominal ones."

 

[Brosky]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]set the timing at 12 BTDC to start.[/QUOTE]

Absolutely correct, PB.

Key words above are "to start".

 

[poolboy]

Believe me Paul, I wasn't trying to correct you. As a guy who has, what, 3 dizzys, all with different advance curves and the micro adjust wheels, no doubt that you know how to fiddle with the timing.

 

[Brosky]

Oh I know you weren't doing that. I was just agreeing that all of the things that you pointed out, particularly the carbon issue and fuel quality, can add to the pinging/driveability headaches.

Fiddling is a key word too. My car was running great for three weeks. Hmmmm, same tanks of Shell gasoline. I had to fill it on the road and it wasn't the same Shell high test. Oh-oh, now it idles rough and just isn't quite as smooth....

But I'll leave the settings alone for now and just add as much good gas as I can to the junk that I got.

 

[poolboy]

Bummer. I've had that happen. There's a country store a mile from my house, that as much as I like to give business to, must have a place where water can get into their tanks. Drives me nuts.
I finally just gave up and make it a little drive of 12 miles to fill up. Well,there are a couple of nice open roads I can take to make up for the "inconvenience".
But you, breaking in a new engine and listening for anything unusual....like I said "bummer".

 

[tom628]

I'm not sure yet, but I think one of the things we may be seeing with rough idling is the increasing prevalence of ethanol in the fuel.
I was told by a station operator that, at least here in PA, pumps must carry a notice of ethanol content if it's over 2%. So far, my local CITGO station claims not to have it added.

Tom

 

[rlester]

I made the timing change according to your advice. I runs great now. BTW the engine has been completely rebuilt in the last year. New rings, bearings, crankshaft thrust bearings, complete head overhaul including unleaded gas modification, new valves, new timing gears and chain, new oil pump, carburetors rebuilt. The pertronix modification was the very last step in the rebuild. Now it runs like new.

Thank You all for your assistance.

Rick

 

[Tinster]

Rick-

Glad it all worked out for you!!

Carry a set of points and a condensor with you
for backup. My Petroxin crapped out after less
than 200 miles. I'm sticking with points.

I dump a can of "dry gas" in my tank at every fillup
due to the ethanol sucking in water.

regards,

d

 

[tom628]

Rick-

Glad it all worked out for you!!

Carry a set of points and a condensor with you
for backup. My Petroxin crapped out after less
than 200 miles. I'm sticking with points.

I dump a can of "dry gas" in my tank at every fillup
due to the ethanol sucking in water.

regards,

d

Dale: My understanding is that ethanol will absorb a lot of water in fuel, just like Drygas does. When you then add Drygas (isopropyl alcohol?) to the mix, you're further increasing the ratio of alcohols to gasoline, further reducing the quality of the fuel.

Tom

 

[Brosky]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Drygas (isopropyl alcohol?) to the mix, you're further increasing the ratio of alcohols to gasoline, further reducing the quality of the fuel.[/QUOTE]

AND..............

You are increasing the potential for premature diaphragm failure from the excessive mix of alcohol.