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Vacuum Advance

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mgcassidy1 Mike Cassidy
Bangor, ME, USA   USA
Is it worth the expen$e to swap the retard unit for Vacuum Advance? Performance benefits?



Mike

1976 TR6

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Fogspawn, CA, USA   USA
1974 Triumph TR6 "Machine"
this a good question. i tried on my 74 before i had it running properly
in first place...did not help.this the pitfall. (maybe i am the ds---t slow to realize this.)
Now that i have machine running right, i for one am hesitant to start
swapping retard for advance mechanism.
it would be interesting to see result of this poll. Does this single mod make a meaningful
benefit in one'sTriumph Experience?
wes

poolboy Avatar
poolboy Ken D
Sandy Hook, MS, USA   USA
I had a few extra bucks and was curious about the claims, so I had Rob @ BVU install it on my Lucas 22D6....good guy, btw.
There is a subtle difference under certain, limited conditions, therefore I wouldn't really consider it a 'performance enhancement' unless there were timing problems before installation.
As for as the claim about increased gas mileage....in the 2 years I've had it, I can't say I've noticed...but in all honesty, I've probably only calculated my mpg once or twice on highway trips..I get about 25-27 mpg somewhere around there.

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Attachments:
ADVANCE 2 and 3 002.JPG    58.7 KB
ADVANCE 2 and 3 002.JPG

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
I agree, very little performance difference. Maybe seems just a bit snappier at part throttle; but no effect at all at full throttle. And only about 10% better mpg; which is hard to notice if you don't look hard.



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

barry s Avatar
barry s Silver Member Barry Stoll
Alexandria, VA, USA   USA
1972 MG MGB GT
1974 MG MGB
1976 Triumph TR6
1980 MG MGB
I installed the advance on mine because I thought that the 'retard can" was ruptured. I simply disconnected the vacuum to the distributor and advanced the timing. I was happy with performance. On a lark I installed the vacuum 'advance' unit. I think that there is a subtle improvement. Afterward I realized that the 'retard' can was still functional.

I think the equation should be as follows. If the retard works, let it alone. If it were me, I'd still disconnect and rely solely on centrifugal advance. If the 'retard' is actually ruptured and you want to replace, buy the advance unit and ditch the retard unit. I've never heard a good argument for relying on the OE retard.

Bpt70gt Avatar
Bpt70gt Brian T
Westmoreland, NH, USA   USA
About 2 months ago I went to a tech session put on by Rob, Talked about this subject for a couple hours. The man knows his Lucas distributors. As Ken said, he's a very nice guy and very worth a call to him if you want the real scoop. He's got the knowledge and machines to make the distributer better than it was new. He'll set the curve up for your particular engine.

glcaines Avatar
glcaines Silver Member Gary Caines
Hiawassee, GA, USA   USA
I had Rob at British Vacuum Unit rebuild my Lucas distributor and install a vacuum advance unit for my 73 TR6. He also converted my distributor back to points which eliminated sporadic problems with he Pertronix system, which was causing the ignition to cut in and out. My fuel economy has increased slightly and the engine seems to run much better and is snappier starting off. As others have said, Rob is a very nice guy who helped me with several e-mails and phone calls while sorting out some other issues. I for one would recommend the vacuum advance. My distributor looked brand-new after Rob finished with it.



Current: 1973 TR6 W/Overdrive

Previous:
1963 TR3B W/Overdrive
1962 TR3A
1961 TR3A
1960 TR3A
1960 TR3A

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Darth V8R Avatar
Darth V8R Vance Navarrette
Beaverton, OR, USA   USA
1980 Triumph TR8 "Wedgie"
In reply to # 1508596 by mgcassidy1 Is it worth the expen$e to swap the retard unit for Vacuum Advance? Performance benefits?

A vacuum advance improves your highway fuel economy. There is no performance benefit.

Vance



1980 Platinum Metallic TR8, navy blue interior
Bare metal respray, Crower cam, raised compression
ported heads, modified Zenith carbs, 0.060" overbore

POW Peter Wirth
HEBRON, NH - New Hampshire, USA   USA
My early TR6 manual, covering cars with vacuum retard, states ignition timing @ 4° ATDC stroboscopic and 10° BTDC static. Since 10° BTDC is where you want your engine at just off idle I always timed stroboscopic there with the retard hose off the distributor and plugged. Then with the retard hooked back I just let the timing fall back to whatever it may and adjusted the idle accordingly. My 70 had both retard and advance but my '71 has only retard. Both 6's heated up in stop and go noticeably faster when retard was working.

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poolboy Avatar
poolboy Ken D
Sandy Hook, MS, USA   USA
The 72, 73 and 74 cars had a Thermostatic Vacuum Switch installed in the upper radiator hose.
It's purpose was to block the vacuum to the vacuum retard when the coolant reached 212*F, thereby disabling the retard, advancing the timing.
The increase in idle speed rpms resulted in increased coolant circulation and cooling fan speed.

POW Peter Wirth
HEBRON, NH - New Hampshire, USA   USA
In reply to # 1509115 by poolboy The 72, 73 and 74 cars had a Thermostatic Vacuum Switch installed in the upper radiator hose.
It's purpose was to block the vacuum to the vacuum retard when the coolant reached 212*F, thereby disabling the retard, advancing the timing.
The increase in idle speed rpms resulted in increased coolant circulation and cooling fan speed.

In addition to increased idle speed as a result of advancing the timing, advancing the timing alone makes for a cooler running engine. Case in point. A TR6 engine timed @ 4° ATDC and idling at 700 RPM will heat up quite a bit faster than one timed @ 10° BTDC and idling at 700 RPM. Likewise, the retarded engine engine will heat up faster than the advanced engine with both at 1200 RPM as well. My TR8 behaves exactly the same way. @ the book's TDC idle spec, the engine heats up faster at idle than at my 10° BTDC setting. At 850 RPM.

glcaines Avatar
glcaines Silver Member Gary Caines
Hiawassee, GA, USA   USA
I would guess that timing set at 4 deg ATDC would be somewhat harmful to valves compared to 10 deg BTDC. That late timing must cause the exhaust valves to run very hot.



Current: 1973 TR6 W/Overdrive

Previous:
1963 TR3B W/Overdrive
1962 TR3A
1961 TR3A
1960 TR3A
1960 TR3A

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
In reply to # 1509218 by glcaines I would guess that timing set at 4 deg ATDC would be somewhat harmful to valves compared to 10 deg BTDC. That late timing must cause the exhaust valves to run very hot.
Only happens at idle though, with the throttle closed. So EGT should still be on the low side (tho definitely higher than with faster timing). I believe the whole point of the retard is to help fully burn the fuel by keeping the temp and pressure up at idle.

Soon as you crack the throttle, the timing jumps up to a more normal figure.



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

POW Peter Wirth
HEBRON, NH - New Hampshire, USA   USA
In reply to # 1509227 by TR3driver
In reply to # 1509218 by glcaines I would guess that timing set at 4 deg ATDC would be somewhat harmful to valves compared to 10 deg BTDC. That late timing must cause the exhaust valves to run very hot.
Only happens at idle though, with the throttle closed. So EGT should still be on the low side (tho definitely higher than with faster timing). I believe the whole point of the retard is to help fully burn the fuel by keeping the temp and pressure up at idle.

Soon as you crack the throttle, the timing jumps up to a more normal figure.

All true, what makes for a lame running engine is timing @ 4° ATDC stroboscopic but not realizing your vacuum retard can is bad. For all practical purposes this results in an engine running 14° retarded...

BigChill Avatar
BigChill Silver Member Big Chill
Norwood, MA, USA   USA
Would a timing advance help on a motor with a supercharger???

I am thinking it would be getting vacuum from the carb side of the equation.

Just a dummy w/ questions...

Thanks in advance,



Big Chill

'75 TR6 slowly coming back from the dead...

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