• The Roadster Factory Recovery Fund - Friends, as you may have heard, The Roadster Factory, a respected British Car Parts business in PA, suffered a total loss in a fire on Christmas Day. Read about it, discuss or ask questions >> HERE. The Triumph Register of America is sponsoring a fund raiser to help TRF get back on their feet. If you can help, vist >> their GoFundMe page.
  • Hey there Guest!
    If you enjoy BCF and find our forum a useful resource, if you appreciate not having ads pop up all over the place and you want to ensure we can stay online - Please consider supporting with an "optional" low-cost annual subscription.
    **Upgrade Now**
    (PS: Subscribers don't see this UGLY banner)
Tips
Tips

TR2/3/3A How long should an SU damper top up last?

karls59tr

Obi Wan
Country flag
Offline
Seems to me I topped up the dampers on the SU's about a week ago. Now the level is down substantially. I did use "3 in 1" oil as some people recommend. If I switched to SAE 20 would there be less of a leak down issue or is there something else going on with the carbs? How long, on average ,should the damper level stay at it's correct level before it starts to go down??
 

Geo Hahn

Yoda
Country flag
Offline
On a TR3 there is nowhere for that oil to go & oil, if it evaporates at all, does so very slowly. So what is going on?

I suspect you are overfilling the reservoir. No harm in that, the excess is just being sent thru the intake and out the exhaust.

You might re-read the fill instructions though once you notice the level has gone down you essentially have the right level.
 

CJD

Yoda
Country flag
Offline
If anyone dis-assembled the damper valve, it could be put together wrong and is shoving the oil out. The symptom of that is that the piston has little or no resistance when being lifted...and of course excessive loss of oil.
 

bobhustead

Senior Member
Gold
Country flag
Offline
Use only 20W nondetergent. There is a book available free on the web called "practical hints" that gives recommended frequency. The oil does evaporate.
Bob
 

gbtr6

Jedi Trainee
Country flag
Offline
I have been using ATF. That seems to work well and it is less viscous than motor oils. Any feedback?

Perry
 

Geo Hahn

Yoda
Country flag
Offline
Varies based on many factors including ambient temps. It was possibly the temperature factor that resulted in the rule of thumb to use the same weight oil in the carbs that you use in the crankcase.
 

Darrell_Walker

Jedi Knight
Silver
Country flag
Offline
Some have the view that you should use something thin, so that the pistons react quickly. But what that does is cause a lean mixture on acceleration. A thicker oil will cause a temporarily richer mixture on acceleration, which is usually what you want. The reason I think people suggest a thinner oil is that they think opening up the needle faster will cause a richer mixture, but it also reduces the air speed over the jet. Using a thicker oil will keep the piston down longer, so while the jet opening will be smaller, the increases air speed over the jet will actually pull more fuel.
 
OP
K

karls59tr

Obi Wan
Country flag
Offline
Some have the view that you should use something thin, so that the pistons react quickly. But what that does is cause a lean mixture on acceleration. A thicker oil will cause a temporarily richer mixture on acceleration, which is usually what you want. The reason I think people suggest a thinner oil is that they think opening up the needle faster will cause a richer mixture, but it also reduces the air speed over the jet. Using a thicker oil will keep the piston down longer, so while the jet opening will be smaller, the increases air speed over the jet will actually pull more fuel.

So you would use 20SAE or ?
 

Roger

Luke Skywalker
Bronze
Country flag
Offline
You can spend many happy hours experimenting with different viscosities and springs, until you get it how you like it. There aren't any hard and fast rules.
I find Marvel Mystery works well in the dashpots of the Strombergs on my Europa Twin Cam, arrived at by experiment. If it stumbles at low revs, try a higher viscosity, if it's sluggish higher up the rev range, try something thinner.
 

CJD

Yoda
Country flag
Offline
The laws of combustion are extremely hard and fast. The ability to interpret them is what alludes most.
 

Roger

Luke Skywalker
Bronze
Country flag
Offline
The laws of combustion are extremely hard and fast. The ability to interpret them is what alludes most.

Since you alluded to my post by quoting it directly, I gather that the correct word eluded you. ��

What I mean is that there's no hard and fast rule about viscosity of dashpot oil. Springs, temperature, engine tune, and lots of variables that today's cars sort out with computers mean we compromise as best we can.
 

HarryL

Jedi Trainee
Offline
I've been using Marv's mystery oil for some time with no ill effects. When I run out of that
will probably go to ATF fluid. Mainly because that's what I got laying around in the garage.
Harry
 

poolboy

Yoda
Country flag
Offline
Anything will work..anything from air to water to STP, but some things work better than others when it comes to affecting acceleration and you'll never know the difference unless you try different viscosities
Having ZS carbs with the O-ring seal, I use a blend that contains a seal preservative..but if I had SU's I'd use something equivalent to a straight 30 wt motor oil.
 

Geo Hahn

Yoda
Country flag
Offline
...I find Marvel Mystery works well in the dashpots of the Strombergs...

Plus it has that delightful Wint-O-Green smell.

What I mean is that there's no hard and fast rule about viscosity of dashpot oil...

Indeed, I know of one application (Weller engine in an AC Ace) where the SUs use no oil at all. Look like other SUs but just a brass cap - no damper under it.
 

Roger

Luke Skywalker
Bronze
Country flag
Offline
Plus it has that delightful Wint-O-Green smell.



Indeed, I know of one application (Weller engine in an AC Ace) where the SUs use no oil at all. Look like other SUs but just a brass cap - no damper under it.

Common pre-war practice. Heavy pistons, no spring or damper. Gravity was your friend!
I had 2 x 1" like that on my Austin Seven special.
 

CJD

Yoda
Country flag
Offline
Since you alluded to my post by quoting it directly, I gather that the correct word eluded you. ��

What I mean is that there's no hard and fast rule about viscosity of dashpot oil. Springs, temperature, engine tune, and lots of variables that today's cars sort out with computers mean we compromise as best we can.

Little alluded me. I started working on my first engine in 1st grade...a cox .049 glow engine. That started my love of anything engine related for the rest of my life. I have found that either One understands carbs and mixtures and how to tune them almost intuitively,...or they never will. I truly meant no offense in my remark. In fact, you have had the most accurate response to Karl's questions so far on the thread. Rather, I was really expressing the frustration I get from these "what oil do I use" threads. As you pointed out...there is no correct answer for every engine. You must understand what the oil does, and then you can find the correct mixture for YOUR particular engine through tuning. Some will get it...most will not
 
Last edited:

luke44

Jedi Warrior
Silver
Country flag
Offline
For what it's worth, the standard race car trick on my old Spitfire was to remove the plunger altogether for much faster throttle response. I don't think it's really critical what you use, but stay with something lightweight. On my streetcars I use 3-in 1 sewing machine oil.

50da0c66-f19c-4275-82c2-5f03317c5796_400.jpg
 
Similar threads
Thread starter Title Forum Replies Date
bluemiata90 Buying car long distance, how should I do this Triumph 23
B How long should it take to obtain oil pressure Austin Healey 5
78MGB How Long Should They Last?? MG 3
B TR6 Crankshaft long seal surface Triumph 5
jfarris Message too long error FORUM Navigation Questions 8
L My 1951 Triumph long ago British Motorbikes 0
apbos New long term project. Sprite powered rear engined race car. Spridgets 9
KVH General Tech Flywheel Bolts Too Long For Main Seal Triumph 13
W Generator and Starter Long Bolts Spridgets 0
Popeye TR4/4A Slave rod seems too long but is not Triumph 7
A Land Rover V8 3.9L long block core for sale Rover / Land Rover 1
Jayplum For Sale SU HS6 for sale along with a long intake Triumph Classifieds 3
Zitch Engine Oil Leak After Long Drive Austin Healey 19
K TR2/3/3A Clutch "Long Throw" Slave Cylinder? Triumph 4
G TR2/3/3A Finding a long lost TR3 Triumph 4
R The long road home Spridgets 1
Y MGB An odd (and probable long-shot) request... MG 5
roscoe Rear end crown and pinion gear swap. 4.11:1 to 3.54:1 [long read] Austin Healey 12
R TR2/3/3A Restoration of 1954 TR-2 Long Door Triumph 6
T BT7 throttle relay levers short and long Austin Healey 2
S For Sale 3000 BJ8 Laycock 4 speed with 22% OD trans & 2 6 cyln engines / long blocks / BUNDLE Austin Healey Classifieds 1
Michael Oritt Post- Open Roads 2002: Tahoe to MD the long way Austin Healey 19
R TR2/3/3A Restoring a 54 TR-2 Long Door Triumph 10
boxofparts TR2/3/3A My long term 30 yr project Triumph 5
K For Sale Long and short TR3 and 4A Intake manifolds Triumph Classifieds 0
Joe Schlosser Thoughts on a long traffic Light Spridgets 11
R TR2/3/3A Restoration of 1954 TR-2 Long Door Triumph 22
D Long Lost Midget Spridgets 0
E Long lost Sprite Spridgets 10
roscoe Leakdown test [long read] Austin Healey 11
aero3113 Healey Shop on Long Island Austin Healey 9
britlover Wanted TR4 Hood long bubble Triumph Classifieds 0
D MGB Painted rubber bumpers. How long will they hold up? MG 1
T C42 BJ8 generator long screw needed Austin Healey 2
PeterK General TR Time for a long ride Triumph 3
D After a long break.... Spridgets 6
Lotus Club SoCal Ballast Point Long Beach Social Lotus 2
Popeye TR4/4A Found this odd long bolt in my fuel tank... Does anyone know what it is? Triumph 17
GTP1960 Not the "best car ever made" by a long shot Other Cars 14
L TR6 need help on long dead TR6 Triumph 16
Sarastro Morris Minor in Long Beach, CA Spotted 1
D TR4/4A extra long oil filter attachment stud Triumph 9
D TR4/4A flywheel bolts maybe too long Triumph 15
Sarastro Red TR3 in Long Beach, CA Spotted 0
Jim_Gruber I woke up Bugsy this afternoon after about a month long nap and he was cranky Spridgets 7
TomMull Post-War Other Herald: Holy Moly! [Why it took me so long to make the accelerator bracket] Triumph 2
Marla TR4/4A Take the long way home Triumph 11
steveg Very interesting very long blog posting - racing oil and zinc Austin Healey 44
Got_All_4 TR2/3/3A Tr6 a type overdruve in my tr3 too long Triumph 10
TomMull TR2/3/3A Long Door anyone Triumph 16

Similar threads

Top