Huge improvement.... Kevin Brinkerhoff , boy genius

[Terry Horlick]

At the suggestion of Kevin Brinkerhoff I pulled off and inspected my jets. They were not included in my carb kit so I had reused the originals. I purchased new jets from Moss and then compared them to the old. The old ones had a hint of wear on the outside diameter. I then replaced the upper cork seal (second time in three months!) and re- installed them. The fellow at Moss cautioned me to keep the spring compressed while installing so that the cork seal isn't damaged. I also cleaned out the piston dampers and installed light oil. Kevin suggested "O"- ring seals in place of the cork... I just may do that soon. I noticed an immediate improvement in the car's running. The valve train is quieter as is the exhaust. I have much more power. The maximum RPM is now around 4000. The lean popping is now stayed until high rpms and is very minor there. I need to go through the adjustment procedure again and if I am still running lean at high rpm I will have to go to a standard or a rich needle. It is amazing how the tiniest skuff on a jet can allow a leak to occur. Kevin's point was that at idle the car will run rich due to the leak, but at high rpm the vacuum is lowered and the leak decreases causing a lean condition to occur. This is precisely what has been occurring. The improvement has been huge so that I am absolutely sure I am on the right track now. This sure is nice after checking and re-checking everything else. I wish to thank everyone who has turned their attention and talents to the problems I described in the running of my TC. I took a short spin up and back on our local freeway and was very pleased with the results. Most of all I wish to thank Kevin Brinkerhoff, boy genius, who seemed to tire of the rest of us putzing around and calmly informed me of what the problem must be.... what a guy! Terry TC2295

[ian thomson]

I am glad that things seem to OK now Terry but can't quite understand your description of the way the lean condition occurs. Am I right in understanding that the problem was a worn jet? If so I would expect that the increase in jet size due to the wear would lead to a rich mixture throughout the range which would it would be possible to adjust out depending on how bad the wear is. On the other hand if the problem is an air leak into the carb after the jet high vacuum will cause a lean mixture not a rich mixture as you describe. Or have I just completely misunderstood what you are describing? Ian Thomson. ------------- --- Terry Horlick thorlick@sbcglobal.net> wrote:

> > > At the suggestion of Kevin Brinkerhoff I pulled off > and inspected my > jets. They were not included in my carb kit so I > had reused the > originals. > > I purchased new jets from Moss and then compared > them to the old. > The old ones had a hint of wear on the outside > diameter. I then > replaced the upper cork seal (second time in three > months!) and re- > installed them. > > The fellow at Moss cautioned me to keep the spring > compressed while > installing so that the cork seal isn't damaged. I > also cleaned out > the piston dampers and installed light oil. Kevin > suggested "O"- > ring seals in place of the cork... I just may do > that soon. > > I noticed an immediate improvement in the car's > running. The valve > train is quieter as is the exhaust. I have much > more power. The > maximum RPM is now around 4000. The lean popping is > now stayed > until high rpms and is very minor there. > > I need to go through the adjustment procedure again > and if I am > still running lean at high rpm I will have to go to > a standard or a > rich needle. It is amazing how the tiniest skuff on > a jet can allow > a leak to occur. > > Kevin's point was that at idle the car will run rich > due to the > leak, but at high rpm the vacuum is lowered and the > leak decreases > causing a lean condition to occur. This is > precisely what has been > occurring. The improvement has been huge so that I > am absolutely > sure I am on the right track now. This sure is nice > after checking > and re-checking everything else. > > I wish to thank everyone who has turned their > attention and talents > to the problems I described in the running of my TC. > I took a short > spin up and back on our local freeway and was very > pleased with the > results. Most of all I wish to thank Kevin > Brinkerhoff, boy genius, > who seemed to tire of the rest of us putzing around > and calmly > informed me of what the problem must be.... what a > guy! > > Terry TC2295 > > > > > > > Yahoo! Groups Links > > > mg-tabc-unsubscribe@yahoogroups.com > > > > > >

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[Terry Horlick]

> Am I right in understanding that > the problem was a worn jet?

Yes.

>I would expect that > the increase in jet size due to the wear would lead to > a rich mixture throughout the range which would it > would be possible to adjust out depending on how bad > the wear is.

One would expect that, but one would be wrong.

> On the other hand if the problem is an > air leak into the carb after the jet high vacuum will > cause a lean mixture not a rich mixture as you > describe.

Yes that is a great clue which should have ruled out an air leak.

> Or have I just completely misunderstood > what you are describing?

Yes, again. What you are assuming is that a jet can only wear in it's inside bore. Mine was worn on the outside diameter not the inside bore. That is why I felt ok on re-using them... the hole was round and sharp edged, looked good. The outside had evidence of wear in a vertical stripe pattern when it rode on the old (then the new) seals. If the outside of the jet isn't smooth enough the fuel which is supplied to the area with the spring (between the lower and upper seals) can leak past the upper seal. This causes the rich idle I was experiencing. Then aparently at full throttle the vacuum is lessened so the jet leak delivers a smaller quantity of surplus fuel. I see now that I overlooked one important fact in my analysis which should have clued us in to what was happening (ain't hindsight wonderful?). I extended the needle until it would hold the piston up. Then I pushed the piston down to the bottom of it's travel and tightened it's set screw. In effect I set my carbs so that the piston should close off all fuel flow at idle. I did this in an effort to get a correct mixture, but ended up with a persistant rich mixture. This told me my jet was leaking. I think it told a previous owner the same thing as I have a lean needle in the carbs. It doesn't matter how lean you go with the needle because that isn't where the leak was! In summary the jet was leaking fuel from it's outside diameter, not air so it was running rich. After doing various things to lean the mixture it still ran rich at slow speeds. But at high speeds the leak was lessened so the effort to obtain lean running succeeded there and the car ran way lean! I have uploaded a photo of the original jets. Go to: http://pages.sbcglobal.net/thorlick/images/jet1.jpg If you look closely you can see the wear from the old seals. It is subtle. I am amazed that this little skuff can wreak so much havoc on the performance of a TC! All this brings me back to my original question of a week or so ago: What needle do I need. I have an AP which is aparently too lean. The Moss guy says it should be ok for my location, aprox 2000 feet elevation. If after I get the carbys tuned with the new jets I find the AP is too lean, should I get the standard or the rich needle sold at Moss. Or should I get the gas analyzer and figure out the profile I need and go to the needle chart. Are those needles on the chart available? Where? Terry

[ian thomson]

Thanks for the very full explanation Terry. It is certainly a new one on me and I will be checking my jets very carefully next time I have them out. A full set of SU spares is available from Burlen in Salisbury UK, who are now the owners and manufacturers of all things SU. Their catalogue alone is worth the money they charge for it. No garage bookshelf should be without it. Happy motoring. Ian Thomson --- Terry Horlick thorlick@sbcglobal.net> wrote:

> > > > Am I right in understanding that > > the problem was a worn jet? > > Yes. > > >I would expect that > > the increase in jet size due to the wear would > lead to > > a rich mixture throughout the range which would it > > would be possible to adjust out depending on how > bad > > the wear is. > > One would expect that, but one would be wrong. > > > > On the other hand if the problem is an > > air leak into the carb after the jet high vacuum > will > > cause a lean mixture not a rich mixture as you > > describe. > > Yes that is a great clue which should have ruled out > an air leak. > > > > Or have I just completely misunderstood > > what you are describing? > > Yes, again. What you are assuming is that a jet can > only wear in > it's inside bore. Mine was worn on the outside > diameter not the > inside bore. That is why I felt ok on re-using > them... the hole was > round and sharp edged, looked good. The outside had > evidence of > wear in a vertical stripe pattern when it rode on > the old (then the > new) seals. If the outside of the jet isn't smooth > enough the fuel > which is supplied to the area with the spring > (between the lower and > upper seals) can leak past the upper seal. This > causes the rich > idle I was experiencing. Then aparently at full > throttle the vacuum > is lessened so the jet leak delivers a smaller > quantity of surplus > fuel. > > I see now that I overlooked one important fact in my > analysis which > should have clued us in to what was happening (ain't > hindsight > wonderful?). I extended the needle until it would > hold the piston > up. Then I pushed the piston down to the bottom of > it's travel and > tightened it's set screw. In effect I set my carbs > so that the > piston should close off all fuel flow at idle. I > did this in an > effort to get a correct mixture, but ended up with a > persistant rich > mixture. This told me my jet was leaking. I think > it told a > previous owner the same thing as I have a lean > needle in the carbs. > It doesn't matter how lean you go with the needle > because that isn't > where the leak was! > > In summary the jet was leaking fuel from it's > outside diameter, not > air so it was running rich. After doing various > things to lean the > mixture it still ran rich at slow speeds. But at > high speeds the > leak was lessened so the effort to obtain lean > running succeeded > there and the car ran way lean! > > I have uploaded a photo of the original jets. Go to: > > http://pages.sbcglobal.net/thorlick/images/jet1.jpg > > If you look closely you can see the wear from the > old seals. It is > subtle. I am amazed that this little skuff can > wreak so much havoc > on the performance of a TC! > > All this brings me back to my original question of a > week or so > ago: What needle do I need. I have an AP which is > aparently too > lean. The Moss guy says it should be ok for my > location, aprox 2000 > feet elevation. If after I get the carbys tuned > with the new jets I > find the AP is too lean, should I get the standard > or the rich > needle sold at Moss. Or should I get the gas > analyzer and figure > out the profile I need and go to the needle chart. > Are those > needles on the chart available? Where? > > Terry > > > > > > > Yahoo! Groups Links > > > mg-tabc-unsubscribe@yahoogroups.com > > > > > >

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[Donald Wilkinson]

Hey Terry: RE: " All this brings me back to my original question of a week or so ago: What needle do I need." It occurs to digitaldon that if you have lean needles now, as needles are pricey @ Burlen's, it would be a good opportunity to experiment with sanding these puppies down at the various stations as shown by Des Hammill in his book about power tuning SU carburettors. He advocates chucking 'em up in a drill press & applying sandpaper, rather than just flat filing on 'em as those guys in the Abingdon racing shop useta do. digitaldon has not personally tried this as yet, but plans to in an upcoming XPAG turbo project where he will be on his own mixture-wise. Don TC 7993

[Terry Horlick]

Don, Sorry to have taken so long to respond. I have trekked down to the Bakersfield pre-war swap meet to look for parts for my 1902 Locomobile. I found a group of parts just about right to combine with my parts and end up with two complete cars! Unfortunately I had my wife along (why this swap meet... first time in years) so no purchase could be aranged. Oh, well I did come away with three TC knock on caps for $10... no I won't tell meet organizers these post- war parts sneaked in there! I have been thinking of doing just what you suggest, but chucking the needles up in my lathe. I guess it doesn't matter what you chuck it in as you will be sanding by hand. I got some needle information on- line, but do not have that SU book. I guess I will try and get one tomorrow. The website for su needles I found relies on exhaust gas analysis to tell how the mixture is doing. Do I have to buy a pricey Gunnison gastester or is there another way to know what you are up to? I can't wait to get back home and get going on tuning these carbies! Terry TC2285

[joecurto@aol.com]

Gentlemen I have over 800 different needle numbers in stock, at least 200 of them are suitable for .090 jets which are in T type carbs, some are not as expensive as others, once you have modified a needle with sandpaper or file and it does not work you have junk, and repeatability is tough, I also make a high quality jet for H type so if you are in USA give me a call. Joe Curto [Non-text portions of this message have been removed]

[Donald Wilkinson]

Terry: Start by getting yerself a copy of Des' book, (see Amazon.com, 27 of 'em on there right now from $13.98). digitaldon scored a couple Gunson gastesters on eBay for relatively cheap, they're approximately OK. One needs to remove the indicator from the main box & extend it's wires in order to use it inside the car on the road. The Best thing (IHHO) is an in-dash air fuel ratio monitor. The Greddy one is good, although a scoche pricey. It has a needle rather than a buncha flashing led's, but is still a single wire sensor type. The best kinds use the 5 wire O2 sensor, and give a continuous A/F ratio curve, rather than jump from rich to lean right at stoichiometric. For SU tuning,check out: http://www.team.net:80/www/morgan/tech/tuning.html However the K&N monitor mentioned here is just another single wire O2 sensor type. digitaldon hasn't checked out the "Suneedle" program mentioned here, as it's not Mac friendly. He'll have to bite the bullet and try it on the stupid PC. digitaldon also finds colortunes useful. He like to install four of 'em. One hasta have a care doing this, however. One can't buzz the engine way up with impunity, without blowing these things outta there. Ennyway, if you have any success whittling your needles to shape, you can then measure 'em up to get an approximation of the one you need. The SU needle handbook (with all the dimensions) is a must. Joe Curto sez he has lotsa needles, although he frowns on hackin' on needles. Later. Don TC 7993 Don, Sorry to have taken so long to respond. I have trekked down to the Bakersfield pre-war swap meet to look for parts for my 1902 Locomobile. I found a group of parts just about right to combine with my parts and end up with two complete cars! Unfortunately I had my wife along (why this swap meet... first time in years) so no purchase could be aranged. Oh, well I did come away with three TC knock on caps for $10... no I won't tell meet organizers these post- war parts sneaked in there! I have been thinking of doing just what you suggest, but chucking the needles up in my lathe. I guess it doesn't matter what you chuck it in as you will be sanding by hand. I got some needle information on- line, but do not have that SU book. I guess I will try and get one tomorrow. The website for su needles I found relies on exhaust gas analysis to tell how the mixture is doing. Do I have to buy a pricey Gunnison gastester or is there another way to know what you are up to? I can't wait to get back home and get going on tuning these carbies! Terry TC2285 Yahoo! Groups Links To visit your group on the web, go to: http://groups.yahoo.com/group/mg-tabc/ To unsubscribe from this group, send an email to: mg-tabc-unsubscribe@yahoogroups.com Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/