Newsletter of the
www.SLTOA.org August 2007
August Meeting, Tuesday August 21st, 2006, 7:00 PM, at Tom and Ann Stark’s,
Arrive anytime after ; meeting will be at . The Starks will provide grilled chicken or beef or shrimp kabobs. Members can bring sides, deserts, and your favorite beverage to share. If conditions are good, parking will be on the lawn. Bring a lawn chair.
Hi all! We had a great meeting at Johns house in July. The weather actually cooperated with us for a change, we had some good discussions, & most importantly enjoyed each others company. Thank You John, once again for your hospitality, from all of us.
It's time again to gear up for our fund raising booth during the All British car show. This will probably be the predominant theme of our discussions next meeting at Tom's house. I'm sure directions are posted both on the web site & page one of our news letter. If you get lost, call one of us - we'll guide you in!
Tom & Ann always go above & beyond, so again, this is also a "must attend" event! Kurt is researching the possibility of adding funnel cakes to our menu. He believes there is substantial profit to be made, however it has its own idiosyncrasies what with the grease etc. Also a couple of extra bodies will be needed if we decide to do that. So, I'm asking every one to chip in & help for at least a little while during the event, roll up your sleeves get involved - it's a great way to break the ice with members you may not know well yet. Also, very important, pray that it doesn't rain!
Ex Pres Dave Massey should be on hand to entertain us with the latest in his travels to TRF & VTR - another good reason to make the meeting.
I think I was long winded last month so I'll give ya'll (I NEVER used to say ya'll 'till I moved here!) a break this month. Creig usually has plenty to fill the pages that's much more entertaining anyway!
Do try to make the meeting, the larger the crowd, they more fun we have - see you there!
Meeting called to order at at the home of Vice President John Lamberg.
President’s Report: Craig Madsen:
oPresident Madsen opens debate on the thought that the current SLTOA dues should be raised as funds in the chapter account has been steadily declining. After some debate, Vice President John Lamburg makes a motion to raise dues by $5.00 for both members receiving an email newsletter and for those receiving a hardcopy. The motion passed unanimously.
oMadsen also makes a suggestion that the June, “Summer Meeting” be changed from its current weekday evening (the third Tuesday of the month) to a weekend evening to accommodate out of town members and, to generally increase the attendance. There was some debate but no decision has been made.
oThe All British Car Show is coming up and President Madsen has spoken with a SLTOA member about adding funnel cakes to the menu this year.
oThe next SLTOA meeting for August will be held at the home of Tom Stark in Ladue.
Treasurer’s Report: Bonnie David:
oThe Treasurer’s report was given by President Madsen. Bonnie was able to have the bank’s monthly fee dropped on the SLTOA account.
Calendar of Events:
oSeptember 9th Wheels in Motion
oSept. 15th - 16th All
British Car Show at
oSeptember 23rd Car
Show and Swap Meet at
oOctober 14 SLTOA/MG Fall Color Tour
oOctober 19th -20th European
Auto Show in
oOctober 27th MG Rally
oDecember 2nd SLTOA Xmas Party at Bevo Mill
Please check the chapter website for the complete list of events.
Old Business: None to report.
New Business: None to report.
Meeting adjourned at .
Jim Taylor is a retired design engineer with over 40 years experience rebuilding SU carburetors and fuel pumps. The following is a continuation in a series of articles on the most common problems that Jim has observed in carburetors that come to him for service.
The following article is reprinted here by permission from Jim Taylor. Please refer to the April SLTOA newsletter for Karl Schmitt’s introduction of Jim. There are several articles that will be reprinted over next several months in this newsletter. Make sure you keep the April and May copies available for reference back to the detailed SU drawing.
V. CORK SEALS ON H-SERIES SU CARBS
On the old original SU H-series carbs, cork seals are used around the jet and also the jet locking nut. The jet gland seals are small and fragile. To facilitate installation without breaking, it is desirable to soak the jet gland seals in engine oil for about 24 hours before assembly. This softens, lubricates, and slightly expands the cork. There is nothing more frustrating than to have 4 seals for 2 carbs in your rebuild kit and to break one. Before replacing cork seals it probably is a good idea to have a few extras on hand. The large cork seal around the jet bearing locking nut is a static seal and does not need lubrication. Soaking it in water for about 30 minutes is sufficient to soften and expand it slightly before installation.
VI. FLASH METAL REMOVAL - SU CARBS
In the factory machining of SU carb bodies there always seems to be some rough flash metal protrusions left, some quite prominent, where the horizontal bore of the body proper intersects the vertical bore for the piston. These protrusions create turbulence and increased resistance to flow. Flow characteristics can be enhanced if these protrusions are removed creating a smooth transition at this intersection. I use a cutting bit on a Dremel Moto-tool to grind out the protrusions. I then polish the complete bore with a fine wire brush on the Moto-tool.
VII. SU NEEDLE MARKING
SU jet needles are identified by letters and occasionally numbers stamped in the needle shank. This causes an upset in the metal at the letters and may make it difficult to push the needle shank into the hole in the bottom of the piston. Don't ever force the needle in the hole or you may never get it out again without ruining it. Take an ignition point file and judiciously smooth the ridges around the letters until the needle will slide in easily. To remove an old needle that you may want to re-use:
remove the jet locking screw and pull gently on the needle with your fingers. If it doesn't budge, resist the urge to grab the needle with a pair of pliers. Squirt some choke cleaner in the locking screw hole and leave for about 30 seconds followed by an aerosol penetrating oil. Gently tap the needle inward (usual movement about 1/8"). This breaks the needle loose as well as lubricating a dry area of the shank. Pull gently again with your fingers. If it still doesn't move, clamp the needle in a vise with Masonite faced jaws and gently pull and twist the piston. If all else fails you can still resort to the pliers and sacrifice the needle.
VIII. SU CARBURETOR FLOAT VALVES
The use of Grose-Jet float valves has done more to improve the reliability of SU carbs than any other single improvement that I am aware of. The double ball design meters well and shuts off tight. The balls rotate in the flow stream so wear patterns are minimized. The balls are retained so they don't fall out on disassembly of the float lid. The only problem I have ever encountered is that the seating ball will stick shut if left sitting with stale fuel in it for 6 months to a year. But that's not the only place stale fuel causes problems. Petroleum refiners never intended for gasoline to stay in inventory over 90 days. Gasoline in your tank for long periods is not a particular problem. It's when it sits in cracks and crevices in fuel pumps and carburetors for 6 months or more that it causes problems. Gum will coat the jet needle and varnish will set up around the jet and fuel pump valves almost like an epoxy. Disassembly and cleaning with a commercial carb cleaner is about the only cure other than avoiding the stale fuel problem by driving your car every few weeks.
IX. OVERFLOW PIPES ON SU CARBS
The overflow pipe off of the float bowl lid on SU carbs serves a dual function. It provides for overflows (which are rare with Grose-Jet float valves) to be directed to some non-hazardous location but more importantly it is the means of venting any vapor buildup out of the float chamber. A fuel level is maintained in the float bowl by the float and float valve assembly. Fuel flows by gravity to the jet orifice. If the vent pipe for some reason becomes blocked, vapor pressure can build up in the float chamber and cause severe flooding at the jet. I have seen gasoline squirt 2 feet in the air out of the jet when a vent was plugged off. The following causes have been observed:
1. End of overflow/vent plugged with dirt or rust
2. Plastic vent line got against exhaust pipe and melted end shut
3. Owner vented one float chamber into the other float chamber (tied them together)
4. Owner tied vent line from carb into vent line from fuel tank
5. Rubber vent hose kinked where it went into carbon canister
6. Vent lines cut off with side cutter pliers thus crimping tube ends
7. Carb I.D. tags put underneath overflow/vent banjo thus blocking off annular vent area.
X. A. THROTTLE RETURN SPRINGS FOR SU'S
Most H series carburetors and HD-6's used a helical throttle return spring around the throttle shaft. If too little pre-load is used there is insufficient force to shut the throttle. If too much pre-load is used it makes the throttle awfully hard to open. I find 1/2 turn of pre-load to be about optimum. With the throttle closed, rotate the spring clip in a direction that will be winding the spring up. Turn until free movement is eliminated, then wind or pre-load 1/2 turn and tighten pinch bolt.
B. INLET BANJO ORIENTATION- SU-CARBS
Separate inlet banjos are frequently used with flexible fuel lines, such as on the HD-8 Healey carbs. These brass banjos have one flat face and one recessed face. A fiber washer is used on each side. It is essential that the banjo flat side go towards the float lid and the recessed face go towards the bolt head. If installed backwards the rim around the recess will make metal to metal contact with the float lid boss before the fiber washer is fully compressed. This is so basic I'm almost reluctant to mention it but I do see an awful]y lot of them backwards.
XI. A. SU DAMPERS - ADDITIONAL TIPS
The purpose of the SU damper is to retard the rapid upward movement of the piston on rapid throttle opening associated with acceleration. This delay in piston movement causes a momentary decrease in pressure at the throat thus achieving a momentary increase in richness much the same as with an accelerator pump. The weight of the oil in the damper determines the amount of dampening. A lot of race mechanics use automatic transmission fluid for some misguided reason obscure to me. I think it is too light for normal use. SU publications recommend 20 weight which I would follow. Do not overfill the damper. The proper procedure is to fill to 1/2" below the top of the hollow piston rod, not 1/2" below the top of the chamber neck. Overfilling just spills over into the suction chamber and makes a mess. One easy check is to remove the damper and then re-insert it. If you feel resistance before you roach the threads on the cap you have enough oil.
B. DAMPER RODS - SU CARBS
The damper rods can occasionally get bent which will force the damper piston off center. This will create a drag or side force on the hollow piston rod and restrict normal piston movement. Remove the suction chamber and look at the end of the damper rod with cap screwed snugly into the chamber neck. If the end of the rod appears to be in the center of the bore, everything's OK. If the rod is noticeably offset in one direction, mark the cap with a magic marker in the direction the rod needs to be bent. Remove damper and gently bend rod in the indicated direction. Several passes may be required to get it right. Visual centering is adequate as there is some lateral float in the damper piston. Just as a matter of interest, the new SU plastic capped dampers have a ball socket in the cap which allows the rod to be self-aligning.
XII. VACUUM DROP TESTS - SU CARBS
SU carburetor suction chambers and pistons are furnished as matched assemblies from the factory. There is a controlled clearance and thus controlled air leakage between the piston and suction chamber bore. A convenient means of checking this is a vacuum drop test. The proper damper should be in place. Chamber and piston should be clean and dry. Check piston for any spots of drag or interference over full travel. Spray piston rod lightly with WD-40. Turn assembly upside down with piston against top of chamber. Plug holes in the bottom of piston with windshield caulking (commonly referred to as Dum-Dum). Measure the time for the chamber to slide down and fall off the piston. Specified times are as follows:
1 1/4" and smaller carb = 3-5 seconds
11/2" and 1 3/4" carb = 5-7 seconds
2" carb = 7-10 seconds
If vacuum drop time is too fast carb will tend to run rich. If drop time is too slow carb will tend to run lean. If both carbs are too fast there is nothing you can do to correct. Chances are someone has sanded inside of chambers to clean them which is a no-no. If they are too slow you can polish the chambers or pistons or both, very lightly and recheck frequently for compliance. If one carburetor is fast and one is slow there is a good chance pistons have been interchanged. Try switching them. I recently had a pair of 1 1/2" TF carbs where the front was 5 seconds and the rear was 8 1/2 seconds. Switching pistons gave me 7 seconds on the front and 6 1/2 seconds on the rear—just lovely. It is ideal if both are alike and right in the middle of specification. It doesn't happen very often. Minor disparities from specified drop times can be accommodated by tuning adjustments. If I had a 1 1/2" carb with a drop time of 4 seconds I wouldn't fret about it. If it was 1 second or 1/2 second (which I've seen) I'd hunt for some different parts. It should be noted that if you do interchange pistons, it will be necessary to re-center both jet assemblies. Ideally this type checking should be done at the time of a major rebuild.
XIII. SUCTION CHAMBERS & PISTONS - SU CARBS
Suction chambers and pistons are machined to close tolerances and furnished as selectively matched assemblies from the factory. It is essential for proper operation that the piston move freely in the chamber. The piston is center guided by the piston rod and there should be no contact between the large outer diameter of the piston and the chamber bore. With both parts thoroughly cleaned in carburetor cleaner and dried, it should be possible to spin the piston over its full length of travel without any drag or interference. Over many years service it is possible, with external dings on the chamber and burrs on the piston, for interference to occur. To remedy this I coat the large diameter of the piston with a thin film of rubbing compound and rotate the piston in its chamber. If the interference is minor, the compound will knock off the corresponding high spots on both components and the problem is corrected. If the interference is more severe, the rubbing compound will leave a black smear on the offending area in the chamber. This smear serves as an indicator of the spot that needs to be sanded out. I use a fine grit sanding drum on a Dremel tool as an effective means to remove a spot caused by an external ding. If the compound leaves a black smear uniformly around the complete circumference of the chamber bore, chances are the pistons have been interchanged or a piston (improperly sized) has replaced the original. If black smears show up 180 degrees apart it is likely that the chamber is slightly egg shaped either from being dropped or being heat distorted while polishing. A few judicious raps with a rubber mallet near the open end of the chamber will often restore its roundness. After the piston free movement is restored, remove all traces of rubbing compound with choke cleaner on a paper towel.
XIV. PISTON SPRINGS - SU CARBS
A piston spring combined with the weight of the aluminum piston provides the necessary downward force to maintain essentially a constant pressure loss (depression) at the throat of the carburetor. The springs are initially color coded with paint for identification. The paint disappears with time. Common piston springs are as follows:
Code Force in Oz. at Height
Blue 2 1/2 2 5/8"
Red 4 1/2 2 5/8"
Yellow 8 2 3/4"
Green 12 3"
Red & Green 11 1/4 3 7/8"
It is difficult to identify springs visually since ones with the same load rating may have different free lengths, different wire diameter, and different number of coils. The springs may also sag slightly with age and use.
To identify and check for proper specification I have made cylindrical weights from aluminum bar stock corresponding to the above table. I put the spring in a glass tube with the correct weight on top of it and measure the compressed height. If the spring is too tall it must be replaced. If it is not over 1/2" too short it usually can be stretched. Springs can be brought back exactly to spec and matched with each other. A squirt from a can of spray paint will serve for future identification.
We are official. The hobby shop off Rt. 30 a mile or so west of 141 has been incorporated by Arlie King, Mike Lewis, Dave Massey, Mark Marshall and Creig Houghtaling. The lift is in, parts cleaner, grit blaster and other specialty tools. If you have a project you would like to work in the shop contact one of the members. (A few extra bucks to help pay the rent might be welcome.) If you need help with a welding project, Arlie has a fellow who can come and do it. We also have professional mechanics who can do any kind of work desired. Or perhaps we might find a club member who could lend a hand. What do you want to do? Let’s talk. One other possibility is there might be one additional membership slot available. Membership gives full access to all equipment, facilities, and experience of other members any time.
Let’s get together some day and have a club gathering at the shop. We’ve got a fridge and a grill. What better way to spend a weekend? Perhaps we can have an oil-change party? Let’s talk about it next meeting.
Classified Ads: Contact Creig Houghtaling at , the address listed below, to place a free ad in this newsletter.
1972 Triumph GT6 for sale -- This is a car that my father in law and I did
a rolling restoration on about 7 years ago. The motor is rebuilt with higher
compression pistons, fast road cam, rebuilt carbs and
The car comes with lots of spare parts. There are two engines, a transmission, two differentials, starters, alternators, complete front and rear suspension, spare carbs, complete spare exhaust, windshield, doors, rear hatch and glass, wheels, guages, brand new rotors and boxes and boxes of odds and ends. Way more than I could list here.
If you have a spitfre use the spare parts to make yourself a Spit6.
I love the car and hate to see it go but I have too many other toys and some looming bills. It has always been in the garage since the restoration. The last few years have been in a heated garage. For the car and the truckload of spare parts I will take $6500 or best offer.
Dan Trigg 636-244-6669
Curt Shepard, Vice President, Love Funding Corp, 212 S. Central #301, St. Louis, MO 63105 - 314-512-8566, 314-922-3121 Cell
Creig Houghtaling, Editor