Excerpts from the March 8 meeting of the Chicago Club

during Tom Kovacs tune-up demonstration.

By Jim Carruthers


Plugs recommended were Nippon. - ND W16EX-U gapped at .025" or WI6REX-U resistor type.

Plug Wires need to be either steel or copper core because the distributor cap holds the wires with a spike, which destroys the carbon. (Audience suggestion - use carbon wire from coil to distributor for radio suppression. use resistor plugs for the same effect.)

Points-recommended "Standard-Blue Streak" LU1617 XP gapped at .016 because they are twice as big as Lucas and are ventilated. Suggests using a screw starter when installing points.

Distributor- check the advance mechanism by sucking hard on the vacuum advance tube at the carb to see if it is functioning. Lubricate the cam lobe with "cam lube". Advance mechanism springs:

The fine spring is engaged all the time, the heavy spring comes in part way through the stroke. "Recurving" springs is possible but only worth it if you are seriously racing-only maybe a 1/2 HP gain Says that G. M. springs at the parts store work fine. Check the tower inside the distributor cap, carbon button and spring below it. Tom says he has used a 2 pencil Lead on the road in an emergency. Be sure to free up micrometer adjustment on distributor.

Timing- set at factory spec. with out advance. Tom’s timing light had a device to set final advance-say 32° so you could use the same pointer. The "Snap-On" timing light and the Sears 28A2 194 are the same ($99.). If your advance mechanism isn’t working you lose 100. No power at speed. Says to use 32-34°. With the Sears timing light you can check the whole range as per Haynes plus dwell on RPM.

When reinstalling the distributor be very careful to ensure that it is seating properly, otherwise the unit will self-destruct. (Lower distributor housing will be cracked). Tom doesn’t believe in scopes or dwell meters (Dwell meters only tell you if you have gapped the points correctly or if the distributor shaft is loose. I feel that you can do this better with your hand for a lot less investment.)


"SU" stands for Skinner Union - an English plumbing company. SU HD-6’s can be set up to idle like a dream. HD-8’s are a pain to set up and in his experience on about one in five will idle worth a damn (Larger throat diameter makes for poorer mixing of air and gas at idle- same problem tri-carbs have). Set them up lean for power

Overhaul- recommends Echlin needles and seats (NAPA 2-3568 $3.67 ea.) Similar to SU, but 4 lobes on needle -same neoprene tip - but a slick little spring loaded "tip" on the other end of the needle, so the float lever can gentle the needle into the seat. Tom commented that he likes to set the float level a little lean. (I like the level lower because it prevents the gas from boiling rich in heat and it makes for easier hot starting). When doing a check over always examine for bent needles, or needles that are not seating properly in the piston. Recenter the jet.

Jet Centering. Get the jet all the way up and the needle all the way down. Temporarily set the needle 1/8" low in the piston - then the jet can be more readily centered, even with slight binding - because the jet is lowered anyway in tuning, and you can reset the needle to its proper position in the piston. Really works well, no second try needed Don’t put the air cleaners on upside down, you’ll blank off two holes above the air cleaner bolt holes and get little or no air to the underside of the piston to raise it Lowered air pressure to raise the piston and needle in the jet to richen the mixture comes from the back of the bridge, up the two holes in the bottom of the piston into the top of the piston cylinder. Don’t worry about perfect gasketing between the air cleaner and the carb since, as Tom points out, small birds can fly through the mesh of the air cleaner anyway I used some stick. on Dr. Scholls shoe padding for gasket material.

Manifold drain Plugs- there are two fine drain tubes at each end of the intake manifold. They are there to drain out raw fuel from the unit. If they have been removed, leaving holes in the manifold, tuning will be next to impossible (Very lean on 1 and 6 except under 3/4 to full throttle). It’s OK to crimp off, cut off, etc. these tubes, but plug the holes

Lubrication- Contrary to the "book", Tom recommends that instead of engine weight oil in the dampers, that you use automatic transmission fluid - like Dextron II. It doesn’t overdamp the piston when cold. (The engine "comes on" quicker - check for correct dampers in pistons). The only other lubrication on the carbs is perhaps a touch of 40 wt. on the throttle shaft journals. Make very certain that the piston is free to ride the piston cylinder easily- use 600 wet or dry sandpaper or 4’0’ steel wool very carefully dry.

Needles- it’s nice to have two needles in your carbs that have the same specification number on the shank- like both having "UH", if you want standard needles How about using other needles like "UL’ , lean, in HD-8’s? (Better to use rich needles and set the carbs lean).

Piston springs- it’s important to have the same springs with the same length in both carbs There should only be one spring in each carb. Use a postal scale to determine that they are the same after checking their length.

Piston Dampers - Nice to have one in each carb the same as the other, like "8103’s". A backfire can drive the pistons up so fast that the damper rod will accordion. This will also blow the rod through the top of the plastic cap. Check to see that the resistance of each damper piston feels about the same when pushed into the oil. Don’t overfill the dashpot. Tom likes the vented caps that will blow out any overfill.

Fuel - Tom says, "Use straight regular gas ? " Gasp, choke - get a rope What about dieseling? Stop it in 4th straight through the box. Tom doesn’t think there’s any problem with detonation. How about lots of timing retardation? Not necessary set timing at 6° at 800 RPM. Super unleaded is not too great anyway. There’s a big sweat in the Experimental Aircraft Association’s push to go to auto gas to replace expensive avgas, by the oil companies, in that many distributors are sneaking methanol, say at the 5% level into their auto gas. Then the dealer sneaks in maybe another 5.7% methanol - at 2/3 the cost of gasoline Anyhow, it does great things for the octane ratings, but does it ever eat out rubber wing tanks in planes - at three big ones per side It’s not too good for seals and gaskets in carbs or fuel pumps. I like a mix of 75% super unleaded to 25% regular. Maybe I’ll go 50 -50 on faith, and see what happens. Like Tom says, a little lead will help your top and a lot.

Oil - Tom’s not too hot on my new favorite oil - Castrol 20-50 GTX. He says that when its temperature/viscosity enhancers break down in no time, you’re left with a too thin oil. It’s now in my Olds diesel replacing the spec 10W-30 in winter, and straight 30, Olds recommends in summer. Its SF-CC is just like my old Penzoil, but I want the 50 viscosity at operating temperatures. Tom says he recommends, or lets say he uses Kendall CT- I 40 weight racing oil. 50 weight is too heavy for short trips. Tom says switching to OT- I 40 will improve oil pressure at idle.

Cooling - If you overhaul, knock out those frost plugs and boil her out, it really helps the old heat transfer.

Mechanical - After setting the valves - do it regardless of "the book" start the car with the valve cover off Then you can see where all your oil pressure is going. If oil is squirting onto the ceiling, then "pin" the oil relief holes in the rocker arms with a 4 finishing nail, driven in (don’t hit the shaft), cut off, and peened over. You might just recover some lost oil pressure.

Low Oil Pressure Check List

1) Check the rocker relief holes.

2) Check to see that your oil filter spring is installed properly.

3) Check that your oil pressure relief valve hasn’t been jammed open or is so scored that it won’t hold anything.

4) Cam bearings.

5) Main bearings.

If You Have Your Rocker Shaft Out - Install the oiling line to the rocker shaft, before tightening down on the rocker shaft - could be a lot less expensive that way

Valve Cover Gaskets - If you get one you like - like it doesn’t leak, after cleaning it and the valve cover thoroughly, glue the gasket to the valve cover with 3M Super Weatherstrip Cement - saves gaskets.

Compression - Normal is 155-160 PSI. If you’ve got one or two low ones, put some oil in the plughole to seal the rings and try again. A 20 PSI difference between cylinders is a lot. Tom’s car has 195-200 PSI compression and he runs regular in it.

Carburetor Set-Up and Synchronization Idle Air - Tom says start your idle airscrew at 3 turns out, instead of 2-1/4 per the book. My Haynes says 3 1/2 turns.

Synchronizing - Start at 1000 RPM, and then on one carb use the fast idle screw to speed it up to 1300 - 1400 RPM. Mellow out the engine with the jet adjust screw. Back off the idle to 1000 RPM. Repeat the procedure on the other carb.

Tom says that you can synchronize the flow with a venturi flow gauge, or in its absence, get things pretty close by ear. I’ve had my carbs drilled with an extra 55 hole in both carbs symmetrical with the vacuum advance hole in the rear carb so I can use my motorcycle "Carb-stick" (mercury manometer) carb balancing gauge on the two SU carbs. Naturally I had to have another plate and gasket made to cover the new gauge hole in the front carb.>