Tech Tips: Fall 2000

Speedometer and Tachometer Quick Check

When picking through the instrument box at a swapmeet or looking at a British used car parts store, bring along a battery-powered portable drill. Set it to the highest speed setting and install a large Robinson screwdriver (or similar) bit in the chuck. Insert the bit into the cable input on the back of the tachometer or speedometer and turn the drill on. Most high-speed drills will show about 2000 rpm on the tachometer and about 40 mph on the speedometer.

 J.R. Rehfrew

Victoria, BC

Twin SU MGB Manifold Clearance

When fitting a twin SU MGB manifold up to the head of an MGA/MGB, be sure to check for adequate clearance between the head valve cover gasket rail and the ends of the manifold balance tube. If interference occurs, the surface where the manifold mates with the head cannot lay flat against one another, jeopardizing the seal of the gasket and/or compound used at the joint. If failure occurs, the result will be an air leak, a lean air/fuel mixture, and subsequent poor running.

Correction is simply a matter of material removal on the head or manifold. I chose to file a small relief groove at both ends of the manifold where the contact occurred.

The likelihood of your engine having this problem may be small, but a simple visual inspection can save a lot of unnecessary labor in the future.

Ronald Hlavka

Alta Loma, CA

Tech Tip Alignment Correction

Mr. Cordon Perry recently wrote in to your magazine to say that the 0.38-degree toe-in I described in my string and eyeball alignment method was too much. I believe that he is correct. I based my original statement on the MGA workshop manual, which describes the correct toe-in as “wheels parallel” and gives no tolerances. The 0.38-degree toe-in has given me excellent handling and long-term tire wear, but the geometrically similar MGB lists that allowable toe-in as 1/16 to 3/32”, using the measurements Mr. Perry describes. It would be a simple matter to eliminate the trailing edge of the front tire and stretch the string across these spacers when adjusting the alignment (the difference between the front and rear track is 1-1/4”, which is 5/8” on each side of the vehicle). This effectively makes the front and rear track identical, so the string and eyeball method will set the toe-in to “wheels parallel.” Scraps of plywood should work fine as the spacers. This is, after all, a string and eyeball procedure, which is only intended as a quick way to get a rough at-home alignment.

Steve Tom

Acworth, CA

Wrinkle Finish Paint

Here is something I found out that might help others who want to paint with wrinkle finish or textured paints. My 1965 Sprite’s dashboard was originally painted with this textured paint, and when I had the dashboard off to have the car professionally repainted (inside and out), I decided to repaint the dash myself. I removed all of the instruments and sandblasted the old paint off. I used a premium gray primer and lightly wet sanded with a fine grit sponge-type abrasive instead of sandpaper to get into the cracks easily.

I then applied three coats of jet black wrinkle finish paint and another coat in 5 minutes as the instructions indicated. A relatively heavy film thickness is required for a product to wrinkle. I waited two hours, and the paint had only wrinkled in one or two places. I applied more paint and the result was still unsatisfactory. I stripped the paint and primer, re-primed and re-sanded, and was ready to try again. This time I used the force-dry method to improve the finish. I repainted the panel just as before, but after I had finished, I put the panel under four heat lamps. The paint began to wrinkle within seconds, and the whole dash was wrinkled in a few minutes to a very original-looking finish. The trick with this paint is to use heat to accelerate the process.

Glen Alvis

Wichita, KS

Condensation Prevention

For many years I have had problems with keeping any and all moisture out of my MGB and MGA turn signal/brake light units. Even with new seals between the lenses and the units, when I would remove the lenses for cleaning, there would be moisture or condensation on the lenses.

My solution turned out to be very easy. I placed one packet of silica gel in each of my rear turn signal units (being careful to keep it away from the bulb), mounted them with a bit of double sided foam tape, installed a new gasket, and then replaced the lens.

The result: no condensation inside of the units after winter hibernation. For the concours people, it is very easy to remove the packets before any meet or show.

Brian Toye

Portland, OR