Saturday, April 23, 2005


After the carb reassembly I went to fire up Ms. Legs and she cranked but didn't fire. Now one always wants to go back to what last changed, and look there first. But in this case, after a physical check for the obvious (gas line not connected, coil wire off) none of which showed any faults, I considered what could have, in dissassembly and reassembly of the carb, could have caused a complete failure? The answer is nothing, if you assume the carb is delivering its dose of air/gas. A substitute shot from the ether can acted in place of that but still no start.

So, the next thing to suspect is the electrics. Sigh. Didn't we just go through all this? After more wiggling of wires, it is time to bring the meter back out. But think again: what was the last thing to change in the electrics?
I had filed the points in an operation just previous to starting this blog. The point-filing was to address some voltage bounce seen in a previous test during hand-turning of the engine while trying to set the point gap. It turned out the points had some tits on them and there was an inconsistent spark--different times, sometimes not at all!--due to the gap and uneven surface. So the points are cheap and easy to replace and may be out of spec from ham-fisted dressing anyway. You should only dress (not file, burnish--rub with xxxfine emory if you don't have a "burninshing tool") points in the field, to get back home. Because you have to ensure parallel mating of the surface. Burnishing should only removed deposit tits caused by arcing--the points tips are actually pretty hard--but enthusiastic polishing could result in points that are misaligned. They're one of the cheapest parts on the car; replace 'em.

I'm off to the parts store....

Right hand carb

I took the lid off the left hand carb after running it up to where it was stuttering, let it stutter for a while and
then killed it by pulling the coil 15+ wire. With the lid off I could see that the float level was good. The theory was that the check valve was stuck closed or the float was stuck up (previously stuck down) and the carb was being starved for gas. This wasn't the case. The level was good and the check valve was operating freely.

So I turned my attention to the other carb. I removed that one and disassembled it. I found nothing unusual nor any clogged jets. I put it back together without replacing any part--although the accelerator pump skirts on both carbs are a bit ragged. The kits I used for last winter's rebuild were not the variety that had the accelerator pumps. You can't get them separately, so that meanss new kits. Which is fine; now that I've had them apart a couple of times, I'll need some rebuild kits in the spares. I didn't measure acclerator pump output, which is probably the great sin of the weekend.

Reassembling I put the new phenolic block in, matching the other side. I used blue locktite on the new manifold studs, no gasket glue (perhaps a mistake; though isn't there an old saw about using tack where it is in wet contact and not if it is air? An intake manifold would be...which? Atomized wet?). The addition of the block raised the carb height about 1/2" (didn't measure the block thickness--gotta remember those details), which changed the necessary length of the down-link from the throttle crossbar linkage.

The carb came up to the crossbar, so the link had to be shorter by that same 1/2". The linkage has a semi-heim joint at each end. It is really a ball-and-cup affair; a heim joint has a through hole for a bolt. The joints are threaded onto a rod, typically with a backing stop-nut. In this case, the rod had a stop nut welded on at the base of the threads at one end. The other end was threaded longer, but the joint's internal threads bottomed-out before the correct length could be achieved. Attempts at switching sides, going to the parts box for other joints of different body length (some shorter but none longer) didn't yield a good result. So out comes mister cut-off disk on the Dremel. The amount of thread to cut off was determined casually; I made the linkage as short as possible, put it on at one end and eyeballed how far away the other cup was with no tension on the rod (any tension on the rod can cause the accelerator linkage on the carb base to move--and an even ever so slightl opening of the butterflies can play havoc with idle response. The linkage must be against the screw stop on the carb body at rest. I added two tread turns in my head to my eyeball measure to give some additional play, cut that number of turns off the rod, dressed the edge and without some small difficulty started the cup joint back onto the rod. The rods are reverse threaded at one end. as are their matched cup joints: this allows turning of the rod while attached to the linkage to lengthen or shorten the throw in small amounts--remember the nut welded to the rod? On a rainy day I need to go through the cup joint collection in the parts bin and sort them by right-hand-thread and left-hand-thread. Some white lihium grease in the joint cups and reassembly was a hand press-fit.

Monday, April 04, 2005

Stuttering above 3000

After the compression check and plug inspection I put the sparkies back in and attached the timing light.

A new timing light, from Sears provided some interesting configuration challenges. The light is 12V, Legs is 6V. Keith was borrowing the Audi to get an alternator for his Mazda, so he graciously lent me his 12V battery out of his car to run the timing light.

You have to hook the light to the battery, then ground the 12V battery to the car(!), then put on the induction clamp. I guess the induction clamp needs the common ground loop back to the light. I didn't try running w/o it. A coil of 18g wire from the travel box did the job. I grounded it by laying the bare wire against the 3rd piece, nominally held in place by a loop around the genertor clamp. If it hadn't worked, I would have used an alligator clip or tape. But it did.

Timing was static at 5 BTDC on the Bosch 050 distributor. On the pulley, a 1.5" mark is supposed to be 30 degrees advance. This per the Distributors section of " The Maestro's Little Spec Book". From what I could see, I was on that mark, but at 3k rpms it was jumping around a lot as the engine stuttered. Of course, there was no causal information therein: was the stuttering engine causing the timing mark to jump around under the light as the motor changed speeds dramatically and momentarily, or was the timing causing the engine to stutter as the advance went all wacky for a moment or three.

Sunday, April 03, 2005

Compression check

Today I ran a compression check on Legs. First time since I've owned her. Here's what I found:

Test number: #1 #2 #3 Median

Cylinder 1: 132 135 130 132
Cylinder 2: 135 135 135 137
Cylinder 3: 109 125 120 120
Cylinder 4: 135 135 135 135

This is actually better than I was expecting. That number three was the lowest of the four also wasn't any surprise. The compression checker I used was from a box of free stuff that was on the sidewalk outside Volks Cafe in Santa Cruz about three years ago. But today was the first time I'd used it and the first time I'd looked at it closely.

A homebrew contraption, it was made of four fixtures. Down at the sensing end, there were two threaded inserts. The endmost one was probably just an extension...not sure why. It added about two inches to the length of the tester. It fortunately ended in a 18mm nut, which allowed me to thread it out of the sparkplug hole when it came disconnected from the next piece on the tester. The second piece had a check valve and was also threaded for the spark plug hole. Both this tip and the extension had O-rings at the base of the threaded ends. Nice. Its other end was fitted to a 2-ft tube that appeared to have washing machine hose fittings at both ends. Hey--works for me, they're strong clamps. Into the other end of the washer hose was a pressure relief valve. It's a press-button to relieve the air pressure in the rig. Teflon taped into that is an air pressure guage that goes to 200 lbs. That puts the typical range, 100-150 right in the middle of the gauge, helping with accuracy.

I ran the test with five "pfut!" cranks at each go. I started with three, but it wasn't gettin up to full go. Theoretically, it should, but the gauge hadn't been used in three years. At one point I put some silicone lubricant into the pressure relieve valve and re-ran cylinders 3/4. The results were more consistent after the lubrication, so those are what are recorded here. The time on the starter motor was very similar for each cylinder. So even if the numbers aren't absolutes, they're consistent and good for that inter-cylinder 10% target.

The final indication that compression in the engine is good, is that while the starter will turn over juuust fast enough to start the motor in run-ready trim, with all four plugs pulled, it will spin the motor fast enough to make the oil pressure light go out. Note to self: if you ever have to limp home (or across the finish line) on the starter motor, take out as many plugs as you can....

Some statustics to start

This is pretty much just a test to get started.
New to the blogging thing.

Car: Porsche
Year: 1959
Model: 356 (356A, T2)
VIN: 106728
Date of Manufacture: March 1959 (approximate, no Kardex info)
Engine: non-original, no 3rd piece stamp. 616/1
Color: Silver over black
Original Color: Ivory