Woo Hoo - running at last!

OK - got it running - well even!

A quick recap - third gear in the transmission failed last November, but the car had otherwise been running pretty well, except for some vacuum leaks on the carbs. Worked on the gearbox over the winter and replaced the layshaft and bearings. While the engine was out, I repainted it maroon (RustOleum Burgundy). I also tore down the carbs, re-bushed, re-shafted and rebuilt them. The goal was to get the car running really sweet for this driving season.

It was frustrating, then, to put the engine and gearbox back in the car and have some teething problems - rough idle, cutting out, leaking heater valve, sooty plugs (rich) - all things that I wasn't really experiencing before (at least not this acutely). Especially disheartening was the lumpy idle. I was counting on the new damn-near-perfect carbs to idle beautifully - no air leaks now!

So - I spent some late night hours reading the archives here and on mgcars.org.uk and went out to the garage today with a plan!

The biggest issue was the lumpy idle. Not a high idle like I was experiencing last year - fixing the carb shafts - no leaks - seems to have fixed that finally. Originally I set the carbs up on the bench by turning the mixture nuts down 12 flats on each carb as I have been taught. As it turns out, this is NOT the best way to begin. Today, I used my digital vernier caliper to actually measure the distance from the bridge to the top of the jet when the jet was fully home (up) in the jet bearing. I set both sides to 0.10, ignoring the number of flats. I cycled the choke many times and then rechecked to make sure they were still the same - all good, so I put the dashpots back on and filled them with MMO. (I had earlier checked the jets to be sure they were centered, and they still are). I then went back and much more carefully set the float arm fork heights to 7/16" using a drill bit, making very sure that the flat part of the arms were flat and straight, and the fork arms were evenly contoured. The end result (once I solved the ignition problems) was that the car now idles well even at 800 rpm's and the idle not is much smoother and sweeter - no loping. The plugs are all an even tan color and they are now the same across the board whereas before the fronts were pretty good and the rear plugs were very sooty (even though they had been set "correctly" to twelve flats). I checked the sync with the SU tuning bars, and it was spot on.

The issue here I think is that what you really, really want is for the jets to be metering the same amount of fuel to each carb so they are nice and balanced. Counting flats is very accurate (turning a measured distance around a fine thread of a known pitch is how micrometers work after all), but other things come into play - the accuracy of the carb body casting, the compression of the cork gland nut, the length of the jet itself, the thickness of the upper and lower jet bearing washers, etc. If all these are identical, then counting flats gives you an identical result on each carb. Measuring it directly and setting accordingly seems like a much better method, though. I had read that you are shooting for a distance "down" of between 0.062 and 0.120" - depending on whom was doing the posting. Most often cited, though, was 0.072 to 0.075 which I think is actually a T series spec. I knew my carbs were rich, though, and I measured them at about 0.12, so I arbitrarily picked 0.10 as my target, and it seems to have worked out great. Now that they are the same, I could adjust by counting the same number of flats to enrichen or lean them out without having to take the dash pots off and re-measure, provided I am careful to keep them the same. If you don't have a caliper, cut and file a 1/16" notch in the end of your SU carb wrench and you will have a handy special tool for checking this setting.

The ignition problem was caused by the heater valve leak. The rotor and cap were covered with glycol, and there was some glycol in the distributor itself. Boy is that stuff hard to get off! I ended up having to dunk the parts into my parts washer, scrub them, and then dry them off. They still didn't work and the car would not start! After letting them dry out for a while, though, the car finally fired and I was able to set the timing. Odd thing - I set the timing to 10*BTDC statically, and it was too advanced - I retarded the timing to more or less where I had set it the last time and it was much better, so I think I probably just did a bad job of lining up the mark on the crank pulley - but I didn't go back under the car to check since setting it "by ear" seemed to work fine. BTW - I repaired the heater valve by lopping it off and tapping the base to accept a stanard 1/4" ball valve (see Manchusen's Garage site for more on this). I had to disassemble it again to add the teflon tape I had forgotten, but now the leaking is banished.

The test drive with the wife was glorious...just around the neighborhood and to the gas station to fill up - but what a huge difference! It is so smooth now, it sounds great, shifts well, etc. etc. - very relieved that I was able to get it sorted! It will be interesting next week when I get my vacuum venturi spacers back to see if they actually are the same by directly measuring vacuum! I bet they're damn close.

I did figure out that we had put the speedo cable on the transmission, but never actually tightened up the fitting, so it was sort of just hanging there in place. I just did that, so haven't actually checked yet that the speedo now works - but it should.

Now I can go back to my list of little things to fix, since the big things seem to be done! I'll update them at my blog - http://mgarestoration.blogspot.com. I need to also update my "carb rebuilding" article!

Coolant Leak Shuts Down Car

One failing on these cars is the crappy heater control valve on the side of the engine.  Mine was very corroded internally before, so I cleaned it up before reinstalling.  Now, it leaks coolant in steady small stream as I am driving.  Unfortunately, the location of the valve puts it right above the distributor, so the coolant leaks onto the distributor cap.  Distributor caps do not like to get wet - the car starts running rough or dies altogether.  On my last trip downtown and back, I had to keep restarting it with the clutch since it would die at random intervals!

To address this, I am cutting off the valve and making one out of standard plumbing.  You lose the adjustability from the cockpit, but that never worked well anyway.  In fact, I have the heater core itself isolated from the system, since that was leaking coolant onto my feet in the past, and the core needs to be replaced or repaired.  Since I am not driving the car in the winter, it hasn't been a priority.

See this site for a description of the fix I am doing.  I'll post my own pics as well.

http://www.britishcarforum.com/bobmuenchausen/12272.html

At least I am not alone in this - it seems the heater valve on MGA's and MGB's is a problem - or at least the modern replacment valves are a problem.  My first one lasted over 50 years, so it's hard to say that it was really that terrible.  The new ones apparently leak out of the box.

IT'S ALIVE!

Saturday:

I started the car for the first time since I toasted the transmission in November.

My friend Tom and I got the engine and gearbox in last weekend. Tonight, I finally had a chance to fire it up. Ran the starter a bit to prime the carbs, and then it started on the first turn of the key!

I want to drive it a bit and get it warmed up before trying to dial in the mixture and idle - but it already sounds better with the new throttle shafts.

I put a new Moss plastic radiator fan in - WOW - that thing MOVES air!

But, there is a curious thing. My car is now, and was before, making a curious low-frequency Br-D-D-D-D-P noise at around 1500 to 2000 RPM's upon deceleration. I used to think this was the fan vibrating in preparation for imminent blade departure.

Operating the throttle from inside the engine bay, it sounds like it's coming from the front of the engine bay - I made sure to put the jam nuts on the backs of the MGA ovals so they don't vibrate. It might even be the inner front grill vibrating against the shell, but I just can't tell. The bonnet is up, so it's not that. I'll have a helper come out with me soon so that I can hunt around better while having the helper step on the gas.

It's probably innocuous, but it's going to drive me nuts until I figure it out.  UPDATE - I am pretty sure it was the hood latch opening rod that is vibrating. 

The gearbox has oil in it now, and shifts through all the gears and reverse well - very smooth but with NO slop at all - like I imagine a new or nearly new gearbox would feel, perhaps. I hope it doesn't explode when I try it out!


Sunday:

 I actually did manage to drive the MGA today! Funny story.

Last night I was happy that when I finished assembling the car, it started right up - good feeling. Then I remembered that I had not set the timing - just dumb luck that it happened to be almost perfect when I checked it (static at 7.5d BTDC). Just before I went to bed it stopped suddenly on its own, but I thought "OK - out of gas, time for bed"

Today I filled up the 6 gallon gas can and filled up the tank. I then got in and tried to start it again - great cranking but no spark, apparently! Trying to recheck the timing, the test lamp would not go out no matter how far I turned the dizzy. Weird. I pulled the distributor cap off and could not see the point gap at all - hmmm...closed up. I pulled the dizzy out, and no amount of adjusting could get the points to open up. I found a set of NOS points that I had collected and they went in, got adjusted and the dizzy put back in. Started right up!

The old aftermarket points failed suddenly - not sure why...?! It's like the rubbing block got rubbed off or moved over a bit. Where it hits the cam it seems to be at a bit of an angle rather than parallel to the cam - touching more at the bottom than the top. I did notice last year that they were already near the end of their adjustment range when new - it's like the geometry of the base plate was incorrect. If I can find the box and tell you the brand, I will do that, but not sure I kept it.

Anyway, went for a short drive around the 'hood to check out the tranny - seems great! Fuel gauge is still binary, and the speedo doesn't work. Not sure if the problem is in the speedo or in the way I put it back together in the transmission! Will have to investigate, though the speedo was not calibrated and I have not been depending on it anyway, and in fact was planning to send it out as soon as I get one to fill the hole in the interim.

When I got back home into the garage the car smelled "hot" - but the temp was only about 190*F. I think it's the smell of whatever oil I spilled burning off and possibly the new engine paint or the new header wrap tape "burning in". Will keep and eye - and a nose - out for that. It doesn't smell like insulation burning, thankfully - more like an oily smell.

I am going for one more short drive tonight - eventually will be confident enough to go further afield. I am happy for now that all the gears work so well!

JIM in NH

Decisions, decistions....

I have a decision to make. My "A" is back together, but Friday will be the first time I can test it out. Rebuilt transmission and rebuilt carburetors with zero time on them.

Assuming it starts and runs, I am hoping to go on the MA/RI "drive your MGA day" (May 5th) run to Sakkonet Point in RI - but it's about 2.5 hours to get to the starting line, 2-3 hours of driving on the event, then 2.5 hours home. That is a lot of driving in a car that I am not too sure of yet (given that I have never rebuilt a transmission before).

I will certainly drive my MGA - just not sure if I want to drive it that far (yet).
What is a suitable testing interval for the transmission?  I just don't want to get 100 miles from home (the AAA towing limit, I think) and then have it die.  I am nervous that I did something wrong and haven't figured it out yet.

Friday is the test drive - will let you know what happens!

UPDATE -

it's Friday and I did get the car started.  Put oil in the transmission, hooked up the tacho cable, set static timing, set carb sync mechanically (don't have the gauge ports hooked up yet) - car started right up!  Cold and wet out and I am tired, so test drive will be tomorrow - but NOT going on the club run to Sakonnett Point, RI.  It's 2 hours to the starting line, 2.5 hours on the ride, then 2 hours home, minimum - and we have other commitments around the 'hood this weekend as well...so Carrie and I will go somewhere fun on Sunday - like to Peterborough for a pint or maybe Portsmouth or Rye...or heck, even just downtown in good old Nashua.   We like to go downtown early and have breakfast.  There is also a great breakfast at the municipal airport - Boire Field - in Nashua.  I still don't know if the transmission works yet!


JIM