Carbs, Part II.

As I mentioned in my last post about carbs, I threw caution to the wind and decided to rebush my SU's at home after discovering my throttle shafts were leaky.

Before I go any further, I should note that there are professionals out there that do this for a living, charge a modest fee for the service, and do a much better job than a shadetree mechanic. Prominent figures in the world of SU ressurection include: Rhys Kent of Island Automation, Advanced Performance Technology, Joe Curto in New York, Chester Gillings, Paltech, and Z-Therapy. Prices and individual experiences vary; I can say that I've spoken with Rhys Kent on the phone, read his posts on Brickboard, and would send him my carbs in a second.

That is, if I weren't a total cheapskate. As my friends and relatives will attest, I am a true cheapskate, and in true cheapskate spirit, I forged ahead with the work myself.

Clutch slave.

Back in August last year, my clutch slave sprung a leak. It happened after I topped off the fluid - maybe the new fluid reacted with the old and eroded the seals? Perhaps some sediment got forced through the system?



Replacing the slave cylinder seals was a pretty straightforward task. The hardest part was getting the right rebuild kit: there are two cylinder bore sizes common to Amazons - 3/4" and 13/16". Both are available from Swedish Treasures.

I ended up ordering the wrong kit the first time around. Lesson learned: I should have removed the slave and measured the bore before ordering parts.

Carbs.

The carbs on my Amazon have given me grief since I got the car. After trying a multitude of fixes, I finally decided to heed some sound advice: tune up the rest of the motor before touching the carbs. I could have saved myself a good deal of frustration if I'd taken that simple advice.

That being said, there was still a good amount work to be done on my tired old SU's. Luckily, there is a wealth of information and tech advice on SU's on the web - much of it from the MG and Jaguar community. (I've linked to helpful sites below.)

On the road again.

Wow. Has it really been six months since I worked on the Amazon?

The 122 has been sitting in the back yard gathering cobwebs since I moved last November. Finally, last week I charged the battery, pulled the choke, crossed my fingers, and- sure enough- the motor fired up on the first try! Yet another testament to Scandinavian reliability.

Unfortunately, the motor was still running rich. I've struggled with my Amazon's carburetion since I got it, vacillating between so rich that I had to drive with the windows down, and so lean that I couldn't get out of the driveway.

I'd already spent countless hours fiddling with various jet settings, needles, and even gone so far as to re-bush the carbs- all to no avail. I finally decided to heed some essential advice regarding SU's: tune up the rest of the motor before touching the carbs!

I really can't emphasize enough how important it is to tune up the rest of the motor before touching the carbs. Here's a checklist:

1. check compression - factory spec is 156-185 psi, with equal compression between the 4 cylinders

I got readings of 160, +/- 5 psi between the cylinders

2. valve lash - I set mine to 0.020 (cold) using the "Rule of Nines" method

I used 0.020 "go" and 0.022 "no-go" feelers

3. points and condenser - replaced (point faces were pitted) and set to 0.018

I tried to file the point faces flat, but the pit was too deep


I used 0.018 "go" and 0.020 "no-go" feelers, cam and rubbing block were lubed prior to installation

4. distributor cap, rotor, spark plugs, and plug wires- replaced distributor cap and rotor (carbon traces and pitting were evident on both). I looked up the Bosch number on my distributor and got parts locally because I was impatient, but honestly, iPD's tune up kits are a hard deal to beat. I cleaned and gapped the plugs to 0.028 and "refurbished" the plug wires and boots -- I was too cheap to replace the plug wires (which look good), and instead, snipped about a 1/4" from each wire until I got to what looked like "fresh" copper and screwed the plug boots back on.

filing the contact faces just ended up scoring them... and isn't that a crack, anyway?


I installed plug wire separators for extra insurance against misfires

6. timing - OK, I fibbed. I still need to get my hands on a timing light.

7. fuel filter - replaced

gross.

8. eliminate vaccum leaks - replaced PCV valve and hose

not sure if this was necessary, but it was cheap insurance

9. finally, tune the carbs - cleaned, re-bushed, replaced throttle shafts, set float height, re-centered jets, matched piston drop rate, sync'd, and set mixture

Lesson learned - it's impossible to tune SU's without having the rest of the motor in good order. After all of that, the Amazon seems to be running like a champ! (Or at least like what I imagine a 44 year old car should run like.)