Tuesday, April 7, 2009

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.


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.)

Monday, April 6, 2009

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


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.)