CAROLINAS AUSTIN-HEALEY CLUB

  
 

This article Copyright 2001 - Chris Kotting  ckotting@wideopenwest.com. 

Permission to reproduce is freely granted upon request

Tuning 101:

Getting your SU's set properly.

...or...

How to get your car running the way you want, without frustration.

Continued

Step 2: Adjust the Valves

Some people skip this step, at their peril. Remember our first First Principle? (Vacuum controls everything else...). The vacuum is created by the airflow into the cylinders from the intake manifold and the flow of gases out of the cylinder through the exhaust manifold.  The valves control that flow of gases. So the first thing to get done is to adjust the valves.  Valve lash controls three things, one of which is in direct conflict with the other two.

Valve lash is the final arbiter of valve timing (smaller lash opens earlier and closes later, wider lash steals power).

Valve lash is the final arbiter of valve lift (smaller lash opens the valves further, wider lash steals power).

Valve lash provides the only opportunity for the valves to dissipate heat into the cylinder head, where it can be carried away by the cooling system (smaller lash makes burned valves more likely, wider lash keeps them cooler).

The valve lash specified by the factory is a compromise between the first two and the last one.  Personally, I don't like doing valve jobs, so the fact that the factory is conservative is fine with me.

Okay,let's get to it:

 

Preliminary: Are your valves supposed to be set HOT? Then start the car and get it to operating temperature.

Remove the spark plugs (this makes it easy to turn the engine over). Set them where you'll be able to remember which cylinders they came from.

Remove valve cover. If the previous mechanic had their act together, and the valves were last adjusted sometime this decade, it should come off easily. You only need a new valve cover gasket if the old one gets damaged in this step.

Look at the table of valve adjustments that you copied down in the preliminary step. It will tell you what valve you want to see all the way open, to adjust the one that's all the way closed. Turn the engine over and watch the valves.

Some people bump it over with the starter. I prefer to use a hand crank (if you've got one) or put the car in 4th and pull it towards you. Much easier to get the right position.

Another trick is to put the box-end wrench for the adjusting locknut on the rocker that's OPENING. It's easier to see the movement of the shiny wrench than the dark rocker arm.

Loosen the locknut on the CLOSED valve & slip the feeler gauge in between the valve stem and the rocker. Turn in the screw until you just feel drag on the feeler gauge. Hold it there while you tighten the nut. Repeat (3) and (4) for the other valves.

Check your work after you tighten the locknut. Use a feeler 0.001" larger and one 0.001" smaller than the desired setting. The smaller one should have no appreciable drag, while the larger one should have a lot of drag, if it fits in at all.

If your checks seem to always come up off, make sure you're holding the screw steady while tightening the locknut. You actually have to apply some counter-clockwise force to the screw as you tighten the nut down, or it'll close. But be careful, apply too much, and it'll open.

You don't have to crank down on the locknut with all your might. In fact, you shouldn't. Just "snug" will do.

Replace the Valve Cover (with a new gasket if needed). If you have to replace the gasket:

Clean both the valve cover where the gasket goes and the top of the cylinder head scrupulously, and don't let any of the crud fall down the pushrod openings.

Use a gasket sealer between the gasket and the valve cover, and a wipe of grease between the gasket and head, and you'll be able to use that gasket for years.

Take a look at the plugs before you put them back in. Take notes, because this is the best look you're going to get at what goes on inside the combustion chamber, unless you want to spring for a Gunson Color-Tune.

The electrodes should be nice and square, the gap should be right, and the deposits should be a light tan and dry.

White (or no) deposits mean you're too lean.

Dark and dry means you're running rich, dark and wet (smelling of gasoline) means you're REALLY rich, and you may have some problem in the carb. We'll get there later.

Black and oily and you're burning oil.

Compare the different cylinders, it may show you something useful about what is out of whack with which carb.

If you've got access to a compression tester, this would be the time to use it. All of the cylinders should be close to the same reading. If one's way off, put a teaspoon of oil down that bore and test again. If that fixes it, you are looking at a ring job, the sooner the better. If it's still way off, re-check the valve lash for that cylinder. If it's still way off, you're looking at a valve job, the sooner the better. You can finish the tune-up, but understand that with a compression loss in one cylinder, there's only so good you're going to get.

Put the plugs back in, or replace them with new ones if it seems reasonable to do so.

NOTE:I consider a Gunson Clik-Adjust to be one of the best "specialty" tools I've ever purchased. I can adjust the valves on either of our MGs in about 15 minutes with it (from Cover off to Cover on) and know that they're right on the money. Setting one up is well described in the instructions that come with it. If you're curious as to what it is and what it does, go to http://www.mgcars.org.uk/MG_Elec-Tech/Clikadjust_0.html. A few people have also asked where to get one. Other places may have it, but I got mine at Little British Car Co.

Step 3: Vacuum Leaks

Okay,now you've got the baseline vacuum as stable as it's going to get. Start it up and let it come to operating temperature. With the car running, spray your carb cleaner or starting fluid on the carbs where they meet the manifold, the manifold where it meets the head, the throttle shafts at the carbs, and all vacuum fittings. If the car seems to run differently when the spray hits, you've got a vacuum leak there. Fix it. If it's the throttle shafts on the carbs, you may have to put up with it for a while, or shell out $$$ for rebuilt carbs.

 

Do not seek perfection until you have the vacuum leaks resolved, for down that road lies madness....

 

Incase you do not have the specifications for your Healey, I am including those that I know.

6 cylinder Healey Specs

Firing order 1,5,3,6,2,4

Model

Breaker

 Dwell

Timing

Gap

Static

Strobe

BN4

 .014/.016

BN6

 .014/.016

MKI

 .014/.016

-380

50

150@600 rpm

MkII

 .014/.016

320-380

100

150@600 rpm

MkIII

 .014/.016

320-380

100

150@600 rpm

Valve adjustment . numbered from front to back.

Rocker Clearance .012 cold intake and exhaust

Valve fully open

12 

6

4

11

8

3

1

7

9

2

5

10

Adjust this valve

1

7

9

2

5

10

12

6

4

11

8

3

 

4 cylinder Healey Specs

Firing order 1,3,4,2

Model

 Breaker

 Dwell

Timing

Gap

Static

 Strobe

948

 .014/.016

50

60@600

1098

 .014/.016

80@600

1275

 .014/.016

100@600

100-4

 .014/.016

60

Valve adjustment . numbered from front to back. ( Sprite)

Rocker Clearance .012 cold intake and exhaust 

Valve fully open

8

6

4

7

1

3

5

2

Adjust this valve

1

3

5

2

8

6

4

7

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