single Su HIF 44

[Peter J Larsen]

over the last couple month I noticed that
sparkplugs No. 2 and 3 ( esp. 3 ) are always to rich( dark)
No. 1 and 4 are fine.
Ihave a red spring and a BDL needle and I tried a lot of different
sparkplugs to no avail.
the car performs good under those cirumstances once a while 4 was fouled out.
Could be the problem the intake manifold from mini spare center ? , which I have.
Are there any other intakes available for this setup?
Engine size 1362 elgin fast cam 264/268 singe HIF 44

Dist. 123 set at 6
and if I lean out the carb then the No. 1 and 4 get leaner and leaner, no good.
appreciate any input.
peter

[mascher]

The BDL needle is the standard needle for an HIF44 on a 1275. Using this needle you have most likely richened it to get it to work but it is not balanced throughout the RPM range. You may need a richer needle to get the mixture correct throughout the range. I think BDK is the one most often used.

Do you have a K&N air filter or some other free flowing air filter? This would also require a richer needle.

There are other possibilities but these are the most likely.

Kelley

[Peter J Larsen]

yes, I have cone shape K&N on it.
I had the BTK needle on it in the beginning, cannot remember why it went to BDL, but will try it again

thks

Peter

[Jerry]

Are the plugs sooty or oily? Done a plug cut?

[Andrew.Bertschi]

What do you mean by doing a plug cut Jerry?

[Jerry]

A plug cut, to my understanding, is a method to determine an air/fuel ratio at a predetermined engine rpm. Say you want to know what the carb is doing at cruise, about 3600 rpm. You make sure that all of the standard tune up requirements have been met; clean plugs, timing, clean air filter, etc.; run the car at that rpm, then simultaneously, push in the clutch, turn off the ignition and coast safely to the side of the road. Now is when to take the plug cut; pull the plugs and check tips for color. Calver says that with unleaded fuel, the nose of the insulator should be light-to-mid slate or gray. The purpose of all of this monkey motion is that the result of the 'plug cut run' is not contaminated by other running conditions. Or the club could go on-line and buy a wide band O2 sensor for the tool room. We paid about $120 for ours. Anyone else is free chime in-my feelings wont be hurt.

[mascher]

That's the basic idea of a plug cut but the engine has to be under load. This means it really has to be done on the road. Choose a road with a safe reliable place to pull off. Run at the RPM of interest for at least a 1/2 mile (my guess, more is better) and then switch off the ignition and coast into the predetermined parking place. Put on leather gloves, open the hood and check the plug color.

I've never noticed the "light-to-mid slate or gray" on the insulator. The color I look for is light brown. Maybe it has something to do with what the put in the gas in England or Calver's using a lead replacement additive. It may vary a bit with the time of year here since the fuel formulation changes. Most men are so bad at judging color it's probably best to say it shouldn't be black and it shouldn't be white.

In Peter's case I suspect that the lean needle has been adjusted to compensate for a lean off idle condition and as a result it is running rich at or near idle. This the main reason that you can't adjust the jet on an SU to compensate for large changes in required mixture.

Kelley

[Peter J Larsen]

thks for all the input/explanations
yes the sparkplugs # 3 and 2 are sooty not oily.
what about using different types hotter colder sparkplugs in the mix.
hotter burning one for No. 3 and 2 and colder ones for No. 1 and 4

peter

[megamiles]

Hi Peter, sounds like you and I have a similar set-up. BDK is the needle I have, 276 cam and GT5 longman head. I performed most of vizard's mods on the SU. works great but #3 is always showing a bit rich compared to the other three. The mixture of the carb would not cause a variance between cylinders. In fact, I cannot imagine the carb influencing this at all, more likely in the intake manifold.

[Peter J Larsen]

thanks, yes that what I was thinking too . the intake manifold.
because I did everything from
needle spring plugs leaning out minimize using the choke.
That was my initial question, are there any other intakes around ??

peter

[Jerry]

I agree with Tim. Assuming a decent head with good flow properties, it's got to be in the inlet runners of the manifold. What needs to be done is to increase flow/speed on the inboard side of the runners and/or decrease speed/flow on the outboard side of the runners to balance the flow into the head. Don't know how to do that without a machine shop and some sort of flow bench.

[Peter J Larsen]

what about using a:
MG metro alloy intake ( watercooled) to use,
anybody had any expierence?
peter

[Jerry]

David Vizard liked the Metro intake. After some modifications, he also liked the Oselli Torque master and the Howley intakes. Keith Calver states that his design, the Mini Spares intake that everyone uses, better than all three.

[mascher]

Keep in mind that Tim said he was using a BDK needle in similar engine to Peter's. Peter said he is using the stock needle (BDL) in an engine that has significantly improved breathing and larger capacity than stock. This would indicate that the first step would be to fit a richer needle.

My guess about the problem with the spark plugs is that to make the BDL perform reasonably off idle it has been adjusted to run very rich at idle. The rich mixture isn't allowing the fuel to be evenly dispersed in the air stream at idle (slow air speed and a lot of fuel) and the liquid fuel is following the shortest path which is to the center cylinders.

Even if I'm wrong about the cause of the problem, I'm pretty confident that the BDL is the wrong needle.

Kelley