Need help with tune up and fault identification

[SteveJ]

That's the one I bought. I found mine on eBay.

[Willoughby Z]

Hi,

...I'll let you know if I am succesfull. If the tune up does not deliver the results, I will start chasing vakum leaks.

A proper tune-up starts with components and parts in good condition. First, you have to insure that there are no vacuum leaks. Second, that all electrical connections are clean and tight. You're wasting your time to try and perform a tune-up before you have created a stable electro-mechanical baseline.

[240260280z]

Careful with the synchronometer choice. The STE has two versions. Get the BK (Silver) one as it can read higher flow.

The STE meters seem to be designed for lower flow from a single cylinder per carb throat. A Z with SU's has 3 cylinders drawing through one carb throat. The Unisyn is better for higher RPM balancing @ 3,000rpm.

[LeonV]

Careful with the synchronometer choice. The STE has two versions. Get the BK (Silver) one as it can read higher flow.

The STE meters seem to be designed for lower flow from a single cylinder per carb throat. A Z with SU's has 3 cylinders drawing through one carb throat. The Unisyn is better for higher RPM balancing @ 3,000rpm.

Are you sure about that, Phil?

http://www.classiczcars.com/forums/carburetor-systems-s30/46788-ste-syncrometer-higher-rpm-balancing-arghhhhh.html

[wenzlern]

Hi,

I found out that zcarparts.com is just near my work, so I could get a STE directly from them.

I know that the general tune has to be proper to do a proper tuning of the carbs. However most hoses seem to be in good condition and I have already gone through the rest of the ignition and the valves. Having said that... There is of course a vacuum leak .

With the help of the gauge I could get a good idle tune, but at 1500 the front carb can not be tuned to the back one completly, even with the balancing screw all the way loose. With other words, something on the front carb is leaking. I will get a bottle of carb cleaner tomorrow and start chasing that leak...

It was still no wast of time, since it is a lot better than with what I started (I have 6 perfect looking spark plugs, instead of 3 good and 3 black ones), a low and stable idle and a good initial pickup.

Thanks for the tip's, especially about the STE gauge, it works really well!

Regards,

Nils

[e-tek]

Sounds like you are well on your way to figuring it out! The issue of stumbling at a higher rev point or load, is almost always due to either (vacuum or centrifugal) advance not allowing the distributor to advance, OR, a fuel restriction. While you want to be sure both carbs are sucking, you can do that very quickly by putting your hand over the intake area of each carb. So long as they both suck the palm of your hand in, you are good to look elsewhere first. Once you iron-out the basic SPARK-FUEL issues, you can then balance the carbs.

I did a 100-point restoration (meaning EVERY ITEM WAS NEW OR REBUILT) on a vehicle last year and was chasing a very similar issue. I had gone through EVERYTHING imaginable, including removing the fuel line and pushing air through it, as well as measuring the volume of fuel coming to the carb when cranking - which was normal. After another few hours of chasing my tail (3 fuel pumps, rebuilding carb 3x, rebuilding distributor 2x and more!), I found it to be a 3" long flexible elbow in the fuel line that was collapsing when the engine was loaded (revved up)! ARRRGH!

It's a learning game for me - repeated daily!

[wenzlern]

Sounds like you are well on your way to figuring it out! The issue of stumbling at a higher rev point or load, is almost always due to either (vacuum or centrifugal) advance not allowing the distributor to advance, OR, a fuel restriction. While you want to be sure both carbs are sucking, you can do that very quickly by putting your hand over the intake area of each carb. So long as they both suck the palm of your hand in, you are good to look elsewhere first. Once you iron-out the basic SPARK-FUEL issues, you can then balance the carbs.

I did a 100-point restoration (meaning EVERY ITEM WAS NEW OR REBUILT) on a vehicle last year and was chasing a very similar issue. I had gone through EVERYTHING imaginable, including removing the fuel line and pushing air through it, as well as measuring the volume of fuel coming to the carb when cranking - which was normal. After another few hours of chasing my tail (3 fuel pumps, rebuilding carb 3x, rebuilding distributor 2x and more!), I found it to be a 3" long flexible elbow in the fuel line that was collapsing when the engine was loaded (revved up)! ARRRGH!

It's a learning game for me - repeated daily!

Hi,

God, I hope (and will assume for the moment) that my problem is not that sneaky .

The plan is to first figure out where it sucks wrong air. If I have to take of the manifold to fix it, I am going to be tempted to just get rid of the whole emission stuff at the same time. I also still have to check the float level at the carbs. This could also be the reason for the behavior at 5k (fuel starvation). Hopefully I will get a chance to put it on a lift this weekend to determine the state of exhaust, exhaust manifold and bushings. This will then determine what to do next. As soon as the mechanical is in a good condition I'll have to start with the interior (Reno car, no rust but all plastic parts are shot) and put the doors and the trunk lid in straighter than they are now.

Regards,

Nils