Dino missfire

Hi I'm struggling with the Dino again. I ran the engine and got it nice and hot then I removed the plugs and took compression readings
1= 165
2= 160
3= 160
4= 160
5= 110
6= 135

It's running lumpy and if I remove the HT leads in turn 6 makes no difference. I tried a new plug, and the checked the HT lead fires and that's fine. The plug is very wet with petrol .
Any ideas would be gratefully accepted

 

5 & 6 are low but it could be valve shims to tight.

If you are 100% sure the timing, plug is good and getting a healthy spark then the cause of flooding can only be carb mixture screw not set correctly ie out to far and dumping too much fuel into the chamber. The accelerator pump circuit could be jammed open and dripping fuel in the barrel as well.

Adjust the mixture screw back in until the engine smooths out.

 

Thanks I will try that when I'm back on it next week. Thank you for the ideas. The carb was set up by a Ferrari specialist a few months ago but they read the compressions and felt the fault lay there. I feel it's carb related. Could the low compression be because the bores is being washed with petrol.
Are there any pictures of timing marks on the forum I would like to confirm it's all aligned properly.

 

Ive had very similar experiences in the past - I'm with Tony; go for the carbs. however I would take off the problem one (actually easier to do all of them) and give it a really good clean out - it really does make a difference -then when you turn the screws, something actually happens!

 

While the one cylinder is low it is not diabolical either so I do not think that is your smoking gun. As Tony mentioned it could be tight valves so your fastest and cheapest bet would be to remove the cam covers to check. While you are at it you will be able to clearly see the factory timing marks that are only visible with the cam covers off. By putting the engine to PM 1-3 you will be able to confirm if the cams indeed are correctly installed (all 4 timing marks on the cams should align).

On the ignition side you will want to confirm that all 6 spark plugs are firing. Your problem could be as simple as a bad ignition wire and if your engine note does not change when removing the #6 HT lead that could be an issue right there.

Lastly the carbs themselves should be checked. It may have been looked at by a 'specialist' but I put little faith in that title as most of the self proclaimed specialists I have dealt with are more suited to cutting meat rather than working on cars. With the engine running look down the bores and make sure the accelerator pumps are not leaking into the cylinder. If you have the cam covers off then take the whole carb group off (only 4 bolts) and check to make sure that everything is operating smoothly and that none of the base plates are cracked or broken. Remove all of your jets and blow them out with air to ensure you do not have a small blockage. Also remove your idle screw and again make sure there is no dirt in there. Lastly carefully remove the carb tops and check to ensure that the float bowls are clean and free of dirt. This may seem like a lot but a competent tech should be able to do everything on the carbs in under 2 hours.

Problems like this always can be traced to something. The low compression on one cylinder is something that demands further attention but should not be your primary issue for the rough running you report. Look for the smoking gun and a metered and scientific approach is the best course of action to a solution. Good luck .