no compression

[zdude1967]

Hi,

I just had my 260 engine rebuilt. It is running like s**T. I did a poor mans compression test (finger over the spark plugs while cranking engine) and the # 5 seemed to have no compression. In any case the engine is under warranty and the company that rebuilt it seems to be rather clueless. I say this because they want to check the carbs as they think this may be the issue. Now I do not claim to be Mr. Goodwrench but my understanding of this engine leeds me to believe that if there is no compression or very weak compression it would either be the valves or the rings. Would someone please let me know if there could be other reasons besides the rings or valves or if I am clueless with my ring/valve theory. By the way they claimed they checked the valves and that they are fine which is why they are moving to the carbs.

Thanks

Glenn

[SteveJ]

You could always buy a gauge and test the compression yourself. While you're at it, buy a timing light, too. Also, how do your plugs look? Are you sure you're getting enough fuel to the carbs?

Get a set of feeler gauges, a remote starter, and a socket set. Take off the valve cover and check the clearances. The measurements are all in the FSM. If you're not sure if something looks right, take pictures and post them.

There aren't enough facts in you post to tell you whether or not you're on the right track.

By the way, did you get the rebuild done by a place that specializes in early Z cars?

[zdude1967]

Steve,

It is a Japenese engine rebuilding company..The owner has a few Z'S and there were a few customer Z'S in the lot as well. Since the engine has only a few hours run time on it and is under warranty it is probably best for them to seek out the issues. I guess I am trying to determine if I should be as concerned as I am because I do not see the connection to no compression and the carbs. I am not Mr Good wrench but I do not see the carb connection. They said they checked the valves and they are fine, I would think the next moves would be either head gasket or rings. How does the Carb figure into this-if it does then I guess I must have confidence in there approach if it does not then maybe they do not know what they are doing. The number 5 and 6 spark plug seemed to have a much darker look then the #1 through 4 plugs. Everything has spark, the engine starts but runs very rough like it is missing and with the finger compression test # 5 does not push back on my finger at all which at first would, in my opinion seem to indicate a stuck valve however they said valves are fine and since the # 6 seems weaker then the #1 through 4 I am thinking head gasket. They said the plugs are not wet so it cannot be the rings, they also did not remember the compression test readings from the compression test they claimed to have performed. Not very happy at this point. What are your thoughts?

Glenn

Edited July 14, 2011 by zdude1967

[SteveJ]

My thoughts? Well...

Empirical tests are typically more trustworthy than subjective tests. Compression gauges aren't expensive. It's easy to do a compression check. If you think it's the valves, that isn't too difficult to check, either. If you're not feeling too comfortable doing those tests, buy some beer and find a friend who is comfortable with checking.

As for the plugs, it 5 & 6 aren't wet, it's probably not too much oil/gas. Rings have to seat.

The shop is fingering the carbs because they believe the compression is good and that poor fuel delivery is causing the car to run like crap.

[5thhorsemann]

If you still have the original flat top carbs on the car, that would be my starting point as well.