Healthy compression reading?

[Healey Z]

I'm dragging a car home this weekend with an L26 and I have a compression guage ready to go. What do these engines usually measure when they are healthy?

[jmortensen]

Don't look at the psi number. In fact, if the motor doesn't start and you can't warm it up before you test, don't bother testing compression at all. Read this, and look at what his compression test showed without a warm up first:

http://www.classiczcars.com/forums/showthread.php?t=39578

[Healey Z]

Thanks John,

The motor starts and runs but it stumbles and bumbles and is lacking power.

I'll follow the advice:

Warm engine to normal operating temp.

Remove all spark plugs.

Wedge throttle to wide open.

Conduct your compression test, preferably with a screw-in type of tester.

thx,

Ken

[Healey Z]

Pretty healthy I would say. Only concern is color of plug #4, any ideas anyone?

[Gary in NJ]

Perfect compression I'd say.

Were those fresh plugs? A proper plug reading should be performed with fresh plugs. #4 could be dark for some very simple reasons; i.e fouled plug, broken wire, defective cap or a spark plug wire that wasn't properly seated.

I'd perform a proper tune up (including a valve lash adjustment) and see if that doesn't cure the rough running.

[Healey Z]

Hey Gary, thanks for the reply. I pulled the cap to see what I had in there and BINGO, I found the vacuum advance wire disconnected from the disti. I slipped back on and the stumble and lack of power is gone.

I swapped the plug for another and I will see if it follows the plug or the wire.

What would you recommend for a spark plug / gap? How about for spark plug wires?

Edited October 10, 2010 by Healey Z

[Travel'n Man]

If you still have discoloration at the plugs - wet with oil or gas - you may want to back down on your carb setting - FWIW

[Gary in NJ]

Healey

I like the tune-up parts that MSA carries. It's all the same quality of the stuff I use to get in the 80's. They also carry NGK plug wires. I've always liked those too.

[beandip]

For this engine I recommend NGK by all means. And this number. BPR6ES with a stock ignition set them at .035". I have found NGK plugs work the vary best. The number that I gave you are not all that expensive either. Don't waist any money on those mulitple electrode offerings. Prices vary from store to store but just go to your local parts store . I paid $10.25 for my last set. I bought a set of Taylor plug wires but I am now running a ZX ignition.

Gary One more thing, are the carbs flat tops or round. SUs?

Edited October 11, 2010 by beandip

[Healey Z]

thx beandip, the carbs are weber down drafts

[black gold]

Hi every body this pic may help you, actually it is for 240 but I checked 260z manual and I found it same..

I think your reading is fine its from 171-185 psi

Edited October 11, 2010 by black gold

[jmortensen]

thx beandip, the carbs are weber down drafts

There's your problem.