Running poorly

[fe]

 :(Hi
I have a grey engine 138 and its a little tired ,lately its had a bad miss and doesnt improve with acceleration.Ive put a new dizzy cap and cleaned all the sparkplugs and cleaned the points ,Ive checked the timing and all appears ok
Im hoping someone can shed a little light on other ideas I can try

[snuff69]

Leads Dave

[ACE]

Compression Test
ACE 

[Harv]

Get the vehicle to miss whilst parked in the driveway. Pull the plug leads off one at a time while it's missing - if the miss gets worse, then that plug lead is not the culprit. if the miss gets no worse when you pull a lead, you've found the crook lead/plug.

Is the rotor button sitting down properly? New Bosch rotor buttons are pretty snug, and if "sitting up" can cause an intermittant miss. Slop in the dizzy main shaft can do the same (don't ask me how I know  ).

Has someone stuffed around with the carburettor at all? If it's lunning lean, it may surge or miss (particularly if someone has farted around with a variable main metering jet). If it's got a variable main, you can screw it out a bit and see if the miss goes away.

Tried hunting down a miss on a 308 VK Calais at one stage... spent a small fortune replacing electricals... still couldn't find it. Ended up being a worn cam lobe leaving the exhaust valve shut (Ace's compression test should help pick that one).

Cheers,
Harv

[Rod]

Support Compression test also. Sounds like it could be a burnt valve.

Rod

[KFH]

As Harv said try shorting the plugs out one at a time and note if there is any difference to the miss.  If it is a spark related issue try a new or different spark plug.  I have, had on two different occasions, plugs causing this type of problem.  One of them was almost new.

Keith

[fe]

Hi Thanks guys ,I appreciate your help
I will try new leads and check the spark plugs
I have no instument to measure the compression

To give you more info on the engine , its missing constantly ,Ive cleaned the spark plugs and they appeared ok
it farts when under heavy load and you have to back of the power ,I think its worsening

I will give you the results soon

[fe]

UPDATE
I changed all the leads today and there is no improvement at all
My next guess is to change all the plugs
Im very frustrated
Does anyone know of a mechanic who enjoys fixing old Holdens on the Central Coast

[mcl1959]

Buy a compression tester - they're not very expensive. I support all the other people on this thread who suspect a burnt valve. Don't bother chnging the plugs unless you can see an obvious defect like broken electrode.

Ken

[fe]

Hi Thanks Ken
If its a burnt valve ,what are my options

[mcl1959]

Pull the head off and replace the valve. Not a real difficult job as long as you follow all the steps correctly.
The compression test will tell you straight away clear as day if it is. You will get readings between 100 - 120 lbs/sq in on good cylinders and 0 on the cylinder with bad valve.

Ken

[fe]

ok I will do that
So Im in the market for a compression tester
anyone have one for sale or I can borrow

[57effie]

Like Ken said, they are cheap new. Don't muck around with 2nd hand. Buy a new one. Then your mates can borrow it off you.

Mark