think I have a misfire

[English]

Managed to find a place near me that does both compression and leakdown tests, it's booked in for Friday.

Movement on the balancer is only visible with the timing light hooked up to cylinders 5 (wanders) and 7 (slight wobble) all other cylinders show a rock steady balancer.
I've made sure the spark leads for 5 & 7 do not cross.

I'm wondering if the movement seen in the balancer is a result of bad firing due to sticky valves, or a result of the spark occuring at the wrong point because of a timing issue (chain? old distributor?); but if it was timing, wouldn't all cylinders be affected?

[enaberif]

How many miles on the motor? And do you know if the chain has ever been done?

[English]

Odo wasn't working when I bought it, and it's not the original engine, so very much an unknown. Plus it's an import with virtually no history!

[enaberif]

Odo wasn't working when I bought it, and it's not the original engine, so very much an unknown. Plus it's an import with virtually no history!

Well I would get the two tests done then I would visually inspect the harmonic balancer and see if the rubber is cracked or in bad shape.

From there I would possibly think about a timing chain change.

[bd]

You can easily check the balancer and timing chain yourself with minimal tools:

• Check the balancer using a piston stop and the method described in Not 100% sure what's wrong here.
  
  
• Check timing chain wear using the method outlined in 86 C10 Loping, augmented by the last bullet in 305 Issues, need your help.

[English]

Picked the truck up from the garage yesterday. They did both compression and leakdown tests, and the verdict is that I have a leak between cylinders 3,5 and 7. The other head is fine.

Bad news on the one hand, but at least I have a verdict now, instead of chasing my tail trying to work out what's wrong. And it ties in with what I've been experiencing and what I've found with the timing light and vacuum gauge, so I don't think they're trying to mug me off- always a worry when going to a new garage (my regular guy retired last week).

So it's either the head gasket or a cracked head. To find out they need to start stripping down, which means it's time to spend money. Or... I asked about getting a long block and swapping that in instead, and to my surprise they said the labour cost would probably be the same! I am SERIOUSLY considering this as an option now.

[roundhouse]

I would just swap
In a new engine
We are going to do this also
Ours has a wiped lobe on the cam and a couple other issues and we are planning on swapping in a LS engine

Guy near me sells LS engines with the wiring harness and modified computer.   Ready to run , for $1100


Sent from my iPhone using Tapatalk

[philo_beddoe]

In general, how do you know if you have a misfire?