Asthmatic 2286cc (Series III)

[changill]

I have a 1983 Series 3 LWB Ex-Military 24v. I rebuilt it about 5 years ago and all has been well up until recently when the engine has become noisy. I didn't rebuild the engine.

The noise is difficult to explain, but is best explained by me as a ticking noise. The noise is quieter at idle and increases in volume under load, but becomes quieter on the over run, presumably as the Revs drop and the engine isn't under load.

I have changed the manifold gasket, inlet to exhaust manifold seal and carb to inlet seal, but that made no difference. Then dropped the exhaust downpipe (again) and used exhaust sealant on re-assembly. Still no difference.

Checked the tappets and all good at 0.010". While checking tappets I found that at the start of every 2nd downward movement of the starting handle a slight wheezing noise was evident. At the end of every 2nd rotation the wheezing was worse.

I took out all the spark plugs and felt for suction and compression in all 4 cylinders. I know its not scientific but with my thumb over the plug aperture I felt both compression and suction on all four cylinders. On putting a spark plug in each hole in turn there were no weird noises but when I put a spark plug in number 4 cylinder there was some wheezing evident. All other 3 cylinders were open.

I ran the engine with 3 plugs in and number 4 removed. The engine ran but it was too (other noise) noisy to hear the underlying noise. All back together and engine runs but the noise is still there. On engine shutdown there is a sucking noise, almost like its about to backfire, but doesn't.

If I am honest the engine might be a bit down on power compared to a year ago, but the change has been gradual so I really haven't noticed.

My next plan is to buy an engine compression tool and see what that tells me. My money is on a burnt out valve (s) on Number 4 Cylinder. I don't know if the head has been converted to run on unleaded, but I would say it was doubtful. And yes I have been using unleaded without lead additive.

Am I barking down the right path? Do you think it sounds like I need valve seats replacing? I have mechanical experience but not on "sucking chest wounds"!!!!

Any thoughts appreciated

Ta

Chan

 

Edited October 16, 2019 by changill

[Bowie69]

Simple way to see if you need to open it up, is a compression test, for £10 worth of tool it has to be worth it.

[steve b]

If it is valve seat damage from unleaded you can start by checking the valve clearances - the valve sinks into the seat to simplify it and closes up tappet clearances . Once these are set do a compression test with the right tool .

cheers

Steve b

[changill]

Compression tester on order. I'll post up when Ive done the test. Thanks

[changill]

So its taken a while to get some time to do the test, but I did the compression test today. Manual states that Compression should be 145psi. As a reminder I thought my noise was coming from No4 Cylinder. Results after 2 tests on each cylinder.

1 = 124psi

2 = 121psi

3 = 121psi

4 = 112psi

Adding oil to each cylinder made no difference.

Took the head off and head gasket had blown between No4 Cylinder to the rear edge of the block at the metal head gasket's thinnest point.

As the other 3 compression figures were so low I'm going to get hardened valve stems fitted and a head overhaul.

So my noise was exhaust gases escaping from No4 Cylinder.

Thanks for reading and contributing

[Gazzar]

Thank you for the update. That's a sensible approach, did you consider a "performance" upgrade?

[Bowie69]

Good find

Think about getting a bit more skimmed off the head, raise the compression ratio slightly and will improve performance for next to no outlay. The machine shop, if any good, should be able to advice how much to go for.