Running out of options!
have a 1954 XK120 that in November of ladt year while completing an update interior restoration develop a metal to metal sound and started miss firing
i have done a complete head job(springs valve seats etc) reassembled with caution by master technician insuring valve timing was correct with full compression(110-140) and still running rough and misfiring. Last efgort was a complete new solud state 123 ignition with proper firing order 153624 #1 being close to the firewall.
We have concluded the fault is above our pay grade and thus any assistance will be greatly appreciated

 

So the valve timing was set using the camshaft setting tool, yes ? Please tell us more about the 'metal to metal' sound. Back in the day, around 1993, when I rebuilt an XK engine around a replacement bare block due to cracking between the bores, the head had been done some 12 months prior, so on reassembly I just plonked the head back on and reinstalled the engine. When I started it I got a rather loud tappet noise and found one of the inlet valve clearances was very large. I had bent a valve !! I had stupidly not stripped the head down again and made sure all the valve guides were lubricated before reassembling. Have you checked your valve clearances and cylinder pressures again ?

 

Thanks for your quick reply.
The metal to metal was apparently the camshaft hitting on valve socket that had loosened up. Corrected during the head job by installing hold down brackets as recommended by one of my suppliers. The valve timing was done with factory tool verified with cylinder 6 at tdc against the flywheel mark. Same with the ignition replaced with 123 solid state distributor assembly and spark verified with the correct firing order 153624 one being close to the bulkhead. Currently starts right up but still misfires and has a coughing backfire sound
Timing chain appears in good condition and tightness. Lower of course chain has not been inspected Valve clearance doubled and tripled check! Again thanks for your help

 

Sounds like an awesome project and think you are wll on your way to sorting it out.

I saw an XK140 coupe last month at the local Jaguar Club Show. Nice car. Expect yours is soon to be ready soon.

Have you a leak down tester and carb rebuild kit and sphygmomanometer? The leakdown may show topend and bottom end all buttoned up well and carbs rebuild would be next.

Let us know.

Best Regards,