Cheers guys. It will be another week or more until I can get back into it. The plugs are new. I’ll look to get a few parts in the interim so they can go straight in when I am able to get at it again.

With the Holley idle mixtures, Holley spec's to use a vacuum gauge and get the highest reading. Turn each mixture screw the same amount.
Power valve may need playing with if it was not set up correctly. rough guess is you would need a 6 or 8. Again the vacuum gauge will tell you what vacuum you are getting at cruise and the power valve really needs to be shut at that.
There are plenty of tuning videos etc on these.
Just redid one on an F100 with 351, goes hard.

Cheers Steve

On a side note, Holley now uses a blue gasket material that is re-usable, handy if having to change the power valve when tuning.
Cheers Steve

Thanks Steve. Appreciate the advice.

The carby kit finally turned up at the local automotive store. Unfortunately it had the older black gaskets in it but that’s life. Removing the rock hard old gaskets took some persuasion and was by far the hardest part of the refurb. Once installed it certainly has cleaned up throttle response but if anything highlighted the miss fire even more.

After that not helping I did what I should have done at the start and tracked down a compression tester. Cylinders 1, 2, 4, 5 and 6 had 125psi which is great for the inline 300 but......that leaves cylinder 3. Cylinder 3 has ZERO PSI. Damn it.

Haven’t had a chance to look into it yet but thought I should put a bit of an update in here as it’s been a few weeks. Hoping it’s a valve issue and nothing too sinister. From memory they were the valves which were a bit sticky when I tapped them prior to putting the lifters, rods and rockers back in place. I’ll do a dodgy version of leak down testing to source the issue as soon as I get a spare couple hours.

Other than this I’ve tidied up some grounds and replaced a few perished cables. It now cranks over as it should instead if being very lazy. Have also removed some suspect brake line sections which I will have made up replace for piece of mind.

If I’m not back in here beforehand, have a decent Christmas period and thanks for the help with my first project of the transportation type.

Since it has hydraulic lifters, there is one quick thing you can try. While running with the rocker cover off, try backing off the valves on #3 until they rattle. I have had dodgy lifters pump up before after doing a valve job and they would not go down! (holds valve/s slightly open)
Unlikely, but you might get lucky.

Thanks for the update, Jarrod.

get an Oil pot & pump 3-4 Pumps of Oil down the plug hole & see if It makes a Difference to the Compression.

Hey. Tried both of those plus took the manifolds off to see if I could tell what’s going on but no real luck, well in saying that it is building 25 psi now. Meant to take photos of the valves but forgot. Will be pulling the head off at this rate unless there is an easy way to clean all of the crap out of the valve whilst installed. Did try to hit it with degreaser and carby cleaner as that’s what I had handy but it didn’t help. Are the engine cleaning products any good. I’m really sketchy about using them but if it saves work I’d be tempted. Thanks.

The exhaust valves may have cracks around the edges......Ford used some pretty cheap valves back in the day......Ford invented the use of aluminised steel for exhausts ,considerable saving on the alloy steel other makes used ......catch was the aluminized coating meant the valve could not be ground or faced.....or the coating was gone.

Sometimes there are NO short cuts worth taking. I would pull the head and be done with it, sort it out and refit.