308 won't fire

[Big Rob]

Yep, you look like you have a set of rocker bridges that were machined for a reground cam, and now you've installed a new cam that is std base circle, so the valves are staying open.
After measuring everything, you can put washers under the bridges to pack them up to the correct height, but it will take a bit of mucking around.
It's probably best to take all the rockers off and the pushrods out and do each pair at a time (turning the motor over by hand of course).

I ground cams for over 6 years for Watson Racing Cams back in the '80s and early '90s and have encountered this problem a squillion times.

[HK1837]

Last I knew GMH still had new bridges, if not Rares will have them now.

[Sandaro]

Thanks to everyone for all the good advice above, gave me some good diagnostic help.

Thankfully have got the motor going, sounds great running straight out the extractors without pipes. Hopefully take it for a blue slip in the next week.

Turns out I had 2 problems. First was the pushrod/rocker problem not allowing the valves to properly close, which I fixed with shims under the bridges (may revisit shorter custom length pushrods later) and then once that was done it would run only with the bypass wire, had to replace ignition switch too.

Its been one of those jobs.