You have spent considerable money on your engine & done it wrong.
answer these questions if you can.
1. What thickness lash pads did you use to get the rocker wipe correct?
2. what is the piston to valve clearance?
3. Did you do a search on this forum before building the engine.
4. Did you read this?
http://www.datsport.com/racer-brown.html
5. why did you machine the head to get more compression instead of using the right pistons?
Understand this... I am trying to help you as I have done for many others over many years.
I have built more L series than most people alive.
I have just about had it with people not listening to good advise.
My time is worth money & I have supported this forum since day one. Just because I like to help.
Read it.
I have never seen rockers on the angle of your engine that would not run off the cam & destroy it.
Nor will your engine last if you leave the tensioner loose.
You should search this forum for the info you need to fix up your engine before you spend money doing it again.
I will tell you this..... amongst other thing.... as engines rpms rise the centrifugal force of the chain will over come the pressure
of the tensioner causing the chain to rise up on the cam sprocket. This retards the valve timing..... causing the exhaust valve to close later.
The piston is always chasing the exhaust valve.... so if sufficient valve to piston clearance was not allowed for disaster follows.
You also missed reading NADs questions about 5 posts down on how to correct a loose timing chain.
I would suggest you read it...
_________________
A little knowledge is a dangerous thing.
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"R.I.P. Baz. 29 April 2022. Thank you for all your contributions to the Datsun community over the years. You will be missed." - OZDAT