Hi - looking for some zetec guru's out there.
I'm doing my first full engine build - my 2lt block is away being bored out to suit some forged pistons and I have some steel rods to go with them. The head has been fitted with some bigger valves and thoroughly ported and I have some high lift cams which are suitable for hydraulic followers. The pistons are pocketed, etc, etc. It should be a nice engine when finished.
However, while the block is away, I've started thinking about the next stages and I got to researching the valve - piston clearance method and have hit a snag. When the engine is running it will have oil pressure - when I check it it won't. So, my understanding is you swap the hydraulics followers temporarily with some solid followers so that the valve opens correctly. Along with some soft checking springs you can check the clearance easily with some plasticine.
But - how big/thick should the temporary solid followers be? Am I right in my understanding that the follower will be slightly pumped up even when the valve is opening? How much is this amount? Is it constant? The follower then pumps up further as the valve lift reduces, thus taking up the 'valve clearance' you normally shim to achieve on a solid engine. Is that right or am I missing something obvious?
My followers are drained down so I can't measure them, and even if not, how would I know I was measuring what the valve would see as lift? The Haynes manual only states the diameter of the follower... so I'm feeling a little baffled
Doesn't only apply to Zetec's either I guess, anything with a hydraulic follower would give the same problem. Anyway, I'm confused - can anyone enlighten me?
Cheers,
Phil