Round Three – Head Re-building and Valve Clearance Setting.
With the heads all stripped and cleaned the next job is to rebuild them. Valves will need to be lapped in to ensure an accurate seating is achieved. Lapping in valves is a bit of a chore in some respects, but an absolute essential if you are to get the full performance out of your engine. When Bill started to check the valve clearances he gave me some great news. If you remember I mentioned in the first phase of this project that the compression on No 4 cylinder was well down. The reason was that there was no clearance on the exhaust valve, therefore it was never shutting properly, hence the lack of compression. PHEW !!!!!
Some of the essential tools you’ll need for the rebuild. Feeler gauges, shims of different thicknesses, micrometer and out of shot spring compressor.
Bill doing his ‘favourite’ job of lapping in the valves.
Lapping tool in situ. With lapping paste on the valve and seat you now employ the boy-scout fire-starting reciprocating stick rotating technique which grinds away small amount of the seat and valve against each other ending up with a perfectly mating valve and seat. It would be much easier to find a boy scout and pay him to do the job in the first place!
Everything is now ready to go back into the head now.
The bottom couple of coils of the valve springs are coiled slightly tighter than the remainder, so be careful to put them back the right way up.
The valve clearances can be a bit of a game. Each clearance needs to be measured with the cam in place. If the clearance is wrong the way you correct it is to ‘calculate’ the difference between what it is and what it should be and then measure the shim currently in place. (The shims are located on top of the spring assembly under the cam follower/bucket). By ‘adding’ the difference to the dimension of the current shim, you will now have the thickness of the required shim to give you the right clearance. Clear? Not a chance! Here’s an example which hopefully makes it a bit clearer. Current valve clearance = 25 thou. Required clearance = 18 thou. Difference = +7 thou. Current shim thickness = 48 thou. New shim required = 48 + 7 thou = 55 thou. Clear?
While Bill was busy working on the valve clearances I spent some time cleaning up and painting the various bits that we’d taken off.
Inlet manifold looking good.
I put a block of wood under the front cover to support it whilst I belted out the crankshaft seal. When I say ‘belted’ I of course meant to gently persuade the seal to come out.
MORE TO FOLLOW……
PLEASE NOTE – these are NOT instructions on how to undertake this job just some pics and words of our experiences, always consult professionals when undertaking any repairs or restorations. (please refer to the disclaimer on our about page)