There are a few things you need to check that are more important than the
restrictors. Flat tappet cams either, solid or hydraulic, the lifters have
to rotate. The easiest way to check this is to install the cam and lifters
and timing gear but no chain. Put a speed wrench on one of the bolts for the
gear and use it to spin the cam. Look at each one of the lifters to make
sure it is moving. They don't move that fast but if you put a mark on the
edge of each lifter you will be able to see if they are rotating. It will
take a few minutes of cranking on the speed wrench to see this. If they do
not rotate it can be caused by the timing gear being machined to the wrong
dimension. The cam lobe is not flat it is ground on a slight angle and the
bottom of the lifter should have a very slight crown on it. This is what
causes the rotation. If the Cam is not at the correct depth or the lifter
bores are not in the correct location relative to the cam you can have a
problem.
Other things to check for.
Valve lash wrong causing either binding or excess lash and pounding.
Rocker arms binding at full lift especially stock ones with non stock cam.
Push rod length wrong causing rocker arm problems.
Cam bearings either spun or installed incorrectly blocking oil holes.
Rod side clearances very tight so no oil is thrown out on cam.
Vacuum pump on crankcase set too high.
Valve springs broken or binding.
Valve spring pressure too high.
Years ago with very wild flat tappet cams we used to have 'break in springs'
that were much lower pressure or removed the inner springs to break in the
cam. generally for 20 to 30 minutes at 2k to 2.5k rpm. Then had to reinstall
the inner springs to race the engine.
Most any of the 'How to hot rod a SBC' books or the GM power book have all
this info and more. I would doubt if it is the block unless it is brand new.
I would be suspect of anything that is not OEM GM..
Personally I am a big fan of roller cams and shaft mounted rockers with a
good rev kit. restrictor size depends on oil viscosity and temperature,
don't rev the engine until the oil is warm. If you go too small on them you
have no oil to cool the valve springs. Look in Stef's catalog and see if
they also sell spray bars to add oil to the top end to cool the valve
springs.. Then ask yourself how important the restrictors are. They were
originally used to keep more oil in the oil pan if the sump was small and
the rpm high.
Dave
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