273 mech rocker problem

shim up the shafts with general hardware washers
use a sharpy to colour the valve tips
rotate engine over to check clearance and you should have a clear scraped off ink, window on each coloured in valve tip. adjust shimming until the window on the valve tip varies across the widest part of the valve tip and the rocker tip pushes valve down before the rocker hits reatiner
when good measure the washer pack used and buy appropriate shims to set that rocker shaft up by the same value.

if it can't be done this way

get crane cams multifit retainers with offset, these are offset up or down, you need offset down.
these have a standard hole and you pair them with thicker or thinner collet to cater for stem diameter. It rasies seat and open pressure a little but could get you the clearance.

and/or off-set collets from the same source. you can raise or lower the retainer a smidge this way on a valve that is custom to the application. smaller increments than with retainers, and yes you can also get them in multi fit thicknesses for use in multi fit retainers.

this process should be done with a custom adjustable pushrod or a home made one with shims/small washers added into its length. cut rod in an accessible place where adding washers to its length won't clash with other hadware . wind/press in threaded rod into its middle
stick on some washers and put the other end of pusrod back onto the threaded rod.

aim to get a line through the rocker paralell to head/deck with the valve at half lift and maintain your nice pattern in the sharpy ink on the valve tip.

when all good, measure the washers you used to shim up the rocker shafts and get proper shims.
measure the shim washers you used to legthen your pusrods and get pushrods made longer by that much.

I've been through this on an aussie 6 with massive cut to block and head, stud mount 1.72:1 rockers off a ford, narrow stem ferrea valves suitble for edlebrock big block heads that were a smidge too long

offset collets and offset retainers from crane
and some smiths bros custom pushrods...longer..... got me bang on right

the tip of your rocker needs to press the valve down before the "armpit" of the rocker hits the retainer...

In my view a geometry fix attempt is needed before buying off-set rocker shafts.
This is just normal custom engine build stuff, that is avoided if you use a well worn recipe, where somone else did the hard graft. But is standard if all the parts come from a range of suppliers and were designed for another motor.

you have a lot of rocker tip, the current set up has the wrong bit of the tip hitting the valve tip, and too close to the rocker i.e too close to edge of valve tip. shifting the shaft up can make this worse if the same area of the rocker tip is used, but you have loads of tip space on that standard style rocker. I suspect the rocker shaft lift will get an area closer to the end of the rocker tip in contact with the valve tip and in a more appropriate place on the valve.

it may make it better it depends on how bad the geometry is how laid back your rocker is when the lifter is on base circle. really you can only see that if you watch a full cycle.

basically rocker should be neither biased tail down or nose down at half lift, and the contact between it and valve should be as close to the diameter line of the valve tip as possible


but nobody will know until you try

while you are in there and once all set up with correct lash, little smidge of lube on pushrod end at rocker, check for coil bind at full lift
check for retainer or bottom edge of collet, to guide or seal.... impact
put white line on all pusrods in paint or nail varnish just below rocker.
turn engine over with plugs out 10-20 times check all pushrod marks have moved round a little bit indicating that the lifters are turning if one doesn't what is wrong. find out first before trying to start it.
if they all turn you reduced the likelyhood of wiping the cam by about 99%


can't say i'm telling you the correct way to do this i just did what i had to and it worked for me

Dave