I am servicing the valve operating parts on my 1964 356C and read in the manual that I should inspect the pushrods, the tappet adjusting screws and the rockers for wear before reassembling them.
I can see that the face of the rockers which push on the valve end where the clearance is measured, do have some wear evident and will be lightly ground to resurface them.
But, how do I check the pushrods and their associated adjusting screws for wear?
Any suggestions are welcome, Thank you, Robin.
Robin Walker
1962 356B S90 Coupe. sold.
1964 356C Coupe RHD
1973 911S Coupe LHD
1983 924 coupe RHD
Look at the ends of the pushrods; unless they have begun to wear into the adjusting screws, you're good to go.
I have never seen a worn adjusting screw.
Your rocker tips need to be reground if they have any sort of wear. This is not something you do at home. the tips need to be reground on a radius so they are smooth as they move across the valve head. Then they will need to be hardened again. On push rods from the early 60's may have a wooden dowel inside. This ws to control the oil flow to the valves. Usually the wood bouncing on each movement caused the end of the wood to become circular approximating the hole size in the push rod. You should probably replace these push rods sooner or later the wood will end up in the main and rod bearings. OUCH! Roll your push rods on a flat surface to make sure they are not bent. al zim 53 years in this love affair.
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Al (and others) already mentioned about checking pushrod straightness and rocker tips (I've done that for years, too), but the wear of the rocker bores and shafts are critical to minimize their maximum clearance-wear of .002". The oil flow thru the rockers are above the shafts and they'll wear out of round along w/the rocker bores; Shafts can be flipped over to the good side if the rockers are decent enough--no "pickup/scoring"--NOTE: This is on the later aluminum rocker stand.
The steel rocker stand was replaced due to twice as many clearances w/floating shafts and "eye wear"--especially the exhausts, but those rockers had an internal oil "pocket" surrounding the shaft and almost never wear out. There's not enough room for that in the intake rockers. I've re-bushed the exhaust "eyes" (the intakes rarely) several times vs supplying the later cost-wise assemblies.
I've removed the wood "fillers" from early pushrods due to their age becoming "check-valves" blocking the oil flow!
Finally, overtightening the adjusting screw locknuts will tend to stretch the screw-threads (next to the oil hole) and you may have trouble adjusting the screw w/in its range of valve clearance. Most likely, you won't be able to remove the screw and it'll have to be cut apart. NOTE: When setting the clearances, you must check for internal oil flow by "backing out" the screw(s) for 2-turns.
If not able, you'll need to add link-pin shims under the rocker stand and re-check adjustments.
Thank you gentlemen for your helpful replies.
The push rods (long steel ends) have shiny ends and you can blow air through them easily, I don't think the wood is inside them. The tappet adjusting screws are free in their threads throughout the full adjustment length so not stretched. The rocker tips are shiny and showing some wear but without any lips, so I will clean them up and reassemble the rocker gear and also seal up the ball check hole in the rocker covers that should not be there (S90 rocker covers on a 356 C engine that was made in june 1964 eng no 713839).
Robin Walker
1962 356B S90 Coupe. sold.
1964 356C Coupe RHD
1973 911S Coupe LHD
1983 924 coupe RHD
