trt74 Posted June 26, 2021 Report Share Posted June 26, 2021 Hi all, After a complete rebuild of my 1969 engine I’ve experienced a unexpected problem with the rocker shaft while breaking in the engine. After driving just 500 miles the engine started running rough and the rockers sounding very loud. After removing the rocker cover I discovered that the rocker shaft at cylinder 3&4 had run completely dry, causing damage to the shaft and extreme wear of the rockers on the shaft at these cylinders. This caused also extreme gaps at the valve stems, making the engine running on 4-5 cylinders. The strange thing was that cylinder 1&2 had plenty of lubrication. Any ideas on the possible cause, possible other damage to for instance valves/cam followers etc. and best route to follow will be much appreciated. many thanks, cheers, Tim Quote Link to post Share on other sites
Motorsport Mickey Posted June 26, 2021 Report Share Posted June 26, 2021 Prior to fitting and startup, did you clean out the rocker shaft yourself and check for flow down and out of the rocker shaft holes feeding the rocker arms ? Mick Richards Quote Link to post Share on other sites
ed_h Posted June 26, 2021 Report Share Posted June 26, 2021 Followup to Mick-- Was it a new shaft? The last two shafts i bought had debris inside large enough to block a rocker feed hole. One was machining swarf, the other was possibly dried up chemicals from the nitriding process. Ed Quote Link to post Share on other sites
trt74 Posted June 26, 2021 Author Report Share Posted June 26, 2021 Hi Mick and Ed, No, I didn’t check the flow down and out of the rockers myself, but at a trial run without the rockercover there seemed to be enough oil at all the rockers. We used my old rocker shaft with new rockers. I can only think of swarf from the machining of the block, that wasn’t cleaned out before assembly. Any ideas on what to check to assess possible further damage resulting from this failure? ( preferably without pulling the head...) many thanks, Tim Cheers Quote Link to post Share on other sites
PodOne Posted June 26, 2021 Report Share Posted June 26, 2021 No expert but an old shaft, new rockers then perhaps there may have been the chance of them cockling and binding resulting in rapid wear. Personally I would have renewed the whole assembly so the clearances would all be in spec. Andy Quote Link to post Share on other sites
john.r.davies Posted June 26, 2021 Report Share Posted June 26, 2021 It's not an ideal design, oil supply for one end of a long shaft. Once wear occurs, the oil escapes from the rockers nearest supply, and starves the far ones. That will be accelerated if a worn shaft is used. Sorry, but poor decision! Shafts aren't costly! Just as a new cam shaft needs new followers, new rockers need a new shaft. Experience is expensive! Good luck! John Quote Link to post Share on other sites
Motorsport Mickey Posted June 26, 2021 Report Share Posted June 26, 2021 Hi Tim, With the rocker shaft and rockers removed check for visible damage on any component. Drop a straight edge along the top of the valves stems as a rough check, I'd expect them to be all about the same, suspect any that aren't and keep in mind. Wiggle whatever you can around valve caps/stems, excessive movement may mean oil starvation has caused wear to valve guides. I guess you are at the stage where replacing bits from the top is the only option. If there is any debris or swarf or iron filings knocking about on top of the head, flush off the top of the engine with a brush and paraffin, Remove the push rods trying to minimise anything going down the pushrod holes, plug with clean rags, and check pushrods for straightness by rolling on a flat surface...kitchen worktop, glass cooker lid etc, save pushrods in order in a piece of card with holes in, they have to go back in the same positions. New rocker shaft and rockers first. Clean out the new rocker shafts by flushing through with whatever you are using...paraffin etc. Make sure you can get a flow through EVERY rocker feed hole in the shaft, clean them with a soft hooked wire (don't snap it off inside) and also flow down and through the shaft itself. I've got a 4 cylinder so check if there's removable caps or screws in the ends of the rocker shaft, if so remove and flush through. Drain the oil from the sump, drop the sump and clean inside...look for debris and clues, drop the oil pump and clean and check the rotors and their clearances, if ok fit a new filter and prime wherever you can by filling the oil cannister etc. Check the oil level in the sump, if it's about right I would add an engine oil flush product to it and before starting the engine and without the rocker cover on remove the spark plugs and fill each cylinder with 5cc of engine oil, spin the engine with the fuel pump and distributor disconnected and see that oil is lifted and and pushes out of EVERY rocker arm on the shaft. This can take minutes, depending upon how much oil has drained out. Then get the engine running to see what defects show up, If no knocking, tapping or heart seizing noises try the car on a run of maybe 15 or 20 miles, return and with the engine hot drop the oil and change the filter again and refill etc. If lucky you may get away with it, and you'll have a running engine to start diagnosing whatever may be needed and hopefully without a head lift. Be suspicious of clacky noises in case the camshaft or cam follower has a problem. Good luck. Mick Richards Quote Link to post Share on other sites
trt74 Posted June 26, 2021 Author Report Share Posted June 26, 2021 Thank you very much for your replies. Mick, thanks for taking the time to write down your comprehensive advice. I will follow it step by step, fingers crossed that we’ll get away with it! Quote Link to post Share on other sites
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