Being brought up on Franks machines, ( Frank Perkins of Peterborough now CAT) I am struggling how to relate a turbo change with Robin Hoods Bows ( bent pushrods ) Do you think you have been told the full story here? Any one had a go at adjusting the tappets when changing the turbo perhaps and said nothing? I remember well back to the 1960's when normally aspirated engines started to appear with turbos fitted. Not on standard engines as to start with the cranks were different and to bolt a turbo onto what had been a non turbo engine was asking for trouble big time. It would beat the big ends out in no time. I understand from what you say the engine is a four cylinder but was the turbo air or water cooled? Which model engine? Why was the turbo changed for overheating? The air cooled turbo with the heatshield off would, at nighttime glow cherry red when pulling 85 per full load no problem, seen it loads of times. Allways cooled down ok and never, ever had any heat distortion present. Why was it changed because of a joint blowing? We used to carry loads of those tin pressed joints between the exhaust manifold and the turbo sometimes having to file flat the joint faces where bowed. Was the blow on the centre clamp bolt seal? We also used to fit loads of kits back then, turbos were very new and expensive so kits were fitted every time. Two oilite phosphor bronze bushes, seal kits, new circlips, new shaft bare. Remember well the side clearances/end float was very important. Never had a problem with balance, ever. A new turbo or kit ( Holset were the majority of ones fitted, now Cummins ) out the box would have .0025 thousands of an inch play. First off this seemed allways almost as bad as the one you just took off. Clonk clonk the spindle would go in the bushes, scary. But you had to remember the spindle was supported in midair by the oil feed supply, allways changed oil and filter or No Warranty. No blipping the revs up as some people used to do on shutdown as the shaft spindle's burst speed was approaching 100,000 rpm and the oil pump would have stopped minutes before the turbo shaft would. This meant that the shaft was not running and supported entirely by oil but turning on the bottom of the oilite bushes, thus causing premature wear and ageing the turbo causing the impeller blades to touch the casing. New/ newly kitted turbo fitted, stop control out, crank over till oil gauge lifting off the zero on the gauge. Some turbos had brass columns of oil fitted as a Y piece in the oil supply pipe to prefeed engine oil supply. Charge air / Intercoolers? Never heard of them affecting pushrods, seen O rings go, tube stacks come un soldered, into the acid bath for two days,allways found it better to use a hot air gun than a big old soldering gun, was a tricky job soldering them, reassemble, make up and fit a Shrader valve, onto the airline and watch the gauge for any drop in psi before refitting. If the tubes or the end plate were corroded then new tube stack required but sometimes when you got the knack ok like everything in life, no problem, the final test would be off with the header tank pressure cap, attach the right adapter and pump up the system to just over its normal running pressure, 16 psi approx, Bowmans charge air coolers/ inter coolers were the most common fitted. Over revving? Seen the two lead seals, one for tickover and one max rev settings on the DPA pump broken by operator, the 6.354s would be set at 2450 approx rpm but would free Rev to 3000 rpm no probs. Even the rattle old V8-510 engine would Rev way over its governed rpm with no valve bounce. I have to say old Franks engines were everywhere, pumps, diggers, gensets, welding machines, taxis, boats, compressors, everywhere in fact and were pretty reliable.You could see a clapped out Perkins, a real oil burner/smoker and with the heel of your hand push down on the valve springs they were so weak but not ever any valve bounce noted. The main cause of Perkins bent pushrods would be in trucks and allways at the foot of a large hill. Driver sees a large long hill, maximum speed, neutral selected and speedo way over the legal limit coasting. Comes the bottom of the hill, thrill now achieved, into gear, take up the drive and Rev counter goes right round up against the stop, poor old engine doesn't have a hope in hell whatever name he is badged under. Bent valves/pushrods, head off a valve maybe. New one piece head, piston, liner and the worst scenario a new block. Engine , if runnable banging, exhausting out the air cleaner etc and allways at the foot of a well known local hill. Anyone out there been alongside an engine with excessive wear in the oilite bushes, turbo shaft running on the oil seals, leaking out both ends? The report says engine revving up and down on its own, even with fuel shut off? Reckon I have seen this a few times only over 55 years and it's most probably the most scary thing that can ever happen to you. Air in the system springs to mind. No, not that. Spend maybe a couple of hours trying to simulate this revving away on its own to no avail. Then, maybe much later, engine is away, revving up and down on his own. Rotary DPA pump governor problem? No not that. Now it's screaming away, out of control, very frightening. Don't forget it only came in for revving up and down on its own, now it's heading for a total loss situation and it's all down to you. Quick, back off all injector pipes, stop control out, all makes no difference, he is running on his own oil, racing way, way over his top governed rpm, completely out of control. Either strangle his air supply or make for the door and hope you are out of the range of the Conrod that is shortly going to make an appearance out of the side of the block and at some considerable speed at that. So now back to the clipped valves / bent pushrods problem. So now image the scene is, you have seen the damage caused, stripped the engine, renewed as necessary. You have not, however located the cause of all this damage. Dare you try a start? Highly risky indeed. Want to repeat the damage? Of course you don't want to appear to have not carried out the repair correctly so what do you do next? My answer has always been to check the valve timing. So off with the timing case cover, whip the injectors out, T bar and socket on the front pulley and carefully wind him over to line up the marks. Marks all line up. What's next? Continue turning the engine slowly over, clunk, we have a lockup. Wind him back the other way past the marks, clunk, another lock up. Recheck the marks, yes, all correct there. Now here's a good one for you, WHY? What's next? What's left? What's happened? First time this ever happened to me it took me hours to work it out, but like other similar problem child happenings its photographed forever in the back of my brain, never to be forgotten. Clue? The cost of this part that caused perhaps thousands of pounds worth of damage? About £2.00 sterling. Well? Ideas anyone? ( no twisting moments here, crank or camshaft ) PS What's the final outcome on your Perkins? We need to know to complete the learning curve. Or did someone take the cowards way out? Oh, it's clocked 14,000 hrs run, smokes a bit, excessive crankcase compression, oil pressure drops when hot, tapping noise on a cold start, these new common rail engines run on fresh air you know etc etc etc. Buy a new common rail unit complete. Seeing the amount of bent pushrods you had surely you must have clipped the valves? Don't leave us hanging, we need to learn further. Educate us, we all never stop learning.
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.