It is possible that had I pulled the pistons when I first bought the car 20,000 miles ago, I might have saved having to re-bore now, but it is also possible that the damage was already done. Had I known that unlike the early P4 motor, the piston comes out through the top of the block complete with conrod, I might have check the rings sooner ... but here we are.
Loss of compression on one cylinder was the reason for the strip down, that and the scoring apparent in two bores. Ouch! I think this piston is a little past repair! 5 of 6 pistons had a broken top ring. Each top ring was significantly more worn than the second ring, so much so, that I can visualize that at the top of the stroke, on changing direction, the ring will rock in its groove, creating a torsional stress on the ring. I am guessing that this is what broke the rings. On several pistons, the top ring groove was so widened and the ring so worn that broken bits of ring doubled up in the ring groove. I am guessing that is what caused the segment of piston to break away.
You can see the effects of the ring and ring groove wear on the bore: there is a hollowed out area in the bore, just below TDC. You can also see just how wide the ring gap is - 1.3mm (approx 55 thou).
So, my question, can anyone recommend a source for a +20thou piston set? I am waiting for a call back from Nornda (previously JP Pistons). I believe the piston should be the same as in Series 3 (?) Landrovers (and 95 /110 Rovers).
That engine has done a lot work David...maximum clearance on the top 2 compression rings within the ring lands should be no more than .004". If they're loose in the lands the engine becomes an oil pumper...so I guess oil consumption would have been high too. The second ring would have been taking the brunt of compression load and masked the failed top ring till it gave up as well. The oil rings also look as though they're jambed in the lands and flush with the piston skirt surface.
I realize this was discussed briefly but if the other cyls are within spec you could still have pressed in cyl liners fitted to the damaged cyls and bored to standard...then locate some good used pistons and have the top lands machined for an oversized ring or an insert (JP Pistons do this type of work.) The skirts can even be ceramic coated by HPC to add .001" or .002" if needed. That's my 2 cents worth of advice. Good luck with whatever you decide to do.
Thanks for the quick reply. I did see that ad for a NOS piston. Unfortunately they only have the one! I am still waiting to hear back from someone in NZ who was advertising a set of pistons at a reasonable price. I certainly have been thinking about the sleeving idea, but now I have seen the bores, with their scooped out area at TDC, and at least two with score marks, I am heading towards re-bore and OS pistons. The other 5 pistons are also pretty badly worn in their top grooves. I don't think I would trust the metal above the top groove to not be fatigued and break away sometime in the next 100,000 miles - just as it did in number 4.
The engine is out and fully dismantled. I now have some questions. Starting with the easiest first:
How do you remove this tube from the base of the block?
Next, the exhaust rocker shafts are clearly completely shagged. The last time I saw this, it was on a early Honda CX500 head before they modified the oil feed holes. So is this normal wear and tear after 180,000 miles, could it be the result of using 30W-70 oil? Or is it something else entirely? And of course what do I do to avoid a repeat.
Next is the camshaft. There is moderate wear on the cam lobes only except number 1 inlet which has cracked through the case hardening. Is this fixable, as in - can the camshaft be re-ground and hardened again?
Interestingly, the camshaft has a lot of end float, as in several millimetres. Is this normal? If not, then what is supposed to limit the float?
The next problem is how to get parts. In particular the cam followers do not exactly grow on trees. A complete set seems to consist of 6 different part numbers. Anyone happen to have a complete set for sale, or know where to buy them? I am assuming, given the state of the rocker shafts, that I will need new followers. I had considered bushing the old ones, but that would not restore the white metal running surface for the rollers.
On a positive note, the exhaust valve guides seem to be in perfect condition, which is a surprise after my experiences with the P4.
You could still post it to them. They will also resurface and harden the valve lifters but in your case they're roller lifters (like my 1942 WLA Harley Davison) so the roller and pin may be worn and need replacing. I'd phone Clive he's extremely knowledgeable and helpful and camshafts are their staple business. Few know more about this field.
As an aside Harley Davidson Rollers and pins are available going back to the 1930s. I have no idea of compatibility though.
Cam followers, mostly unobtainable, I have three new ones donated from a friend of a friend, Wearings says "please call for price", and Wadhams NA. My part numbers are 5368625, 5368635, alternating, and 273105.s, 273104, 273105, 273104, 273105, 273104.
Cam bearings run 100, 125 and 75 exc vat for front, rear and middle, so I am looking into the costs of re-metalling the old ones. The advantage of doing this of course would be that I could take 3 thou o so off the camshaft and add it to the white metal, thus restoring factory clearances.
Before you go and spend a gazillion $$$s on some virtual unobtainium why not speak to Clive first he may have a solution or be able to rebuild them. He might also have a solution for your camshaft journals. Also don't forget to try Mark Richmond he has all sorts of bits and pieces stashed away. I know he bought a mountain of 3 litre parts from a now deceased friend of mine quite a while back.
Hi Vince, I discussed the camshaft with Clive. For welding two lobes and regrinding all 12 plus the 6 journal surfaces, he is asking a quite reasonable $544. This includes undersizing the journals.
I am sure it is an option to weld up the journals and grind to standard too. Then I would have to buy a set of standard bearings from Wadhams which are are eye-wateringly expensive (pounds525 or about $800).
Re-casting my old bearings will be $520, then probably another $100 for a friend to ream them to suit. I also got quoted $900 elsewhere for cast and finished set of 6 bearings.
I have to wonder if machining the bearing halves to take a set of bearing shells from another application might be an option.
I didn't mention this company before David as it's easy to get overwhelmed with an extensive rebuild like yours.
Crankshaft Rebuilders in Blackburn Victoria do serious engine work/modifications (not solely crankshafts) where needed to refurbish classic and vintage engines. Their reputation for engineering quality is second to none. Although distant from you they may be able to provide viable options.
They fabricated and machined a centre bearing thrust insert for a damaged P76 V8 block. It now uses a set of Japanese car thrust bearings.
It certainly wouldn't hurt to speak to them about your issues.
I spent a very long time last night examining the camshaft journals, and am still unsure. In comparing a worn area of a journal with the adjacent un-worn area, there did not seem to be appreciable erosion in the worn areas.
At least two manuals state the journal diameter to be 0.999" and the bearings to be 1.000", ie a 1 thou clearance. The specs for the service limit however vary from 1.5 thou to 2 thou. 1 thou is also what is recommended all over the internet for generic camshaft journal clearance (1 thou per inch dia).
My camshaft has cross-hatching grinding marks on the journals that are not completely polished away even on the worn bits. I checked the dia with two different micrometers, and came up with 0.9985 on both the worn areas and the non-bearing part of the journal for comparison, ie negligible wear, but significantly greater clearance than Rover spec.
Are my micrometers out? I double checked both for zero point, and with a 25mm calibration rod. They were both very close to correct.
I think it unlikely (but not impossible) that the camshaft has been out and reground. I don't remember seeing it in any of the original owners extensive notes. Were Rover camshafts from new ground with a cross-hatch pattern? Or has someone taken the journals down a thou sometime later.
As I have come across a source of NOS camshaft bearings at a bearable price I am once again considering using new bearings rather than grinding down the journals and using shells. However, I am reluctant to put back a camshaft with journals at the service limit with an engine rebuild likely to run into thousands of dollars in parts.
I just referenced 3 Factory work shop manuals. First one for a standard BMC B series engine camshaft in block .001" - .002" clearance. The second for a MGA twin cam motor...2 camshafts in the cyl head (a la Jaguar) .001" - 002" clearance. The third for a P76 6 cyl OHC .001" - .002" clearance and for a P76 V8 cam in the block .0005" - .0035" clearance. The largest variation of those shown.
If it were mine I'd simply refit it if the camshaft lobes don't require a regrind. Truly I wouldn't want any less clearance as I'd be more concerned with binding.
If you still have the block why not refit it and assess its smoothness of rotation.
PS. The bearings and journals that take the hardest pounding in an engine are the big ends due the reciprocating nature of the rods attached to them.
Using a good quality assembly lube is probably one of the most important things you can do prior to starting a fresh engine to protect both bearing and journal surfaces.
Thanks! You are reassuring me that 2 thou clearance on the journals is OK?
The camshaft definitely needs both welding up and the lobes regrinding. Several of the cam follower discs are cracked so need replacing, so it makes sense to grind those lobes flat again. In addition the two lobes for inlet and exhaust on 1 both show wear through the hardening, those I guess need welding first.
What is annoying is that I am sure I have answered the same question elsewhere when posed by another forum member.
I need a new set of pistons in +040. There are approximately three choices:
1) the "correct" 8.5:1 pistons from Nornda (aka JP pistons) at $183 each, plus GST, plus shipping. These are Three ring pistons. They are however marginally too big, in that the compression height and overall piston length or the piston are approximately 2mm more than the piston I just took out. I probably should fit these, but there is a real chance that the engine will be unhappy on 91 octane (98 octane is a LOT more expensive here).
2) a set of NOS AE pistons, but in the lower comression 7.5:1 4 ring style. These are substantially cheaper at $450 for 6 without rings. I am sure the engine would be happy with 91 octane. There would of course be a small power decrease, but an on-line calculator estimated that at around 3%.
3) a set of new 7.5:1 pistons, again 4 ring, but made by Hypatec. These come in at $322 inc postage, again sans rings.
I realise that the correct answer is (2), but I am more than a little OCD about "getting it right".
Option 2 looks good to me...and you could easily do a cyl head volume check and have the head milled accordingly to bring the compression ratio up to 8:1 or so? Then just check the valve lifts to ensure adequate clearances.
Keep the info coming as it's interesting (at least to this individual )
* Come on Phil (?) ...I'm waiting for you to chime-in here!
Post by Phil Nottingham on Oct 25, 2019 17:38:34 GMT
I have been following this with interest and clearly option 2 is "right" as it is closest to build spec almost 60 years ago. However whilst 10 years ago I may have gone for 2 now I would not even go for 3 as I suspect I will never get anywhere near full use of them.
I know correct spec may help increase a future resale value but certainly a none working engine will reduce it and if you want to drive it now then you may need to do something or just wait till it it stops completely.
Phil - 1964 P5-Coupe PMB***B & P5B-saloon LHO***L & other classic Rovers & Land-Rovers
8.5:1 is in the manual as the usual compression ratio, with 7.5:1 as an option. The gentleman doing the re-bore will be ringing around his suppliers for me on Monday to see if anyone else has some NOS.
JP / Nornda option 1 would be more acceptable despite their price if they did not tend to produce overweight pistons. From memory, my P4 pistons were 20% heavier than the original (they were also lower compression). Not a problem if I were pottering around country lanes at 40 mph, but I like to rev it up a bit! Not that I am a donut burning petrol-head of course!
I have been advised that these rarely give any trouble, nevertheless since I have the engine out, I though I would check.
The two gears look in excellent condition. The pump body is very lightly polished inside at the point that oil enters, but without affecting the internal diameter.
The end float on both gears is easily within the 1-2thou tolerance. The radial clearance on the alloy idler gear is a shade less than the 1 thou specified, and there is minimal wear on the post that it rotates around.
There is a problem of course or I would not be posting. The steel driven gear shows no signs of wear, but the radial clearance is massive. It has to be at least 10 thou. I was so surprised I spent the next hour trying to figure it out.
Is it the pump body or is it wear on the gear? Checking the pump body with a vernier I was unable to detect any difference in the internal diameter between the driven and idler gear cavities.
I looked more closely at the teeth on the driven gear. The tiny serrations along the tip of each tooth are absolutely regular, and I am sure are the original machining marks, nevertheless the driven gear is 10 thou smaller than the idler gear.
Can anyone shed any light here? It makes no sense to me to have 1 thou of end float and then have 10thou around each tooth that the oil can piss through!
What was the oil pressure like before you disassembled the engine? If it was within spec for the engine prior to the strip-down it's certainly not going to be any less after the rebuild/recondition.
To my knowledge the pump works in the following manner. The pump has 2 sprocket like gears. Pressure is produced by picking up the oil feed from between the gears and then carrying it around the outer internal perimeter of the pump gears against the internal housing where it is then directed into the oil galleries as the gears mesh together. There's nothing particularly unique about this type/style of oil pump.
I do not have a record of the oil pressure before tearing the engine down. The electric gauge showed "normal" pressure with cold / fresh 40W-70 and below normal with old / hot oil. Given the clearances in the rocker shaft and camshaft bearings, this would not be a surprise even if the oil pump were perfect.
The radial clearance I am showing in the picture above is 0.40 mm, roughly 17thou. That needs to be divided in 2 approximately to account for the gear not being centrally mounted for the measured, but that still makes it 9 thou rather than the regulation 1 thou.
I am sure that engine is original. I believe the main journals may have been replaced at some time in its life, I have no record of it, but judging by the big difference in wear between 6 of the journals (easy to get at) and the rear-most journal (impossible to get at without detaching the gearbox) 6 are newer. If that is so, it is possible a new set of oil pump gears were thrown in too. The split pin on the mesh filter below the oil pump looked new.