Adjustable push rods and lifter pre-load

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stopover

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Was UK. Now 30 + years in the Isle of Man
Darn it! After 156,000 miles the camshaft on my 2000 4.6v8 needs replacing, getting a missfire. I fitted recon heads about 10,000 miles ago and because they were skimmed etc have decided to use a set of adjustable pushrods with the standard new camshaft and hydraulic lifters. It was a real pain and very time consuming to put shimms under the pedestals last time.
My question is this: the normal range of pre-load is between .040" and .060" RPI say that purists would go for .040" and Real Steel say .055" is best. anyone have experience of setting these adjustables and how they got on would be useful. ps I did see a thread somewhere where a chap who builds engines on a regular basis uses .020" ???
 
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Unless you have had a lot more than the acceptable amount skimmed from the heads shimming the rockers should not be required.
 
wammers said:
Unless you have had a lot more than the acceptable amount skimmed from the heads shimming the rockers should not be required.
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That's the point, when I had the heads skimmed a lot more material was removed than I had hoped (amount unknown). Result after measuring I had to put shims under the rockers (different side to side). I used the original pushrods on the old cam. I just think that the original cam, at such a high mileage, has finally given up the ghost! Infact it has as can be seen when I rotate the engine. The lobes are bad especially on couple of cylinders ( the missfire) and are starting to get scores behind the lobes.

I was hoping that when the heads were done that the cam had some more life in it and I suppose it had that ten thousand miles but its time for a new one. When the heads were done it was faily straightforward but doing the cam means taking the sump off, timing cover, water pump (will replace that) and the radiators, plus air con etc). Will post some pics of the process.
 
stopover said:
That's the point, when I had the heads skimmed a lot more material was removed than I had hoped (amount unknown). Result after measuring I had to put shims under the rockers (different side to side). I used the original pushrods on the old cam. I just think that the original cam, at such a high mileage, has finally given up the ghost! Infact it has as can be seen when I rotate the engine. The lobes are bad especially on couple of cylinders ( the missfire) and are starting to get scores behind the lobes.

I was hoping that when the heads were done that the cam had some more life in it and I suppose it had that ten thousand miles but its time for a new one. When the heads were done it was faily straightforward but doing the cam means taking the sump off, timing cover, water pump (will replace that) and the radiators, plus air con etc). Will post some pics of the process.
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The shim you have in now should be ok. Cams wear on the lobe or toe, not a lot on the heel where you need the clearance.
 
Yep you are right, but I have a set of adjustables that I think will be better than the shimms as shims alter the geometry which is not so good. Would be better to skim the base of the rockers!!

As I said you are right. If I didn't have the adjustables that would be the thing to do but I am keen to have ago with the adjustables as I know that every pushrod should be correct accross.

I am really keen to hear from someone who has used adjustables.
 
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stopover said:
Yep you are right, but I have a set of adjustables that I think will be better than the shimms as shims alter the geometry which is not so good. Would be better to skim the base of the rockers!!

As I said you are right. If I didn't have the adjustables that would be the thing to do but I am keen to have ago with the adjustables as I know that every pushrod should be correct accross.

I am really keen to hear from someone who has used adjustables.
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If you skim the base of the rockers you will need thicker shims.
 
OK right again. When I did the originals they were all over the place which indicates to me that the skimming wasn't very accurate. I just want a consistent value. The idea of the pedestal base skim would be to bring it all together but not doing that as the adjustables will take out the small differences.?
 
stopover said:
OK right again. When I did the originals they were all over the place which indicates to me that the skimming wasn't very accurate. I just want a consistent value. The idea of the pedestal base skim would be to bring it all together but not doing that as the adjustables will take out the small differences.?
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You will have had to have skimmed a lot off the heads to make shims be needed. When you rebuilt engine you should have depressed all the tappets in a vice and put them back from where they came, then turned engine over by hand until each tappet was sat on cam heel. Then checked for clearance with feelers and recorded them. Say for instance you had a minimum 10 thou on them all, but wanted 40+ for safety. You would need a 15 thou shim under the rocker pedestals. The 15 thou shim would lift the rocker shaft 15 thou clear of both the valve stem and the pushrod. So 0.015 + 0.015 + 0.010 + 0.040. Think maybe you are getting a little too technical when it is not yet needed. You won't know anything worth knowing until you have the new cam and tappets installed.
 
Update
067_zps7381f3ac.jpg

the new one is on the right. Original was completely worn out, surprised it ran at all. Can you spot the difference? like no lobes on two!!! So have found the reason for the missfire.
065_zps1cbbffc7.jpg

Chain was very, very, very slack.
 
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Left one could be regarded as past it's best. Make sure new tappets are depressed. Lube cam. Turn over by hand once to make sure not fouls. Re lube cam and don't turn over again until it's started. Make sure you have plenty of cam lube on cam and tappet bearing face when you restart 2000 RPM minimum for five minutes or so. New cams can be destroyed in the first couple of minutes of running if it's not done properly.
 
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Business as usual for high mileage Rover V8 cams - no lobes left! The swarf will find its way into all soft metal bearings and the gap between the rocker shaft and rockers - all will need replacing. This is why you should check and replace you Rover V8 cam before the wear starts to get too heavy. Unfortunately the hydraulic tappets keep everything nice and quiet until it's too late! :eek:
 
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