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Post by petervdvelde on May 4, 2014 22:28:35 GMT
During my latest RV8 engine refurbishment, i haven't looked at if the pistons are symmetrical. But i agree with Enigmas that how the piston is fitted would not influence the balancing even if the piston would be asymmetrical because the pistons are not rotating and have a straight movement. Did the engine builder fit new pistons? I assume the answer is yes but if not then the question pops up why separate piston and con rod?
I had a look at the picture of the flex plate and the holes for the torque converter looked a little rough, especially the one on the RH side on the picture. Do the torque converter bolts have a tight fit? If not then the torque converter could not be in the center fitted and this could cause a lot of unbalance.
Peter
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Post by Welsh Warlock on May 4, 2014 22:34:43 GMT
Do you think having two pistons a different way around to the others is likely to be the balance problem? Or is it more lilely as enigmas says that it doesn't matter which way round they are installed on the con rod? I can't remember the origins of your engine, but later pistons have arrows on, which need to be correctly aligned to the front of the block. www.manualslib.com/manual/523577/Land-Rover-V8.html?page=58Harvey, I cleaned up one of the piston crowns and I can find no evidence of arrows. The Engine will almost certainly have had new pistons fitted. They are Hepolite pistons and I am taking the orientation based upon the writing on the inside of the skirt Peter, the engine was run with the torque converter unbolted and still vibrated so its not the TC. The problem is definitely in the engine and not any of the ancillaries.
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Post by johnwp5bcoupe on May 5, 2014 4:59:08 GMT
Not that it matters as the problem is still the same Is it a 3.5 or a 3.9 lump Alan? It seems like you are "on the case"
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Post by enigmas on May 5, 2014 5:35:48 GMT
Here are some Rover & P76 pistons to peruse with regard to pin location and marks illustrating the front of the piston. Note that the Rover piston has the gudgeon pin boss centred. Note that the P76 gudgeon pin boss is offset to one side and that the piston has either a notch indicating 'front' or the word 'FRONT' stamped on the piston.
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Post by djm16 on May 5, 2014 8:56:14 GMT
What are we betting that the pistons are all the same weight and the problem is a bent crank? Prophet of doom? Me? No!
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Post by Deleted on May 5, 2014 9:31:36 GMT
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Post by Welsh Warlock on May 5, 2014 11:10:30 GMT
John, its a 3.9.
Enigmas, interesting info and I'll clean up the piston crowns fully and see if there's any noticeable marks. The link that Harvey posted shows that the Rover pistons have a 0.5mm offset. Hence I asked the question of Harvey if he thinks that would be enough to cause the imbalance.
djm16, I'd like to think that if it was a bent crank the symptoms would be somewhat different (Did you read the Shudder at 2000rpm thread) and that people with the experience of a development engine builder would pick up on that.
Resurgam - once again, cool story. Don't see the relevance.
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Post by Deleted on May 5, 2014 12:05:35 GMT
John, its a 3.9. Enigmas, interesting info and I'll clean up the piston crowns fully and see if there's any noticeable marks. The link that Harvey posted shows that the Rover pistons have a 0.5mm offset. Hence I asked the question of Harvey if he thinks that would be enough to cause the imbalance. djm16, I'd like to think that if it was a bent crank the symptoms would be somewhat different (Did you read the Shudder at 2000rpm thread) and that people with the experience of a development engine builder would pick up on that. Resurgam - once again, cool story. Don't see the relevance. Just trying to break the tension and there is some mechanical relevance albeit on a massively more destructive level. Take heart, they sorted Blue Peter out eventually!!
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Post by johnwp5bcoupe on May 5, 2014 12:34:34 GMT
John, its a 3.9. Enigmas, interesting info and I'll clean up the piston crowns fully and see if there's any noticeable marks. The link that Harvey posted shows that the Rover pistons have a 0.5mm offset. Hence I asked the question of Harvey if he thinks that would be enough to cause the imbalance. djm16, I'd like to think that if it was a bent crank the symptoms would be somewhat different (Did you read the Shudder at 2000rpm thread) and that people with the experience of a development engine builder would pick up on that. Resurgam - once again, cool story. Don't see the relevance. I thought I remembered it was a 3.9 so you can eliminate the 10.5-1 pistons being fitted? maybe? I suppose with composite gaskets that would still give you a workable CR? just? if std 3.5 heads fitted?
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Post by harvey on May 5, 2014 13:10:27 GMT
Hence I asked the question of Harvey if he thinks that would be enough to cause the imbalance. I would say it's difficult to know if you've always fitted them the right way around. I don't think that the pistons will have offset pins if there isn't an arrow on the crown to denote "FRONT". I don't think you can just use any writing cast into the pistons as a reference either. What you could try using that for is to find out exactly what type of pistons they are, and from that any info on how they should be fitted.
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Post by Welsh Warlock on May 5, 2014 13:13:09 GMT
John, they aren't the original 3.5 heads. They came with the engine and were fitted with tin gaskets.
It will go back together with composite head gaskets.
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Post by harvey on May 5, 2014 13:13:35 GMT
I thought I remembered it was a 3.9 so you can eliminate the 10.5-1 pistons being fitted? maybe? I suppose with composite gaskets that would still give you a workable CR? just? if std 3.5 heads fitted? 10.5 pistons were only fitted as standard on the early 3.5, so as the 3.9 is an overbore of that they won't fit, so they'd have to be aftermarket high compression pistons.
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Post by harvey on May 5, 2014 13:15:12 GMT
Since it's come apart all the pics seem to have stopped.
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Post by johnwp5bcoupe on May 5, 2014 13:16:59 GMT
I thought I remembered it was a 3.9 so you can eliminate the 10.5-1 pistons being fitted? maybe? I suppose with composite gaskets that would still give you a workable CR? just? if std 3.5 heads fitted? 10.5 pistons were only fitted as standard on the early 3.5, so as the 3.9 is an overbore of that they won't fit, so they'd have to be aftermarket high compression pistons. That shows you what I know harvey I thought they stroked the engine in a grey moment then realised there are different gaskets involved! I told you I was a 3.5 man ::)but it would be interesting to know the part number on the heads?
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Post by harvey on May 5, 2014 13:19:52 GMT
I told you I was a 3.5 man TBH, I think that's a far safer option.
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Post by enigmas on May 5, 2014 13:29:15 GMT
Eastmidsrep, I posted the pictures of the pistons just to illustrate the severity of the offset on the P76 piston pin boss. I have a set of Rover low comp pistons fitted to the SD1 V8 in my Magnette coupe project car. There is no discernible gudgeon offset on these pistons either. When I rebuilt my P5 Coupe with the P76 engine, I fitted Rover pistons to it. Many rebuilders in OZ have done this with the P76 V8 due to the difficulty of obtaining OE pistons for this motor. I had all the rotating and reciprocating components (including the harmonic balancer and drive plate)dynamically balanced when I rebuilt it 20 years ago and it's still a smooth engine. I can't see how an offset of .5mm would affect anything. It seems like more of a manufacturing error. Although if you fitted an original spec piston in a P76 the wrong way around I'm certain the motor wouldn't like it!
I still believe you could have some odd weight rods in the motor.
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Post by Welsh Warlock on May 5, 2014 16:13:55 GMT
I'll post some more pics later on - been busy cleaning up the piston crowns for ID marks.
I thought the 3.9 was just a stroked version of the 3.5?
Presumably from what was mentioned above it has a different bore so the 3.5 head gaskets I have won't be suitable?
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Post by harvey on May 5, 2014 16:20:14 GMT
Lifted from a well known Rover engine specialist's site. (Should there be some strategically placed inverted commas in there somewhere?)
3.5.=89.5mm bore Std 3.5 crank 3.9.=94mm bore Std 3.5 stroke crank 4.2.=94mm (3.9 bore ) plus and 4.2 longer stroke crank 4.0 is the same capacity as 3.9 but uses later big journal crank and is cross bolted 4.6. + 94mm bore ( As per - 3.9 & 4.0) but uses later big journal (long stroke) crank and is also cross bolted as is the 4.0.
I can't vouch for the accuracy, but it will give you the general idea.
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Post by Welsh Warlock on May 5, 2014 18:07:42 GMT
That makes sense Harvey as the rough bore measure I did last night with my cheapo digital calipers was 93.8mm
Some pics shortly which I know will open a whole new can of worms.
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Post by Welsh Warlock on May 5, 2014 18:25:59 GMT
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Post by johnwp5bcoupe on May 5, 2014 19:05:18 GMT
Taken off the V8 forum may be of some use?
How are these identified on the pistons themselves?
I've stripped both engined down and found the following markings on the pistons themselves;
Early Engine;
AM413 758404 Hepolite 22059 AE HRC1828
The top of the piston has a "dimple" in it and is marked with an L
Late Engine;
413P 758414 AE HRC 1828 22059A
the top of the piston has the following marks 22059 Z07 M6 MY
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Post by petervdvelde on May 5, 2014 20:13:05 GMT
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Post by enigmas on May 5, 2014 23:56:30 GMT
No I didn't Peter. P76 remains seem to appear out of the ether every now and then. This lot has probably been stashed in a shed for years. If you know what to do with the parts you can cobble up a good torquey engine.
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Post by Welsh Warlock on May 10, 2014 14:33:22 GMT
Time for an update:
For a number of reasons I've decided to turn around the two pistons and rebuild the engine as is.
2 reasons for this: 1. I trust the engine builder 2. If I take the crank out and have it balanced with rods pistons etc I will never know if the pistons caused an issue.
So, a leap of faith or plain stupidity. I'll let you decide. But at least we will know (at my cost) what the problem was.
The pistons are in, sump is back on and I broke a bolt putting the base plate back on the oil pump - Phil, if you're reading this I have sent you a PM to see if you have a spare you can bring to the P4 National tomorrow please.
Now then: Back to the garage to fit followers, pushrods and heads etc.
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Post by johnwp5bcoupe on May 10, 2014 16:11:20 GMT
Hi Alan I may be there tomorrow? just in case which bolt? 1/4" UNC 1" long?
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