5 litre piston rattle - what cost to fix?
Discussion
So my Chim 500 has the god awful rattle on overrun that seems to plague a lot of 5 litre engines. Only does it when warm but it drives me mad because it really does sound rubbish-especially when blipping the throttle which lets face it is what a TVR V8 is all about! I've noticed in the extensive service history I have that the engine has had pretty much a total top end rebuild within the last 10000 miles from a previous owner trying to chase down this fault and it is mentioned in the history going back at least 20k miles so I guess it's nothing that is going to destroy my engine any time soon. That said it really does bug me! So assuming it is piston to pin wear as suggested on other posts I've researched and assuming my engine doesn't need a top end rebuild, what sort of cost would I be looking at to have the pistons replaced in a 500 to sort this? Cheers, Matt
I have the same issue. My engine was completely rebuilt but the pistons and little ends were considered within specification and not replaced. The bores were honed and new rings fitted. You can imagine my disappointment after having all that work done and ending up with a rattle. The engine didn’t have this rattle Pre-rebuild. Perhaps the honing of the bores has created just enough clearance to create the rattle which is actually piston slap or the extra power has created extra play in the little ends. I’m interested in options. Perhaps new top hat liners and pistons will fix it but at large cost!! Very disappointed with the engine builder! I’d happily of paid for new pistons. I think he couldn’t be bothered because the pistons are not standard and difficult to get. Dunno. Might be worth speaking to the experts, I’d say Powers, V8 developments or JE know their stuff and could come up with a cost effective suggestion.
I’m not sure in the case of the 500 pistons but I always thought the stock pistons are stronger than aftermarket ones which is why it’s favoured to keep them.
The little ends are known to suffer from poor lubrication so whatever you do there’s a chance it will come back.
All hearsay, it’s usually the 5.0 engines so could be to do with cut down pistons but I’m no expert, just remarks I’ve heard over the years.
The little ends are known to suffer from poor lubrication so whatever you do there’s a chance it will come back.
All hearsay, it’s usually the 5.0 engines so could be to do with cut down pistons but I’m no expert, just remarks I’ve heard over the years.
lancelin said:
Thanks boosted. What are the options for rectifying it? In the case of piston slap or little end wear, is it possible to rectify the problem without a complete engine rebuild?!!!
New slightly oversized pistons?
You have to diagnose the fault. If it's wear in the piston pin bore you'll need new pistons. if you have a bushed little end then that could be measured. As for piston to bore wear, pistons can be coated with a hard moly coating to increase the size slightly. This will reduce the clearance and reduce friction. The pistons have to be in excellent condition before coating though.New slightly oversized pistons?
The best solution if it is piston slap would be custom forged pistons with forced pin oilers and an increase in skirt length if possible allowing for counterweight clearance. You could also offset the gudgeon pin slightly.
citizen smith said:
I would also measure the cylinder bores for size, ovality and taper top to bottom.
Honing a cylinder bore will take out material - could be a few thousands of an inch, but did it take out the ovality and was the wear measured from top to bottom and corrected by the honing?Accurate measuring tools are required as per attached photo.
Sounds like you need a short engine from a well-known and reputable source.
If you are going to do it yourself which by the sounds of it you're not you could send the block, crank pistons and rods to a reputable engineering company. Something like Chesman Engineering.
Definitely top hat the block after having it checked for porosity. Have the pistons checked. Probably new ones required and have them fitted to your rods. Have the crankshaft journals checked. After all that you can have it all balanced with the crankshaft front pulley and flywheel.
Bobs your uncle.
If you are going to do it yourself which by the sounds of it you're not you could send the block, crank pistons and rods to a reputable engineering company. Something like Chesman Engineering.
Definitely top hat the block after having it checked for porosity. Have the pistons checked. Probably new ones required and have them fitted to your rods. Have the crankshaft journals checked. After all that you can have it all balanced with the crankshaft front pulley and flywheel.
Bobs your uncle.
Is it worth discussing the possibilities with a specialist company like X-Works? I'm sure they've come across this problem.
http://www.xworksservice.co.uk/
Good luck
http://www.xworksservice.co.uk/
Good luck
It definitely isn't piston slap. I know what that sounds like and that happens under load. I have no noise under load it is just when the pistons are 'floating' during overrun so I don't expect piston to bore clearance issues. It also doesn't use any oil. The odd thing is it only occurs when hot which would kind of discount it being as simple as just wear related as surely I should get noise when cold as well. It's very strange!
Try adding some Quality thicker mineral oil to your 10/40 semi.
Add about a litre and see what happens when it’s hot.
You can change it out but it’s worth the experiment.
I sometimes just think it’s oil that’s very thin especially when hot and 10/40 is very watery when hot.
It’s a tolerance issue with modern oils when hot if it’s ok at other times would be my guess.
Add about a litre and see what happens when it’s hot.
You can change it out but it’s worth the experiment.
I sometimes just think it’s oil that’s very thin especially when hot and 10/40 is very watery when hot.
It’s a tolerance issue with modern oils when hot if it’s ok at other times would be my guess.
Boosted LS1 said:
When a piston is loaded it can't slap about. When things are hot some clearances will increase. Some measurements would find the issue but until then some 100/50 oil should quieten things down. :-)
Did you did say this started after a rebore/hone iirc?
These engines ran on gloop as in 20/50 for decades, it’s a simple experiment that often works.Did you did say this started after a rebore/hone iirc?
I’m not suggesting 100/50 am I mister.
Why does it only happen when hot then!
Funnily enough some of the advice I've read is opposite and suggests a thinner oil. Apparently there is no feed to the little ends and it relies on being splashed which is less likely with a thicker oil. Who knows, I've not tried any of this. I did read a thread where someone had their pistons replaced and his problem was fixed. I'm certain it was the same problem as mine because that chap posted a clip of the sound and it was exactly the same. Hence why I was curious about the cost as I wouldn't be doing the work myself
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