Piston Slap - VXR8

[paramoreg]

I've seen various forums on this topic and noted on another thread that R1Mark had his engine replaced due to Piston Slap.

What car was this on Mark? My VXR8 Carbon was back at Picador last week due to Piston Slap.

It’s been steadily getting louder in the 4 months I've owned it (second hand from Wortec through Picador with 18k miles on it). The noise used to go after a mile or two, but now takes a few miles at least before going to the background.

Picador/Wortec changed the oil (Mobile 1 to Red Line apparently) and the noise has dulled due to the nice new oil, though its still always there. they are now using the GM 'it’s normal' stance, though when I first went in Picador service said they’d never had a VXR8 in themselves with that issue.

Can’t say I blame 'em for not wanting the hassle (and expense) of taking an engine out to replace a piston but to use the comment on another forum, if it was normal, every car would suffer the same, not 1 in x cars so it’s still a concern for sure. Also I’m sure as the oil degrades over the next couple thousand miles it’ll start coming back as it was before.

I read somewhere that Ford simply swapped out engines when they experienced piston slap and seems Mark had similar success with his car.

Picador and Wortec have been pretty good to date on the other issues I’ve had, so I’ll see where this goes.

I wouldn’t expect VX to touch the issue as it’s been modified, though I’ve told Picador if the noise comes back as it was before I’ll be taking it back to them.

I guess my main remaining concern is assuming the car doesn’t suddenly start guzzling oil after my Picador/NetworkQ warranty runs out, if I decide to sell at some point, it will be devalued due to the rattly noise with prospective buyers taking their money elsewhere! Not a pleasant thought having shelled out a good amount of money with them for the car in the first place!

Anyone have an LS2 or LS3 with similar issues? If so, would be interested in your experience and thoughts.

[MyM8V8]

My LS2 did it when new, but funnily enough now its done 31k kilometres it's ok. I put it all down to giving it a good caning - at the strip.

Edited by MyM8V8 on Wednesday 18th March 19:30

[essexhsv]

paramoreg said:

I've seen various forums on this topic and noted on another thread that R1Mark had his engine replaced due to Piston Slap.

What car was this on Mark? My VXR8 Carbon was back at Picador last week due to Piston Slap.

It’s been steadily getting louder in the 4 months I've owned it (second hand from Wortec through Picador with 18k miles on it). The noise used to go after a mile or two, but now takes a few miles at least before going to the background.

Picador/Wortec changed the oil (Mobile 1 to Red Line apparently) and the noise has dulled due to the nice new oil, though its still always there. they are now using the GM 'it’s normal' stance, though when I first went in Picador service said they’d never had a VXR8 in themselves with that issue.

Can’t say I blame 'em for not wanting the hassle (and expense) of taking an engine out to replace a piston but to use the comment on another forum, if it was normal, every car would suffer the same, not 1 in x cars so it’s still a concern for sure. Also I’m sure as the oil degrades over the next couple thousand miles it’ll start coming back as it was before.

I read somewhere that Ford simply swapped out engines when they experienced piston slap and seems Mark had similar success with his car.

Picador and Wortec have been pretty good to date on the other issues I’ve had, so I’ll see where this goes.

I wouldn’t expect VX to touch the issue as it’s been modified, though I’ve told Picador if the noise comes back as it was before I’ll be taking it back to them.

I guess my main remaining concern is assuming the car doesn’t suddenly start guzzling oil after my Picador/NetworkQ warranty runs out, if I decide to sell at some point, it will be devalued due to the rattly noise with prospective buyers taking their money elsewhere! Not a pleasant thought having shelled out a good amount of money with them for the car in the first place!

Anyone have an LS2 or LS3 with similar issues? If so, would be interested in your experience and thoughts.

Maybe loads of wear was done when reving the nuts out of it when the engine was cold, a very bad idea to any engine.

And here is your R8 having the nuts rev'd out of it ate Ace. Not sure who was pushing the loud peddle.

But if the engine was at running temps then i cant see it doing much damage.But it was well cold that day.

http://www.youtube.com/watch?v=dPn3OFDU8hc.

[stevieturbo]

Piston slap is more of an annoyance, than a real problem.

And generally any warranty work for such a problem, would entail a new short or full motor.

At least thats how other manufacturers deal with it.....probably because their technicians dont know how to build engines, or just cant be trusted.


Just how loud is it ??

[SimonV8ster]

What exactly is piston slap ? Whats the definition of it?

Is there an easy way of noticing it ?

[Magic919]

essexhsv said:

Maybe loads of wear was done when reving the nuts out of it when the engine was cold, a very bad idea to any engine.

And here is your R8 having the nuts rev'd out of it ate Ace. Not sure who was pushing the loud peddle.

But if the engine was at running temps then i cant see it doing much damage.But it was well cold that day.

http://www.youtube.com/watch?v=dPn3OFDU8hc.

Correct URL http://www.youtube.com/watch?v=dPn3OFDU8hc

[Boosted LS1]

^ I'd be surprised if this was the case. You should be able to rev a modern angine from cold without issues even though it's not sympathetic. I've seen VW/Bentley conduct piston scuff tests and basically they hammer an engine from cold and try to wreck it. Then they look for signs of wear on the skirts and design in improvements to the engine specs if needed. I'd expect GM to do the same, after all piston slap was a known thing on the early LS engines. It shouldn't happen now with the tighter clearances and coated skirts which were remedys to prevent piston slap.

[EssexHSV]

Magic919 said:

essexhsv said:

Maybe loads of wear was done when reving the nuts out of it when the engine was cold, a very bad idea to any engine.

And here is your R8 having the nuts rev'd out of it ate Ace. Not sure who was pushing the loud peddle.

But if the engine was at running temps then i cant see it doing much damage.But it was well cold that day.

www.youtube.com/watch?v=dPn3OFDU8hc.

Correct URL www.youtube.com/watch?v=dPn3OFDU8hc

lol, yes thats the one cheers

[robkarloff]

SimonV8ster said:

What exactly is piston slap ? Whats the definition of it?

Is there an easy way of noticing it ?

It's caused by wear on the piston skirts usually in low mileage occurances and a combination of piston skirt wear/damage and bore wear in higher mileage engines. The wear allows an excessive bore to piston clearence, meaning the pistons can angle and rock in the bore as they change direction at each end of their stroke in the bore. That creates a "slap" sound, which is audible. It often doesn't produce any loss of power or cause oil burning, as the rings still seal adequately in the bore. It's purely a case of too much gap between the piston and bore. Sometimes you find pistons that have a very shallow skirt depth have two extended tabs either side down towards the crankshaft (thrust tabs), which are there to keep the piston oriented square in the bore and prevent movement and slap occuring. On cast pistons these can break off under extreme stress, land in the sump and allow slap to occur. When I took apart the small block Chevy that was originally in my HQ, it had lost several of the thrust tabs on the cheap aftermarket ally pistons into the sump, and I suspect this was due to detonation and cylinder pressures that were more than they could handle (the blower was run 1:1 which is about 8-10psi on a 6/71 roots in reasonable fettle, and the motor was stock compression...). Not sure of the design of the factory LS pistons in that respect, sure the Fish or Boosted will comment.

[SimonV8ster]

Thanks for the info

So can the 'slap' be heard at idle or high rpm or across the rev range ? Just thinking of viewing cars and the best way to detect it.

It may well be so obvious I can't miss it but never having experienced it I don't know whether it will be something easy to detect.

Edited by SimonV8ster on Thursday 19th March 11:15

[Boosted LS1]

^ That just about sums it up. Stock pistons on these engines don't have tabs on the skirts and they also are a short skirt design.

[r1mark]

I've a Monaro VXR 6 litre model of the 07 vintage and it only had about 7.5k miles on the clock.

[robkarloff]

SimonV8ster said:

Thanks for the info

So can the 'slap' be heard at idle or high rpm or across the rev range ? Just thinking of viewing cars and the best way to detect it.

It may well be so obvious I can't miss it but never having experienced it I don't know whether it will be something easy to detect.

Edited by SimonV8ster on Thursday 19th March 11:15

It's hard to diagnose by sound unless you have a lot of engine experience and knowledge and know what a healthy V8 should sound like. Usually best heard at tickover, higher RPMs mask it with intake and valvetrain roar.

Worry ye not unless you have an unusual sound that you know is there and is not of the norm for that engine type. At the end of the day most engines will piston slap quite happily into the many hundreds of thousands of miles without missing a beat. To pull the block out and stick new pistons and rings in is no great worry really, and if you have a blower already then it's a good excuse to get some high quality pistons and rings and a lower static compression to better suit your forced induction. That way you could pile on the 9psi pulley and probably more without worry or belt issues.

PS : You stock piston chaps running blowers may just have to expect this over time, the increased cylinder pressures and forces can cause and exacerbate this if the stock pistons are short skirt. Good under-piston oiling with a good quality lube will help here. We have found that Red Line oil performs best in the dry-sump nitro engine in our fuel funny car, we suffered a lot of piston skirt "black death" when we first ran the car and were changing pistons and liners like they were going out of fashion! It wasn't tune-up related as the crowns and plugs were ok, went away when we put a dragster wet sump and pump on the car. The dry sump system didn't leave enough oil flying around the bottom end of the motor and also kept the oil too cool as it was stored in the tank at the front of the car. Anyway, Red Line seemed to reduce our piston skirt issues compared with other oils we ran like Lucas and Amelie.

Edited by robkarloff on Thursday 19th March 14:07

[Boosted LS1]

I had a thought about the OP's post. It may not be slap in the sense that there's piston to bore wear. It could just be wear in the piston rings as they do tend to provide support for the piston. That would be good news and an easier fix.

[hsv_v8]

Piston slap is apparently a common trait of the LS engines due to the short skirts on the pistons but if you speak to the Fish they will tell you more about it but it's nothing to worry about. I found mine sounded louder after I fitted an open K&N cone filter but after around 2-3 mins of running it's gone from cold, the noise is like a faint background rattle/whirring sound, even after oil change I noticed no difference in the level of noise.

[robkarloff]

Boosted LS1 said:

I had a thought about the OP's post. It may not be slap in the sense that there's piston to bore wear. It could just be wear in the piston rings as they do tend to provide support for the piston. That would be good news and an easier fix.

Even so, you're having to pop the slugs out to put new rings in, so wouldn't you recommend a customer to spend the extra on some aftermarket pistons with better skirt support as well as some good rings? Given the average mileages covered, wouldn't expect the bore to be out enough to warrant any more than a quick run with the hone brush and pop the new ones in? On a FI motor I would guess a new set of rings alone wouldn't last long before allowing the same to occur?

[Boosted LS1]

^Maybe but this is probably for others to decide. If it's just worn rings then that's all that will need replacing. Piston skirts and bores may look quite good. Improvements and upgrades cost a lot more plus would need a rebalance which probably means crank and engine out of car. I was just looking at this in a positive light.

As for FI, you just have to pick the right rings and they should seal fine.