QPV 4.7S: variators rattle - even after cam caps modification?

P

petrD

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And sorry, I should've followed on this topic with some update:

When we dismantled everything, the O rings were not in best condition (check valves, seal rings on camshafts..), as well as chain tensioners. Seems seals could contribute to this issue (their lifetime is not endless..)

So everything replaced (variators, solenoids, o rings, chain tensioners..), 10k km since that repair and no rattles, no issues, engine runs much better, even consumption dropped for about 2 liters. Happy owner so far :) (touchin wood now...)
 
conaero

conaero

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We have heard of a chap who undertook the modification himself at a local engineering shop.

It’s in at another indie while they strip down the entire engine to find the missing ball bearing that came out of the modified cam cap check valve.

If you want to save a few hundred quid, be my guest.
 
philw696

philw696

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When the caps are done through Maserati you have the paper trail to back it all up.
I have met some clever people especially when in NZ but never doing mods on exotics always the run of the mill stuff.
 
Felonious Crud

Felonious Crud

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JJbing said:
I must've been extremely lucky with mine when I had it, did 30k miles and sold it with 54k on the clock, never a hint of a rattle.
Click to expand...

Ditto. Took my GTS from 19k to 53k and it was as sweet as a nut throughout. Fecked variators are by no means a certainty (though I'd not want them!)
 
A.S. Motorsport

A.S. Motorsport

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OK so let me chime in with some generalities

Cam cap modification
  • Works only preemptively on light rattle
  • Engines that rattle after a few hours this wont work
Variators
  • Preferably with cam cap upgrade
  • Needs to be replaced if the car rattles every start with in a few hours
Chains
  • Replace if heavily rattling
  • Replace if rattling warm whilst running (misfires are good sign and engine braking from 6k rpm)
  • ALWAYS check crank to first timing sprocket (the small chain) often brakes it's tensioner due to variator rattle
Oil
  • 5w40 (I use Shell Helix ultra like factory) replace yearly!
  • DO NOT use 10w60 in F136 Engine, (4200GT, Quattroporte , GranTurismo) this should only be used in 3200GT and older or if you have a late series F140 V12
Later engines
  • the issue was permanently fixed with the introduction of 60 degree spiral spring variators (roughly 2011)
  • FYI these engines overlapped, I've had for example a full face-lift Quattroporte 4.7 with old variators, (F136Y series) i recall it was permanently used F136YK onward, i'd need to check my lists here though)
 
conaero

conaero

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To add to the above we see a lot of broken chain guides on engine requiring a full variation job. If you are doing it, make sure you change them all as a preventative measure and inspect them thoroughly.

The end of the chain guide usually nestles at the bottom of the timing case...if you're lucky.
 
A.S. Motorsport

A.S. Motorsport

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198
Yes this is a very true thing, you don't hear a lot about the lower chain guide.
We do i think about two a month here and you see chain issues lately in about 1/3 of them having a damaged or near failing chain guide.

Hence I as a general advice always recommend replacing chain kit, variators and doing the checkvalve upgrade in the cam cap.
This is particularly prevalent to wet sump engine.

Dry-sump issues are there too but it's different, i'll not start clogging up a GranTurismo topic with 4200GT/QPV specifics.
 
Jamin

Jamin

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238
This may be a little naive but it seems that the original variators are good for at least 40-50k miles,
may I ask my learned colleagues your opinion on simply replacing original timing variators with the original part at a cost of £185 ea. and not carrying out the more specialist end cap mod or uprated variators at £350 ea.

I'm sure it's not this simple but the video does suggest it may be achievable by a competent mechanic??

 
philw696

philw696

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Need to be set up using dial gauges to get it spot on.
It's a very time consuming job that's for sure.
Only needs to be slightly out and it can throw the engine management light.
 
A.S. Motorsport

A.S. Motorsport

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198
That's not fully how it works, we've gotten quite a few cars sent over after they did it that way and messed it up.
OK so in detail:
  • As per Maserati/Ferrari the dents aren't your timing marks, they can be off a few degrees from factory
    • My theory this is done at the factory during assembly to get them roughly there, FYI the cam lobes have no relation to the cam "shaft" as it's a machined tube the lobes are pressed on in the factory and crimped (hence the 30mm hex don't align the same way)
  • Pulling the variator equals undoing the bolt = no timing anymore you will need to retime
    • Especially when torquing the cam it will easily move off timing
  • The cam cap modification is required if you intend to do. (yes it's up to the customer but still do a good job first time around it will save a car)
    1. Have it be permanently good or at least for the next decade
    2. Do a proper job
  • If you do your timing job (dial-gauge) correct you can still end up with a check engine and non-synch error
    • with in a certain range this is fixable but i recall only SD3 or MD can fix that by doing a resycn and timing writing session
Sure some people might get away with just hastily doing a job and perhaps the marks did align but if the Russian roulette didn't work out you're doing the whole job again
I've seen the points being off from factory
 
T

Tifran

New Member
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does anyone know if the “new“ and improved variator PN 248019 on post 2012 models can be retrofitted in place of the old variators PN 253625 on a Granturismo 4.2 2008 - I am looking to do my 2008 4.2 GT variatiors and want to make sure I get the updated ones and that they fit. My chassis number is ZAMGH45FX80038435. I tried contacting the dealer spares department but they just looked up the book and said the new part is listed for post 2012 models only. Has anyone successfully fitted the new ones on the older 4.2 engines?
 
stevo

stevo

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371
petrD said:
Hi To All, another newbie on this forum - Am the happy owner of Mas QPV 4.7S for about half a year (MY2008, now 75k km on the clock). Shortly after I purchased the car (70k km at that time), the engine started to rattle - typical sound of variators...It got worse, even when the outside temperature went higher (rattling 8 out of 10 starts). The engine suffered misfires (barely noticeable, but seen on diag tool) and that strange "slapping" noise (going away when open the oil filling cap). So we decided to do a variator job.

When dismantling cam caps, we noticed that those were probably already modified. Also the check valves are not sitting at the same height, and are not staked (pics attached).

I just wanted to ask the forum couple of questions:
  • is that cam caps modification done (properly)?
  • could the "sagging" check valve block the oil flow, causing the lack of oil for variator?
  • would the chain tensioners be a main cause of rattle similar to variator rattle, or just a contributor? (when we "pressed" the timing chain, the tensioners were pretty "soft"...)
Thanks a lot for any help or advice.

Peter
Click to expand...
I had my cam caps modified but the rattle returned shortly afterwards. I then had the variators replaced and alks been well I suspect that pre cap mod the lack of oil damages the variators so they need replacing
 
conaero

conaero

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Stevo, if my memory serves me correct we found your timing guide in the bottom of the timing case too.
 
O

ofpoets

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Hi All. It seems I likely have the infamous variation rattle on my 2008 Granturismo (4.2). I'm happy to install the cams myself but looking for a reputable machine shop in the UK to do the modification. Any suggestions please ? Also, and don't shoot me down on this ! Is it worth using Castrol Magnatec ? I'm not expert on oils but from reviews it apparently does cling to engine components so curious as to if this may help in reducing the wear/rattle on startup. Mad idea or plausible ?
 
philw696

philw696

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25,470
ofpoets said:
Hi All. It seems I likely have the infamous variation rattle on my 2008 Granturismo (4.2). I'm happy to install the cams myself but looking for a reputable machine shop in the UK to do the modification. Any suggestions please ? Also, and don't shoot me down on this ! Is it worth using Castrol Magnatec ? I'm not expert on oils but from reviews it apparently does cling to engine components so curious as to if this may help in reducing the wear/rattle on startup. Mad idea or plausible ?
Click to expand...
Having done a few when I worked in a Dealership it's a very time consuming job doing it as per factory using dial gauges.
Best to get the caps done through Maserati and have a paper trail to back up the work.
Good Luck.
 
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