Forged pistons for 2002 Jaguar S Type R 4,2 V8 s/c

[Sid447]

Try emailing,

some Custom Piston manufacturers. There may be a company that supplies these to some motorsport fraternity and could even have them "on the shelf" in stock.

Mahle deal direct to manufacturers and are o.e. suppliers to a lot of different companies. They are not going to react to an individual requesting a special order.
You'd need to go to the division of Mahle that makes forged pistons. I believe this is in the USA.

[zcuvalo]

Did all that. I have sent out some 20 e-mails to different piston manufacturers or resellers - Pistons online, AJ pistons, and others I dont even remember now. Mahle did reply twice to my e-mail and have promised to see if they can help me. Main problem is that one cylinder is scratched and I need to re-bore it and then I have to find pistons that should fit new cylinder dimension - in Croatia it is almost mission imposible. There is one or two persons who can do re-bore good, but then there is a problem to find pistons for that dimension. I did have received one link with one company in England - Farndon - they have experience with this problem - they increase volume to 4,5 L and deliver pistons that fit that dimension. But transport costs are higher then a price of a rebuild engine I have acquiered yesterday. So I gave up - perhaps when this engine dies I shall have more time and patiente to finish my project. Arden has offered to do all of that job but the price was 30.000 E - a bit too much for me.

[Sid447]

zcuvalo,

How deep is the scratch in the cylinder? can you measure it?
e.g. if i is less than 0.005" or 0.127mm this can easily be removed by re-honing to first over-size which is normally 0.005." You would need to check on this.

[zcuvalo]

Hi Sid447,
The scratch was inspected by 2 mechanics and they claime it can not be polished, it has to be rebored to stage 1. But as I was told then I need 1st stage pistons - and nobody has the idea where to find them. Mahle pistons are OE, but they sell it through Jag dealers only, and the local dealer is zero interested in help. More then 3 weeks they did not reply for small engine kit quest. I have the photos of scratched cylinder and I shall try to post it here tomorrow. I am giving up of this engine, it will be collected by Jag dealer from NL, he is selling me his rebuild engine for lower price (5.600 E with transport). Many things would have been easier if I was in UK or Germany, here thera are only few good mechanic for that issue, and they have never, ever dealt with Jag engine (I did contacted them all). My idea was to rebore to 1st stage or to 4,5 L and then have aluminum or titanium forged pistons installed, but in 4 weeks did not receive any positive reply. Jaguar (England) engenieers did some plan for to help me but they were to slow and I have decided to cut through, get a new engine (rebuild) and get back on the wheels again.

[zcuvalo]

Bellow is a direct link on my Picasa web album with 3 photos in high resolution showing the broken piston and scratched cylinder. Note that cylinder and piston in question on 1st photo is the one on the far right.

http://picasaweb.google.hr/CoberHr/J...eat=directlink

[Sid447]

Hi zcuvalo,

This is almost exactly what happened to my GM V8 some time ago. In the same cylinder too by the look of it (#7 which is left-side rear).
Unsure of the cause for my piston cracking in virtually the same place as yours but mine caused more than just a cylinder scratch! The piece of (cast) piston got trapped between the piston and cylinder wall and fractured the block cylinder wall. I had to buy a complete new engine block and rebuilt the engine from scratch using (yes!) forged (Lunati) pistons for better reliability.

GM build quality and the fact that with most V8's the left rear cylinder runs hottest (because of the way the coolant flows around the engine) and this then caused detonation only in that cylinder was the most convincing reason for my engine failure, I think.
As like yours, all the other cylinders/pistons in my original engine were perfect with no signs of detonation damage or even discolouration from a weak mixture.

Sorry to hear and see the trouble you've had. I found a set of forged 99mm pistons quite easily and the rebuilt engine has run without missing a beat since (2005).

[zcuvalo]

What shall I say, lucky you - you are right - it is a last cyilinder in the row just in front of a driver, on the left if you are looking from the driver seat forward. I was warned by few experienced mechanics that it was most probably the case with both of my engines - now I am paying attention to put new fuel injectors (they cool the piston head when working properly), and to be honest have no idea what shall I do with my new engine regarding this problem - it is a engineering problem - most likely I shall try to find forged pistons, titanium when possible (if not to expensive) - hoping that they shall cope with this general flow. You say that Lunati works fine with your V8 engine - how about checking with them if they have set of forged pistons for my V8 4,2 L. Just to have reserve if things start to go wrong (again)..

[Sid447]

Improving the coolant flow,

around the engine somehow and/or fitting a bigger radiator helps zcuvalo.
I fitted both a cylinder head coolant vent tube modification and a heavy-duty motorsport radiator, plus! a 30cm x 30cm engine oil cooler to try and bring engine temperatures down and improve cooling flow around the engine.
Fitting the forged pistons gave piece of mind, as they tolerate detonation better and are much tougher than cast pistons (you can't get pistons made of titanium, by the way!)
The fuel injectors don't cool the piston as such, it's the amount or ratio of fuel mixture that is injected into the chamber and mixed with air thatv can be adjusted to keep cylinder head temps down; and if you are running a super-charged engine it should be at 12.5:1 AFR when in Power Enrichment or Transient Fuelling mode (to keep it on the rich side for this purpose exactly).
The injectors will only be a problem if they aren't flowing correctly.


On this website it says the 2003 model Jaguar 4.2 SC-V8 engine comes fitted with forged pistons......???

Read here:-
"........The 4.2-liter V8 engine delivers truly spirited performance.Jaguar has redesigned this engine, ...................Changes over last year's 4.0 engine include new cylinder heads, forged pistons, a new exhaust manifold, and many other changes

I found this information, here:-

http://autos.aol.com/cars-Jaguar-S_T.../expert-review

[zcuvalo]

Hi SID447,
I agree with you in regard with fuel injectors. Yes, S Type R comes with forged pistons - I have heard that from jaguar engine engineers, I am in contact with one of them via e-mail. They were preparing a solution - proposal to me, but they were a bit slow, in two weeks I havent received anything from them - its a long procedure, they say, but I could not wait that long.
But your idea of improving coolant flow is the only viable solution to this problem, I think. Can you describe for me this cylinder coolant tube modification - if it is not too complicated I may have my mechanic look in that and do something in that sense - what is it - how do I get it. Radiators are going to be new, all pipes cleaned and replaced, all in favor of better engine cooling.
I think I have a lot to learn from you about this issue - you did your thing very good, obviously.
Regards,
Zvonimir

[Sid447]

Hi Zvonimir,

My V8 had blanking plugs in the cylinder head that were used in earlier models but deleted for some reason after 2001 so I just had to buy the parts from an earlier model and remove my blanking plugs to fit it.

Post #2 in this link shows a picture of the later type vent-tube (it's slightly bent in a "v" shape to clear the PCV breather tube with the red plug cover on it) crossing at the front of the engine only, with the blanking plugs just visible at the back on each cylinder head.....

http://www.ls1tech.com/forums/genera...ent-tubes.html

Then this link shows a picture of an earlier engine with the older (better) style coolant vent tubes which run not only across the front but back along the valley plate cover to the rear of each cylinder head also.

The 9th picture down the left side bar.........

http://www.ls1howto.com/index.php?article=5

So it was pretty straight-forward for my modification. I am not familiar enough with the Jag V8 to know how to improve cooling for the hotter #7 (left-side rear) cylinder. You need a good engineer!

Regards, Steve.

[zcuvalo]

Hi Steve,
Thanks for detailed answer, text and photos did help me understand issue a bit better. What I shall do, if you dont midd, is to go straight forward and ask Jaguar engineers directly about this issue and show them how you delt with it on your car. Perhaps they will be able to provide some tips on how to improve coolant flow on existing engine. One thing I shall do for sure is to inform my mechanic about your post.
Many thanks for very thorough post. I shall keep in touch and let youknow about what I did.
Regards, Zvonimir