Xu10J4R Forged Pistons

[sub205 5]

Hello,

 

i'm searching for forged pistons for the XU10J4R (132bhp).

The issue with the stock pistons is that larger hub cams don't fit.

Is it possible to fit the GTI6 pistons?

 

The XU10J4R lacks spray-bars, so i can only use the non-floating con-rods.

 

Any ideas what route to go?

 

The block itself is freshly rebuilt, honed, new shells etc, so i don't want to waste it.

 

Kind regards,

Stephan

[welshpug 1,657]

Rfs has no more valve clearance, just a smaller dish to gain 0.4 compression.

 

Some rfv do have spray bars, but why do es that affect conrods??

[sub205 5]

I own some catcams for the RFS. On the RFV there are about 3.5mm inlet and 1.5mm outlet missing!

The conrods for engines without spraybars are for the non-floating-type pistons and have a small bore to let oil spray from the crankshaft trough the shell onto the piston.

I'm not sure how safe it is to mix this, especially using XU10J4RS conrods and pistons in this engine without spraybars.

Is the diameter of the pin identical in floating/non-floating configurations and just the size of the eye in the conrod different?

[welshpug 1,657]

RFS and RFV rods attach in the same method, they may even be the same part.

[sub205 5]

Are the GTI6-conrods non-floating-style with pressed pins?

[welshpug 1,657]

shrink fit/pressed yes just like D6B 8 valve, no circlips like RFY/D6C/DFW.

[sub205 5]

Hm ... any idea why the catcams 4903110 did not fit and i had several millimetres valve clearance missing?

It is getting more and more mysterious.

 

XU10J4R engine, 4/10 skimmed head and the mentioned cams, nothing else... :-/

[welshpug 1,657]

what is 4/10?

 

 

you have 2.95 / 2.45mm lift @ TDC, there is no hope whatsoever getting them in over a standard piston, if you wanted ones that fit you should have used 4903164

 

http://www.catcams.co.uk/cgi-bin/sh000001.pl?WD=4903110&PN=XU10J4RS_Full_Profile_List.html#a166

 

 

4903110 is a rally cam and will probably need springs and retainers as well.

Edited July 10, 2013 by welshpug

[sub205 5]

Sorry, did a mistake while copying& pasting, i got the 4903156...

[petert 586]

You need to use XU10J4RS pistons. Unsure if they'll fit an XU10J4R rod however. I'd bush what ever you have anyway, and make them full floating.

[sub205 5]

Ok.

I think the difference between the 2 conrod-types is that the J4R have a small hole going from the upper bearing shell trough the rod to allow oil spraying to the bottom of the piston whereas the J4RS dont have this one because of the spray-bars.

 

Order-Numbers are 060360 (RS) and 060365 ®.

Maybe someone can verify that?

 

Why make them floating? How shall i attach the clips for keeping the pins at the right position?

What advantages have the floating pins over the fixed ones?

[welshpug 1,657]

0603 60 is used in the J4R until RP 06950 (November 19, 1995) so this must coincide with the removal of the spray bars in the RFV block, the oil spray hole in the rod is easy to add however if you know a machinist, its just a hole drilled in the rod.

 

 

In the RFV the same 0628 C8 piston is used on both RFS type rod and the later drilled RFV rod, so yes they are compatible.

Edited July 10, 2013 by welshpug

[sub205 5]

Mine have this hole, so i see no problem in using them.

[petert 586]

Ok.

 

Why make them floating? How shall i attach the clips for keeping the pins at the right position?

What advantages have the floating pins over the fixed ones?

 

I've never seen an after market forged piston that isn't full floating.

[sub205 5]

Take a look at this shop:

 

http://shop.weiss-motorsport.com/product_info.php?products_id=381

 

Only pistons ans rings, no pin and no clips. The pistons are plain exchange parts for the oem ones, with the same mounting principle.

 

the Turbo-capable pistons however are with a 22mm pin and clips, you also need special conrods for these.

[welshpug 1,657]

they will not fit a standard conrod, the pin is 20mm for those, they do use clips, all wossner kits advertised elsewhere include pins clips and rings.

 

http://www.woessner-kolben.de/en/downloads/catalogues.html

Edited July 10, 2013 by welshpug

[sub205 5]

I recently talked to wössner directly. They told me i can use them with fixed pins and floating pins, both variants are working and supported.

:-D

 

So the only mechanical differences between the R and the RS are:

 

- Spraybars (no problem)

- Pistons (will be wössner forged pistons)

- Valve diameter (cannot change, anyway, not that big problem)

- external components (exchange with gti6-parts)

 

Have i forgot something?

[welshpug 1,657]

valve springs, vale stem seals+seats.

 

you need to check that there's enough clearance on the radius of the valve cutouts in the piston to accept the larger RFV inlet valve.

[sub205 5]

I will keep the XU10J4R valves & head, so i think the RS-pistons should have enough clearance?

The head is skimmed for about 0.4mm

The mentioned catcam is for the RS

[welshpug 1,657]

J4R inlet valve is larger than the RS

 

0.4 is beyond the safe 0.25 limit also, which would move the valve closer to the side of the valve cutout unless a repair gasket was used, so it is imperative to do a dry build as one should normally do when building something like this, to confirm not only the valve clearance in height but sideways in the cutout.

[sub205 5]

Do you have some values you can provide me?

f.e. valve diameters

 

Maybe i'll grind the valves with a angle-grinder and a drill press.

That should give me some more space.

[welshpug 1,657]

inlet:

 

RFV 34.6 mm RFS: 34,10mm

 

 

exhaust:

 

RFV 29.6mm RFS: 30.00mm.

 

 

 

 

please get a pro to do the machining!!

 

you need to use different valve springs, for which will require RFS stem seals and possible machining of the top of the valve guide.

[sub205 5]

Sure?

4903156

282 / 282°

248 / 248°

10.00 / 10.00mm

3.30 / 3.30mm

F.I.A.

 

The cams only have 10mm hub, and catcams tells all parts can be kept at stock.

 

Hm, i found several different infos about this cams.

Some say "stock", some say "uprated"

Edited July 11, 2013 by sub205

[petert 586]

 

Maybe i'll grind the valves with a angle-grinder and a drill press.

That should give me some more space.

Quote of the decade!

[sub205 5]

This method is really working, a mate of mine is doing TU heads for racing purposes and has really good results with this.

Important is that you have a decent drill press and the valve is rotating nicely.

Then you can use an angle-grinder and remove some of the outer material.

A tool like a dremel is also working, only takes longer.

 

Edit: Of course you cannot work on the sealing surface with this, its only useful for getting the outer diameter of the valve nearer to the sealing surface.

Edited July 11, 2013 by sub205