QSC "2.4L" Waterboxer pistons

tencentlife · Post by **tencentlife** » Fri May 25, 2007 7:33 am

Oh, right, my bad then.

Post by **Piledriver** » Tue May 29, 2007 12:50 pm

Interesting development:

The steps in the AMC heads are .040 thick.

Shockingly, I found mine are also NOT machined in, they are gaskets, tight fit.

Discovered that when giving the valve retainers the obligatory whap with a rubber mallet befor pulling the valves.

Loose deck with AA or QSCs no longer a problem, should be ~.035 now, w/o spacer//gasket, perfectly acceptable on a motor with a <6K rev limit.

Having the water jacket sealing surface .050" cut to match. (less squish on the rubber gasket is supposedly a feature...) and the heads cut for std dual springs per Marcos spec. I'll be using the CB springs I have on hand, very close specs, I'll order some of the SCATS for the pile, no certain way to get them this week.

tencentlife · Post by **tencentlife** » Tue May 29, 2007 4:02 pm

Shockingly, I found mine are also NOT machined in, they are gaskets, tight fit.

Y'know, I was wondering about that, but not having an AMC head to check at the moment, I didn't mention it. I remembered the AMC heads I've used being flat just like stock. I thought maybe you had an odd set, or maybe I had, or I was just losing my mind (happens about weekly, so it's not really an alarming occurrence). So I'm glad that question is cleared up.

I'm back at my shop with the new QSC P&L set, so I'll be posting the specs soon.

Post by **Piledriver** » Tue May 29, 2007 4:09 pm

They actually seem to be steel (possibly SS) shims, might be multi-layer....

For all I know they are the std bloody head gaskets, it's just they were were stuck in the heads (appeared to be one piece) when I got them with a warning in the box not to use the std head gaskets, citing a machined in step as a feature of the heads...

Who was I to argue...

.050" off the water jacket surface by tomorrow afternoon, trying to find decent new ex valves cheap, the faces were hammered in on mine, stems,guides.seats look perfect.

The machinist I went to (with a reasonable turn around time and not 4 hours R/T away) doesn't have a small enough valve spring cutter, so I'm going to see if the CB dual springs are too close to bind. I might make my own cutter... I have a Bridgeport available.

tencentlife · Post by **tencentlife** » Tue May 29, 2007 5:08 pm

Well, I know that the sealing rings almost seem part of the head when you take a used one off. It's hard to tell where the seal ends and the head begins. I always need a very sharp scribe to get under them without gouging the sealing surface, then of course they fall right out. I've always thought they were aluminum. I suppose a magnet will tell, unless they're stainless, but I can't imagine why anyone would choose stainless. It has the wrong properties for that application, particularly low ductility. I really favor the copper ones for better heat coupling. I used to hand-lap aircooled cylinders into the heads to avoid using a sealing ring, but in the end I prefer having something with a bit of give in there, to assure a really tight seal. Matter of taste, mainly.

Post by **Piledriver** » Tue May 29, 2007 9:17 pm

Upon closer destructive inspection and checking with a magnet, it is the stock style multi-layer head gasket, .040 thick after 65K miles of use.

I guess they had them glued in or something, and the little warning note about having the step built in and not using head gaskets confused issues. I KNOW I didn't install them.

The T4 AMC heads actually HAVE a step cut, and the same warning. Oh wait... No, That's right unless Adrian at HFM clean up flycuts the gasket

I'll be lapping in. Seen too many blown out gaskets.

The AA and QSC (Chen Shin) pin height now (sorta) makes sense.

tencentlife · Post by **tencentlife** » Tue May 29, 2007 9:58 pm

When you mill off the head face and use no rings, the Chinese pistons will put deck right at 0.030". Even a little tight. You could shave 0.010" and set it right at 0.040", and get a small increase in CR to boot. You'd lose about 1.25cc.

So were the seals ferrous, or aluminum?

I miked some other used seals at 1.25mm.

Post by **Piledriver** » Tue May 29, 2007 10:03 pm

Magnetic/steel.(Ferrous) just like the stock ones.

.030 is excellent IMHO, esp for a low revving motor w/4140 conn rods, and given the engines desired characteristics.

We'll see what the Play-Doh says probably tomorrow night and decide on a shave or not then.

...Still thinking on the lifter oiling issue.

The stock hydros have a 1.5mm deep "waist" ~17mm wide for oil to get by, in a location I can't turn down my hollow CB Lightweights much safely, _.090" wall at end, maybe .125ish in main body just after the lifter cup, snap ring groove kinda makes cutting it impractical)

Will probably connect the oil holes in the lifter bore with a dremel-tool induced groove all the way around. Simple, guaranteed to work. Might even make a proper tool for it...

tencentlife · Post by **tencentlife** » Thu May 31, 2007 8:44 am

OK, here, at long last, are the numbers for the QSC P&L set:

Piston weight= 402g (a 94mm Mahle OEM piston is 433g)
Pin Height = 35.75mm
Pin diameter = 24mm
Dish volume = 48cc
Dish volume @ 1.59mm below top for correct deck with a 5.5" rod = 40cc
Piston OD @ pin bore = 95.45mm
@ skirt = 95.98mm
Ring thickness: top = 1.7mm
2nd = 1.95mm
oil = 3.5mm

Cylinder ID = 96.04mm
Cylinder weight = 1610g

Key cylinder dimensions were identical to an OEM cylinder. A quick comparison of weights, figuring for the removal of 0.5mm from the inside wall of the OEM unit, showed tha the QSC cylinder is at least as heavy by volume as the OEM, ergo similar material composition.

I don't have very precise tools to measue cylinder roundness and taper. If I have any observations about that after further inspection I'll post them.

The rings supplied look pretty crappy, but the thicknesses are all the same as OEM, so better sets should be available. GW will have sets for their Wiseco pistons, and remachined copper sealing rings as well, if all else fails.

Post by **Piledriver** » Thu May 31, 2007 9:50 pm

Thanks for the info!

Are they Chen Shin pistons?
(CS logo cast inside)

OT, but may be useful info...
Think I figured out a possible solution to the HD valve spring installed height that doesn't involve probably ventilating the intake ports on a WBX...

GB281A retainers have .150-.200" extra installed height for the spring, which possibly works out as std installed height... May/may not clear std adjuster screws or 1.4 rockers, the original source that mentioned them for another purpose (Type4unleashed) says they require 911 adjusters...

Should allow .500+ lifts with std springs, bit heavy though.(But should work perfect with all the usual CB/SCAT/GBE T1 dual springs)

tencentlife · Post by **tencentlife** » Fri Jun 01, 2007 4:23 pm

Inside the piston skirt is a cast embossed logo, two stylized letters, either "DE" or "OE". No other identifying markings on the piston, except "STD" engraved on the crown. No markings whatsoever on the jugs, nor on the box they came in.

So, any ideas as to which factory they're made in?

One other oddity is that the bottom of the valve pockets are pebble-surfaced, so they look like they're actually cast in, while the rest of the dish is clearly lathed to final shape like the rest of the piston.

Post by **Piledriver** » Fri Jun 01, 2007 8:30 pm

So it's not a bigger "C" with an "S" inside?
(Without seeing what you're describing, from here it could still look like a OE, or DE sorta)

Hmmm. Somewhat surprising, Chen Shin makes a metric buttload of different pistons for everyone...

tencentlife · Post by **tencentlife** » Sat Jun 02, 2007 9:50 am

Definitely could not be read as anything other than DE or OE, assuming the letters are Roman. C and S are not in there, for sure. I guess I can get a picture up, in a while.

Of course I haven't any idea what the letters might mean. But that's all there is.

51MAN · Post by **51MAN** » Sun Jun 03, 2007 2:34 am

I had a set of head seals "jambed" in too, but sharpe tool hooked them out..
The set of AMC heads I have are flat..
So the pistons look descent quality then?
Think I will order a set for the test engine, but have to get my head round the work required to ensure good CR (at least 9:1, but no more than 9.6:1) But plans are a little in flux.. may be moving.. so could just Audi 5cyl or subaru it....
Still think the WBX can be improved though...

51MAN · Post by **51MAN** » Tue Jul 17, 2007 3:41 pm

Have to get on with the project "torque meister" engine soon.. any more feedback on the quality of those 2.2 piston kits?
Cheers