Over the past few days I've started the final buildup of Wibble's WRX headded VW engine. For those that missed the other thread where the concept was being developed.... the goal is to build a large displacement high reving engine that uses subaru DOHC water cooled heads.
The advantage of the subaru heads is that the built in performance capability of them. The ports are huge!. Add to that reliability, 4 valves, hydraulic operation, water cooled, the list goes on. Naturally aspirated heads have small combustion chambers and will be on the engine in its final build, but in this built it will have a pair of MY98 WRX heads with 55cc combustion chambers. This means a low compression ratio and as a result reduced performance. (about 190hp i'm hoping for).
The 2180 will redline at 7300 RPM. The limiting factor being the subaru valve train and the mahle forged pistons. To go above that we'd need to run wiseco's and aftermarket valve springs which will be a simple bolt in affair when its all done. The wiseco's MIGHT be needed depending ont he valve pocket depth that has yet to be cut into the pistons, as the mahle's can only handle pockets to a depth of about 0.140".
So after designing and machining about 5 different versions of head stud adapters I decided in a final design. There was a lot to consider with making the head stud adapters. My main problem was that we'd bought an engine case that used 10mm head studs. This complicated the whole project because it meant there were no "off the shelf" bolts available that would allow the plates to be bolted on properly and still clear the barrels.
About the empi alloy cases, after seeing one I think i'd prefer the CB alloy engine block. Having 6 shuffel pins for a start, but also being a CB product its probably better quality and better machined too. One of the shuffel pins on the empi case was loose because the machining tolerences were out... Typical Empi quality...
This is the specs of the engine so far...
78mm osraka german forged billet crank
scat 5.7" h-beam 4340 rods with 3/8th rod bolts
empi alloy case with 10mm head studs
A stock cam is used for an oil pump drive, with clearancing for the conrods as the 3/8th bolts make them fat!
Welded stock lifters, installed to block the oil galleries. Glued into place with silicon for the moment, but after the engine proves itself the oil gallery plugs will be drilled and tapped, and plugs will be installed to allow oil supply to the lifter bores to be closed off. I didn't want to modify the block too much incase the whole project goes sideways...
mahle 94's with total seal 2nd rings
CB dry sump pump , full flow fitting on the front of the case will be t'd off to supply oil to the heads via external hose plumbing. Oil return via some custom tubes that will return via the pushrod tube holes in the case.
custom head stud adapters, 10mm plate bolts to the block and 12mm head bolts. All grade 12 high tensile steel.
MY98 wrx heads with modifed water cooling supply and returns.
The next part of the project requires 12mm to be machined off the base of the barels so the fit inside the engine case again and the deck height is restored to 0. Setting the actual deck will be done with a 0.040" copper head gasket and barrel shims. I'll be getting the barrel machining work done next week once we are all back from holidays.
After that its heads, timing belt, oil supplys and returns, intake manifold and then a test start. (who needs an exhaust) Timeframe is about another month... so we'll see if I can keep that.
Here's the pictures...
I'll keep posting updates as things progress.
Cheers,
