Rebuilding an EG33.

[akschu]

Ross,

The ECUTune guy said he would build the engine for $5500 if I omit the head porting and aftermarket camshafts. So here is the question:

Is $5500 worth having it professionally built, turbo specific pistons, better crank tolerances, way better rods, arp fasteners, balanced, and 2lb lighter rotating assembly?

I figure I could get a SVX engine pretty cheap and rebuild it for $1500 so I'm really looking at a $3000 premium for this stuff.

Is this way overkill or reasonable? Should I just do this instead:

http://cgi.ebay.com/ebaymotors/ws/eB...m=330239962930

I have a bad habit of way over doing things so just looking to see if I'm going overboard.

Thanks,
schu

[rv6ejguy]

Yep, if you are going to run a turbo with 91 octane, much safer to drop the CR into the high 8s.

I think forced oiled pistons means either the rod column is gun drilled (unlikely) or he is referring to the pins being oiled from the oil ring groove/ scraper, probably the latter. A good idea but it does not cool the piston like the turbo engines. Probably no need with forged pistons however.

With a turbo, I think weight will be 20-30 lbs. heavier than an O-540, but you'll have a lot more power, especially at altitude. It will be much quieter than a Lycoming and much smoother.

I'd guess the turbo will be just under $1K with all the bits. Add a few hundred for an intercooler and a few hundred more for some 321 stainless tubing.

If you only need 180 hp or so, I would not bother with a turbo unless you are flying in high terrain. You will certainly be lighter than the Lycoming sans turbo system, even with a serious muffler.

The PSRU is as important as the engine. If either takes a dump, you are going down. Best to compare total cost of this to a fresh O-540, then it seems like a bargain. I can put you in touch with Marcotte. They are based in Quebec, Canada. Slow to deliver unfortunately.

If you have engine building experience and access to a GOOD machine shop who understands Subarus, then the JDM core would save you a lot. The stock rods are fine, you just need forged pistons and the rebuild parts. Be aware that these are a relatively complicated engine and don't tolerate mediocre assembly. If you are not experienced with DOHC Japanese engines, I'd be very careful. $5500 for the engine, trick parts and labor is a good deal IMO if the work is truly quality.

A few notes on pistons here: In my experience over the years, the custom piston makers can turn out beautiful parts, just not often to your specs. They often have "better" ideas how to do things. Beware of that one- about 50% of the pistons I have had custom made by JE, Wiseco and Venolia have had to be done again. Secondly, you can choose between alloys either a high silicon/ low expansion 4032 or a 2618 higher expansion tougher alloy in the JEs. For your application, the 4032 would be a better choice but you still have to open up wall clearance a bit over the OEM cast pistons. You will either have to hone or get the pistons made slightly smaller than stock.

Subes have an innovative way of extracting the piston pins and what the aftermarket guys supply for pin locks makes installation a nightmare.

The EG33 uses a tabbed oil rail so be sure this is incorporated into the new ones if using OEM ring sets. Get a straight bore pin or your life will be miserable when it comes time to pull them out.

You can get pin offset or not. Center seems to work ok. OEM is offset.

The pin boss to crank counterweight clearance is minimal on these engines as is clearance to the block webs. Be sure the piston maker does not add material below the stock pin boss dimensions- or it won't turn over.

Now are you seeing that all this takes a lot of time? This is just the piston part. You should see the heads!

Good news is that you don't need the forged pistons if you go atmo (no turbo). In fact if the JDM has good compression and leakdown, clean oil and good oil pressure, you might choose to use as is. Many people have.

[rv6ejguy]

Schu,

I PM'd you with contact info for Marcotte.

[longassname]

Matt showed me this thread and suggested I join up and post here since he was asking me questions spawned from this thread.

My 9.3 compression pistons are from 4032 forgings and use rings from the same manufacturer as OE with the tabbed oil rails. They are also (as all my pistons are) specially machined to use the OE Subaru pin locks. The force fed oiling is as suspected--the pins are force fed oil from the oil ring groove. This does not cool the piston it prevents pin hole wear and friction by forcing oil onto the top of the pin at the same time pressure is being exerted on the piston trying to force oil out. The thermal coating on the top of the piston is important to the piston fitment. It helps keep the piston cooler making it possible to use smaller sidewall clearances. The anti friction skirt coating is also important to fittment. If the piston should ever get hot enough to cause scuffing it will wear off the moly friction coating instead of the actual piston swelling into the bore. Engine builders often use larger sidewall clearances than are best with forged pistons because forged pistons do change in size while operating more than cast pistons do and they don't want to risk the piston swelling into the bore. It is also correct that pistons are rarely actually the diameter specified. For proper piston fitment I have the pistons made first, then measure them, then hone the block to the necessary bore for each piston to have the exact desired sidewall clearance. Doing this and machining to tight tolerances allows the sidewall clearance to be set dead on to ensure the piston will never swell into the bore while maintaining quiet operation and improving cylinder seal thus increasing MEP. My 9.3CR pistons also have light anti-detonation grooving and a v notch between the 1st and 2nd compression rings. If I end up building an engine for Matt I will set the sidewall clearances to .0025" for the coated pistons.

I favor this piston for Matt's application because it will provide excellent performance both naturally aspirated and with forced induction. If the engine is run naturally aspirated he will be able to use all pump gasolines including regular unleaded. I suggested he might consider supercharging and using two bypass valves--in which case even if his supercharger completely seized up the engine would still function reasonably well.


The rod and main bearings and oil clearances are even more critical on these engines. The OE tollerances are quite sloppy and some engines have what I consider grossly unacceptably small oil clearances from the factory. The OE rod bearings are tri metal bearings. I have moly coated high silicon aluminum bearings made for both the mains and rods. All bearings are caged (that means the block is assembled with the bearings but without the crank and the rods are assembled with the bearings and not installed on the crank and the bores of the bearings are measured with a brown and sharpe intrimik) The crank is then machined according to the caged bore measurements to obtain the exact desired oil clearances. With my coated bearings I favor 15 tens for both the rods and mains except the bearing with the thrust surfaces which I give a few more tens to increase the oil flow.

[Mike S]

Mike, welcome to VAF.

Good to have you on board.

Enjoyed the tech info. Thanks.

[rv6ejguy]

Welcome to VAF. This is the proper way to assemble and check these split case engines and I'm impressed by your attention to detail. As I said, with these parts and method of assembly, your prices are more than fair.

How is your supply of these engines from Japan?

[longassname]

thanks Mike, thanks Ross,

The US and JDM engines are the same. I use US engines for cores. They are readily available. These engines are all of the age that they have bad head gaskets no matter what country you get them from. Between bad head gaskets, cars with blown transmissions that cost more than the car, cars crashed by high schoolers, and cars that have been driven on salted roads their whole life without maintenance of the undercoating there seems to be plenty of good engine cores around.

[akschu]

LAN,

You mentioned that these have the bad head gaskets, which you also mentioned on the phone where the gaskets only last 10 years then fail. Can you tell us aviation guys how this translates to safety at annual? Can you easily detect the failed gasket with a compression test, and does it cause sudden failure or is this something detectable early on? If it's sudden then how do we deal with this in the aviation world? Replace the belt and head gaskets every 8 years? Also, does your step deck machine work and a good gasket like a cometic solve this?

As far as me buying an engine, the current plan is to purchase one from you. The parts and knowledge are worth the money, but after parting with a very large chunk for the airframe I'm still catching up. The order will probably come in at the end of the summer.

Thanks,
schu

[longassname]

First let me explain what a step deck is so that others reading this will know what were talking about. Cylinder heads bolt to the cylinder block. That much I'm sure anyone interested in this conversation will know. The block side mating surface..flange if you will..is called the deck. The cylinder head mating surface is normally resurfaced perfectly flat and the deck on the cylinder block is normally resurfaced perfectly flat in most engine builds. A step deck is when we cnc machine off a very small amount of the deck everywhere except for right around the cylinders. In this case the area around the cylinders is slightly higher than the rest of the deck. When the heads are torqued down the head gasket is compressed more and a greater percentage of the clamping force exerted by the head bolts/studs is exerted directly around the cylinders. This allows us to hold in greater cylinder pressures with the same amount of tension on the head bolts/studs. We don't need a lot of pressure on the head gasket around the oil passages or coolant passages. Coolant and oil are under very little pressure as compared to combustion pressures. So while a step deck is beyond the abilities of most automotive machine shops it can be very beneficial.

Most head gasket failures in performance applications are actually head bolt/stud failures. Bolts or studs have a yield strength. When stretched beyond that they don't spring back to their original length thus clamping force is lost and then the head gasket leaks. By doing a step deck we can contain the higher cylinder pressures of performance applications without torqueing the head bolts/studs so tight that they are in danger of being stretched past yield due to thermal expansion if the block runs hot.

The OE head gaskets are very good. In fact I use all OE seals and gaskets in my engine builds. The cars that these engines are coming out of were made in 91-96 though. It's just to be expected that the head gasket will go bad after that much time. 12 to 15 years isn't a bad run for a head gasket.

I don't have a private pilot’s license and ground school was a long long time ago for me so I don't really know anything about annual requirements.

When the head gaskets fail they are actually very hard to detect by normal means. The engine just likes to overheat when the head gasket is bad. It's never a massive failure so you don't see steam out the exhaust or have a noticeable loss of coolant until your radiator boils over. I've block tested engines exhibiting these symptoms and they never test out bad. Then I rebuild the engine and there's always a cylinder that I can tell had coolant leaking into it.

Originally Posted by akschu

LAN,

You mentioned that these have the bad head gaskets, which you also mentioned on the phone where the gaskets only last 10 years then fail. Can you tell us aviation guys how this translates to safety at annual? Can you easily detect the failed gasket with a compression test, and does it cause sudden failure or is this something detectable early on? If it's sudden then how do we deal with this in the aviation world? Replace the belt and head gaskets every 8 years? Also, does your step deck machine work and a good gasket like a cometic solve this?

As far as me buying an engine, the current plan is to purchase one from you. The parts and knowledge are worth the money, but after parting with a very large chunk for the airframe I'm still catching up. The order will probably come in at the end of the summer.

Thanks,
schu

[longassname]

A remote oil system would be a big plus for you guys wouldn't it? I have a vertical machining center with .00005" resolution and 50x20x6 travels--plenty big enough to machine pans for a remote oil system.