Confused on engine condition, turbo 4g64

[1Gina2G]

I'll try to make this short as I can with detail. What I have is a 2.4 SOHC 4g64 n/t engine that is now been rebuilt and turbo'd. Me and my cousin (cousin for the most part) did the block entirely, cleaning, new bearings and OEM piston rings, got the pistons and everything looking new. Gapped the rings according to the manual, OEM headgasket. Had the machine shop redo the head completely and this engine uses headbolts rather than the studs the 4g63s use, torque to yield, so I just replace.

Anyways on the the issue;

We can not figure out if our piston ring job was actually good enough or not, even though the car drives good for the most part, but sometimes does feel notchy, hard to explain.
- Excessive blow by out the crankcase, the valve cover is just like the DOHC 63s, 1 breather port on the side that works both ways, supposed to be breathing in at idle, mine exhausts out.
- PCV valve works fine
- Some air not much from dipstick/oil fill, hard to say
- Reading good vacuum -20
- Perfect air/fuel ratios at all times on wideband
- All cylinders make perfect compression since right after rebuild till now 190-210 for the 4g64
- No oil consumption or loss in anyway, actually rebuilt because of oil consumption.
- Leak down test has air come somewhat back into the area of the injected cylinder. This is of course with the tested cylinder being a TDC of the compression ect.

The car drives without issues really but I wish I knew why I have this much blow by and how bad is the block actually since it seems to hold power at 14 psi just fine with stock 4g63t turbo parts and ECUs, small 16g turbo rebuilt by the way on stock 450cc.

Anything else I can check? I think my exhaust may be too small or something just an aftermarket stock GST exhaust kit I got from someone. I hear exhaust flow may have some relation to blow by pressure, not sure. thanks all.

 

[spyderdrifter]

I think you should have used a 4g63 DOHC head instead of the SOHC. I will be doing that combo later for my build. It could be your rings, but could also be the bore job on the cylinder walls.

 

[4Gwannabe]

Did you hone the cylinder out prior to the piston install?
Did you check the cylinder bore for out of round, or just kinda put her together?

 

[curt-s]

There is quite a bit of movement in the crankcase during operation. Not only is the crankshaft moving around causing air turbulence, but you also have pistons and rods going up and down and itty bitty explosions above them that result in at least a TINY bit of leakage past the rings even with a correct seal. To overcome all this air turbulence and actually cause a complete vacuum within the crank case at idle, you'd need some serious ports to a vacuum source (IM or intake), hence why people start adding -6 through -12AN ports off the top. The rinkydink stock lines don't really do that very well; it's a lot of volume to evacuate.

What do you consider excessive blowby? Have you put a gauge on your crankcase to see how much actual pressure is being created under all driving conditions yet?

General question: With the stock PCV system, has anybody been able to suck a shop towel through the oil fill cap?

 

[1Gina2G]

I think you should have used a 4g63 DOHC head instead of the SOHC. I will be doing that combo later for my build. It could be your rings, but could also be the bore job on the cylinder walls.

There's been a lot done with this N/T SOHC engine right as it comes out from the factory. I've found it to be most cost effective to have the head rebuilt at the local machine shop. I was also curious to see how it'd perform owning a 6 bolt swap on my last build.

ANYWAYS, it was already looked into for the most part, adding a DOHC head with the factory N/T internals will create a really high compression ratio, 11:1 or something similar. Yes we did rebuild the block with new factory internals, which use higher compression piston rings vs the lower compression rings in a factory 4g63. The block on the 4g64 is a bit bigger than the 4g63, which would mean to get the ideal low comp rings I'd have to get a forged setup, which is worth it but still a lot of money for what you get. The compression ratio is lower with the SOHC head with the higher compression rings.

Did you hone the cylinder out prior to the piston install?
Did you check the cylinder bore for out of round, or just kinda put her together?

I watched my cousin hone the cylinders out and wipe em up good after wards. Put the oil rings on by hand, and used a ring tool to put on the compression rings. Measurements taken and compared.

There is quite a bit of movement in the crankcase during operation. Not only is the crankshaft moving around causing air turbulence, but you also have pistons and rods going up and down and itty bitty explosions above them that result in at least a TINY bit of leakage past the rings even with a correct seal. To overcome all this air turbulence and actually cause a complete vacuum within the crank case at idle, you'd need some serious ports to a vacuum source (IM or intake), hence why people start adding -6 through -12AN ports off the top. The rinkydink stock lines don't really do that very well; it's a lot of volume to evacuate.

What do you consider excessive blowby? Have you put a gauge on your crankcase to see how much actual pressure is being created under all driving conditions yet?

General question: With the stock PCV system, has anybody been able to suck a shop towel through the oil fill cap?

I was really wondering if I should try that and I think I will now that you mentioned that. I'll go ahead and get some bigger fittings to add to my manifold and valve cover, it just seems it doesn't escape fast enough so it just has to exhaust out the side port, I wonder how it's affecting operation.

What kind of gauge do you use to measure crankcase pressure? I'll buy one.

 

[1Gina2G]

I was told I can use my vacuum gauge to measure the blow by, can I?

Wouldn't this bad to do if the breather port is always exhausting out?
Any idea of what readings I'm looking for?
Should be positive pressure in this case, why I'm wondering vs the normal vacuum it's supposed to have aka negative pressure

Also wanted to add that I double checked timing, balance shafts in phase and all going to check right now if my PCV and added check valve are restricting flow, if I don't post back on it I will proceed to have my ports drilled out when I can afford the welding job, just confused about how I should take the baffling out inside the valve cover, mostly just to get it back on.

Would like to know how I can measure the crankcase pressure before I do though, Im scared that too much pressure will build up once I have that port plugged into the gauge.