Blowby

[turbodaytona87]

I have a rebuilt 2.2l engine in my Daytona. It was rebuilt around 5000 miles ago using stock parts. Its bored/hones .030 over, new pistons, new rings, I did the run it hard and engine brake method of break-in. I have a serious blowby problem though, and only in boost.

Idling, I can feel some pulsing through the oil cap or the PCV tube off the valve cover. After a 10psi run however, the dipstick tube is up and before the pcv system was completed the oil cap liked to spit oil and I had a rear main get pushed out of the retainer. I do have the PCV system hooked up now though and running to a catch can and exhaust evac setup (which I'm not entirely sure is working properly, but my vband at the downpipe is also leaking). I also have a pressure gauge attached to the PCV system so I can see what its pulling. At idle its around 7-10" Hg (seems to have started reading lower lately, but I may have also cracked a fitting on the can, it'll be repaired tomorrow). At WOT the vacuum in the PCV system drops off to basically 0. There isn't a lot of oil in the catch can, the bottom drain cap is just slightly wet with oil, not enough to even drain out.

While idling the engine itself pulls 20" of vacuum, it spools a GN turbo (S70 basically) to 10psi by 4k and starts to boost around 3k. It doesn't really smoke at WOT or at idle. It drives nicely other than my idle misfire issue (randomly misses).

86shelby mentioned doing a leakdown test, which I will tomorrow hopefully. But does this sound like bad rings?

[turbovanman²]

It could be rings, a leakdown test will confirm.

[puppet]

What details of the rebuild can you offer up here? Methods, parts used (rings/ type & manufacturer, pistons & clearances used, hone finish, .. etc.) Break-in oil used ... did you then switch to synthetic? ... at what point?

Definitely do a leak down test.

[turbodaytona87]

What details of the rebuild can you offer up here? Methods, parts used (rings/ type & manufacturer, pistons & clearances used, hone finish, .. etc.) Break-in oil used ... did you then switch to synthetic? ... at what point?

Definitely do a leak down test.

This was from a couple of years ago so I'll do my best.

Pistons: NOS .030 over Clevites (cast, not hyper)
Rings: Perfect Circle from my machinist
Clearance: Instruction sheet that came with the pistons said the pistons were designed to have the cylinder bored .030 over and the pistons had the clearance built in.
Hone Finish: Not sure, the machine guy did it.
Assembly: Block was hot tanked, Rod/Crank journals were plastigauged, everything was torqued according to Chilton's guide, engine assembly lube was used, cylinders were oiled with regular oil before pistons/rings were installed, ring gaps were offset according to instructions included with rings (end gap was not checked), engine primed before starting
Break-in: Did some second gear pulls with engine braking back down the RPM range. The oil was changed right after the second gear runs and pretty frequently in the first few thousand miles for various reasons (oil pan gasket leaked eventually, front main leaked from the get go). I used regular oil for at least 1000 miles, then I've switched between synthetic and regular oil. I started using regular oil when the rear main was pushed out since it was going through oil fairly quickly. Engine has probably had 4-5 oil & filter changes in 5000 miles, and probably a couple more oil only changes.

[turbovanman²]

Only a leak down test will confirm,

[turbodaytona87]

I'm looking for less than 10% right?

[turbovanman²]

I'm looking for less than 10% right?

10% or less, yep, used engines will generally be around 10-20%.

[turbodaytona87]

#3 was about 35% according to the leak down tester (which was still on its low range).

The tester I used is the kind that you connect to an air compressor (with the compressor's regulator set to 100psi), then adjust the tester's regulator until the right gauge shows 0%. Then you plug in the hose that was screwed into the spark plug hole. The percentage the gauge shows then is the leak percentage.

There was considerable pressure coming out the oil fill hole. I tested #1 and wasn't using it quite right then, but it still had considerable pressure out the oil fill hole. So I'm guessing a rering is in order, or at least taking the engine apart.

My question is, why did the rings not seat well? I took it out and ran it hard at 7 psi. Both accelerating and letting the engine decel in gear to pull a lot of vacuum on the rings. Even people who drive on their new engines easily have less blowby.

[supercrackerbox]

Won't know for sure until you tear it down. You might have cracked a ring land or smoked a ring. You might even get lucky and find the rings just lost their temper and collapsed against the piston, like on my CSXT.

Was this your first engine build? The gasket and seal problems concern me . . .

[turbovanman²]

Could be bad rings, improper hone and ring gap-which is most likely the culprit as you didn't check that, and it could have been to small and they butted together. I just put my short block together and the rings were tight, like .005" tight, if I hadn't checked it, would have been a mess, Now file fitted to the correct gap.

[wallace]

What was done to the cylinder head when you rebuilt the shortblock? It could be worn valve guides also causing your crankcase pressure.

[turbodaytona87]

Adam- Yes, first engine build. Which gasket and seal problems are you talking about?

Wallace- Nothing was done to the head. I just ran it. That thought did cross my mind at one point.

[puppet]

Tested warm or cold engine?