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Discussion Starter #1
I'm posting this in FI because I think my issue is certainly made worse by FI.

I've a dedicated track car that runs on the zetec powerplant. I had recently bought a second built motor (my primary spun a rod bearing and spent some time at the machine shop) which has some issues.

The motor:
JE 9:1 pistons, eagle rods, massive speed ported head, crower springs and FI cams, ARP hardware. Running SVT JRSC BBK (slotted to fit the zetec).

The problem:
Running a road racing event this past weekend, for the first time with this blower (the motor ran two events previously very mildly boosted ~4psi) at full boost I found I'm burning about 1/3qt of oil for every 20min race session...so A LOT of oil. There was power but not as much as I would've expected from an M62 at full boost. I ran the weekend (~10 sessions) and burned through about 3 quarts. When I got home I ran a compression test with nothing obvious, but then I got to a leakdown test and it is when it got weird...

I ran the test several times on a warm motor (on TDC for each cylinder) and set the pressures at 5psi and then at 10psi (with everything connected). The reading by cylinder are as follows:

5psi
Cyl1: 28%
Cyl2: 40%
Cyl3: 25%
Cyl4: 40%

10psi
Cyl1: 1-2%
Cyl2: 20%
Cyl3: 0%
Cyl4: 20%

I didn't bother running much above 10psi since the readings drop off.

When connected to either cylinder 2 or 4, there's plenty of air leaking noise out of exhaust, at the throttle body and there's air flow coming out of the other cylinder (if connected to 2, air is coming from 4 and vice versa).

My question. Does this all seem like just a head gasket issue or should I be worried about the rings as well? I suspect that because I'm moving air from a cylinder at TDC to a cylinder that's got valves open, i may just be hearing air on exhaust and intake due to it passing that way rather than having valve issues. The main reason I'm asking is because I'm trying to figure out if I should be pulling the motor or if there's a decent chance just pulling the head will get me what I need. Any input / opinions much appreciated.
 

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Hey Pete! It's Denny, had to change my handle (long story!)

I'm pretty sure that leakdown has to be checked at a specified pressure, should be called out in the instructions with your gauge. I seem to remember most using 100 Psi input, and the pressure it holds corresponds to the leakdown percentage as the metered orifice in the gauge can only replenish the pressure so fast. I've never heard of using 5 or 10 psi for a leakdown test, part of the reason for using more pressure is that it does force the rings out against the cylinder walls, better simulating running conditions. Otherwise, your basically doing a compression test without using the starter.

To your observations, it would seem to me that if the head gasket failed into the water jacket on both 2 and 4, you could be having the sounds and leakdowns you are seeing, and the pressurization would certainly force a lot of oil out of your PCV/catch can. Let us know what you find!

Denny
 

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Discussion Starter #3
Hey Denny! Good to see you're around!

So yeah, part of the problem with the gauge is that i'm using a harbor freight one (yeah, i know) and they say to set the pressure such that flow gauge shows zero before you start (which is ~10psi). Cranking up the pressure any higher does not give me a reading. That said, just because of the sound and flow of air on the two cylinders i'm pretty sure there's a problem. I thought about leaking to coolant but dismissed it for two reasons 1) i'm not overheating - temps are holding perfect 2) there were no bubbles at all coming up through the overflow tank when doing leakdown, nor is the coolant looking brownish like it tends to after pushing exhaust to it. It looks like it might be busted to an oil valley instead. I'm pulling the head this weekend - hoping the head gasket is the only issue.

Cheers buddy!
 

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Pete, what did you find when you pulled that head?

I've finally got a handle on Advantage/PRP, car is running pretty well now! Drives real nice, just have to take it to a dyno to get the WOT set and see what numbers it pulls.

Denny
 

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Discussion Starter #5
Pete, what did you find when you pulled that head?

I've finally got a handle on Advantage/PRP, car is running pretty well now! Drives real nice, just have to take it to a dyno to get the WOT set and see what numbers it pulls.

Denny
Hey Denny, I found 4 cracked valve guides and some very light damage to the head gasket. Valves, springs, seats all look good. The valve stem seals looked ok as well, but they're getting replaced since the guides have to come out. The head is at a machine shop now getting the guides replaced and being checked for warping (and possibly decked). The guy at the shop didn't think the cracked guides would contribute to such a significant oil consumption so I'm pulling the rest of the block and taking it into another shop to have cylinder walls checked for clearance - there's no obvious damage on them so I suspect the rings instead...will see about that one. Meanwhile I'm going to drop my other block in so I can run the car. It's been a slow spring with this car since I joined a chumpcar team and been racing an old rusty 280zx crapcan.

Good to hear you have it running again. Would love to see the numbers.
 
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