Bad news on the Nomad

[MGVWfan]

I was driving in to work today, and suddenly (at idle) the engine seemed to drop one or two cylinders, and making an intermittant expensive-sounding clattering noise. Oil pressure OK, no holes in the case, no oil coming out the exhaust...

Fortunately, it was only a mile or so from the house. A friend and I towed it back, and now I'm trying to figure out what happened. I've removed the rocker shafts (to see if I've got a dropped valve), no obvious dropped valve. I pressurized the cylinders (with the rocker shafts out so valves SHOULD be closed), #3 and #4 OK (very slight leakage through the rings, normal when cold), #1 and #2 leak HEAVILY through the intake valves (air coming out the throttle body). It's been running perfectly, no oil burning, smooth, powerful, then this. Well, I guess I'll be dropping the engine to see what's up, probably two partially dropped valve seat inserts on #1 and #2 intake.

[vwbill]

Man, sorry to hear about the Nomad!!!! Dang! Better to pull the engine and do the work then try to do it in the car! But that still doesnt sound like what you wanted to be doing at this point!! Can you do a test with a compressor and blow air in the spark plug hole and listen for air? Did you get a reading on the compression?? Sorry again! I wish I had a spare motor seat up to go for you! bill

[MGVWfan]

Thanks Bill. I pulled the rocker shafts to close all valves, and pressurized the cylinders. #3 and #4 are OK, #1 and #2 are leaking from the intake, so based on the rest of the signature, it sounds like the right bank head intake valve seats are loose, and were jamming the valves at max lift, causing the valve head to hit the piston. With the rockers off, the seats are still not sealing.

I've seen something very similar in my old 1982 Plymouth Turismo 2.2L, aluminum head, steel inserts, and it's on its 3rd head now due to intake inserts dropping.

Man, I hope the pistons are OK, and I just have to do some (more!) head work.

[MGVWfan]

Oh yeah, here's a possible explanation for the clattering noise that came and went. I'll bet when a valve seat insert got stuck out at full lift, the rocker hitting the valve stem made the clattering noise, and when the valve seat went back down, it went away. I don't think the T4 valves are opened enough at full lift to hit a piston with 0.040" deck height (total)...

I sure hope it wasn't a valve hitting a piston!

I'll know for sure in a day or so, after I pull the engine.

[Bowman74]

Man, sorry to hear about the Nomad!!!! Dang! Better to pull the engine and do the work then try to do it in the car!

I'll second that. I pulled one of the heads off and replaced it while the engine was still in the car once. I'll never do that again. Much easier to drop the engine.

Thanks,

Kevin

[MGVWfan]

Hey, can you leave the AT connected to the halfshafts and still get enough travel on them to tilt the drivetrain enough to pull the engine from the AT? I don't relish the thought of removing those 12 bolts and bagging the inner CV joints again.

[raygreenwood]

Yes you can. It is actually easier on teh auto as there is no tail cone sticking through the rubber bumper donut. I would pull teh tranny rearward slightly though to keep from bunging up teh donut. Ray

[MGVWfan]

Thanks Ray. When I pulled the engine last, I pulled the whole thing as a unit, but this time it'll be engine only.

[vwbill]

Hey, so is your motor a 1.8L or 1.7L? So will you be doing the total rebuild or inspected and rehead? If the total rebuild. you gonna do the pics of the process???? Sorry that you have the motor issue!! bill

[MGVWfan]

It's a 93mm x 66mm (1.8L), was originally a 90mm x 66mm (1.7L) EA-code engine.

Unless I find piston damage, it'll be a top-end-only job...and yeah, I'm planning on taking pictures of whatever carnage I find in there , and the repair job as it comes along. The bottom end was completely redone (about 30K miles ago now, some 25K on the engine when I got it), and sitting 8 years didn't seem to affect it. However, if I lay me hands on some 1.8L domed P&C's... ...that might make me change my mind.

Anyone know if Japanese NPR's are any good?

[MGVWfan]

I got the engine out, and the heads off this week. Just a small ding on the crown of #2 piston (7cc dish), nothing serious. The valve seats were in there OK, though...hmmm! #1 and #2 intakes were pissing air out when I pressurized the cylinders, what gives? Well, I had to drive #1 and #2 intake valves out, they didn't come out easily...and #2 has indications of galling on the stem. It looks like the heads weren't set up with enough guide-to-valvestem clearance when the new guides were put in. I didn't check that personally, but now I know it's critical, so I'll be double-checking that clearance from now on.

I'm reading in the various service docs that something like 0.005" minimum clearance is required on the intakes, so out come the reamers! At least it's not like having a seat drop, I have the tools and expertise to ream intake guides myself.

Should be a quick fix, sometime this week it'll be back on the road. I even have a spare set of intake valves to work with, and the exhaust valves look good to go back in.

Any thoughts on optimum stem-to-guide clearance for T4 heads in normal (non-racing) use? Is 5 thousandths inch OK for intakes? What's a good number for exhausts?

[raygreenwood]

You noted a ding on the piston. You have valves that will not come out. You have bent valves. Check the cam as well. If it is not stock...there may have been too much lift.,...and as you note....not enough deck set into it. When the re has been contact between valve and piston...also check the gears on teh crank for looseness and dents. Ray

[MGVWfan]

Valve lift is OK, it's a stock-lift aftermarket cam. Also, I'm using OE-spec 7cc dish Mahle pistons in Mahle 93mm jugs, with a 0.010" base shim and a stock head gasket. The whole thing checks out at something like 0.030" deck height.

Yeah, the intakes are getting replaced, I don't trust a valve that's kissed a piston, even if it's just a "peck on the cheek".

I don't think excessive lift is the issue. From the clatter, and the fact that the valve stem had seized in the guide, it looks to me like a valve that somehow got just a bit too far open and stuck there long enough to just barely meet the piston coming up. The ding is very, very small, a lot smaller than the one I saw on my '82 Turismo when it dropped a valve seat (now how did that one kiss the piston, when MoPar 2.2's have tremendous excess deck height and positive clearance at full lift? I never figured that one out). BTW, the valves went into the guides when I got the heads like a nice trombone slide, which should have set off big red flags (that's not enough clearance, probably something less than 1/2 thousandths, not enough for oil to get in there!).

So, any thoughts on stem-to-guide clearance? I'd like to get this thing going, and I figure you guys (Ray!) probably know this one so I can borrow/beg/buy the right sized reamers to open the guides up a bit.

Oh yeah, I think I got lucky on the valvetrain...looks like it didn't push on a "stuck-closed" valve. I've checked the pushrods, no bends, the rockers, all intact, no signs of damage, and I'm pulling the lifters to check them and peek at the cam lobes to see if anything got messed up. I see Ray's point on checking the cam gear, if the valvetrain tried to open a "stuck-closed" valve, it might have damaged the cam gear. Any way to inspect that gear without splitting the cases?

[MGVWfan]

Well, after re-reading the material at hand, it looks like the "recommended clearance" (inferred from subtracting the min/max guide ID from the max/min stem OD) is 0.0022"-0.0047" intake, 0.0036" -0.0075" exhaust...so, how does that sound? On H2O cooled engines, 0.001"-0.003" clearances are normal, so 2.2-4.7 thou intake and 3.6-7.5 thou exhaust sounds reasonable for an air cooled engine, and a lot better than what I thought I read before.

Update on the lifters...#2 intake lifter has some very minor scuffing (circular pattern) on the face that wasn't there when I put it back together. And I found out why the valve got "extra" lift...the pushrod came out of the socket in the lifter, and got "pushed" by the unmachined area around the pushrod socket in the lifter, in the process dinging up the lifter. After looking at the pushrod end carefully, I can see damage from hitting the wrong spot on the lifter, argh!!! So, that's how the valve got opened far enough to hit a piston.

With this bit of wonderful news, I'm thinking I need to split the cases and see what condition the cam and cam gear are in. From peeking in through the lifter bore, no apparent damage to the cam, but I'd rather not be surprised again...at least lifters are available online, and cams and gears, unlike heads!

[MGVWfan]

I pulled the jugs just now, and the cam lobes appear to be equally shiny on both ends of the lobe for #2 intake, as well as all other lobes, no scuffing, so it looks like the damage is just one lifter dinged up, and one pushrod flattened on the ball end.

I'm wondering about the cam gear. There's no way to see it without tearing things down, and that's the only other thing I can think of that might be damaged by this incident (thanks for the reminder Ray). I'd hate to have damage there and not know it, but tearing it down is almost equally painful. Maybe checking for backlash all the way around (2 complete crank rotations) might do the trick...

BTW, the cam has "EP83" cast into one end between lobes...Webcam 83 grind?