U20 Engine Problems

[PandaBoy]

Was coming home last night from a fairly short run when the car started running a bit rough. Missing on acceleration & then about a block from home it really started sputtering then revving really high & making a lot of clanking noises in the engine. Turned it off & pushed it up the driveway & into the garage. Decided to wait until morning to try & determine the extent of any damage and my next steps.

Did a compression test this morning (cold) & found:
1 - 165
2 - 145
3 - 165
4 - 120

Then I removed the valve cover & found the following:

[fj20spl311]

Can't tell from the pictures, is the valve retainer on that exhaust valve lower then the intake. It might just be a broken valve spring. Something caused that valve to loose its adjustment. When the valves get way out of adjustment or very high RPM, they can lose the lash cap.

[SLOroadster]

Can't tell from the pictures, is the valve retainer on that exhaust valve lower then the intake. It might just be a broken valve spring. Something caused that valve to loose its adjustment. When the valves get way out of adjustment or very high RPM, they can lose the lash cap.

When I broke a valve spring on my head, I was turning 8K rpm all weekend long. Didn't know I had a broken valve spring till the day after. (I knew something wasn't right, but it made no horrid noises, and I didn't find the broken spring on the initial 3 looks while I was at the track.)

My guess is that the valve clearances were way off, and it tossed the lash pad, then the rocker. Double check your valve clearances, then check the rocker arm for damage, the lash pad for damage, and the retainer. If there is no damage to anything rotate the engine around so that the cam lobe is straight up, run the valve adjuster all the way down, install the lash pad, then the rocker arm (with the retainer spring) and and adjust your valves accordingly.

That said, I don't know that it will fix your low compression numbers on #4. I'd double check all your valves and retest. You should be seeing somewhere around 195 psi for a healthy engine. (run the compression test with the throttle wide open, and see what you get. It might be as simple as the throttle wasn't open that gave the low test numbers.)

Will

[theunz]

With low compression on that cylinder I’d be looking for a bent valve. The valve may have bent and not let the spring fully rebound thus creating excessive clearance on the rocker arm. Just a possibility.

[PandaBoy]

My guess is that the valve clearances were way off, and it tossed the lash pad, then the rocker. Double check your valve clearances, then check the rocker arm for damage, the lash pad for damage, and the retainer. If there is no damage to anything rotate the engine around so that the cam lobe is straight up, run the valve adjuster all the way down, install the lash pad, then the rocker arm (with the retainer spring) and and adjust your valves accordingly.

Valves were adjusted less than a month ago & the car was running well.
Should I drop the oil pan & check for anything visible from below?

[unklpat]

What did your valvetrain sound like lately, any ticking? The lash would have to be way off to let the lash pad come out of the cup. Was it a spirited drive? Maybe your adjuster wasn't tightened enough, and worked loose. Check your adjuster, and see if it's loose. That's my guess. Pat

[redroadster]

It can't be bent much with 120 psi but likely tweeked
Ya maybe the springs let go and tapped the Piston
Cars that set most of the time are known for slow valves too but you need to reassemble and compr test it that way

[Gregs672000]

I've had that happen before. Most likely the valve lash was a little too loose for whatever reason... the fact that you had the valves adjusted a short time ago suggests that it was the likely cause. One probably didn't get tightened down with the locker nut (19mm) and loosened up over time. As said, if you see no damage reinstall it as Will described. Your compression was low in #4 because the valve wasn't Opening! Regarding dropping the pan, no need... nothing bad has likely happened. Only other thing to inspect is that spring... look at it closely, but my guess is it's fine.

I run my valves at a tight 6in and 8ex COLD, they will be 8 and 10 hot. By tight I mean I can work a 6 in but not a 7, etc.

When this happened to me, part of the issue was that I was running a different cam and thicker lash pads, and was setting my valves 10 and 12 cold as the manual states, which results in 12 and 14 hot (manual incorrectly states they tighten with hotter temps, makes sense, but they do the opposite).

[unklpat]

I also adjust mine to 6 and 8 cold, and run .o4o over lash pads. No problem to 6k RPM so far over 6 months of driving. B cam. I also say run it, the noises were most likely the follower gettin beat up by the other valve, or the cam. Thanks greg! Pat

[PandaBoy]

Put everything back together & adjusted the valves to 6 and 8 cold as advised by both Greg & Pat. Car started right up & sounded good so I took it for a short run & everything felt fine.

Did a new compression test & found:
1 - 165
2 - 160
3 - 160
4 - 160

My only concern was that the spark plug was bent fully closed on #4 & I found the the following bits of metal in the Solex Air Cleaner Assembly.

Should I be worried? I took a longer "spirited drive" in the afternoon & even when pushing it everything felt great.

[rwmann]

Was the 'semi-polished metal' found in front of (outside) or behind (inside) the filter element?

[unklpat]

Did you happen to check the tension nut on that adjuster? I am curious if it was loose. Pat

[fj20spl311]

I don't know what those metal bits are, but it sounds like you sucked one of them up into the cylinder 4. It must of got hung up on the exhaust valve which allowed the lash cap to be spit out. I would suggest you check the cylinder with a bore scope to make sure the bit passed through the cylinder. Sometimes it can get stuck to the head or piston and break loose later. causing the problem all over again.

[unklpat]

The bent spark plug would support Phil's theory. Did you check the locknut on the tensioner? We all want to know, I'm sure.
Depstech makes a really inexpensive borescope, tiny camera, for about $35.00. It is 720p. You can connect it to a smart phone, or laptop, 16' long, with adjustable light. Pat

[Linda]

Supposedly Autozone has this bore scope as a loaner tool under their Loan A Tool program, good deal:
https://www.autozone.com/loan-a-tools/l ... ion-camera
Linda