engine and drivetrain Poor Tii Burnt Valves

[tlapham]

So I have been driving my tii allover the place this summer, from the trip to waldo lake OR, across Carson pass to Gardberville NV and back at least 25 times to see my girlfriend, (my house 3000 feet, pass 7500 feet, her house 4000 feet.. over 50 miles one way. Plus a few times to san francisco and back. I have driven her hard. and she has taken it. like a dream. it hauls ASS. soo nice, only issue i had was some loose rear hubs in oregon, which was easily corrected due to a provedential parts source nearby.

 

I purchased her more than 2 years ago, with very little history. it needed a lot of tuning. seller knew nothing. not even that it had a 5-SPEED!!! I could tell the engine had been rebuilt, RTV sticking out of the timing cover, oil pan. I found it had a 292 shrick cam, lowering springs, pertronix, IE sway bars, fixed camber plates, battery in trunk. I ended up finding it had a small coolant leak into one of the cylinders. new head gasket and it was good to go. ran like a champ. I have been using Mobil 1 synthetic oil, until last oil change before the oregon trip, i tried out AMSOIL high zinc synthetic.

 

Today i had to drive to Oakland to take care of some business. (130+ miles one way) Business as usual. life in the fast lane.

 

Unfortunately, about halfway home this afternoon on the freeway, the engine suddenly lost power and made an awful racket. it sounded at first like it was pinging horribly if i had anything more than 20% throttle. I immediately pulled over thinking the distributor must have come loose. It would barely idle, and backfired out the intake. distributor looked good, all the plug wires were tight. looked it over and over. nothing changed. I tried merging back on the freeway. bad idea. no power. barely made it to 50 MPH on a flat road, and limped along. temperature started creeping up. I guessed it was burnt valves.

 

I made it about 15 miles to where some family lived. they had a timing light. I checked it and while revving, i could see the ball on the flywheel. it was close enough. I pulled the valve cover and found no issues. valve clearances felt normal just by rattling the rockers while they were off the lobes. there was no way i felt comfortable driving it the additional 60 miles home. Thankfully, I have AAA, and i called a truck.

 

I got home, pulled out the ol compression tester. #1  and #2 spark plugs looked good, pretty normal light brown. #3 and #4 were sooty and completely black.  #1 cyl, 90 PSI. #2, 75PSI. #3, 0PSI #4, 0PSI. WOW. really both #3 and #4 cylinders??  (engine was cold, cylinders dry)

 

How does this happen like that all at once?

 

I have never experienced a bad valve, wether it was burnt, bent, cracked, or anything... I am just amazed that 2 would go at the same time. plus cylinders 1 and 2 had such low compression. i tested it after doing the head gasket job 2 years ago, they were all above 160 warm...

 

Trevor

 

[GoFaSSter]

Sounds like a blown head gasket between the two cylinders. Happened to me at the beginning of summer.

[TobyB]

+1 for the head gasket- a leakdown will tell the tale in a heartbeat.

 

t

[tlapham]

Dang, I didn't even think of that. Thanks, i will look into that first thing tomorrow! I hope I didn't burn away any metal in the process...

[Mike Self]

When you pull the head, be sure to check the head mating surface for

(1) burn marks/etching between cyls 3 & 4 where the gasket blew

(2) flatness--use a steel straightedge--or have it done by the machine shop

(3) water passages that are under the exhaust ports--make sure there is plenty of metal between the ports and the edge of the combustion chamber.  They've been known to erode due to localized coolant boiling after shutdown (exhaust ports are pretty hot) until they break into the combustion chamber.  Match passage shape with that of the head gasket to check.

 

If you don't know when the engine was rebuilt, you might consider having the valves ground and valve stem to valve guide clearance checked (and replace guides if necessary).  Also use the later style valve stem seals--much longer lived than the original style. 

 

Yeah, I know it's mission creep, but while you're in there....

 

cheers

mike

[OriginalOwner]

 +1 head gasket.

 

 years ago my 6-cylinder Chevy engine ran perfectly, no missing, no idling problems, nice and smooth.  Seemed like I had less-than-normal power, so one day I did a compression check:  2 cylinders had zero compression.  Pulled the head:  burnt intake valves in 2 cylinders, all else normal.

   Hence, an engine can run just fine with bad valves under the right sort of circumstances, and you won't know it.

 

So your experience:  IMHO it's "gotta be" something other than valves when performance changes so drastically and so quickly.  Head gasket is the "obvious" culprit.

 

Cheers,

 

Carl

[bent]

Head gasket...  Ask Paul Wegweiser.  Funny thing is, he went through the same thought processes and actions when it first happened as you did.  However, we were all at the Vintage in NC last year and far away from home.  So trailering the car home was an option, but just replacing the gasket in the hotel parking lot was a better/faster/easier/cheaper solution.