#6----dead

Tadpole · 04-14-2009, 02:49 PM

Hi guys,

Quick update: About 3 1/2 weeks ago I had I asked about weber adjustments. You guys were a big help and I was able to get the running of the car alot closer, but it would still backfire thru the exhaust.

Using a Gunson colortune I was able to pinpoint that all the backfire was coming from the #6 cylinder.

Pulled all the plugs and did compression test.
#1---110
#2---110
#3---110
#4---110
#5---100
#6---0

Where I'm at now---Pulled the valve cover and found that #6 valves were way out of adjustment: .015 for the intake
.020 for the exhaust ( backside adjustments )
Readjusted the valves for #'s 4,5, and 6. Redid the compression test. No. 5 came up to 110 lbs. and #6 is still at 0.
So I put air into the #6 cyl. and heard air coming out the exhaust. Pulled the header and found that the exhaust valve will not close. Backed the foot the all the way off the the valve and it still doesn't close. What do I try now?

911pcars · 04-14-2009, 03:59 PM

The valve may have touched the piston and bent the valve head, preventing it from fully seating.

On the oft-chance a chunk of carbon is blocking full valve travel, using a mallet, tap on the valve end and see if that will dislodge suspected carbon and allow the valve to fully close. Okay, that was a long shot.

Compression is also on the low side. How many miles on the engine?

The next step may be to remove the head(s) and inspect, then perform an overall assessment of the engine factoring in compression pressure, miles, oil consumption, age, general engine condition and the amount of labor and parts needed to bring this up to spec. Compare with other engine options (rebuild, replace).

Best wishes for an economical solution,
Sherwood

Tadpole · 04-14-2009, 04:26 PM

Thanks Sherwood,
I know the numbers appear low. I was hoping that maybe the gauge is a little off. (real old gauge).Mileage on motor is around 109,000.
Looking thru the exhaust port I don't see any carbon buildup. Before I pull the motor to get to the head is it possible to pull the rocker and the spring so I could spin the valve in place to see if it is bent.

911pcars · 04-14-2009, 04:59 PM

To remove the retainer and spring, you must first remove the rocker arm. There's a special tool (About $40) to compress the spring and remove the valve retainer locks.

I wouldn't spend too much time doing that. The valve should be concentric and close/seal at any rotational angle. Does the camlobe for no. 6 rotate (i.e. is the camshaft still in one piece)? Perform all the visual inspections you can before diving into it.

Sherwood

Tadpole · 04-14-2009, 05:11 PM

Visually from what I can see, everything else seems to be OK. I guess I'm just going to have to bite the bullet and pull the motor out.

sixgun · 04-18-2009, 05:25 AM

Mike. the same thing happened to me recently. #5 was dead and when I pulled the ex cover I was rewarded with a bro0ken stud as well as the washer and nut. So I am in process of pulling my engine/tranny out to fix that. Hope you work it all out. Will update you on mine.
George in Ct.