Dead cylinders 77 spider

[TheBreadMan27]

I have two dead cylinders (1 and 2) on my 77 spider. It looks like they haven't fired in a very long time. I have spark and fuel to it in all of the heads but can't get those two cylinders to work. My only guess is a blown head gasket but I can't find any liquids (gas oil or coolant) mixing anywhere. Going to do a compression test today to see if it's the rings completely shot

Thanks in advance

[Nut124]

Head gasket seems likely when adjacent cyls are down. But I would expect some while smoke, steam at startup from coolant leaking into the cylinders overnite.

Did you trace the ignition wires from plugs back to the distributor cap?

[TheBreadMan27]

I did and they are all correct, brand new wires and plugs all getting good spark

[18Fiatsandcounting]

A compression test will very likely point to what the issue is. Let us know what you find out.

-Bryan

[TheBreadMan27]

A compression test will very likely point to what the issue is. Let us know what you find out.

-Bryan

Compression test shows all the cylinders don't hold consistent pressure, looks like I need a whole new rebuild

[Nut124]

What kind of compression numbers did you see? Were #1 and #2 lower than the rest?

Was throttle fully open?

[TheBreadMan27]

What kind of compression numbers did you see? Were #1 and #2 lower than the rest?

Was throttle fully open?

Yea throttle was all the way open. Cylinder 1 didn't even move the needle, 2 got about 50 but bled down, 3 got 90 and bled down and 4 got 130 and bled down

[18Fiatsandcounting]

Compression test shows all the cylinders don't hold consistent pressure, looks like I need a whole new rebuild

Definitely sounds like you need to pull the head and see what's going on, Breadman. And maybe the block, but if it were me, I"d start by removing the head. It could be as simple as a valve job or bad head gasket, and if you weren't burning oil beforehand and the oil pressure was good, the bottom may be OK. But, some people find it simpler just to pull the engine and do it all at once. Your call of course.

And, like Nut124, I'm curious what the compression numbers were. Anything less than 100 psi is bad, especially if two adjacent cylinders are very low. 120 psi is "OK", but I usually look for 140 to 150 psi in a stock engine. Consistency across all 4 cylinders is more important than absolute numbers, unless all cylinders are very low.

-Bryan

[18Fiatsandcounting]

Yea throttle was all the way open. Cylinder 1 didn't even move the needle, 2 got about 50 but bled down, 3 got 90 and bled down and 4 got 130 and bled down

OK, thanks for that. Most compression gauges have a check valve so once the pressure reaches the maximum, the needle stays put. Are you sure your gauge is OK?

That being said, it does sounds like cylinders 1, 2, and 3 have issues. Time to pull the cylinder head, or the whole engine if you're so inclined.

-Bryan

[TheBreadMan27]

Yea throttle was all the way open. Cylinder 1 didn't even move the needle, 2 got about 50 but bled down, 3 got 90 and bled down and 4 got 130 and bled down

OK, thanks for that. Most compression gauges have a check valve so once the pressure reaches the maximum, the needle stays put. Are you sure your gauge is OK?

That being said, it does sounds like cylinders 1, 2, and 3 have issues. Time to pull the cylinder head, or the whole engine if you're so inclined.

-Bryan

Yea going to check the valves first and see if they are adjusted correctly. Also it's a brand new compression tester but it is acting weird. Regardless if the valves are correct then I probably will pull the head and check the gasket, the previous owner changed at least the intake and exhaust manifolds and put on weird gaskets so who knows what else has been done incorrectly. Thanks for all the help!

[davidbruce]

Breadman, is the car new to you? Have you had this engine running? If so has anything else changed other than new ignition pieces? Did you check the cam timing to see if they are off and you have valves open at the wrong time? If so there may be 1 or more bent valves that aren't closing. Knowing if it was running, how well and what has changed would go a long way to helping you diagnose this. Your comment about weird gaskets makes me wonder if the head gasket is correct for the engine or if the PO was a Bozo he may have reused a gasket or any number of creative fixes.
Cheers
Dave

[18Fiatsandcounting]

Given this new information, I totally agree with Dave. There could be a number of "mistakes" made by the previous owner, so I wouldn't assume anything is correct at this point.

-Bryan

[TheBreadMan27]

Okay, to those who are curious this is what I've found (sorry it's been a bit) I took the head off and the head gasket is basically brand new and so are some of the other gaskets. The thing I found the most wrong is none of the shims are correct, not even remotely. The cylinders all had too big of shims so a lot of the valves are always open no matter what. My guess is the PO took off the cams and mixed up the shim cups. I ordered new shims to make them correct and cleaned everything else up. Nothing else looked wrong or bad so once I have shims I'm going to re-do a compression test to check my piston rings but it should all be good now. Thanks for all the help

[18Fiatsandcounting]

The cylinders all had too big of shims so a lot of the valves are always open no matter what.

That would explain things, Breadman, and thanks for letting us know. The valves might still be OK since it sounds like the engine didn't run very long in this condition, but still, you might want to inspect the valves and their seats to make sure they didn't get toasted. If they are, you might need a valve job, which would mean.... wait for it.... New shims!

-Bryan

[Nut124]

Okay, to those who are curious this is what I've found (sorry it's been a bit) I took the head off and the head gasket is basically brand new and so are some of the other gaskets. The thing I found the most wrong is none of the shims are correct, not even remotely. The cylinders all had too big of shims so a lot of the valves are always open no matter what. My guess is the PO took off the cams and mixed up the shim cups. I ordered new shims to make them correct and cleaned everything else up. Nothing else looked wrong or bad so once I have shims I'm going to re-do a compression test to check my piston rings but it should all be good now. Thanks for all the help

This something that could have been diagnosed w/o removing the head, with a feeler gauge. Removing the head is not a minor job.

How did you figure out what shims to order?