Suddenly no compression in #1 & #2 cylinders

[dleapon]

My 1981 Spider has been so reliable for years now so I decided to take it out for a local classic car rally and fall colours drive. We were out for about 20 minutes driving at 50mph when I noticed a drop in power and rough idling and some valve noise that seemed unfamiliar. I limped back home in ignominy. Here's what I've checked so far:

1. Checked for spark, all 4 had nice fat sparks. Also changed spark plugs. The old ones looked normal and similar to each other with some soot.
2. Pulled the injectors and all sprayed and shut off normally
3. I did a compression test: #1 & #2 were both 30psi while #3 & #4 were at 125psi.
4. Pulled the radiator to check the timing belt (changed 2 years ago) and the crankshaft mark with the camshaft marks and distributor rotor. All three agree.
5. Pulled the cam covers to check the cam lobes and tappets, they look ok.

At this point I think my next step is going to be to remove the head. Are there other things I should check before?

[18Fiatsandcounting]

Dan, based on your description, it sure sounds like you have a cylinder head gasket issue between the #1 and #2 cylinders. Unusual for it just to suddenly "appear", but it sure sounds like this is the issue.

I agree that at this point, it looks like a head gasket replacement is in the works. You might check the torque on all 10 cylinder head bolts and correct any that are too low, but this has a low likelihood of fixing the issue.

You betcha.

-Bryan

[dleapon]

Thanks Bryan. That's my suspicion too, that the head gasket blew between the cylinders. I'm going to try a leakdown test on #1 to see if I can hear a leak into #2 cylinder and visa versa.

Ya betcha right back at ya.

[SteinOnkel]

+1 for leakdown.

You could maybe also get a away with using a radiator test kit to pressurize the coolant system. If the needle on the gauge drops and you can't see puddles under the car, it's gotta be going into the cylinders.

That's just a suspicion though, I've never used that method before.

[dleapon]

Interesting idea using a radiator pressure test.

Though now I realize, to do a leakdown test I need an air compressor. Ah, more kit to purchase.

[Nut124]

With adjacent cylinders down, it is almost 100% head gasket. Any white smoke when you start it up?

[dleapon]

No white smoke, just the usual slight, blue tinged smoke. Also coolant and oil are clean and not mixed.

[SteinOnkel]

"just the usual slight, blue tinged smoke."

Nothing usual about that. Do the valve stem seals while you have the head out.

[baltobernie]

If your #1 and #2 spark plugs are normal in color, then you don't have coolant leaks there. Any coolant in the combustion chamber will result in "steam cleaning" the plugs to look like new. You might also check to insure you don't have any milky residue on the underside of the oil filler cap, which would indicate coolant going directly in to the oil galleries.

ps, If you find the need to replace any of your head bolts, I highly recommend Mark's head stud kit.

[dleapon]

I wanted some definitive proof of a blown head gasket. A knowledgeable friend of mine suggested I pressurize #1 cylinder while it is at TDC and listen for the cross leak into #2 cylinder. Problem is I don't have an air compressor. My solution was to use the compression test fittings and hose and blow into the open end with my breath. It worked, I could clearly hear and feel the cross-cylinder air leak.

Thanks everyone for all your tips and experience so far.

My plan is replace not just the head gasket but to replace the head with a reman one from either Vick's or Autoricambi. I've never been happy with the current head, it leaked oil constantly from the cam housing gasket and one cylinder spark plug thread had been poorly helicoiled so getting a good seat with every spark plug was a nightmare. I think the PO had rebuilt the head sloppily, so bottom line I don't have confidence in it.

[dleapon]

Just an update on the suspected head gasket...



Over the winter (as temps permitted) I took off the head and replaced it with a rebuilt unit from Midwest Bayless. A superb piece of work by the way, just beautifully finished. All the forum posts were super useful in helping me put things right. Along the way I had one terrifying moment when the timing belt tensioner spring bolt snapped with the remainder flush against the block. I'll be honest, I was nearly in tears at the thought of having to back that broken bolt out somehow. Then I ran my finger over the stub, felt it move, and with my finger nail on the tiniest edge of the break I slowly backed out the broken bolt. What a relief!

In the end luck was on my side and when everything was reassembled it started and ran on the first try! It no longer smokes, has more power and sounds like Lampredi twin-cam again (instead of a sewing machine).

Huge thanks for all the advice folks!

[tima01864]

Nice to hear

[Nut124]

Dan, glad to hear it's running again.

The tensioner retainer bolt is known to snap. Perhaps folks over torque it because the criticality of the tensioner.

I always replace the stud with a high grade full length threaded stud cut from a bolt. Then secure it into the block with thread locker before installing the tensioner.

What kind of a head gasket did you use?

[dleapon]

I replaced the bolt with one from Midwest Bayless since it has has the correct notch for the spring to seat.

(edited to fix img links)
Blown head gasket:


New head gasket was part of a kit from Autoricambi. I think the brand was Guarnitauto.

[18Fiatsandcounting]

Good to hear that you're up and running again! Bummer about the tensioner bolt, and I have to admit that I have yet to come across a broken one. Let's hope it stays that way!

-Bryan