[MrEos]

Out for a drive and was getting on it a bit... fun while it lasted. Lost power - like it was out of fuel. It still ran, but like it was only on half the cylinders. The only other clue is a rhythmic clacking (louder than a click, less than a knock) that seems to be coming from the timing chain cover (using the rubber hose stethoscope). Idle is rough.

I checked the timing... same as it was before - at least at the pointer/dampner. Checked for vacuum leak/hose knocked off (nothing found).

My diagnosis so far is: 'this is not good.'

Ideas? Things I should check?

 

[Harvey]

First thing I would do is a compression test. How hot was the car running? Shooting in the dark but had that happen to me before and it was a piston with a hole burnt in it. I was staying on it way to long. Everything else was fine but that piston was shot! I know you didn't want to here that.

 

[Bad69cat]

Could just be a valve issue as well....yeah a quick compression test would be usefull if you don't have other obvious symptoms like backfiring or something. At least it's not a knocking sound like something wants out! Doesn't sound catastrophic at this point at least - that's good

 

[towcat]

Check fuel pump arm, or maybe the fuel pump cam.

 

[CougarCJ]

Check fuel pump arm, or maybe the fuel pump cam.

I am leaning this way, too, on this problem.

 

[Bad69cat]

That would make sense on the rattle where it's at ..... hope that's it!

 

[xr7g428]

A few things to look at...

Check to see if the linkage for the vacuum secondary is still attached. Check to see if the throttle plates are opening all of the way. Fuel starvation kills it after you have had your foot in it but it will recover at idle. Does it haul butt and then fall on its face?

 

[Royce Peterson]

You can remove the fuel pump and look in the timing cover to see if anything is wrong there. Sounds like the chain jumped time. I wonder if you have an original nylon toothed timing gear that finally disintigrated? Has the engine ever been rebuilt? If so was a modern timing set used or did someone strive for "authenticity" by using one of the rotten original timing sets?

 

[MrEos]

Thanks for the suggestions. I had already started the process of checking compression... but ran out of time before I had to shift out of holiday weekend mode. Getting #7 & #8 plugs out is a chore unto itself. I pondered whether a flexible extension exists, and indeed it does (

flex extension). I think I'll get one for putting things back in. Hey... it isn't a job unless you buy a tool half way thru it. Anyway, only got three cylinders tested, and they were 170 +/- 2.

Bill - I'll check the carb, but I didn't get power with pedal. Got that ffwup, ffwup, ffwup engine sound and rpms stay low. I didn't run the engine much after this happened.

Royce - the engine was rebuilt 2 owners ago (but never installed to my knowledge until I got it). Unfortunately my seller didn't know any of the internals and had no paperwork. Pig in a poke. Hard to believe that someone would spend money to rebuild and put in one of those failure-prone chain sets. I also tell myself that it would be silly to have not put in hardened valve seats. I'm great at self-delusion. I should of torn the thing down when it was out.... woulda-coulda-shoulda.

Others who mentioned fuel pump. Given the clack from that area, you may be unto something. It is still pumping fuel (into a can right now as I do the compression check). Easy enough to pull the pump and take a look see. I'm going to finish the compression check and do that next, and see how the chain looks. Probably won't get to it until the weekend tho.

 

[polanskys]

You should also look for a broken valve spring, although the location of the sound suggests a tiiming chain or distributor issue.

Steve

 

[MrEos]

Finished up the compression test. Pressure is lower with engine cold, and they all fall within a few psi of 150. I rechecked one that was at 170 warm, and it was 150 cold. So, I guess this rules out a hole in a piston and (am I right?) bent valves/broken valve springs.

Going to take off the fuel pump next.

 

[Harvey]

Good news on the compression test. Will be very curious as to what you find on the fuel pump. That one had not crossed my mind?

 

[MrEos]

Timing chain looks to be a double roller. Tight. No damage from what I could see thru the fuel pump hole.

The fuel pump arm has no visible damage/defect. It is polished where it rides against the eccentric, but I assume that's normal. It isn't scored and I can't feel anything with a fingernail. Eccentric doesn't have any obvious damage either, also looks polished.

Since I'm not sure what "normal" is here... can someone clue me in on the following:

(1) The fuel pump arm has about 1/4" of free play before it becomes harder to move and you can hear the diaphram (pumping air since gas is drained out). Is that "normal." The free play can be moved with one finger; once diaphram engages, it takes whole hand pressure to move it.

(2) The front of the cam/fuel eccentric seems to be right up to the inside of the timing chain cover - probably only a 1/16th inch clearance. Normal?

Any suggestions what I should look at next?

 

[MrEos]

Thinking out loud... does a wiped cam lobe(s) seem plausible? I'd think that would happen sooner than now, but I was at a pretty high rpm when the problem developed. I s'pose I should take off the rocker covers next.

 

[Bad69cat]

I think you would have seen a fair amount of compression diff if that were the case - nothing sounds to out of the ordinary so far...? If you don't have any fuel in your oil the diaphram is OK...hmmm I wonder if the problem is in the dizzy then...? Something whacked on the advance perhaps? Any excessive play (up/down/sideways)? Wondering if the gear is ate up and rattling through the teeth/slipping?

 

[xr7g428]

Sounds like an ignition problem to me. What are you running?

 

[390XR7]

Maybe cam retainer plate broke and cam is "walking" I had it happen on a 351W motor.maybe pull the timing cover off and see what's happening up front.

 

[xr7g428]

You hardly ever see good compression with a bad cam. What does the vacuum gauge show at idle?

 

[MrEos]

Sounds like an ignition problem to me. What are you running?

Stock ignition except Pertronix II (with 12v feed). I looked under the distributor cap and saw nothing out of order there.

I've always been a little leary of the vintage yellow-top coil, for no reason other than age. I'll test that as that seems plausible given the symptoms (except for the clack at timing chain cover).

You hardly ever see good compression with a bad cam. What does the vacuum gauge show at idle?

This is a whole 'nother story. Because I bought the engine as a pig in a poke (as mentioned above), I don't know what cam it has, but suspect it is 'bigger' than stock. Before this problem, I never got good vacuum, and had to install one of those supplemental vacuum reservoirs for power brakes. As I recall, I was getting around 10" vacuum at idle. I didn't check it after this problem developed, and can't until I put things back together.

My thinking on cam lobe wipe was that cam opens the valves... so I'd still have good compression but would lose power to that cylinder. Not sure how to tie that in with the timing cover clack... but again, just thinking out loud by a non-mechanic. Also thinking this because (again) I don't know anything about the rebuild of engine, whether properly run-in, how long it sat after rebuild, etc.

 

[mopardon]

How is your oil pessure. If it dropped your lifters will not pump up.