More than a knock

[tonym]

Been restoring a 1979 Spider convertible 2000. Short history: Block had the deadly Aux shaft blowout hole so replaced it with used block. Had it baked, honed and surfaced then swapped out pistons, crankshaft and bearings which were in good condition. Cleaned all carbon off pistons. Replaced all rings (properly calibrated for clearance), front and rear seals, pilot bearing and plastigauged crankshaft and connecting rod clearances. Torqued bolts to spec. Head was in good condition but had it cleaned and valves re seated, surface checked and cleaned. They did a minor weld repair on one coolant orifice. Cams were all good and did not change seals and bearings on head. Put it all back together with new Midwest Bayless gasket but reused the cylinder bolts after soaking in oil and torqued to spec.

Fired up and ran well by Thanksgiving so went to work on brakes and suspension to get her road worthy. New Years Day, started up, ran for about 10 minutes to make sure thermostat and fan were working. Temp went up to 190 then a little past and started to hear a knock. Shut her down and pulled the valve covers to see milky oil. Since we had a cold spell in Florida, I hoped it was just condensation so I replaced the oil and rechecked valve clearances. A few were a little tight so adjusted the shims and all are now within spec. Did a compression test. Range of 120-150. Did a pressure test on cooling system. Held 15 psi for half hour.

Not sure what could have changed since first run. I did use 87 Octane gas. Tried retarding timing but no change. Now the knock is louder and is more of a banging sound. Doesn't seem to be on any particular side, just center and top side. Exhaust cam had slipped one tooth but that is corrected. I'm prepared to pull the head but wanted rule out any other causes before doing open heart surgery. I'll try to post a video but afraid to run her too long. Any and all thoughts and suggestion would be appreciated, this Forum is amazing.

[tonym]

Forgot to also mention that I disabled the mechanical fuel pump and installed an electric pump powered by the Revolution relay. Installed Aux shaft without cam lobe so no chance of interference ever again. Also, installed the 1800 Intake and DFEV carb and ditched all the EPA stuff.

[mscafide]

What weight oil are you using?
I use 50 in Florida. You might add a can of STP to bump it up.

If that makes it better you will buy a little time but it's time for rod bearings and probably main bearings too.

What's up with slipping a tooth on the belt?

Mike

[tonym]

Thanks for the response. Using 5w-30 with a quart of zinc additive. Will try the STP. Also will run some higher octane fuel. Tooth off I think was my not setting the top of the belt tight enough but could one tooth off cause a catastrophic problem? The 2L is non-interference in the cylinder. Could the knock be normal before the rings wear in? I would also drop the oil pan to have a look at bearings if it wasn't such a bear to remove.

[tonym]

Found the problem. Knock seemed to come from underneath so I pulled the oil pan. And oil pump and breather tube. Not fun. But #4 piston connecting rod bolts had backed out about 1/4 inch. Checked all four pistons and found #1 was a little loose. I had torqued them to spec, 54 ft. lbs.

Now the question is, how did that happen? And how to prevent it from happening again? I don't see any mention of using Loctite anywhere. Perhaps reusing the bolts was a mistake? Love to know before I set upon putting that oil pan back.

[wetminkey]

How did it happen? Unlikely that you'll ever discover.
Prevention is the key,...
My old '53 Studebaker 233 V8 had star washers, bent over the connecting rod and nut, to lock the rod nuts in place,...
And you can always lock a nut in place with a second one, or use a light-weight, stamped locknut.
I've not needed anything special to be done with my '79 2000cc. I hope you have good luck with your's.
Todd.

[tonym]

Thanks Todd. Despite all of the ups and downs, I've really enjoyed resurrecting this beautiful car. After more research, I'm thinking the problem is in bolt stretch and properly torquing in a sequence. I most likely stretched those two and didn't really have an accurate torque reading. Stretched bolt, loose nut, loose rod cap, loud banging. No room for second nut and some say the lock washer may also give false reading and worse, break off under stress. Tempted to put some Loctite on them all but that could also wreak havoc. See if anyone else weighs in. Probably should install new bolts and nuts regardless.

[tonym]

So I double checked my torque with a different torque wrench (needle and dial) and it seems I was under torqued. The Tekton click was indeed off. I also checked the cylinder head bolts and they were a little under too so my head gasket may have been leaking. Tightened it all up and putting it back together. Oil pump and pan are a royal PITA. Keep you posted.

[tonym]

Ran her tonight for about 15 minutes until thermostat opened. All good so far. Need to tune her up now. Lesson learned: use an accurate torque wrench.

[lanciahf]

Wow glad it worked out for you. Enjoy the car!

[Nanonevol]

Did you use new bolts or just torque them tighter? Just curious.

[tonym]

At $19 per bolt times 8 I torqued them properly. Pistons 2 and 3 were torqued right and were solid. I know, a little risky, but now I know the sound of loose rod nuts should this recur. Saving budget for a new hood and a two stage paint job.

[wetminkey]

Good to hear a successful troubleshoot and fix, tonym! Enjoy your Spider!
Todd.

[DieselSpider]

I still don't trust the clickers as I have found too much variation in them. Using my old reliable (bought it 45 years ago) beam and pointer torque wrench to check them for consistency I have found many to be way under or more often 50% or greater over.

[wetminkey]

I have also never trusted anything but my ancient beam torque wrench, DieselSpider. I think I got it when I worked at Sears Automotive in Fort Collins, CO, 1973. Always correct, easy to check.
Clicker is too high tech for me!
Todd.