1962 Triumph TR4 Restoration

Brian Sanborn, Groton, MA

The Engine Banging Noise Mystery

This problem deserves it's own page. I spent all summer trying to figure out why the engine would generate this banging noise when the pedal got down to the 3/4 level. I experimented with everything. After I eliminated something vibrating under load... like the bonnet stay rod, I started down the path of serious engine problems. Not a happy place.

I could make the symptom almost disappear if I retarded the engine timing by a big bunch. That convinced me that it was a worn distributor that was cranking up the advance and producing killer pre-ignition. I tried everything I could think of and all the advice I got from the list. I also took the car to a local very experienced TR restorer. Nothing worked including rebuilding the distributor with new advance springs.

I finally resorted to buying a new TRF distributor for $300. Nothing... same symptoms. Through all of this regular driving with the retarded timing the oil pressure in the engine was a concern. It was still there but not strong even with 20W50 oil. And, having solved the "not warming up" problem by installing a thermostat where there was none in-place.... I was seeing even lower pressure readings after a 30 minute drive with the engine oil at fully hot temperatures.

I started to believe, regrettably, that the problem was deep inside the engine. This was really nailed home when I took the car to Hartford for a car show. This is a 240 mile round trip with mostly interstate driving. The engine was not happy with high RPM high speed driving. It delivered but not smoothly. Lots of vibration above 3000 RPM. I thought it was from the retarded timing. But on the way back toward the end of the drive home, I became convinced that the engine needed a rebuild if I was going to be able drive the car for other than local putting around. The oil pressure was down to 30 lbs at speed and almost 10 lbs at idle. The transmission was also sending signals that lots of its parts where kind of worn.

When the engine cooled... the pressure was back up to 50-55 lbs... but would deteriorate when the engine oil got fully hot. I bit the bullet and decided to pull the engine this winter rather than wait until 1999.

 

The Answer to the Mystery

Have you figured it out yet? Well the answer will blow you away.

The puzzle was solved during the pulling of the engine. As we started to lift the front of the engine... we had to clear the rubber motor mount studs from the front cover of the engine. The drivers side was pried clear but the passengers side separated into 2 pieces. Staring me right in the face.... was a nice shiny metal half of the engine mount that would rap against the top half metal side.... all the rubber was gone. This would happen whenever the torque of the engine would "lift" the passengers side of the engine as the power was laid on. It also turns out that the rear mount rubber was all mush and not doing much of anything to keep the engine tied down. That contibuted big time to the vibration on the interstate.