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Triumph TR3 - Engine Vibration

Have a freshly rebuilt TR3A engine that seems to have excessive vibration around 1400 RPM. The vibration clears about 1700 RPM. The vibration can be felt against your legs through the fenders and really resonates the hood and spring rod lift. The rotating assembly was balanced and the piston and rod assemblies weight balanced. The camshaft is new and of stock grind. The cam degreed in 1 degree advanced at build. Of course all new bearings, rings, pistons and sleeves. Static timing is dead on at 4degrees BTDC. Timing advance, centrifugal weights and vacuum operating. Idles like a champ at 700 RPM. Not a single miss at idle. Mixture is correct and confirmed with Colortune. I can only think of extraordinarliy stiff engine mounts or some undetectable frame crack at this point. Any suggestions or things to check?
Scot Stewart

Does the engine vibrate when you are driving ? Or does the vibration only occur when idling and reving the engine through 1700 RPM when stopped in neutral. Most TR3A hoods resonate between 700 - 1700 RPM when stopped at a traffic light. If this is the case, don't worry about it. I had it for years. The spring loaded hood "plunger" became worn on the outside diameter and the hole in the sheet-matal plate where the plunger is located became oval. I fill welded the shaft wher it was worn and turned it to the correct diameter. Then I welded a plate below the oval hole. This has helped, but I also put a black rubber "cap" onto the top end of the "plunger" rod. When I restored my TR3A 12 years ago, I pulled out the black felt fiber stuffing from the end of the hood near the hinges. I believe that this is meant to deaden the hood vibration.

Don Elliott, Original Owner, 1958 TR3A
Don Elliott

When driving, it's pretty quiet. The engine and hood go through a harmonic when passing through the 1400 to 1700 RPM range when driving and just reving. Growls as it passes through, both with the hood up and down. I have adjusted the rubber stops by the Dzus fasteners to decrease the stiffness when the hood is down, this helped a lot. I can feel the torque slapping into the motor mounts and frame right out through the fenders through that trouble RPM range. Can also feel a fairly high frequency vibration at 2000 RPM in the floor boards while driving, but all is smooth as silk from 3000 and up. Part or most of this is probably my unfamiliarity with the cars and never having driven one prior to this. The car was purchased completely disassembled and brought back from there. Since these cars were around ten years prior to my existance, I don't have anything to compare it too. Appreciate your time and thoughts. Do you plan on attending the British Invasion in Stowe Vt. this year?
Scot Stewart

Scott

As Don responded, I don't think it's anything to worry about, but one other thing to consider might be bent fan blades or the fan balance peice not being in proper position.
"Remember that if it doesn't vibrate it probably isn't a Triumph"

Don to miss the Stowe show? Not likely IMO! He's currently on route to Breckenridge, Colorado for VTR......... anyone who will drive 5000 miles to be with fellow Triumph enthusiasts surely wouldn't miss being at the invasion which is only a 100 mile jaunt for us Montrealers:)

Barry Shefner, 59 TR3A 0TS57675L
Maintainer of the TR2-TR4 Owners website http://www.rucompatible.com/triumph/
Barry Shefner

This thread was discussed between 06/08/2001 and 19/08/2001

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