JD Erisman
Well-Known Member
I wasn’t sure where to post this issue, it could potentially cover many different areas. I am having a vibration problem in my ‘67 notchback Barracuda that is getting worse, bad enough that on the highway, hard acceleration, the 3,000-4,000 RPM and up it is causing the steering wheel to grossly vibrate. About 200 miles ago I had a 408 short block assembly put together and shipped to me, I have only one local machine shop, owned and operated by meth addicts so I will never use them and having this reputable shop build it was my best option. They balanced it (now internal balance), all forged internals, main cap stud girdle, timing chain tensioner; I installed Trick Flow 190 heads, Edelbrock Pro Flow 4 EFI, B&M flexplate and a Fluidamper (for the first time), both for an internal balanced small block Mopar, I’m using adjustable rockers (for the first time), Hughes 228/232 hydraulic flat tappet cam and Mopar performance lifters, custom length Smith Brothers push rods, I have a Dynamic Converters 9” converter with 3,000 stall, and I installed Mancini racing Mag Mount engine mounts (another first time). 8 3/4 rear with 3.55 Sure Grip. Installed a stock Mopar engine-to-tranny brace on the driver’s side (first time ever using those), passenger side wouldn’t fit due to TTI headers. I installed 15x10 Wheel Vintiques steel wheels and 265/50/15 tires in the back, checked for clearance. This is only the 7th or 8th engine build I’ve done, first time having a shop build me a short block, but I’ve never had a vibration issue. I feel it at practically all RPMs, but it’s getting worse, especially at higher RPMs, and in all three gears. I’ve also noticed the exhaust “sound” is not like any of my other small block Mopars, it’s just off but I cannot explain it and whether it’s related to the vibration I cannot see how unless the issue is somehow related to the internals. When I did the engine break-in I followed Hughes guidelines then I drove the car slowly around my neighborhood. For the first 30-60 seconds, maybe more, it seemed OK but I could feel the vibration slightly. Then I heard a loud thunk, thunk, thunk... that increased with RPM/speed (in both first and second gear). The thunk, thunk went away before I could circle back home, about a five minute total drive time. I checked the pulley alignment again, just because the Fluidamper is thicker than stock to make sure the damper was seated all the way in, it was. I again checked the flexplate to converter bolts, all tight (when I installed the converter originally I made sure it was seated all the way in). I checked the lug nuts, tires for rub marks, tranny mount, bell housing bolts, and engine mounts. The only thing I can see that looks different or appeared “wrong” was the driver’s side engine mount; it looks squished on the forward side (I’ll try and post a picture of it). I cannot see how most of the parts I’ve put on could cause such a strong vibration and the engine would have to have been put together really incorrectly, I think, to cause so much vibration, and I doubt they built the short block incorrectly. One issue came up when I installed the motor: I’ve never had such a hard time lining up the mounts to the K-member, it took hours to get the engine installed, I eventually had to drop the tranny down and backwards then still had some difficulty getting the engine in and I could not get the drivers side mount stud to sit any higher than the very bottom of the K-member mounting slot, which caused me to shim that side twice as thick as my previous 360, to clear the headers. Before I start tearing everything apart I’m hoping I’ve described it enough to get some ideas or input from all of you, thanks for any help.
