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WHAT we’re doing, and HOW we’re doing it!

October 12, 2026

If some is good, then more must be better, right? This is the front main bearing cap from a TR4 engine that we just tore-down for rebuild. The arrow shows that one of the main cap bolt heads had snapped off, which explains the loose part noise we heard when turning the engine upside down on the engine stand. There was another one in the exact same condition on the rear main cap as well. It was easy to see that these were not original bolts, both here on the mains as well as the connecting rod bolts. Decoding the markings on the heads, we determined that these were rarely seen Grade 9 fasteners. In fact, our machinists Pocket Ref had no specs shown for Grade 9, but we found tensil strength numbers on the McMaster-Carr website. Normally, Grade 8 is about the strongest bolts you can find. The numbers we found show a tensile strength of 150,000 PSI for the Grade 8, and 180,000 PSI for the 9’s. More strength should be better, right? Obviously not in this case. Perhaps these bolts failed because they were made from the wrong steel, or maybe they were just a touch long and bottomed in the hole, leaving just enough clearance for the cap to walk (wiggle) and eventually snap the heads. Whatever the cause, you can be certain that none of these Grade 9 bolts will be going back into this engine now! We’ll use ARP main and connecting rod bolts, proven to be the highest quality fasteners available for holding an engine together, even a lowly 4-cylinder Triumph motor.

October 5, 2026

Lower dash supports (consoles) for the TR4A-TR6 have usually been modified several times to fit various radios/stereos over the past 50-60 years, so it’s not unusual to find one with little left to install yet another radio into. The fix in these cases is to cut out the butchered area, and TIG weld a new piece of 1/8” aluminum into the opening to completely fill the hole. Next we will cut out and drill the perfect opening(s) for the latest radio to be installed, and recover the entire support with an appropriate cover from one of the usual TR parts suppliers.