Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Monty Takes A Deep Breath

To explore the blocked sports cat theory I've removed and inspected it.



I appreciate the photos are poor, but TBH the core looks fine to me, so maybe it's just my sports cat was always too small, here's what it looks like next to the standard Mk3 Mondeo cat Morgan fitted to Duratec Plus 4s making 145hp tops.



Given the above, I've been measuring and evaluating the original Ford oval cat's estimated internal envelope wich gives a massive 76% larger frontal area facing the yet to be converted exhaust gasses, it also has 15% more volume! I've also studied the cat Caterham use on their 420R and then compared the lot.


The Caterham cat is interesting as a 420R is known to make a genuine 210hp plus, moreover, Northampton Motorsport reports a 420R making 224.8 bhp with its original catalyst still fitted, but then 227.1 bhp with a de-cat, so what they're saying is the factory cat tops out at 225 bhp before it starts to become a restriction.

The evidence does seem to confirm Monty needs a cat that's at least 30% larger, or better still no cat at all, and it's now looking highly likey the sports cat was too small all along. However, I'm holding off gutting it as the only real proof it is genuinely a restriction will come when I run the back pressure test.

This kit should arrive from Temu Land soon, so before long we'll know for sure