From the XJS-Help book:
WHAT’* IN A REDLINE?: Some people, probably accustomed to American pushrod V8’*, feel that the 6500 RPM
redline marked on the tach is really aggessive and far too high for an engine this big for everyday use. Nothing could be
farther from the truth; this is
not an American pushrod V8, it’* an OHC V12 with an unusually short stroke. Roger
Bywater, who worked in the engine development department at Jaguar when this engine was designed, provides a more
realistic understanding of just what that 6500 RPM redline is all about: “6500 r.p.m. is certainly safe and 7000 would
not be a cause for concern. In fact I know of basically standard 5.3 V12s cobbled together with second hand bits being
taken to near 8000 in race cars without suffering any problems at all. On the other hand an elderly engine does deserve a
certain amount of respect. I expect the one thing that would result is that the timing chain and tensioner would start to
show signs of distress a bit sooner if subjected to continual high r.p.m. In reality, there is not much point in revving a
standard V12 beyond 6000 because it will be running out of breath anyway and therefore won't be making much power.
Here'* where my heads come in. They're ported, polished, and so are the intake manifolds, throttle bodies, downpipes, and custom mandrel bent 3" intakes. The engine can now breathe, and with as simple as a vacuum modulator kit, I can crank up that shift point. I think 7500 RPM is what I'm going to shoot for. 5.3L V12 at 7500 RPM should sound downright sexy, and with 80% of torque at 2000rpm and a Turbo 400 with a 2.88:1 rear end, it should also be fast as hell.
I revved it right before pulling it into the garage one last time, at 4000 rpm, with nothing but downpipes on. I have a feeling the whole damn neighborhood heard me.
2005 Pontiac Bonneville GXP - For Sale ----- 1995 Buick Regal GS(X) - L67 madness
2000 Buick Regal GSE - Stock...for now
----- 1987 Jaguar XJ-* V12 - 12>8