Thread: Good engine mods for the 4.0 V8???

Going from my experience with my RRC you DO gain some power with a free flow exhaust but only at full throttle high revs. At cruise there is little exhaust gas backpressure.

By 1992 or so the manufacturers had worked out how to have a low restriction but quiet exhaust by increasing the volume of mufflers which flowed quite well at light throttle.
Look at cars now and you will see humungous mufflers for even 2 litre cars, as noise regs get tougher.

From what I have heard it is difficult to cheaply get extra power from a Thor as the Motronic is quite efficient, even sensing misfire by measuring the crank acceleration between firings. The knock sensors ensure that max advance is always there. I understand that the Thor always runs at Lambda so an afternmarket ECU may yield extra power at WOT, but you would lose the refinement .

However there is a question on the low comp engines as to whether they are tuned for 89 octane or 91 so an interceptor may be able to add some advance. I haven't spoken to Graeme Cooper about Thor piggybacks for a long time but sveral years ago they found it quite difficult to gain much.

So I tend to agree that a bigger capacity is probably best to increase power significantly.

Head mods will help but in my case yielded 6% across the board on a 14CUX and I think similar on a Motronic. I do not have a flow bench so it is possible that a professional with a flow bench may get an extra couple of %. I haven't yet matched and ported my Thor manifold as I was afraid of losing some of my low down power but I would think you may gain another couple of % there as AFAIR it was pretty sloppy around the ports and injector monts.
Regards Philip A

Thanks guys.
I hoped there was something magical and cheap to do but it doesn't sound like it? Will leave it alone for now i guess....

regards
Darian