Retune after manifold change?

[eccles]

Whilst having the engine out to stick a dog box on it, we're sticking a new fancy, top of the range mainflow exhaust manifold on. the old one is a bit tired and been welded after cracking, and whilst on the phone to maniflow they recommended their new manifold which improves torque and is better breathing. it's similar to a standard lcb, but is more curvy, like a bunch of bananna.

i was wondering if the engine would require a rolling road tune afterwards?
my initial thoughts are it would, as if its better at breathing, it might alter the mixture, maybe leaning it off a bit.
its a full race engine, with a very well ported head, running split 45's on a maniflow inlet, pushing out 140bhp at last rolling road check.

any help appreciated.

[fwdracer]

You fancy it leaning the middle and (WOT) top end out in a full race engine?

Get it back on the rollers to confirm mixture set-up and timing. The manifold might may make no difference at all, but having invested in all that under the bonnet can you really afford to take the chance? I think a rolling road session is less than a fifth of a cost of that Dog-box...

Good luck and let us all know what diference it makes. These latest Manifolds are promising the moon & stars to everyone. Do they really work?

[eccles]

i think you're right, also its not been on the rollers for about 3 years (its a hillclimb car, so doesn't exactly do much in the way of mileage though), so a tune up won't do it any harm.
as you say, it'll be interesting to see what difference the manifold will make, the chap on the phone at maniflow rekoned to old one is strangling the engine, and that this new one will release quite a few more HP, and every little helps.

[wadgebeast]

Would have thought you'd have to do some tweaking to the mixture as it's bound to be leaner with a better manifold.

[wildoliver]

My local webber man would rolling road it and set the carb up for about £25 is it really worth the worry for half a tank of fuel?