Rolling road time again

So we had a long afternoon at the rolling road, where we did runs with the GT supplied head and again after changing the later CR type inlet manifolds for the earlier CP manifolds, which have be machined out to enable the CR throttle spindles to be fitted. Ram pipes have also been fitted to the new manifolds to increase the inlet length.

Torque

Power

Blue run is prior to the head change, but still injection and CR inlets.

Green run is with the new head, but still injection and CR inlets.

Black run is new head and CP inlets and ram pipes.

It is clear to see the improvements with the new higher compression cylinder head, giving more power and for longer and the CP inlets giving an extra eight or nine BHP. The engine is still fitted with the relatively mild stock MkII camshaft.

Surprisingly the fuelling is still alright everywhere apart from idle, giving figures, if I remember right, of 3.8 to 4 over the rev range.

I've still a bit of fettling to do to get the inlets to match the ports properly as we were running out of time and I also need to consider making a cold air feed as it does seem to be quite sensitive to temperature.

I'm pretty chuffed with the results, it's all taken a fair bit of time to get this far and I'm sure there is plenty more to be done, but it has given me the ability to see the improvements and gains by fitting the right parts. Also interesting to see how much can be done with a stock camshaft, goes to show that some of them aren't all that bad.

I'll probably end up fabricating a custom air box to give plenty of space around the trumpets and have a couple of cold air feeds. There are air filter baseplates approximately 500mm long, which would be perfect for this, but the filters that fit onto these are around £125, so I may buy an un-drilled baseplate and fit my own box onto this and have filters in-line or at the end of the cold air feeds.