Raised Bonnet Effect!

[Mase]

putting washers under the bonnet is fine just as long as it doesn't raise the bonnet higher than the little catch hook that is designed to catch the bonnet in an accident. So take it as high as that and your set. I've got an rb20det in my silvia/onevia. It's a must for getting the ridiculous higher temps out from the engine bay considering it isn't breathing as easily compared to being in the r32.

[whatsisname]

Raising the back of the bonnet may cause hot air to escape whilst the car is stationary, but when going along not air would come out that way.  Its possibly that cold air would go in that way, but probably not with all the air being forced in through the grill/radiator etc.

For a street driven Skyline I'd personally put more value in hot air escaping whilst stationary or very low speed (btw lights etc) over any potential heat reduction at speed.

On the road the inlet/water temps are "usually" at their highest whilst stationary, or at very low speed. If a simple/cheap raised bonnet reduces temps while stationary (or low speed) by a few degrees I'd say it's worth it, providing the bonnet doesn't become an accident hazard!