[amallagh]

Thankyou Paul, I found that very interesting.

The reassurance that 36mm chokes work well on 40mm throttles is good to hear, but I'm still not sure how the air speed in the 36mm choke is higher than across the throttle when the cross sectional area past the throttle valve is 8% smaller ?

I'd love to go down the bespoke throttle diameter route to get everything better matched for 36mm chokes but that option if too expensive for this projecct. The comment about going back to the 70.4mm crank is only speculative so not particularly relevant and the engine case was originally a 2.7S so the customer has the 2.7 crank anyway. The cylinders are cut down 2.7S.

So I think you are suggesting that 40s with 36mm chokes (or 34mm chokes) is maybe a better bet for this 2.5 compared to 36mm chokes in a 46.

Regarding your other suggestions about how to improve the transition -
- I think the PMOs have idle air correction screws so that is good
- I don't know how the PMO venture compare to the webers and whether they are taller ?
- Interesting what you say about full radius air horns. As you say, very surprising that that could have any marked effect. I'd just be using the big PMO ones which I'm assuming aren't what you mean by full radius.

Regards
Andrew