I need some advice and help with Crossflow mods

[Robin Plummer]

Say I have a 1300GT crossflow engine totally standard.

If I get the engine rebored by + 0.060", skim the cylinder head by 2%. Fit 2 x Webber DCOE 40 carbs and inlet with K/N filters in place of the original carb with a 32mm diameter restrictor plate of 4mm thickness fitted.

Fit a big bore Silcener to the exhaust. And have the Con rods, Crank, Pistons, Flywheel and cluth cover plate balanced.

What will the estimated power increase be over the standard engine?

[Peter Mallett]

Robin,

What are you preparing the car for? With a restrictor it would appear to be for racing?

If so, have the rods and crank crack tested before balancing. Also shot peen the rods and tuftride the crank.

As to power increase, with that resrictor I doubt you will be looking at much.

[Robin Plummer]

The car is for Autograss racing Class2. Would it be better to stay with a single twin choke carb as the restrictor will limit power as you say?

[Peter Mallett]

Its the number of chokes which give you the volume. I would think twin carbs would provide more throughput than a single carb.

Presumably the original carb is a 38mm twin choke? Therefore twin 40s would be better.

Why the restrictor plate anyway? And does it apply to the single carb option?

[Robin Plummer]

The restrictor is required on the single carb. The trouble is, it must fit between the carb and the inlet so wether you have a 40,45 or 48 it allways get's narrowed down to 32mm.

[Peter Mallett]

Er,

Do the rules say you must retain the standard components in their satandar form? Or do they say you must retain the standard manifolds? If the latter there is scope for improvement. A little reaming may help

[yelwoci]

Since you seem to be starting from scratch,
You might want to do two things:
1.Crogenically treat the whole engine components, which will increase their strength and reduce fatigue.
2.Apply some modern coatings to the bores, pistons and time gear to reduce friction.

However before PM murders me(!) I must declare an interest,a s I started a Co.bringing this technology to Clubman racers!

I'll go and hide before the big bad wolf gets me!
:-))
IanC

[Peter Mallett]

Since you're starting out I doubt you can afford what Mr Col Yewi is suggesting. He does have an interest an its purely financial. GRRRRRRRRRRRRRRRRRRRR
If you want to find out more (and this applies to anybody who needs a rebuild) I suggest you e-mail Mr Yewi and spam his addy.

No Adverts here please

[Robin Plummer]

Peter, the rules state this

"1.10 Carburettor adaptor to restrictor plate and to inlet manifold free. Inlet and exhust manifold(s)free."

[Peter Mallett]

Hmmmm,

So. You can use any kind of manifold. You're not restricted to a number of chokes but all are restricted to 32mm dia.

Why not put two Weber 36's with reduced chokes. Match the inlets but don't make them smooth (a rough surface gives better fuel air mix). Match the manifold to the inlets on the head.

For the exhaust use a tubular four into one. Open and smooth the exhaust ports and match them to the exhaust manifold.