Fitting a pair os webers 40 dcoes in a racing head

[fjbm]

Hi

I have an engine head which has been prepared for racing and therefore it had the inlets opened to fit 45's carbs.

I want to fit this head to me fast road engine and fit a pair of 40 dcoe webers.

Will I have any problem if I fit them directly or should I take anything else in attention, as the inlet opening are bigger?

Thanks

[elans3]

I wouldn't be bothered at all fitting 40's to a head with inlets opened out to accept 45's, just make sure you use the very best Misab carb mounting plates and O rings.

I'd be more bothered about the compression ratio, and other aspects of your modified cylinder head. You say it has been prepared for racing, do you know exactly how ?

How much has been skimmed from the head surface, and how will that leave your compression ratio ?

Do you know the valve sizes ?

Have you aqcuired the cylinder head with known camshaft types ?

For instance, if the cylinder head has been modified to accept 45's and has a "racing" connotation, then the chances are that it has been run on a pretty trick bottom end.

Dependent on the answers to the questions above, (particularly if it has larger than Sprint valve sizes):-

For instance, if it has bigger than Sprint valve sizes, , radical cam profiles, and a very high comp. ratio, then you'll find that it may be very difficult to drive on the road.

My old hillclimb Elan was 1820cc, ran slightly bigger than Sprint valve sizes, had special Jim Evans profile "torquey" cams, and ran on 40DCOEs and gave a reliable 165bhp . But it also had lightened steel flywheel, forged pistons, Cometic head gasket, steel mains caps, and ARP bolts holding it all together. Because it had cam profiles selected for torque, and ran 40DCOE's, it was still pretty docile on the road, but a 1558 with lairy cams and high comp. ratio with big valves sounds to me as if it may not be easy to drive under say 4000 rpm.

Not teaching my grandmother to suck eggs here, but unless you really know what you have in the head you've bought, or you may end up being very disappointed.

Best regards
Steve
elans3

[bill308]

I think this post begs the question, can the inlet tracts be recontoured with a high temperature epoxy?

We're not talking about a true structural application here. Will an appropriate epoxy reliably adhere to the id of the inlet track when subject to heat cycling, gasoline, and vibration, for a long time.

Has anybody done this successfully?

Bill

[rgh0]

I have never used epoxy to build up a head myself but I have seen it used on a Hart racing head to fill in the holes created when the inlet ports broke through into the vlave spring pockets. I have successfully built up with welding in the inlet ports when this same thing has happened on one of my racing heads when i got a little to adventurous with a porting exercise once before I started ultrasonically checking in the thin spots.

cheers
Rohan

[AHM]

All things considered it probably wouldn't make much difference.

Personally I wouldn't use any "fillers" It is going to get Hot, cold, soaked in fuel, flamed, vacuumed, pressurised, and vibrate a lot - when the filler falls off it will also be expensive!

Welding would work ? I had a broken mounting successfully repaired ? but then you will also get a bill for the machining etc etc

Looking at the misab(?) plates you could file the inside off them which would get you down to a 1mm step i.e. almost nothing. Then spend the money on having the carbs set-up on a dyno.

Simon

[elans3]

I agree with Simon, don't worry about it. I've used 40DCOE's on 45 inlets for years without any issues whatsoever, like I said before, just make sure you use good quality Misab plates and the best quality o rings.
Steve
elans3