Carb help needed please

[mudhut]

Hi all.

Nearly finished the temporary engine transplant I've been doing on and off all summer. Proposing to use the very good pair of Dellorto DHLA45 carb bodies came on the car but I need a starting point for choke, aux venturi etc etc.

The replacement engine is a good (I hope) standard beta lump with the same 4 to 1 exhaust as fitted to the car when I got it.

The 45s ran really badly on the tuned engine that came with the car and an authority on these engines was surprised it ran at all when I told him the jetting etc., so is there anybody running a pair of 45 carbs who can tell me their complete setup please so that I can actually drive it to a dyno?

My existing DHLA45 set up is:
chokes 38
aux venturi 8011.1
fuel float valve 1.70
idle jet 60
idle air 7850.1
main jet 150
emulsion tune 7772.6
air corrector 160
accelerator pump jet 42

I realise that the choke size is probably rather too large for a standard engine but would rather not have the expense of replacing them for a temporary engine.

Alternatively if anybody has the same info for a pair DHLA40 carbs, that would also be very useful as I already have a pair of these albeit in need of repair.

Weber data would be welcome too as I could translate this into a rough starting point for Dellorto.

Thanks.

[CorseChris]

Peter,

There is a jet size calculator on Dave Andrews' website... I'll post the link tomorrow but a Google may find it for you. The Westfield crowd (among many) reckon it's a good place to start and use it pretty often to good effect.

HTH

[mudhut]

Thanks Chris.

I already have this program and have tried it out although I've yet to implement its suggestions. Just wondered whether anybody had a known good setup they could tell me.

[CorseChris]

Ah, OK. Next idea you've probably already checked....Guy Crofts book? If not, yell & I'll have a look tonight.

[mudhut]

Thanks again Chris.

I've posted the same request on another forum and had this info too! I do not have GC's book (and it seems unlikely I'll get it at the price they seem to go for). For some odd reason, I never thought of this source of carb info - possibly because I've never even seen the book to know what is in it. Think I'll start there even though I'll probably need to ge hold of 36mm chokes for the 45s.

[CorseChris]

Peter,

Have you got the figures you need now Peter or should I have a look for you?

Saw a copy of the GC book go for $300 Australian the other day - madness!

[mudhut]

I have the data now Chris, thanks. The data provided was for a standard 131 2 litre on 40s and 45s.

Maybe I've missed something here - the jetting for both carbs was identical bar a small change in main jet yet GC recommends 32mm chokes in the 40s and 36mm in the 45s - not sure why so much difference here. Does he mention which auxiliary venturi to use - I don't have that info so I assume he did not provide it.

[CorseChris]

Hi Peter,

That is quite a jump. We ran 36mm chokes on a 1690 Xflow making around 140bhp and that was pretty good. 36mm isn't a limiting factor for taht capacity up to silly revs so would work well for a 2l. 32 is a surpsise, but then I'm certainly no expert and it would favour lower down torque.

I'll PM you with some info....

[CorseChris]

...soory, forgot - at first glance, he doesn't seem to mention them....

[Mark Cowling]

Hi Chris were the 36mm chokes in 40s or 45s if in 40s what was the throttle response like as it is close to the butterfly size for the venturi effect, something I am contemplating to try and save buying new carbs, PS what were you revving the crossflow to,Regards Mark.

[Mark Cowling]

PPS Chris what was the duration of the cam Regards Mark.