carb help

[AlanH]

hi all, pretty new to the forum. i'm on building a c20xe powered nova. already have a 92 D.I.S. engine with loom, e.c.u. etc. and am wanting to fit twin carbs, either weber 40's or 45's. i basically want to know what i will need to buy/change and the differences between 40's and 45's as i dont want to lose too much fuel consumption. i know i need carbs, inlet manifold and 1 cam from a distributor xe but not sure on which coil, throttle cable, jets etc. to run and how i go about the remaining wiring/ e.c.u.

[AlanH]

bump

[Welsh Dan]

45's have a bigger hole in them for air to flow through, so they allow more air through, but it moves more slowly.

For the cost of buying and setting up carbs, you could buy and set up management for equal/better gains, and transfer the management to another engine in the future if you so wished.

[AlanH]

like what? set of bigger injectors, chip, adjustable f.p.r., v6 fuel pump and ported throttle body? i'm told carbs give a bigger power increase than all of the above combined but dont have much experience tuning c20's

[Welsh Dan]

By management I mean replacing the ECU with one that can be mapped to use with aftermarket cams etc.. It all depends on your budget but there's lots of documentation around for tuning the C20XE.

Ignore chips and adjustable FPR's.

Also bear in mind that just throwing on a set of carbs and having them setup wouldnt really see you much gains.

For "the works", consider having some headwork done (porting, bigger valves etc.. try www.autosprint.co.uk or a local engine builder for having that done. Some lairy cams will allow more power when combined with the rest that I'm about to list, but will require higher RPMs, in general, to get it. Which means that you'll need pocketed pistons to avoid valve contact, and ARP rod bolts to keep the conrods firmly attached to the pistons and crank. Add to that a set of individual throttle bodies, and some management to handle fueling and ignition (this is where a dispak engine is better as you can map the ignition timing).

If you dont want to go that far, consider a decent 4-1 or 4-2-1 exhaust manifold, coupled to a 2.5" system, and possibly some mild cams that will work with standard management.

[Adam]

Fuel consumption will suffer,badly, if you fit twin 45s.

How much budget do you have? Carbs can seem a cheap option initially, but end up costing more than throttle bodies. And dont give as good results.

[AlanH]

was initially wanting to spend around 5-600 buying and setting up carbs, although i did see a set with manifold pre-jetted for ?400, was gonna do that then fit cams etc. later when funds allow. throttle bodies are too expensive t.b.h. but might go for the cams/4-2-1 and 2.5" exhaust option for now, fancy fitting an arp bolt kit as i'm gonna hone the bores and fit new rings/shells anyway. what would you recommend as a start? as i wanna be able to upgrade the engine as i go, dont wanna take it off the road for too long so would like to get the heavy mechanical stuff out the way before i fit the engine. thanks for the help b.t.w, much appreciated

[Welsh Dan]

Everytime you change the engine spec, ie cams, you need to have the carbs set up again at circa ?300 a time.

[AlanH]

never thought about that one lol, fair point tho. think i'll leave it on injection system atm and sort everything else then consider changing fuelling