The V8 Owners Forum -

john 215 wrote:Hi,

Just a idea, and not the most common option over your side of the world if even poss, but how about 1 3/4" HIF carb fitted to MG Montego's ( please dont laugh !! ) these were a blow through design and compared to the rest of the car were reliable.

Cheap too there a complete engine and trans on Fleabay for £ 50, unbolt the carb and weigh the rest in!

http://cgi.ebay.co.uk/MG-Montego-Turbo- ... 43a6c475d8

Cheers John

Postage to New Zealand might make that expensive.

And it's already been stated the only type of SU he can blow through is that design.

Yeah, the postage would be killer!

I wasn't ignoring the advice given to me. Just wanted to use those 2" SU's as I already had them, have been told they can be modified to handle positive pressure and I have bigger projects that my money is going into. I was always wanting to go EFI but I thought that it was going to be mega bucks as the EFI gear for RV8's is snapped up by the guys with trails trucks over here. Getting sorted now through a mate though so it's all good.

Look's like I've got that EFi motor sorted for a sweet price (less than two Montego carbs before shipping ).

Will throw away the standard ECU and go MegaSquirt with MAP

Win!

cammmy wrote:Yeah, the postage would be killer!

I wasn't ignoring the advice given to me. Just wanted to use those 2" SU's as I already had them, have been told they can be modified to handle positive pressure and I have bigger projects that my money is going into. I was always wanting to go EFI but I thought that it was going to be mega bucks as the EFI gear for RV8's is snapped up by the guys with trails trucks over here. Getting sorted now through a mate though so it's all good.

Look's like I've got that EFi motor sorted for a sweet price (less than two Montego carbs before shipping ).

Will throw away the standard ECU and go MegaSquirt with MAP

Win!

Sounds like a better plan

Think it's a 3.9 and not a 4.0.

Look's like the 4.0 had quite a few improvements over the 3.9 but have been told they had more liner issues (same bore though so not sure what the issue would be unless casting quality went backwards?)?

It's a 3.9

May have second supercharger sorted too

If you are prepared to put up with the looks, another way is to box the carb in and blow through the box. That way, the whole carb is running in the same ambient pressure and it is happy with that. All you need to do then is up the fuel delivery pressure to be higher than the blower pressure plus a bit to allow it to flow into the bowl and job done.
It will take some fabrication as the box needs to be totally sealed off from outside to maintain the pressure differential, but it does work.

Sorry, just saw this reply.

I now have an injected 3.9 so no longer need to use the SU's

cammy - sounds like an incredible project you are currently doing.

I was very surprised (and extremely excited) to hear about your project which is almost certainly the only other one of it's kind currently being considered on the planet....

I too have a 3.5l Low Compression Rover V8 running Twin SU HIF44 carbs. Perhaps more uniquely I am looking to supercharge this engine configuration by blowing directly at the SU's and letting them sit on the current manifold.

I've seen another thread elsewhere about getting the SUs to run under boost. Think you just have to do a bit of sealing but should be able to get away with avoiding to box the little buggers in. Also - mine are new so I want to keep them out and showing off their shiny dashpots

My plan is to stick a roots-type supercharger, possibly an Eaton M90 - off on a bracket to the side of the Rover lump. Perhaps easier said than done. Once in situ, to put some silicone hoses in play, with a Y piece, taking equal lengths of hose to the intakes on each of the carbs. On each piece of hose, just before the carb attachment, I'll be putting in some blow-off/pressure relief valves so that after a quick throttle shut, the pressure can escape before throwing the butterflies in the SU body into the engine!

The main things I'm concerned about at the moment are:

1. Fabricating sufficiently strong and practicable bracketry to actually mount the blower
2. The possible sealing issues with the SUs if my thoughts above prove incorrect!
3. Correct configuration of the blowoff valves
4. Carb tuning - how to adjust the SUs to ensure good fuelling under boost, i.e. terrified of going too lean! And do I need new needles capable of really pouring the good stuff in?
5. How much boost to generate. Don't want to go too nuts but need to calculate somehow how big a radius of pulley is needed so that I get the right Psi.


(Straightforward!) :p

Really look forward to hearing back from you. If you have any thoughts on the above then any advice much appreciated!

I've ended up getting a 3.9 EFI motor which I will be using. I have a shopping list and am now in the UK saving up money to buy everything and ship home. It will be quite some time yet before it all gets underway but it should do eventually

I did a fair bit of research into this and to be honest with you, I think your best bet will be draw through with a suitable charger. You won't be able to use an intercooler but the fuel will help to cool the charge and will tighten up the tolerances in the charger for a bit more efficiency. You'll still be able to show of your carbs, they'll just be bolted to the front of a supercharger.... which is still pretty cool

The chargers I have use electric clutches; EFI will be better able to handle going from vacuum to boost and it also means i'll be able to use an intercooler.