Carb Upgrade

Post by **MrA.Series** » Fri Jan 16, 2004 11:54 am

Acording to David Vizzard, for a bit more power for a Minor, uprading from a HS2 (1 1/4") to a HS4 (1 1/2") carb is a simple and not so excessive way to go, and seeings as twin HS2s are more trouble than good if they are not already fitted to your car, I'm looking for a single 1 1/2" SU.

Are these HS4s?
http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... gory=43120

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... gory=43122

The second one looks like a reversed view one, like the one needed to make a twin carb set.

Also, can I use the original inlet manifold? Or do I have to get a large one/an adapter to make it fit? Did they produce HS4s with the same mounting plates (holes and such) as HS2s?

If so, I might just bid.

Cheers for any repleys

Post by **Cam** » Fri Jan 16, 2004 12:06 pm

Yes it is a HS4, and you will be better getting on old Mini 1000 manifold to use.

Post by **MrA.Series** » Fri Jan 16, 2004 12:12 pm

Cheers!

Do you mean original cast mini manifod with the outlet and inlet joined? If so, do I need to alter my exhaust system if I use one?

Post by **MrA.Series** » Fri Jan 16, 2004 12:13 pm

If I find a seperate mini inlet manifold cheap enough and use the exhaust manifold from the original Minor one by aid of a saw!

Hmm, If i get rid of the hot spot manifold heating by using separate manifolds, I'd better get a water heated one, yeah?

Post by **MrA.Series** » Fri Jan 16, 2004 12:21 pm

Is this the one needed? I know it's not heated, but I'll work that out later!

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... gory=43122

Don't look at the title and be fooled into thinking I'm a fool, it's an inlet honest!

Post by **Cam** » Fri Jan 16, 2004 1:55 pm

That would do. You need to blank the servo take-off off, but it would do the job. Besides which you don't actually need it water heated anyway that's just for a bit of extra economy and it can cause problems in really hot weather.

Post by **Kevin** » Fri Jan 16, 2004 6:18 pm

This would be a better manifold to use with a carb change
http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... gory=43122
You can as Cam says get the standard mini 1000 manifold and trim that down instead of the minor one as the exhaust side is the same diameter so the standard exhaust still fits and the exhaust side is supposed to be better than the standard Minor one and use that with a seperate inlet manifold, if you do decide to get that one I can always pick it up for you.

Post by **Cam** » Fri Jan 16, 2004 10:16 pm

Yes, but be careful! that manifold is for a 1 3/4" carb which is a bit much for a 1098. You would be better off with one for a 1 1/2" carb.

You can't tell exactly from the picture but it looks like the standard HIF44 manifold which is 1 3/4". If in doubt e-mail the seller and ask which it is.

Post by **Kevin** » Sat Jan 17, 2004 9:23 am

Whoops

, you are right Cam I should have mentioned that.
The other alternative is to get another cast mini 1000 manifold and cut the inlet of it, and the exhaust of your Minor one you will then have got rid of the hot spot, so that you have Mini inlet and Minor exhaust, or if you dont wont to touch the Minor one get 2 Mini ones and separate them instead, just play on the safe side with your hacksaw although there is plenty of metal to play with.

Post by **MrA.Series** » Sat Jan 17, 2004 11:14 am

I was thinknig of using the Minor exhaust with the Mini inlet, as I've got quite a few decent minor dual manifolds laying around. The major problem I've found is trying to get a 1 1/2" inlet manifold with the correct carb mounting face. I've seen SU HS4s with both a diagonally slanted oval mounting face, (like found on Webbers) and single manifolds to match. But I've also found out that the HS4 wasalso produced with a mounting face the same as used on the HS2 carbs and so I could just do a straight swop if I found one of them, but then the inlet part of the manifold would still be the original 1 1/4" Minor one.

Hmmm. I'll have to really think about this one!

Post by **MrA.Series** » Sat Jan 17, 2004 12:25 pm

I've found the original style HS4 mini dual manifold!

http://www.minispares.com/imagesbig/12G3279.JPG

Only problem is that it cost £105 + VAT !!!!!!!!!!!!

.....so I'm not goin to be stupid enough to buy it.

Post by **Cam** » Sat Jan 17, 2004 5:03 pm

If you scour the scrapyards for Minis then quite a few had HS4 carbs and water heated inlets fitted by 'boy-racers' just before the cars died! which is what you want really. Also to get an appreciable power gain (15-20%) then you would be better off changing the exhaust manifold for a 3-branch type and changing the pea-shooter exhaust system for something slightly larger in diameter (but not too large).

I'm not sure that changing the carb only would produce a noticable power difference especially if standard cast manifolds are used.

Best bet is to go for the 'stage 1' setup (HS4, alloy inlet manifold, 3-branch exhaust manifold and decent exhaust system) OR keep it as standard.

Don't forget also that the more power you extract then the more stress you will be putting on the gearbox, axle, brakes and suspension. You will probably be OK with stage 1 tuning but I would put some disc brakes on ASAP.

Post by **Matt** » Sat Jan 17, 2004 5:09 pm

and you reckon 15-20% more power with that??? sounds good!

Post by **Cam** » Sat Jan 17, 2004 5:25 pm

It's noticable but I'm not sure if all the hassle of fitting it as well as the upgraded brakes is worth it.

It felt OK when I did it but if driven properly the standard 1098 is not too slow.

Post by **Matt** » Sat Jan 17, 2004 5:33 pm

oh ok then! The standard 1098 seems pretty quick in 1st and second anyway..........

Post by **Kevin** » Sat Jan 17, 2004 8:21 pm

and you reckon 15-20% more power with that???

Remember that is only 7-10 bhp more as the minor only has 48bhp to start with, but think how much you want to spend as a 3 Branch & system will cost you at £200+

Post by **winger300** » Sat Jan 17, 2004 9:17 pm

Would the carb upgrade along with a 12G940 cylinder head be any better an upgrade?

the 3-branch exhaust system seems pricey, and they're very rarely on ebay going cheap (it going at all).

Post by **Peetee** » Sat Jan 17, 2004 9:23 pm

I would try the HIF44 with a suitable alloy inlet, the cut down standard exhaust manifold and stainless exhaust system. The stainless sytem will cost £50 and the carb and mani about £30 on ebay (with a bit of luck). Also on there currently are a couple of 12G295 heads and the very rare 12G206 which is just as good. I can thoroughly recommend these as effective power producing items. In fact the valve throats on a standard 1098 head prove much more of a restriction that a standard exhaust system so on a BHP per £ scale a oversize exhaust system is low on the purchace list.

Post by **winger300** » Sat Jan 17, 2004 9:35 pm

where can a stainless exhaust system be obtained Peetee?

Post by **Kevin** » Sun Jan 18, 2004 12:01 am

Dont use the HIF44 on a 1098 that will over carb it as its designed for the 1275cc engine use the HIF38.
Stainless exhausts Bull Motif £45:00, East Sussex Minors £49:50
MGM £53:00, Bath £59:00 all + VAT and all advertise in the club mag.
They are easier to fit as well being 2 piece rather than the single piece of the standard system.