New Project Help, Cylinder Head / HS4 Twin Carb

[Kojima]

Hi Everyone,

Im new to the Morris Minor scene, i have myself a 1966, 1098cc which is completely standard with all orginal parts.
So far ive fitted a new radiator, spark plugs and a couple of other bits, but now im thinking of doing a little more.

Ive been looking at the website www.minisport.com for a few parts since the mini's also used the a seires engine.

Ive currently ordered a HS4 twin carb and im planning to get a stage 5 cylinder head from them, also some 1:5:1 alloy roller tip rockers.

Can anyone tell me what i need to be looking out for and also anything regarding the parts im ordering.

Thanks.[frame][/frame]

[Neil MG]

WTF?

Well you did ask

Stage 5! Sounds like complete overkill on an otherwise standard car! Not really any benefit over stage 3 (or even 2) for street use!

Twin HS4 are also far too big for a 1098 engine, They can easily fuel a tuned 1800! There is absolutely no benefit in over-sized carbs! Twin 1 1/4 are already (well) more than capable.

To get the most of that head and carbs you will need a high flow manifold and exhaust system and also a suitable camshaft. Just make sure the camshaft is mild enough for street use otherwise it will be horrible to drive in traffic. You will of course have more induction and exhaust noise.

If you start to enjoy the extra power and torque you need to make sure your bottom end, gearbox and rear axle are in good condition and if you are going to be driving faster you might want to upgrade brakes and suspension. In fact you might want to do that first!

[Neil MG]

I was just thinking, (oh and sorry if I was a little harsh by the way) It sounds like you want some extra bolt on power and judging from your radical component selection that you would like a significant improvement?

A much better option may well be a supercharger kit, a bit more expensive but can be used with great effect on an otherwise standard engine. It would provide a lot more use-able power and torque while keeping the car smooth and practical to use!

I still think you need to improve the brakes and suspension, but no need to do anything radical. A disc conversion and front anti-roll bar would make a noticeable improvement.

[Stig]

I wouldn't bother with twin carbs, a single HS4 (or better, an HIF38) would give similar power for less money and without the hassle of balancing carbs. The important thing is to have an inlet manifold that isn't joined to the exhaust as the heat robs you of power - I'm assuming from your shopping list that power is what you're after.

Bigger valve head is a good idea, possibly with a slightly higher compression ratio (but don't overdo it unless you want to spend a fortune on higher octane petrol).

Although the 1.5:1 rockers will give a performance increase there are more cost effective ways, I'd go for a higher flow exhaust system first. If you take the engine out then changing the camshaft to an MG Metro spec is popular.

I'd also check the state of the bearings and bores before lavishing money on other bits.

That's the engine, but what about brakes and suspension? Are they up to the increased power?

[chrisryder]

what head is it you're getting? do you know the casting number? ie: 12G202, 12G295, 12G940?

as far as i was aware, stage 3 is extreme, and stage 4 is just a polished stage 3. is stage 5 gold plated?

if you're planning on putting a 12G940 head on a 1098 engine you may/will get clearance issues. especially if using 1.5:1 rockers as the will open the valves further and hit the deck of the block with a bigger clout. it has been covered on here at length about how to modify the block to take a 12G940 head.

twin carbs are pretty pointless. if you think about how the engine works, only one piston is drawing in air at any one time. so the carb only needs to allow enough charge in for one bore. if you've got 2 carbs, then you have each carb working less often, which will probably rob you of power as it's no longer a constant flow, but a stop-start sort of arrangement. (i've never been good at explaining things...). two carbs = twice as much tuning (and then the fun of balancing!), twice as much to rebuild/service, twice as much to buy in the first place (and the linkages so more than double!)

if you haven't already, get yourself a copy of David Vizards 'Tuning the A-series Engine' and learn everything there is to know about how to make power, and the best way of doing it. it wont really tell you 'buy this, this and this' but it'll give you the knowledge to make the right decisions yourself.

[chrisryder]

do you realise you can pretty much just bolt in a 1275 mg midget or morris marina/ital engine? they're stronger engines and can handle being tuned a bit better.

that stage 5 head: http://www.minisport.com/cgi-bin/sh0000 ... D1098_2eS5

looks rediculous for a road car. and is a small fortune. it does say 'for race or rally'. the valve sizes given could easily be achieved with a 12G940 head. just pick up a cheap second hand one (or a recon one from minisport for 1/3 of the price of the stage 5) and spend the money you save more wisely. on something like disc brakes! or a 5 speed kit.

[Kojima]

Hi everyone,

Thanks for the good advice guys, with regards to balancing out the carbs i have the equipment to do so on the way and funny enough the twin carbs just showed up this morning....so it looks like im stuck with them.

Ive looked into what i need next and such, and a maniflow exhaust manifold with a larger bore exhaust is next on my list.

An improved camshaft also sounds like a good idea, i was also looking into a escort mkII rear axle from www.jlhmorrisminors.co.uk. Plus a disc brake conversion with some gas shocks, i might try a front anti roll bar aswell.


I understand some of this sounds crazy and any advice is better than no advice, so please feel free to swear if needed.

[chrisryder]

we would swear if we could the forum tends to sensor us foul mouthed ones!

i've got a single HS4 on my 1098, and that seems plenty! getting two of them set up to get it to run well could be a nightmare of needle selections and spring weights. a rolling road would be a good start.

i'm a fan of anti-roll bars myself. although apparently the only reason i've had such good results from mine is that i've got 7 leaf springs on the rear as opposed to the standard (for saloons) 5.

you could always flog the twin carbs on. they may prove a bit more usefull on a 1275 set up. weren't twin HS4's found on 1275 mini's at some point?

disc brakes, gas shocks, and (something you haven't mentioned yet) poly bushes, are all good things to go for. poly bushes will take a lot of slack out of the suspension, improving handling and responsiveness, but trading off a bit on comfort and vibration.

[bmcecosse]

As others have pointed out - these carbs are FAR too big - send them back. (And HS4s are surely 'old stock' - the HIF 38 is far superior and displaced the HS4 many many years ago!). You want a single HIF 38 on a good alloy inlet. The rockers are a complete waste of time and especially money - don't do it! You also need to realise that a 1098 engine can only take a very limited amount of 'tuning' - and you MUST NOT rev it above 6000 rpm - or it WILL break. The so called 'stage 5' head is again way too much for a 1098 engine - but of course, some folks stage 5 is someone else's stage 3 !! You seem to enjoy wasting money like mad here.......... Is your engine in tip-top condition anyway ?? Most important to know this BEFORE doing any modifications. The JLH axle/brakes etc are well made - do all that work first before worrying about the engine......and the gearbox.....

[Kojima]

Okay guys,

Ive read most of the comments on here and they are all pretty vaild points, the best choice it would seem is to buy a standard replacement carburettor as the one i have at the moment is past help and start on the brake disc conversion and gas shock suspension and ... Poly Bushes .

I think i may go for my orginal idea of buying a good condition 1275cc and working on that with my wild and crazy ideas.

Would everyone agree that's a bit better? [frame][/frame]

[Neil MG]

You got it!

You will not regret that approach and you will be very glad that you took on board the good advice that you got from the guys on here!

It's a good thing you posted your question, you could have been headed in very disappointing direction!

[bmcecosse]

Actually - the biggest single improvement you can make to the car is to treat it to a decent set of wheels and tyres..........

[chrisryder]

here here, when i switched back to standard wheels while i got my minilights refurbed, it was horrible! on a motorway it was tracking all over the place (big ruts from lorries on the m42 by me) and the back end was hanging out on every roundabout that i used to be able to take much quicker!

[Kojima]

I've been looking at different wheels in the past and have really liked the look of a set of revolution 4 spoke's that quite frankly just look damn sexy.

My main goal over the next 3 to 4 years is to completely restore the original look of my Morris, restore every like piece of trim and chrome but give it the modern handling and engine that it deserve's.

I've also spoken to a brilliant gentleman who I was dealing with some time last year, who knows someone with a 1275cc that is available. And being the mechanical master he is, able to do hopefully pretty much every modification I can think of from rockers to crankshaft.

So I can only wait and hope. ;)

[bmcecosse]

There are very few wheels available to fit the Minor - you may be able to get Revos specially made to suit - and there may be some 13" ones around too. JLH often have good deals on suitable wheels and tyres for Minors. Ask them for a 'deal'!

[Kojima]

Ive heard about the issue with wheels before but didnt quite understand it, the ones ive found are in the picture below.

Ive seen these ones fitted to other cars in the past and also to a Minor as well. [frame][/frame]

[bmcecosse]

Yes - Revolutions - nice wheels, IF you can get them in the correct 4" PCD to suit a Minor.
And - 4" is definitely NOT = 100 mm!!

[Kojima]

Okay, these are the size's and PCD's i have to choose from, would anyone give an idea what im looking at?



Size PCD Offset Range mm Backspacemm Approx Weight kgs

5½x13" 4x3¾" +25 107 4.5

6x13" 4 hole 3¾" > 4½" +16 > +32 104 > 120 5.0/4.8

7x13" 4 hole3¾" > 4½" 00 > +20 100 > 120 6.0/5.8

8x13" 4x108(Gp4 only) 00 112 6.2

9x13" 4 hole 3¾" > 4½" -12 > +13 113 > 138 (Apr '10)

[Neil MG]

Seems like you're looking at lots of wheels that don't fit?

[bmcecosse]

As indicated already - NONE of these are 4" PCD. And therefore NONE are suitable for a standard Minor. I did suggest earlier that you would need to arrange for a set to be specially drilled for you to suit the Minor. 13" wheels look 'lost' in the Minor wheelarches - 14" is the standard size, but some folks fit 15" wheels and they look good too !