998 Build Spec - Carb, Cam, And Other Questions

Mini Technical Sections Problems, Questions and Technical
1

So I’ve been playing with an old A+ engine and have decided to do a complete rebuild.

Currently I have quotes for an engine reconditioner to wash, rebore +060, regrind and balance crank 010/010 and flywheel, machine pockets in block, new cam bearings, and fit the new pistons to the rods.

The spec I am currently building is:
Hypatec +060 dished pistons
New camshaft and change to slot drive oil pump
Late model 12G940 head with some porting and unleaded inserts

The questions I have at the moment are cam, carbs, clutch, and machining, and any other suggestions?

I am trying to get a MD266 but it’s proving to be a little elusive. Is this the best for my set up? (road use, want a nice driveavle car with a bit of get up and go when I want to play)

I currently have the standard carb on the engine in my car, i assume it is an HS4 but haven’t actually measured it. Will a single HS4 be sufficient for this build? Would twin HS4’s be better? Those are my two options really. I have a minispares alloy single manifold to go on but could be convinced to order a twin manifold if it was deemed worthwhile.

Will the standard (new but standard) clutch be sufficient, or should I really be looking to get one of the competition ones? (Orange? Grey?)

How much meat can be taken off the block? I am hoping that the pistons will come up virtually flush, as the standard ones do, however I am concerned that should they not be as high that I will need to skim the block to maintain a workable CR? Is it right to assume that I am better off leaving the head alone as much as possible to preserve what clearance there is for the exhaust valve?

Is there anything that I’ve missed?

I have very little mechanical knowledge really and bought the second engine just to learn on. It’s turning into more than that now, but I love it! I have been given a quote for a centre mains strap, but I haven’t committed to that as I’m not sure whether it’s neccessary for a small bore road engine or not? Particularly with a more mild “sports cam”.

Any help is much appreciated! I know there are many threads very similar to this but I really wanted to tie the answers together for myself. I’d love to have Cooper S-esque power. Aiming for 60BHP. Am i on the right track?

2

the kent 266 cam will be fine for a nice drivable engine, a 276 would be very cammy in a 998 and rubbish as a town engine, with dished pistons you will need to remove around 30-40thou from the head, if you were using flat tops you wouldn’t have had to machine the head .
as for carbs its up to you, the single HS4 will be fine, twin HS4’s will be too much but for the best compromise between the 2 would be twin HS2’s and they would give you a good increase in torque too!
the standard clutch will be fine unless you are going to drive it on the limit every day, heavy duty clutches are fine but they do put strain on the crank thrust washers.

hope that this helps…

keep looking for a 266 cam, one will turn up soon enough.

3

Awesome, thanks for that!

I’d love to do twin HS2’s, but they seem even harder to find than a good camshaft here. There are a few around though so i’ll keep my ears to the ground. On a related note, could an inlet manifold (for twin HS2’s) with a hairline fracture be repaired cheaply and still perform as desired?

I have got a few options for cams at the moment. One is supposed to be very similar to a 266. I will come back with the name of it, i think it’s a 9xx something.

Am i better to take that amount from the head than to take it from the block?

This is fantastic info and hugely appreciated, thank you!

4

Forget twin HS2 SUs - far too small. Go for a single HIF44. Better to sink the exhausts into the head rather than pocket the block which exposes the top ring. If the pistons are flat -the CR will be fine. Old BMC 544 is the one to get (modern version is 286 from various).

5

I would even spend the time for fitting a single HS4.
HIF44 or twin HS2.
And later 940 head already have unleaded inserts, you need to pocket the block to fit a kent camshaft.

6

Awesome, thanks guys!

Jaydee, are you suggesting forget the HS4 and find an HIF44?

BMC, is the BMC544 a really lumpy cam? I will have a look around for an HIF44

7

You could bore to +0.080" and fit Hastings flat-top pistons. That would give you 1060 cc.
Twin HS2 carbs would work well with this so long as you have a better head, such as a 12G295 with a bit of gas-flowing and the compression ratio set for around 10:1. A 12G940 head would be good, but care would need to be taken to ensure the valves don’t hit the block deck. Alternatively an HS4 or HIF38, or even an HIF44 or HS6 single carb could be made to work well, although generally a 1.75" carb is thought a little too big for a 998.
With regard to cams the 266 or MG Metro are very good.
A 3-into-1 ex. manifold and Maniflow or RC40 exhaust system would work well.

Do a ‘trial build’ and have the block skimmed to bring the pistons level with the block deck at TDC. Then measure, calculate and skim the head to give the correct C.R.

A centre-main strap is not necessary for a 998 until you start using very high revs.

You should get around 60 bhp, although you’ll never have the raw torque of a 1275 engine.

8

some people on here make me laugh, they dont read the op’s original post properly and then suggest a completely wrong spec of engine for the purpose of what the op wants.

mailman wants a nice drivable road car…so people are suggesting 544 and 286 cams, hif44 carbs and saying that twin hs2’s are too small…???..he wants a road car not a bloody trackday racer!!..

cooperman has it just about right…as always…

9

I built a 998 with my Grandson as his first restoration. As it was on a bit of a budget we used the following spec:
Hastings +0.080 pistons = 1060cc
12G295 slightly gas flowed with very slightly larger inlet valves and 10.2:1 C.R.
A Cooper ‘S’ 510 cam - Grandson found it in my cam box.
A 3-into-1 original 998 Cooper ex. mainfold with a single-box RC40 at 1.75" Internal diameter, centre-exit.
Slightly lighter flywheel (again off the spares shelf!).
HS4 on a Howley inlet manifold, lightly cleaned up.
Duplex vernier timing gears and chain
Aldon ‘yellow’ distributor (this was a birthday present to Grandson).

He put it together very carefully with a bit of tuition and guidance and it gave 66 bhp at 6000 rpm.
It was lovely to drive and had a 3.1:1 FDR. I fact it was nicer than a standard 1275 as the engine was just so smooth right through the rev range and when really revved it seemed very brisk.

10

544 and 940 head makes an excellent 998 engine. Perfectly driveable and plenty of GO. Anything less is hardly worth worrying about.

11

>
Awesome, thanks guys!

Jaydee, are you suggesting forget the HS4 and find an HIF44?

BMC, is the BMC544 a really lumpy cam? I will have a look around for an HIF44

Mine, with a 295 head so smaller valves than the 940, and no matter what cam i used it always went a lot better with the HIF44, i even tried to ‘vizardise’ the HS4, but the HIF44 was better.

12

>
I built a 998 with my Grandson as his first restoration. As it was on a bit of a budget we used the following spec:
Hastings +0.080 pistons = 1060cc
12G295 slightly gas flowed with very slightly larger inlet valves and 10.2:1 C.R.
A Cooper ‘S’ 510 cam - Grandson found it in my cam box.
A 3-into-1 original 998 Cooper ex. mainfold with a single-box RC40 at 1.75" Internal diameter, centre-exit.
Slightly lighter flywheel (again off the spares shelf!).
HS4 on a Howley inlet manifold, lightly cleaned up.
Duplex vernier timing gears and chain
Aldon ‘yellow’ distributor (this was a birthday present to Grandson).

He put it together very carefully with a bit of tuition and guidance and it gave 66 bhp at 6000 rpm.
It was lovely to drive and had a 3.1:1 FDR. I fact it was nicer than a standard 1275 as the engine was just so smooth right through the rev range and when really revved it seemed very brisk.

you have a cam box? :L

13

Ok, so I have managed to purchase a box of carbs including a couple of HS6’s and HS4’s. They will need a refurb but should be good for my use now.

The next related question I suppose, although it’s a long way from needing to be sorted, but where should I start with needles for an HS6 on this engine.

I have also tracked down two possible camshafts. One is a 948 grind and costs $180NZD (maybe 90GBP) or I can have a 266 ground for about $200-250 (100-125GBP) depending where I go. I am definitely leaning towards the 266, it is just slightly more hassle. Is it worth the premium?

14

The 948 is very mild, would be good for a traffic car..
Needle wise, try BDL but then get it to a rolling road asap.

15

The 266 is, indeed, a lovely cam in a 998.

16

>
The 266 is, indeed, a lovely cam in a 998.

and a 1098…

17

Ok, I have been off gathering some bits and bobs and I’m back for a little more guidance.

I boght a box of SU Carbs containing a pair of HS6’s. Whilst cleaning these up I had a look at what else was there and I found a pair of HIF4’s from an MGB. (AUD434 F/R!.

I have picked one of the HS6’s and I think that the HS6 is in better condition than the HIF4’s. And I have a rebuild kit for it. One of the HIF’s looks pretty good and one looks good but the piston inside is stuck.

Is HS6 better than HIF4 for the build spec i’m going for? If I go HIF4 do I need them as twin’s? And is it much more complicated to set up?

18

do you mean HIF44?..theres no such carb as a HIF4

the HIF44 will be the best compromise…or twin HS2’s will give you more torque.

its not a massive spec engine so don’t over carb it or you will lose power.

if you dont have a copy of david vizards “how to tune BL’s A series engine” then buy one…and read it!

19

Just to correct there is such a thing as an HIF4 (fitted to later MGB’s) and HIF6 carbs. These look like the HIF38/44 variants but use non ball bearing suction chambers and the older HS style needle valves.

AC

20

Yea, it’s definitely HIF44.

I don’t have the Vizard book yet, I keep meaning to get it but it’s so expensive!

I will try and borrow it and have a good read through it.

I suppose I am being a little cheeky, and perhaps asking to much, by relying on you all for advice when there is something like that book available.

I am thinking if I get my HS4 and HS6 carb’s running beautifully then I can choose between the two based on the final build performance.

I think i’ll try sell the HIF’s then.

Thanks again guys.