11 replies to this topic

[Fewtch]

Evening all

I'm hoping to tune my 998cc+40 quite a bit more
1987 Austin Mini Mayfair

- Its going to have a 12g295 Head with 24.5cc.

Problem is and i have been searching and searching, and cant find anything to settle my mind on it.

1.) Kent 266 or Kent 276 cam.
i.)Is there LOTS of power difference between them all. (anyone have any dyno result (picture?))
ii.) Is the power below 1800rpm on the 276 cam the same as a standard 998 cam?
iii.) I Do alot of town driving but also alot of dual carrage way/motor way driving, I like Acceleration alot, but not too fussed about topspeed.

2.)Twin HS2 or a HIF44?
i.) I hear that twin HS2s are very good for power as 1 carb for 2 cylinders instead of 1 for all 4.
ii.) Would there be lots more power out of the HS2s or HIF44?
iii.) Which one would be best for econemy too?

3.) I read a post a while ago, about air speed through the cylinder head, and by having a 276 cam, and a hif44 it could be too much and loose power, as the speed of the air will be going slower throught the ports.. is this true. Or anyone know anything about it the air speed?

I went to minisport about a week ago, and was told to speak to "this" guy, And he suggested to me to get s 940 Head, pocket it, and have a new diff for 80mph @ 8000rpm (3.71 diff or something) with a kent 296 cam and HIF44. And this is completly the opposite of what i wanted.
I'm After Good torque at low and high revs, Lots of acceleration, BUT able to do 90mph easierly but not screaming the engine with a new diff, So im keeping my original diff.
I have already bought the Head, and the carbs, as they were cheap @ fully reburbed. so can always sell them.


Thanks for readying my essay haha.
ANY Suggestions are welcome, so even if you dont exactly know, but have heard something about it. Please do share.
Cheers

Edited by Fewtch, 25 February 2012 - 10:29 PM.

[valve bounce]

266 and twin hs2's all the way in a 998, with twin carbs the mixture spread is better than a single, with a single carb the outer cylinder run slightly ritch and the inners run lean. once twins are set up and balanced all 4 cylinders will run even, ive also found the mid range pull is alot better with twins over a single. a hif 44 is to big for a 998 really anyway.

i had a mg metro in my old 998 and it flew a really good cam, tick over wasn't bad and it drove like a standard 850 below 1700rpm then it improved and once it reached 2750rpm it just really started to pull all the way up the range, the 266 is just a improved version of the mg so yes go for it
if i do another tweaked small bore it'll be 1098 with my fully home ported big rimflow valved 295 cylinder head, with a 266 and twin hs2's

[Cooperman]

266 and twin hs2's all the way in a 998, with twin carbs the mixture spread is better than a single, with a single carb the outer cylinder run slightly ritch and the inners run lean. once twins are set up and balanced all 4 cylinders will run even, ive also found the mid range pull is alot better with twins over a single. a hif 44 is to big for a 998 really anyway.

i had a mg metro in my old 998 and it flew a really good cam, tick over wasn't bad and it drove like a standard 850 below 1700rpm then it improved and once it reached 2750rpm it just really started to pull all the way up the range, the 266 is just a improved version of the mg so yes go for it
if i do another tweaked small bore it'll be 1098 with my fully home ported big rimflow valved 295 cylinder head, with a 266 and twin hs2's

Agree 100%. The 266 (or the almost identical MG Metro) cam is ideal with the 12G295 and twin HS2's. The 3-into-1 exhaust manifold is beat with a single box RC40 or Maniflow. The exhaust diameter should be no larger than 1.75" all the way from manifold end to final exit.
The 276 does make the 998 a bit 'cammy' low down and requires around 6200 rpm to give maximum power in the 998 so it's not ideal.
You'll love it with the 266/295 and twin HS2's. A slightly lightened flywheel is also no bad thing with that specification.

[Fewtch]

I knew that the HIF44 was wayyy to big anyway, does sound very throaty though. At the moment, I have a a 3-2-1 LCB with a DTM. Its getting around 65bhp even with 13:1CR (200psi)

So i'll be going for what you have said:
Kent 266
Lightened Flywheel
Twin HS2's.

Cheers guys much appreciated. Set my mind at rest now!

[oltonlad]

i'm doing a 1098 at the moment with a ported 202 head, 266 cam and twin HS2's, it should go quite nicely

[valve bounce]

the dtm is terrible for performance, please it a single box 1.75in rc40 it'll be alot better

[Cooperman]

the dtm is terrible for performance, please it a single box 1.75in rc40 it'll be alot better

Yes, much better. The manufacturers of the big bore DTM just don't seem to understand how exhausts should be designed!

[oltonlad]

i'm doing a 1098 at the moment with a ported 202 head, 266 cam and twin HS2's, it should go quite nicely

i'm not using the 202 head now as i've found a 295 head which is totally stock......

[Spitz]

You'll have to have that 295 head shaved though

As to the OP.
I'm running a 295 head ( -.080 ) with a SW5 cam.
I've tried twin HS2, HIF38 and HIF44.
The HIF44 is too big. Even 1275 cars came with HIF38 from the factory.
The car ran very nicely with the HIF38 ( AAU needle ).
The HS2 carbs have better acceleration...hands down. IF you are using the correct needles.

Don't be scared of twins...once they are tuned/adjusted, you don't need to touch them again.

[Cooperman]

You'll have to have that 295 head shaved though

As to the OP.
I'm running a 295 head ( -.080 ) with a SW5 cam.
I've tried twin HS2, HIF38 and HIF44.
The HIF44 is too big. Even 1275 cars came with HIF38 from the factory.
The car ran very nicely with the HIF38 ( AAU needle ).
The HS2 carbs have better acceleration...hands down. IF you are using the correct needles.

Don't be scared of twins...once they are tuned/adjusted, you don't need to touch them again.

Agree 100%. Just make sure you do the compression ratio measurements, calculations & machining so that you get it correct. About 10.2:1 would be ideal at that spec.

[jaydee]

You're opening a can of worm with that sentence on the twin hs2 :

i.) I hear that twin HS2s are very good for power as 1 carb for 2 cylinders instead of 1 for all 4.

Thats not correct, each cylinder is sucking through a smaller carb.
Twins seems to benefit of some strange harmonic pulsation, i dont know how to explain.
They give better throttle response and torque, but extra power? dont think so.

[bmcecosse]

It's a serious mistake to imagine that twin HS2s give one carb to each pair of 2 cylinders while a single HIF 38 has to shared by all 4..... You must remember that only ONE cylinder breathes at any time - and so the larger single carb on a GOOD inlet manifold is by far the better bet - allowing each cylinder in turn to breathe through a 1.5" hole - instead of through a 1.25" hole. There is no worthwhile cross flow on the twin carb manifold - in fact the intersection of the cross pipe with the main flow pipe from each carb ruins the flow from the carb...... And yes - go with the 266 cam.