HIF44 or Twin HS2?

[John Gervais]

I've a dilemma...

Berlen Fuel Systems tells me that the HIF38 carb is really good for up to around 65hp.  My 998 is just a tad above that, at 68 -70hp and running out of puff at full-load after 5000 rpm (motorway).   

I could:
1.  Carve the HIF38 carb ala Vizard and get a bit more air through the carb, install a yellow spring to make it pull harder on the jet, etc...
2.  Rebuild a pair of HS2's I've got hanging around - need complete rebuild kit, new manifold, velocity stacks & K&N's...  $$$$$
3.  Rebuild an HIF44 I've got hanging around - need rebuild kit, MG Metro plastic air filter box & K&N filter.  Can use current intake/abutment plate, but might need to reduce the jet to 0.090" to use the plethora of 0.090" needles I've got on hand (pairs of AAA, AAM, BF, AAB, MME).

What do y'all think???  I'm familiar with the improve throttle response of the twins - I had them on my old 850.  I've not tried an HIF44 on a small bore, though - are there issues with bulkhead clearance?  I don't think I want to start moving the engine with different dog-bones if it's not necessary...

Of course, if anyone's got anything cool for sale that could sway my decision one way or other, please, don't be shy...

[94touring]

I rebuilt an old junk pair of hs2's for my 998.  I really like them.  Responsive throttle and look cool.  I've driven some hif's and they just don't feel the same to me.  I found it to be easy and affordable to rebuild the twins.  Here's a link to the filters I used.  http://www.restorationmini.com/forum/index.php?topic=762.0

[MiniDave]

Vizard says the HIF 44 flows more air and makes more power than the twins because of the siamesed ports, but I agree they look pretty cool.

I had twins on my old 1100 and it pulled like a truck!  (that means it was good! :-) )

68-70hp out of a 998 is pretty stout.....

[MPlayle]

68 - 70hp out of a 998 is already to the upper end of a stock 1275!  Nice!   4.gif

[SoCalMiniFan]

I've not tried an HIF44 on a small bore, though - are there issues with bulkhead clearance?  I don't think I want to start moving the engine with different dog-bones if it's not necessary...

Of course, if anyone's got anything cool for sale that could sway my decision one way or other, please, don't be shy...

I'm running a 1275 with HiF44/K&N Cone Filter and I'm using the dog-bone off my 998 with no fitment issues.

HOWEVER: I don't have a plate or metal covering up the Speedo cluster directly behind it so that allows the clearance.  If my Bulkhead was solid the filter would NOT fit without having to adjust the dog-bone length. The bottom edge (larger end of the cone) sits just slightly into the cluster area.

I guess my point is, bigger engine, same dog-bone, fitment minus the plate issue, it fits. A 998, with same dog-bone, bigger Carb might clear even with the bulkhead plate on.  Maybe someone else can chime in with fitment issues. 

[tmsmini]

I eventually went with twins on our 1098. It originally had an HIF(half of Volvo twins) on it when we bought it. There were clearance issues and no spacer was used between the carb and manifold. I am not sure how much that impacted performance. The small bores sit lower, so the edges of the air cleaners are close to the bulkhead.

The car now has an electronic carb and modifications needed to be made to get the air cleaner to fit.

I always liked twins...
Terry

[John Gervais]

I've not tried an HIF44 on a small bore, though - are there issues with bulkhead clearance?  I don't think I want to start moving the engine with different dog-bones if it's not necessary...

Of course, if anyone's got anything cool for sale that could sway my decision one way or other, please, don't be shy...

I'm running a 1275 with HiF44/K&N Cone Filter and I'm using the dog-bone off my 998 with no fitment issues.

HOWEVER: I don't have a plate or metal covering up the Speedo cluster directly behind it so that allows the clearance.  If my Bulkhead was solid the filter would NOT fit without having to adjust the dog-bone length. The bottom edge (larger end of the cone) sits just slightly into the cluster area.

I guess my point is, bigger engine, same dog-bone, fitment minus the plate issue, it fits. A 998, with same dog-bone, bigger Carb might clear even with the bulkhead plate on.  Maybe someone else can chime in with fitment issues.

The small-bore blocks aren't as tall as the large bore; I can't remember how much shorter, but if I recall correctly, somewhere between 1/4" and ½" shorter.  This is why I'm wondering how it'd be possible to get the HIF44 to fit.  I know that there are some UK guys on TMF that have them installed, but I haven't asked over there yet.  There's a really interesting 'Small-bore Shootout' thread featuring all sorts of 998 monsters.  I'm really not as 'comfortable' on TMF as with the 'American' message boards.  Don't know why, must be something cultural.

Anyways, these are the velocity stacks I'll be likely using (http://www.med-engineering.co.uk/med-stub-stacks), and I've already got a pair of those thin pancake filters to accept the K&N's during the summer, moving the K&N's to the MK2S standard filter housing during the colder months in order to utilize the warmer air radiating from the center branch of the exhaust manifold.

In any event, this is going to be fun -

[MPlayle]

The car now has an electronic carb and modifications needed to be made to get the air cleaner to fit.

Electronic carb??

[tmsmini]

The car now has an electronic carb and modifications needed to be made to get the air cleaner to fit.

Electronic carb??

That is what I(and others) call Specialist Components throttle body implementation for the Mini. It uses the same inlet and the throttle body is placed exactly like an HIF.

[MPlayle]

Okay,  I remember now - the thread on the aftermarket fuel injection.

[tmsmini]

I need to start a new thread as after removing and replacing the head for a bent valve I cannot get it to restart again, but that is another story.

I think John should go with the twins. Some people complain about the adjustments, but I learned on a set attached to a 68 MGBGT, so I am comfortable adjusting and syncing.
Terry

[mascher]

Vizard estimates between 2 and 2.2 cfm is necessary per horsepower. He doesn't list numbers for the HIF38 but a stock HS4 is measured at 142 cfm. This would be between 71 and 65 hp for a stock HS4 which should be functionally equivalent to an HIF38.

HS4s are really common in the U.S. and Canada from Austin America and I would be tempted to use one to experiment on before investing in an HIF38. Of course this could just be because I have a bucket full.

Putting a yellow spring in an HIF38 will cause it to "make it pull harder on the jet" but it also limits the max piston rise and probably doesn't help your power at higher rpm but it depends a lot on the needle and the intake manifold.

I would avoid the HIF44 on a 998 because loss in intake velocity would tend to decrease torque at lower rpm.

I'm not sure what carb you are using now but if it's an SU you might want to make sure that the piston is reaching it's full opening height at 5000 rpm. If not that could be where your power limit is coming from. This is hard to do without a chassis dyno.

Kelley

[John Gervais]

Vizard estimates between 2 and 2.2 cfm is necessary per horsepower. He doesn't list numbers for the HIF38 but a stock HS4 is measured at 142 cfm. This would be between 71 and 65 hp for a stock HS4 which should be functionally equivalent to an HIF38.

HS4s are really common in the U.S. and Canada from Austin America and I would be tempted to use one to experiment on before investing in an HIF38. Of course this could just be because I have a bucket full.

Putting a yellow spring in an HIF38 will cause it to "make it pull harder on the jet" but it also limits the max piston rise and probably doesn't help your power at higher rpm but it depends a lot on the needle and the intake manifold.

I would avoid the HIF44 on a 998 because loss in intake velocity would tend to decrease torque at lower rpm.

I'm not sure what carb you are using now but if it's an SU you might want to make sure that the piston is reaching it's full opening height at 5000 rpm. If not that could be where your power limit is coming from. This is hard to do without a chassis dyno.

Kelley

Yeah, I understand that - I've read Vizard's big yeller book as well as his HTMYM which has led me to believe that it's now time to change it.  I've a few HS4's and a couple of HIF38's (one of the HIF38's has around 1500 miles on it, I bought it new from Berlen Fuel Systems not long ago - the other HIF38 I bought new from Berlen to replace an HS4 - it's got around 7500 miles on it - I thought it prudent to have a good spare...).  I've also an HIF44 which I need to pull my thumb out and rebuild it...

That said, I spoke with Berlen on the phone the other day after examining their size recommendation table. They reckoned that the new HIF38 might actually be a bit small for the engine & new Maniflow exhaust system and thought the twins a better option.  Of course, I bought the HIF38 under the classic understanding that it should be absolutely perfect for the application - heck, a brand spankin' new carb is costly.  (http://sucarb.co.uk/hif38-service-replacement-carburettor-for-a-austin-metro-1000-1980-onwards.html , http://www.minispares.com/product/Classic/Fuel/Carburetors/Single/FZX3004.aspx?130202&ReturnUrl=/shop/classic/Fuel/Carburetors/Single.aspx|Back to shop)


The first image below is of the size recommendation table found in the SU Carburetters Tuning Tips & Techniques (available from Berlen:  http://sucarb.co.uk/catalogues-manuals-books/su-tuning-tips-techniques/su-carburettors-tuning-tips-and-techniques.html).  In this table, the 1½" single carb is running into the grey area at around 75hp whereas the twin HS2 a bit further up the scale, say somewhere around 85(ish). - still should be more than adequate, I agree. 

The second image is the image made popular by various magazines and websites.  In this table, the single 1½" runs out of puff at around 60-65, whereas the twin HS2 continues up through 75 ish.

The third table image is a nice coloured Austrailian cubic inch version of the first table.  Walt Disney would approve...

Who knows which table is correct.  If I recall correctly, the HIF44 flows around 12% more air than an HS6 - Vizard has the airflow CFM's  written somewhere, and I think it's around 12% greater with the same size HIF44 vs. HS6 unit.  If so, then I would assume the HIF38/HIF4 vs. HS4 comparison to be at nearly the same ratio. 

I've got a Wideband AFR meter installed (Innovate Motorsports MTX-L) and as far as I can see, I'm neither too lean nor too rich (to any obvious extreme) at WOT 5000+ rpms.  But, it's not an easy thing to check, as you mentioned and 'testing' at 90 mph probably isn't a good thing to do daily (fun though!)... 

Maybe I can find someone to feather the brakes whilst (as Vizard and Berlen both describe when discussing the Colortune) sitting in the garage and I can check 'when' the piston is at full-height. 

Not a bad idea - thanks!

[Spitz]

70hp from a 998....very good ( what is your build spec )
A run of the mill 1275 is only about 55hp

I've driven a hopped up 998 and 1098 on hif4, HS4 and twin HS2.
My favourite from seat of the pants feel is the HS2 pair.
Most definately quicker throttle response off the line and always has the "bling" factor.
Once you get them initially dialed in theres no need to keep dicking with them which is a common thought.
The hif4 gave probably the better performance all around in the pactical sense, but a little slower off the line ( smooth throttle however )

I think the hif6(44) might work well for you with that much HP as well, but I'm still thinking HS2 will be better.  The factory used them for 76HP

[John Gervais]

70hp from a 998....very good ( what is your build spec )
...
I think the hif6(44) might work well for you with that much HP as well, but I'm still thinking HS2 will be better.  The factory used them for 76HP

Yeah, I do like twins also, had them on my old 850 with a small-bore LCB/lightweight flywheel and it really woke the small engine.  I sold this pair of carbs and installed the HIF38 when I installed the 998.  Last year, I was able to buy the twins back - the same carbs, but they'd changed hands twice since I'd sold them.

The engine is pretty much the same as I've had for some time (C-AHT87 cylinder head, 997 cam, etc...) and was 65 hp on Peter Baldwin's rolling road -  but I've made a few improvements though; it's breathing better and my dizzy is now better suited to the assembly.  So I'm figuring that there's an extra 2 or 3 ponys trying to get out.  If I can get 68 out of it I'll be really chuffed...

I found a guy over here that has a rolling road dyno, so I'm actually tempted to see if there could be an issue with the current HIF38 setup.  I have no idea how much he'll charge, though.  If so, I've saved around $500 in rebuilding the pair of HS2's (MSC manifold, complete rebuild kit, linkage - current one is knackered, heat shields - current ones are bent and welded/patched, new floats - one is cracked, new 'forked' petrol pipe and so on - ).  If not, and the HIF38 seems to be at the big-end of it's capabilities, then I could do an 'economy' tune and live with it until I've saved enough to rebuild the HS2's.  For a guy who isn't working, it's a major undertaking...  (Well, keeping the wife from finding out is a major undertaking...)

The 4" airfilters (K&N E-3200) are on backorder from K&N Europe, so are expected to arrive in mid February.  (I wonder why MiniSpares, MiniSport or the other suppliers don't sell these...).

[94touring]

Maybe I should sell them!  All I did was take measurements off the stock filters and go to the K&N website and did a search. 

[John Gervais]

Maybe I should sell them!  All I did was take measurements off the stock filters and go to the K&N website and did a search.

Yep -   77.gif

[Spitz]

A couple of years ago I was lucky enough to buy a set of twin HS4 carbs, manifold, linkages, genuine K&N with embossed K&N chrome covers......$150    :)

I bolted them right on to my 1275 without even taking them fully apart ( I need an inspection ).  Car started right up, tuned them a little......never touched them since.  I auto crossed the car...those carbs sure woke that engine up

OK....back to YOUR carbs...lol 

[MiniDave]

Maybe I should sell them!  All I did was take measurements off the stock filters and go to the K&N website and did a search.

E-3200 is $31.99 at Autozone.....just FYI

[94touring]

I know.  I have them linked in the diy where to buy them.