850cc engine help/advice.
Turbo Mini Forums

Hello gents
I have an on going problem with the HS4 carb on the 850, now ive rebuilt it/cleaned it/sung to it and so on, but its still not running right, plus ive discovered slight damage on the spindles, a bit tired to say the least.

Now, my question is, would a HIF38 be a better carb? maybe combined with a freeflow exhaust manifold etc, (basically a stage one kit i guess)
If anyone can give me some advice or a good route it would be greatly recieved.

cheers
dan

My 998 clubman ran much better with a HIF38 than it did with HS4. The maniflow exhausts are very good, the best IMHO

I think your HS4 was goosed to be fair though Andy. HIF38's do flow better than HS4's however.

If something is worth doing, it's worth doing half of.

i thought size for size the only pro to the HIF is the fuel being under the jet rather to one side

Yes i moved to the darkside

Instagram @jdm_brett

I have no hard evidence V. Just going on what I have read in the past, and personal experience of driving the same car equipped with both carbs. (not a conclusive test I know)

Perhaps I should have phrased my statement.

"In my opinion a HIF38 carb has the potential for better performance than an HS4"

If something is worth doing, it's worth doing half of.

I believe this is the article I read with reference to superior flow potential of HIF carbs.

http://www.mgbmga.com/tech/mgb19.htm

If something is worth doing, it's worth doing half of.

i would place a HIF carb on there,
and dial the mixture in correct
the bottle nec here on the 850 motor is the head in short! ... head 850 head has very! small shrouded valves
ditch the head and fit a 12g295 head on there skimmed 0.070" to give you a relistic compression
this togeather with a lcb and better exhaust system will increase the power around 90%

the standard good 850 engine produces a staggaring 20 hp a bad one around 15hp and a dead on well your guess is is good as mine

hope this helps

thanks everyone, i managed to track down a few topics on TMF too (even with their search function!!)

It does seem quite a few people change to HIF from HS models, and that its a worth while upgrade.

thanks benross, i was thinking of contacting you with in relation to some head work, that will be the next move i think.

So should i be thinking of an LCB manifold?, i thought small bores worked better with freeflow?

in the Vizard book the flow of a HIF6 is 240 CFM vs 210 CFM for an HS6,

the flow of an HS4 is 142CFM, there is no info for the HIF4 but assuming it will be better by a similar proportion as the HIF6 the HIF4 should flow about 160CFM

I just cannot understand why. The internals are VERY similar if not identical. I'll have to measure.

I love HS carbs compared to HIFs. The external float is soo much for troubleshooting etc.

How often do you have to trouble shoot a HIF carb let alone a HS carb to justify choosing the HS carb over the HIF purely for that reason?

Well i havent looked at an HS for many years, but from memory the hif has a much more radiused inlet to it, If the flows were taken with no form of ram pipe this could acount for the difference.Also I think the casting on the HIF was a bit better ie less flashing marks, so tickling out an HS with a dremel could even things up too.