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Which Twin Hs4 Manifold

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#1 KRM_Simon

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Posted 24 October 2017 - 03:53 PM

Good afternoon all.
I have recently picked up a pair of HS4 carbs and I am looking at what the best manifold is to put them on.
There are a couple of different options and was hoping someone would be able to point me towards the option that will give me the best airflow.
First off on an old HS2 manifold I have when examined, the throats where they meet that carb are actually 1.5inch, and if you look at C-AEG488 on minispares they state it to be suitable for HS2 and H4 carbs, so one would assume also 1.5 inch throat, so option 1 redrill the mounting flange on one of these to suit bolt pattern of HS4.
Option 2, buy C-AEG489 HS4/6 manifold, however the throat size on this I presume will be 1.75inch to match the HS6 carb therefore I would have a step change in the inlet diameter.
Or Option 3, minisport sell AUE1015 currently out of stock which is £40 plus more than the minispares options but is designed for HS4.
Is one option better than any of the others? Are there other options I have missed? Maniflow manifold has been ruled out as Im not sure how they would be viewed on a historic event, probably not favourably.

Any help would be much appreciated.

#2 stevegrabba

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Posted 24 October 2017 - 04:50 PM

I seem to remember castings 12G264 and 12G263 with a little work can accept either HS2 or HS4.  They can be modded inside to improve flow too.  Wehether they are better than the other options or not, I'm not 100% sure to be honest.



#3 panky

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Posted 24 October 2017 - 04:56 PM

This any good?

 

http://www.ebay.co.u...TEAAOSwVtZZ703R



#4 stevegrabba

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Posted 24 October 2017 - 05:09 PM

 

That's the same as the Minispares manifold.  At not much of a price saving either.

 

http://minispares.co...px|Back to shop



#5 imack

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Posted 24 October 2017 - 08:26 PM

Last time I was at MED they had a twin hs4 alloy manifold as above that had a lot of weld built up all around the outside of the inlet tracts. This I was told was now ready for porting and flowing for historic race use. I presume they grind right through the original casting and into the built up weld to maximise airflow. I didn't see the finished product so I'm speculating some what.
Might be worth speaking to MED for some more info.

#6 KRM_Simon

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Posted 24 October 2017 - 09:09 PM

The casting I have for the HS2s is a 12G2463. Do you know if f these casting numbers relate to any of the currently available parts or are these casting numbers older manifolds I’d have to find second hand do you know Steve?

Thanks panky but yeah that is another HS4/6 option so would still have the step change in intake diameter.

That’s interesting thanks imack, will get in touch with them. It does make sense though as when I was looking at the HS2 manifold to see what could be done with it one of my concerns was that in some key places you would want to remove material you would be risking either serious thinning or breaking through. That is definitely a job for the professionals though as I don’t have the ability to check I am getting equal gas flow down each throat, I’d limit myself to just removing sharp edges. Would be good if any of the historics guys could confirm if this is the “done thing”.

Cheers.

#7 stevegrabba

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Posted 25 October 2017 - 07:49 AM

With the 12G2463 there is a square cast aluminium seating area which the carb attaches to.  Sometimes you may find that the user has hacked a corner off the manifold for easier access to the exhaust manifold nuts.  However when in tact they can be drilled and tapped so to accommodate either HS2 or HS4 carbs.  When one using one carb type the unused holes can be blocked using an allen key grommet.  So you can experiment and flit back and forth between HS2 or HS4.  They are quite easy to work internally also, and with a vernier measure here and there you can get them almost perfectly symetrical, however never as good as with a flow bench.  But good enough for a layman's work at home.

 

In regards to current castings available, I'm really not sure if the remakes available and a remake of one of the original casting numbers.  I guess that some will claim to be. The cast versions that will accomodate HS4's are routinely out of stock at most of the mini part sellers so if you find one available, pounce on it before it goes.



#8 carbon

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Posted 25 October 2017 - 04:50 PM

This Mainflow steel inlet manifold is generally reckoned to be the best for power when using twin HS4s: http://www.maniflow....54&product=1101



#9 johnR

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Posted 25 October 2017 - 05:30 PM

12G2463JPC4p3J.jpg

#10 KRM_Simon

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Posted 25 October 2017 - 10:06 PM

Thanks for the info Steve, that has been helpful.

JohnR yep that looks just like the manifold I have, except I see that is already drilled for the HS4. Looks like that is my way forward at least to begin with. Just out of interest do you know what thread the right hand hole is (as you look at the picture you have taken).

Cheers

#11 stevegrabba

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Posted 26 October 2017 - 12:12 PM

Thanks for the info Steve, that has been helpful.

JohnR yep that looks just like the manifold I have, except I see that is already drilled for the HS4. Looks like that is my way forward at least to begin with. Just out of interest do you know what thread the right hand hole is (as you look at the picture you have taken).

Cheers

I've just offered my reworked 12G2463 up against the minispares inlet for twin HS4. Port and carb sides the hole dia's are about the same when basic reworking is done to the 12G2463.  Otherwise there are a few little differences.

 

1)  12G2463 has two vacuum holes already present, compared to minispares one hole (yet space to drill and tap another if needed)

2) 12G2463 uses locator rings to mate up with cylinder head, other doesn't.

3)  Minispares inlet has a more generous machined footprint for the exhaust manifold thick washers and nuts.

 

In regards to the holes in the diagonal right on the pic, I think the thread form is 3/8 UNF, however please double check that!!



#12 KRM_Simon

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Posted 26 October 2017 - 02:19 PM

Is that the C-AEG489 HS4/6 manifold from minispares you have just done the comparison to?

#13 stevegrabba

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Posted 26 October 2017 - 03:42 PM

Is that the C-AEG489 HS4/6 manifold from minispares you have just done the comparison to?

 

Yes...that's the one.



#14 mailman

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Posted 28 October 2017 - 07:22 PM

Does anyone know whether the Maniflow twin SU manifolds retain the standard spacing so you can use their original linkages?

I clicked the link above and they are very nice, but they also look straight from carb to port (a good thing), but would that make the carbs further apart?

Edited by mailman, 28 October 2017 - 07:22 PM.


#15 imack

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Posted 28 October 2017 - 08:59 PM

Does anyone know whether the Maniflow twin SU manifolds retain the standard spacing so you can use their original linkages?
I clicked the link above and they are very nice, but they also look straight from carb to port (a good thing), but would that make the carbs further apart?


Spacing on the maniflow is exactly the same as the leyland manifold, so linkages and heatshield swap straight over.
It's worth noting though that I swapped from an internally modified leyland manifold to maniflow with no other changes and the mixture was completely wrong (there were no air leaks) and I had to fit richer needles, I hadn't expected the airflow to that much different that the fueling would be so far out.





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