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jlaird

Great Pumpkin
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Is the 1275 intake manifold larger than the 948?

Do I need the 1275 intake manifold along with the H2 carbs?
 
Yes
 
Good answer, thought so. 1 inch vs 1 1/8. Thanks
 
Jack, are these the SUs from the B?
 
Not think so, Jack said he had H2s in his stash as well. Of course B carbs do me no good at all.
 
Sorry, I knew you wer getting SUs from Jack, I put 2 and 2 together here and got 5!

Hmmmm HS4s on a 1275?
Didn't special tuning put 1 1/2" on thier 1275s?
 
Would not suprise me at all. Got to breath and some of those 1275 breath deep at 130 HP.
 
Yep! But I think that is kind of over-kill for a street car!!
 
I think that there are two manifolds for HS2's, one for the 1100's and one for the 1275's (this is all from memory 20 years ago). The 1100 manifold holds the two carbs about 1/4" closer together than the 1275 ones and requires shorter connecting shafts too. Either set-up will work on a 948.
Bill
 
Remember I am running 998 cc and hope to kick it up a bit in the future with a special head, cam and 1275 exhaust.
 
Bill -

Your memory is good! I thought I was losing my mind when I converted to HS2s and had an 1100 manifold, but 1275 linkage. Finally realized after fighting with the situation for several days that there is a difference between the manifolds as far as the distance between the carbs.
More experienced LBC owners may have already known this, but it sure tested my patience and sanity!
 
Just one of those things that folks take for granted.
 
jlaird said:
Good answer, thought so. 1 inch vs 1 1/8. Thanks

Not quite. The numeric designation on H (side draught) S.U. carbs relates to the number of 1/8ths of an inch over 1".

H1 is 1-1/8, H(x)2 is 1-2/8 or 1-1/4

All as measured at the manifold end of the throat.

Peter C
 
Jack:

They did use them on factory works carbs. I would recommend a 1098 head to go along with it if you don't already have one. Also, I would use an aftermarket manifold as well, they are about $200 bucks.

The original has a bypass tube that is too large and really knocks down the flow. It would not make much sense putting them on with a 948 head and a stock manifold.

Patrick
 
Yes Peter, duh. I knew that.

Hi Pat, yep just putting back parts when I can to improve this little engine.

Figure 998 cc, have
Street cam
206 or 295 head
1275 exhaust
H2 carbs

That ought to do it for this old boy. Think it might go from 43HP to 60 some. 1/3 improvement. No rush though, got to get everything else right first and recover from this money pit.
 
Yoda has read Dave's scripts well. /bcforum/images/%%GRAEMLIN_URL%%/wink.gif
Pat
 
Jack,

About 60 is what you'd get from a stock 1275, at least in theory, so you may find a drop-in 1275 and ribcase to be a good option. Just like drooartz and ncbugeye, and probably many others...
 
Yea but a warmed over engine sounds so much better, hehe.
 
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