[2] HS2 vs [1] HS4

[Atrus]

Once again, per my Megasquirt post on this page, I am trying to determine what I'd want to use as a throttle plate for an FI setup.

I may be thinking about this all wrong, however, currently my 1275 has 2 HS2's. For ease of implementing an FI system, I was now considering swapping to a single HS4.

HS4 = 1.50" = 1.767 sq. inches
HS2 = 1.25" = 1.227 sq inches, multipled by 2 = 2.454

So, wouldn't a HS4 be restrictive on the engine?

P.S. - I am awaiting Vizard's book to arrive, so bear with me! /bcforum/images/%%GRAEMLIN_URL%%/wink.gif

 

[Bugeye58]

Kevin, most of the 1275 single carb conversions I've seen use a single HIF 44. Roughly a 1.732" throttle bore.
I ran a single HS4 on my 1500 Spit, but it was heavily tweaked for racing.
Jeff

 

[Atrus]

Jeff,

Like I said, no Vizard's book yet, but basically I want to perk the engine up a little - maybe some mild head work (porting/polishing), street cam, perhaps a bore - .020" or .030". It's all speculation now until I really read up on how these engines respond to various mods, however, I'd just like to make the car a little quicker and peppier for cruising around here on weekends.

So, if most people do the HIF 44, I'd be safe to think the HS4 isn't being too restrictive?

 

[Bugeye58]

Kevin, depending on the attendant mods, I think you can get away with a single HS4. The HIF 44 is a metric carb, ie 44mm bore, or nearly 1 3/4".
But, on a high performance 1275 I run twin HS4's. The only reason I ran a single on the 1500 was due to rules restrictions.
Jeff

 

[no_cones_ever]

if you could find a HIF 44 you would either have to build your own manifold or get one off of a mg metro and the single is what i am thinking of doing on my 948cc just because i don't want to have to tune two carbs

 

[Bugeye58]

A single HIF 44 is <u>way</u> too much carb for a 948. Remember, they had 1 1/8" carbs originally.
But, what do I know?
Jeff

 

[no_cones_ever]

upon further research i am going to do a single 1.5...and i have an mk2 which means that i have a 9cc enging which means 1 1/4 inch carbs

 

[Bugeye58]

A single HS4 would probably work, with the right needle.
It's a 9CG, not 9cc.
Jeff

 

[no_cones_ever]

oops read the wrong note then...my bad

 

[jcatnite]

But, what do I know?

Jeff...you've probably forgot more than most of us will know about these little cars. Keep the advice coming.
JC

 

[Atrus]

Would you say a 56mm bore on the throttle would be far too big for a lightly modded 1275? (I'm scheming)