OK, Matt at Gear Drive has a 4x2 intake (staggered) that is IRs. Looks like the runners, one for each cylinder. Only half the carb supplies the air and fuel?? A Stromberg 81, 135CFMs will deliver about 67 CFMs per cylinder???????? Does this make sense????????????? Am I way off on this.HELP... Duane...
Hilborn flathead IRs have 1 11/16 butterflies. Our own flathead IR has 1 3/4 butterflies. All IR manifolds have bigger butterflies, due having a single cylinder drawing on them. GeminiEFI
Thanks Ernie..I forgot about that one..That intake was a Lattin and the runners weren't seperated to each cylinder. The whole 97 or 81 would feed the cylinder, not just half the carb. Well, I think it will work just fine. The one thing I remember is that risers do help the flow but just how high of a riser..I guess that will be trial and error also.. Thanks Duane.
Question, if I used a riser the is open not seperate runners the whole carb would feed the cylinder on demand??????? Duane.
Look over how the runners go. Stock '34-53, most common 2 and 3 carb manifolds...each valve sees half the carb barrels. Open plenum...carbs atop a "box" feeding all runners...each valve sees ALL of the barrels True IR...most flathead 4 carb setups are sorta/semi IR but seem to act like IR's...each valve sees ONE carb barrel. Hence...IR can use very large total carburetion, stock/180 manifolds can use more carburetion than the open plenum kind. I've discussed 4 carb flatheads with a few people, including one, Flatdog, who tried everything there was on his coupe before going to a blower. On his huge 300+ inch flathead, he felt he was undercarbed when he went to 4 97's from 3! That strongly suggests that the Edelbrock 4 type does function about like a true IR. SBC's with true IR, weber type setups, can tolerate way beyond 1200 CFM according to tests, on STREET engines.
To reinforce Bruce's comments about the necessity of much larger carbs with IR; we had an import with IR (with small pulsing connector tubes) FACTORY intake on a 121 CID 4 cylinder. Carbs used were two 500 CFM units. And no, it was NOT overcarbed! IR manifolds require a tremendous amount of carburetion compared to a multicylinder plenum type manifold. Jon.
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