General questions

[spl310]

Do Weber carbs require high compression or is 9.6ish OK? Will Webers perform OK with a solid lifter hipo reproduction cam?

[bobcowan]

Compression doesn't really matter.

Any IR system does better with a wide LSA, at least 112*. Less than that, and you tend to get a lot of reversion. That's what caused the "Weber Cloud".

[spl310]

Originally Posted by bobcowan

Compression doesn't really matter.

Any IR system does better with a wide LSA, at least 112*. Less than that, and you tend to get a lot of reversion. That's what caused the "Weber Cloud".

So a K code cam with an LSA of 114 degrees is good to go then.

[bobcowan]

Yes. 114* is optimum for an IR system.

[PDUB]

Originally Posted by bobcowan

Compression doesn't really matter.

Any IR system does better with a wide LSA, at least 112*. Less than that, and you tend to get a lot of reversion. That's what caused the "Weber Cloud".

I'm a member of the "Weber Crowd!"

[PDUB]

Duplicolor...

[KarlzEE Bebout]

Love my Webber 44IDFs....I think

[PDUB]

Originally Posted by spl310

So a K code cam with an LSA of 114 degrees is good to go then.

what are you trying to accomplish with the setup? Do you want something mild and tame or are you recreating the real deal?

[spl310]

Originally Posted by PDUB

what are you trying to accomplish with the setup? Do you want something mild and tame or are you recreating the real deal?

I am not planning to race. I would like a streetable driver that wows people when I pop the hood.

[PDUB]

...but you don't have to race it to build the real deal! Those high LSA's are for EFI cars that have knock sensors that will have a fit with a lower LSA and a bit of rumble. You will give up some low-end with those numbers and no overlap. I'm thinking more like a 108 LSA for mine.

[bobcowan]

Originally Posted by PDUB

...but you don't have to race it to build the real deal! Those high LSA's are for EFI cars that have knock sensors that will have a fit with a lower LSA and a bit of rumble. You will give up some low-end with those numbers and no overlap. I'm thinking more like a 108 LSA for mine.

I would not recommend that. With a narrow LSA, you get a lot of reversion, because there is no common plenum to draw from. That reversion spits air and fuel out the top of carb, creating the "Weber Cloud".

EFI will certainly tame this a bit, and a allow for a much "larger" or more radical cam. But the recommendation applies to carbs as well.

Take a look at the Inglese web site:

What kind of a cam should I run?
Any cam is fine as long as you pay attention to the lobe separation angle (LSA). A 112-114 degree lobe separation is ideal for Webers. I generally discourage the use of anything tighter, like 108, or 106. A 110 LSA is marginal. The problem with a lot of overlap is that it causes "reversion"...which are pulses from the exhaust stroke while the intake valve is still open, that have nowhere to go but up into the carburetor. This disturbs high rpm airflow and causes the engine to think it's too lean at high rpm’s. Without a plenum, the flow is pulsed backward up into the carburetors because there is noplace else for the reversion pulse to go.