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General questions
Do Weber carbs require high compression or is 9.6ish OK? Will Webers perform OK with a solid lifter hipo reproduction cam?
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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". |
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Yes. 114* is optimum for an IR system.
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Hell yah,
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I'm a member of the "Weber Crowd!" |
Frickin' website!
Duplicolor...
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Love my Webber 44IDFs....I think
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Well,...
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Ok,...
...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. :D
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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. |
He has posted 108 as ok in the past. Then it was 110, now it is higher... he won't get call-backs if it is at 114!! Webers snort and spit! They are racing carbs. Yes, you can tone them down, but you miss part of the experience... YMMV, so do what suites you! It is your money.
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Weber carbs are street carbs adapted to race engines, not the other way around. When properly tuned and set up, they do NOT spit and snort. That kind of performance will cost you races. The problem with reversion is that the air:fuel mixture is going up, out of the engine. When the intake valves open, the mixture has to make a 180* turn back into the engine. During that turnaround, there is a brief moment when the air is not moving at all. Some fuel will fall out of suspension, and puddle in the intake tract, and the initial cylinder fill will be lean. To make up for it, the rest of the charge will be rich. That also contributes to cylinder wash down; which is a bad thing. All of that means poor and erratic performance. Not at all what you want in a race engine - or a street engine. I'm not sure why you would want to intentionally build an obnoxious poor performing engine. But, it's your car, to each his own. You do You. |
It is a complex set up, and it's not all about reversion or eliminating it. That is a fairly narrow perspective. That angle has a lot to do with how the engine runs in the powerband and where the power is. Many compromises in the engine speccing/building process!
I already said that it's your money so do what suites you! And, yes, we all do likewise! |
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