Carb choice

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sobiecam

College Student
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Clermont, IN
So right now I have a 73' 225 that beyond an Offy intake and eddy 500cfm is totally stock and tired with 160k without being opened. Over the winter I'm going to pull the engine and do a long rod conversion, a cam, some headwork, and add a header.

Right now the car isn't a big fan of the eddy, it runs okay on the 2bbl but when I had it rocking the linkage to run all 4 barrels it had a horrible bog when nailing the throttle, even managed to kill it on the line during a test & tune!

So my question is, when I put this thing back together I want to do either a Holley vac secondary OR would a 500cfm Holley 2300 2bbl work better? Car is used mostly on the street but 20.1 in the quarter is kinda miserable!
 
holley 390 or 500 (4bbl) offers more adjustability on the secondary side (vacuum spring rate) but the Edelbrock should not stumble when punched as the secondaries are not really open to full vac as the secondary doors are not pulling open yet. Could it be a pump shot issue? Smaller shooter will draw out the pump shot over a longer time where as a larger shooter will literally "run out of gas" faster. you could also try and use a different hole in the linkage. I believe the closer hole to the pivot is the larger shot. the 2300 may work but I have heard the 350cfm version is all you really need. Do the math for your combo.
 
The Eddy carb I have is mechanical secondaires and I've adjusted the pump linkage a few times with no change, I've also played with the timing too but nothing removed the stumble besides taking the secondaries out of the equation so now it's more or less a 220cfm 2bbl with extra weight lol
 
First off, you are already down on torque, why in gods name would you stick a longer rod in it? Thats for guys with head and intake that will support 7 grand and up. As it is, your rods are too long from the factory to make any bottom end grunt.
If anything, turn the pistons around in their bores to pick up a tiny bit of angularity.
If you are dealing with a major bog when the secondaries open, you're not likely giving that thing enough initial timing.
My advice, if you want to run a big carb? Lock out the distributor and set it for 32-34 degrees. Big oomph when you hit the pedal.
One other thing. Once you get rid of the bog, you're going to find that 500 is jetted way too fat for a 225 inch engine.
Ive got a 600 Eddy on mine, and found that .098s in the primaries, and .081s in the secondaries are just about dead on.
Fine tune it with drop rods
 
First off, you are already down on torque, why in gods name would you stick a longer rod in it?

Probably for the better rod ratio (i.e., rod length : stroke length) and its resultant reduced internal friction due to less piston sideloading against the cylinders, and the increased piston dwell time at TDC and BDC with its attendant advantages in completeness of combustion and control of preignition.

Long-rod 225 builds are well known to work well even in near-stock configuration. You don't seem familiar with them. That doesn't mean the idea's nutty and stupid and dumb and ungodly and all the rest, it just means you're not familiar with them.

And it's kind of a distraction, anyhow; his engine isn't running poorly because his rods are too short.
 
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Probably for the better rod ratio and its resultant reduced internal friction due to less piston sideloading against the cylinders, and the increased piston dwell time at TDC and BDC with its attendant advantages in completeness of combustion and control of preignition.

Long-rod 225 builds are well known to work well even in near-stock configuration. You don't seem familiar with them. That doesn't mean the idea's nutty, it means…you're not familiar with them.
I may not be familiar with that particular combination, but it would be impossible for me to be more familiar with the cause and effect of geometrical changes to the bottom end of a high performance engine. Long rods move the torque curve higher. Period.
 
Also it should be noted that I am opening the runners and putting in larger valves, long term goal is turbo the slant but over this winter the main focus is setting a good foundation for the later plans
 
it would be impossible for me to be more familiar with the cause and effect of geometrical changes to the bottom end of a high performance engine.

One thing about people who huff and puff about their own awesomeness with absolute words like "always", "never", and "impossible": it only takes one counterexample to topple 'em.
 
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One thing about people who huff and puff about their own awesomeness with absolute words like "always", "never", and "impossible": it only takes one counterexample to topple 'em.
Dan, I'm not going to get into a pissing contest with you. My name and history speak for themselves
 
Might I suggest a revisit of the secondary hook up?
Stalling on the line from flooring the pedal should have nothing to do with the secondaries, on anything but a DP type carb.
It should have everything to do with airflow through the carb, and the resistance attached to the crank.
That sudden influx of air, needs to be pretty rich to not hesitate, and if the engine cannot rev up quickly enough, it rebels at the whole idea. It's a long way from the butterflies to the valves on a slanty, at least most of them,lol.
I cannot think how disconnecting your secondaries on an Eddie carb could possibly have cured your at-the-line bog. Now, once you are moving, and the rpm is climbing, that would be another story.
Low cylinder pressure is very often hard to work with, and you said tired engine.
Consider the lowly TC,the rear gear and PUMPSHOT, with a strong eye on timing.
I would start with a compression test to see where that is at.And then a stall-test.Then if those look reasonable, then I would tighten up the secondary air-door, richen up the pump,and crank in some timing,most as previously said.
But really what's the point? All the efforts you put into it today may be of no use to you after the planned mods, except perhaps as a learning experience.
In any case all the best to you.

Oh yeah, the stock single exhaust is like trying to fart through a straw. This is resistance felt at the crank; not attached, but felt non the less.At a stop and engine idling,going to WOT this may not be an issue. But it very soon could be.
 
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Scored a new clifford header set for $100 last week, pulled the engine from my parts car (71 Duster) found out it was a 225 and not a 195 like I was hoping but I have a head to cross section for a porting guide and an extra crank now, yay! New running plan is to do a long rod conversion still with a thin head gasket for maybe 9:1 CR with a carb and then stab and Eaton M90 on later down the road
 
Here's my recommendation for a carburetor. Look at the Weber staged two barrel. A big one. I am not completely familiar with their sizes, but a staged two barrel will be extremely efficient and provide great power without over carbureting the engine. They work fantastic.
 
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