How much CFM?
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Senior User
Joined: Oct 2015
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How much CFM?
I looking to put a 4 bbl on my 292. I already have the ECZ-9425-B manifold and want a carb as close to factory as possible. I prefer not to alter a lot of linkage, plumbing and such. I also know too much CFM can cause performance issues and I'm not looking to build a hot rod. Any suggestions on what would be a good range. I can get a pretty nice 600 CFM list 1850. Is this a good choice? My 292 is a '59 up block in a '58. Any suggestions much appreciated.
Cargo Master
Joined: Aug 2004
Posts: 2,575
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From: Greenville, SC
Many years ago I did the calculations and 500 is about right for a 292. I think I came up with something like 550 CFM. So a 600 would be good for a 312 Plus the 312 has larger valves in the heads. I have had a 500 Edlebrock Street Carburetor on mine since 2006 and am very happy. I can however, even with the 500, overload the intake if I really get on it, jetted for street. If you go with the 600, you will likely have to put smaller jets on it.
Note: I have the larger heads and dual exhaust. If you keep the stock heads and single exhaust, I would stay with the 2 bbl or you will be disappointed. The stock engine with the small valves cannot "breath" very well and can't handle the 4 bbl.
Note: I have the larger heads and dual exhaust. If you keep the stock heads and single exhaust, I would stay with the 2 bbl or you will be disappointed. The stock engine with the small valves cannot "breath" very well and can't handle the 4 bbl.
Logistics Pro
Joined: Mar 2005
Posts: 3,771
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From: tujunga, calif
It's beyond me why people think they need huge carbs on small stock engines that have anemic volmetric efficiency. Even on my 292 with an Isky E4 cam and G-heads it only calculated out to about 330 CFM. I'm using a 390 CFM Holley and it runs great at all speeds.
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Thanks for the input guys. I'm with you Jim on the huge carbs. I have just bought ram's horns from Mummert for duals. I need a bowl for a Holley 2bbl on another truck and can get this 600 4bbl for about the same money as a bowl unless I can run across an old junk carb to rob the bowl from. Since I have the 4bbl intake, I thought I might install it when I do the ram's horns and use the whole 2bbl on the other truck. I don't even know the CFM of my 2bbl, but it runs as fast as I want to go and gets there quick enough for me.
Anyone got a old bowl for a 1505 list 2bbl?
Anyone got a old bowl for a 1505 list 2bbl?
Post Fiend
Joined: Jun 2003
Posts: 8,209
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From: Black Hills of SD
According to this chart, the 57-early 58 pickup had the same 1.92 intakes and 69 cc chambers as the good 312 heads, just a little lower compression. In fact it shows 57 and early 58 trucks as using the exact same ECZ-G head. Later 58 had a 72 cc and 59 an 82 cc. I couldn't say one way or another on port volumes of any of these heads but it seems you have enough head to flow the inexpensive 600 cfm carb just fine
http://www.ford-y-block.com/cylinderheadchart.htm
http://www.ford-y-block.com/cylinderheadchart.htm
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Post Fiend
Joined: Jun 2003
Posts: 8,209
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From: Black Hills of SD
Thanks for the input guys. I'm with you Jim on the huge carbs. I have just bought ram's horns from Mummert for duals. I need a bowl for a Holley 2bbl on another truck and can get this 600 4bbl for about the same money as a bowl unless I can run across an old junk carb to rob the bowl from. Since I have the 4bbl intake, I thought I might install it when I do the ram's horns and use the whole 2bbl on the other truck. I don't even know the CFM of my 2bbl, but it runs as fast as I want to go and gets there quick enough for me.
Anyone got a old bowl for a 1505 list 2bbl?
Anyone got a old bowl for a 1505 list 2bbl?
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I've not even tried to identify my heads. This whole idea comes from growing up in the muscle car era and laughing at all our friends with small engines or lethargic ones with 2 bbl carbs. I'm not looking for more performance now, but like the idea of the 4 bbl. So with my bad bowl dilemma, I thought it was a good time to try the 4 bbl, but don't want to get carried away and hurt performance. I could get a 500 cfm 2 bbl if I just wanted bigger, but it's still a 2 bbl. From what all of you are telling me, I could probably run the 600 cfm if I don't plan on putting my foot in it too much. Not sure what I'll do, but again I appreciate the input.
I can get this nice List 1850 for 40.00, and a rebuild kit is pretty cheap. So you can see where the price of the bowl may not be as attractive to me.
I can get this nice List 1850 for 40.00, and a rebuild kit is pretty cheap. So you can see where the price of the bowl may not be as attractive to me.
Logistics Pro
Joined: Mar 2005
Posts: 3,771
Likes: 80
From: tujunga, calif
I see you are between a rock and a hard place. It's always nice to have the 4V rather then the 2V. Thats why I put the 4V on mine. 390 cfm and I rarely get on it hard enough for the secondaries to open, usually just on a freeway on ramp just so I can get fresh fuel in the back bowl. Under normal driving my engine rarely sees above 3,000 rpm. If you go with the 600 you will probably never use the secondaries either. Don't forget you will need a spacer between the carb and manifold, the large venturi size of the 600 won't match with the small holes in the Y manifold. Another reason I went with the 390, small venturi and better low RPM performance.
Post Fiend
Joined: Apr 2002
Posts: 19,311
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From: Waterloo, Iowa
One thing I forgot about when going to Rams horn manifolds, the heat riser and the rest of it goes away, used for carb heat.
Shouldn't those openings in the intake manifold always be blocked off in this instance? Otherwise exhaust would constantly be crossing through the intake and boiling the carb?
Shouldn't those openings in the intake manifold always be blocked off in this instance? Otherwise exhaust would constantly be crossing through the intake and boiling the carb?
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Senior User
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One thing I forgot about when going to Rams horn manifolds, the heat riser and the rest of it goes away, used for carb heat.
Shouldn't those openings in the intake manifold always be blocked off in this instance? Otherwise exhaust would constantly be crossing through the intake and boiling the carb?
Shouldn't those openings in the intake manifold always be blocked off in this instance? Otherwise exhaust would constantly be crossing through the intake and boiling the carb?
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
They often don't work, because they rust in the closed position. Many people wire them open or remove the valve entirely. From what I've read they are mostly designed to prevent carburetor icing, which can occur well above freezing temps. Rams horn equipped trucks never had the heat risers afaik, that's why I am curious about blocking off the intake runners. Somebody wrote it really changes the exhaust note, fwiw thought that was interesting.
Generally we want the fuel charge to be cool, so blocking off the center intake heat riser tunnel should help. Thin aluminum or steel sheet shim stock should work.
Generally we want the fuel charge to be cool, so blocking off the center intake heat riser tunnel should help. Thin aluminum or steel sheet shim stock should work.
Logistics Pro
Joined: Mar 2005
Posts: 3,771
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From: tujunga, calif
I personally don't block off the heat passage on street engines. The heat in the manifold helps atomize the fuel mixture. If that doesn't happen you end up with raw fuel entering the heads which can help wash down the oil from the cylinder walls causing premature ring and cylinder wall wear. Blocking it off maybe fine for a race engine. Millions of Y blocks ran for years without blocked of heat passages and still do. Just use a good insulating type spacer under the carb. Cool fuel charge means cool air not raw fuel in my understanding.
Just MHO
Just MHO