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By fiftysixford - 13 Years Ago
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I was wondering if a 600 Holley would be too much carb for my 272. It is pretty much stock other than headers and electronic ignition.
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By rick55 - 13 Years Ago
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It is a bit large. A 465cfm is closer to what you want. It will run with the 600 but will never be a efficient setup.
Regards
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By lowrider - 13 Years Ago
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It's always better to run a carb a bit smaller cfms for the application over a larger cfm carb. They just seem to work better.
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By Ted - 13 Years Ago
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The great thing about vacuum secondary carbs is that they are difficult to be too large for an engine simply due to the vacuum secondaries only opening up enough to supply engine demands. With that being said, the smaller sized carbs are still more efficient in the lower rpm bands and that has to do with the constant speed velocity thru the primary side venturies being higher. If going for lowend drivability, then go with the smaller sized carbs but if going for a more aggressive driving style, then the 600 cfm carb will be the more suitable choice. While my own stock headed 272 ran well with a 750 cfm Holley, overall street drivability and fuel economy with the current 525 cfm Road Demon Jr. is better.
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By fiftysixford - 13 Years Ago
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Well thanks for all of the advice and comments. I was afraid a 600 might be a bit much. My dilemma is this: I have a good 2 barrel carb to build that would work great. (Motorcraft 2150) But, I would like the looks of a 4 barrel and I love the sound and feel when the secondaries open. I guess I'll stick with the Motorcraft carb for now......you cant argue with their reliability....they just aren't cool lookin'.
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By charliemccraney - 13 Years Ago
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According to the manual that comes with vacuum secondary Holley carbs, you shouldn't feel the secondaries open. They explain what's happening, but what it boils down to is if you feel it, it is not adjusted correctly.
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By Pete 55Tbird - 13 Years Ago
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Too much carb. Well, yes and no. It will be fine because your Holley 2150 that you will rebuild has two verturies that provide about 270 CFM (cubic feet per minute ) while the Holley 600 has two primary venturies that provide about 300 CFM, so thats in the ball park. Then when you mash on the gas pedal with the Holley 2150, no more. Game over. While with the Holley 600 AND VACUUM SECONDARIES you potentially have a lot left. IF YOUR ENGINE REQUIRES IT, ONLY IF. So, your choice. Pete
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By Talkwrench - 13 Years Ago
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IF you have a 600 ready to go then give it a go, A 465 is better, As Ted said its all about velocity. I have a 600 on mine [ its what the car came with] and I have it set up quite well, however I will eventually go to the 465. I found you have to have fuel! I run ,64 jets, blue pump cam 2nd position, 35 squirter, at the moment a standard grey secondary spring, I think going lighter wont achieve much. I can mash my foot to the floor standing start and it wont flatspot.
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By Grizzly - 13 Years Ago
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fiftysixford, You know a 390 or a 465 look like a 600 under an air filter. Buy a nice air filter and people won't look twice. Similar body same bowls. With you bum in the drivers seat knowone is looking at the engine. Cheers Warren
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By HT32BSX115 - 13 Years Ago
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I had a 600 and sold it to buy a new 390 Holley so I could use their accessory throttle position sensor.
With only 272 or 292 (stock) cu-in, A 600 will work, but a smaller carburetor will probably have a little better throttle response. I don't think I would get any beter performance out of a bigger carb. A stock 292 can only suck so much through ANY carb.
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By ejstith - 13 Years Ago
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If by some chance you wind up with a 390 they do not come with large enough jets. I chased a flat spot for 2 years & it turned out to be small jets. Replaced them with 57's & fixed that..
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By speedpro56 - 13 Years Ago
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That seems to fix the 390 cfm holleys everytime. The good thing about holley's is that their easy to work on and they perform well.
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By pegleg - 13 Years Ago
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If I remember correctly, the 390's were originally intended for 6 cyl applications. The intake pulses on the 6's are stronger, and there's fewer. Stronger signals usually require less jet area. I've run one on a TR-6, and actually found it to be too Rich!!
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By HT32BSX115 - 13 Years Ago
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pegleg (3/28/2012)
If I remember correctly, the 390's were originally intended for 6 cyl applications. The intake pulses on the 6's are stronger, and there's fewer. Stronger signals usually require less jet area. I've run one on a TR-6, and actually found it to be too Rich!!
I actually used Holly's carb selection tool and when it suggested the 390, I even called them to ask about using the 390...... they told me that the 390 would work well for my 292 application.
I haven't had a look at the jets that are installed but I'll get a set of 57's for when I actually try it.
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