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By Lex - 12 Years Ago
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I'm thinking about putting on a John Mummert aluminum intake on my stock 312 and maybe a 600 vaccum secondary Holley. Question is do you think I would notice any performance gains and would the 600 be too much carb for that engine?
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By NoShortcuts - 12 Years Ago
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Hi Lex,
One of the features on this site is the search function. Ted Eaton has done numerous series of dyno tests and published graphed results and tables. His testing has included things like different make 3x2 manifolds, different makes, models, and sizes of single quad carburetors, exhaust headers, cylinder head comparisons, and single quad intake manifolds, to name a few that come to mind. Sourcing this information is a little like using an old library card catalog, or searching the Internet. -Use different key words to ensure that you find everything that is available.
The short answer to your question is that for many stop-and-go street driving applications, the '57 FoMoCo style 4 barrel iron manifold is going to serve you well. Too, for the street, small primaries and vacuum operated secondaries will give good, crisp, low speed throttle response. IF you are going to be regularly operating over ~3,000 rpm (fuzzy on the exact rpm, might be 3,500) doing highway driving, the Blue Thunder manifold (which I'm understanding John Mummert helped design at an earlier time) and the newer Mummert single quad manifold will provide superior engine breathing performance.
Again, the search function on this site is an INVALUABLE tool. The archive of information is AMAZING. My apology for being a little glossy with my answer. -I'm sure you'll want the specifics. IF you're working on a 'Bird, you'll have to go with John's low rise unit instead of the high rise because of the hood clearance issue.
Hope this helps. 
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By Lex - 12 Years Ago
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NoShortcuts (5/6/2013)
Hi Lex, One of the features on this site is the search function.
I don't want to be disrespectful but, I'm totally aware of the search function. I was one of the top posters , over 5,000 , on another forum so I know how it works, but sometimes people just don't have time to sit and search tons of pages and just need to ask a quick question then come back later to read some answers. I was always a firm believer also, that if everybody used the search function and browsed through the archives, that there wouldn't be any new topics and therefore the forum would become boring as so many of them are. Just had to express my opinion. Lex
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By Talkwrench - 12 Years Ago
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As No Shortcuts said..
If you have a cam , and your going to be givin' it some often, then go for it.
I had a 600 on my "lowly 292" it ran well with some simple mods , I changed to a 450. there wasn't that much in it to be honest. The problem with going to the smaller Holley has been that damn bowl vent.. It dries out the fuel to quick ! With the 600 I could leave it for weeks, two pumps, start first time every time..
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By speedpro56 - 12 Years Ago
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You'll do fine with the new intake and carb in my opinion. I've run the intakes from blue thunder on fairly stock 312s and do very well, just don't do any porting because they flow great already. 500 cfms may be a little better than a 600 but the 600 should still work fine.
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By charliemccraney - 12 Years Ago
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Go with a Street Avenger 570, if you will be getting new carb and want a Holley in the 600cfm area.
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By Lex - 12 Years Ago
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Talkwrench (5/7/2013)
As No Shortcuts said..
If you have a cam , and your going to be givin' it some often, then go for it.
I had a 600 on my "lowly 292" it ran well with some simple mods , I changed to a 450. there wasn't that much in it to be honest. The problem with going to the smaller Holley has been that damn bowl vent.. It dries out the fuel to quick ! With the 600 I could leave it for weeks, two pumps, start first time every time..
I have the 465 new style carb they use for the replacement on the T-Birds and the 1st thing I did was change the primary fuel bowl to the one without a vent. Been down that same road before with duals on an FE and without an electric pump you have to crank and crank after it sits for a few weeks. Thanks for the input.
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By MoonShadow - 12 Years Ago
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Not too many years ago when I did my first "modern" Y I put on a 600cfm Holley. At the time I think I was a bit over carb'd. Now, with the developments over the last couple of years I don't think thats true anymore. Long story short a 600cfm should be fine on your engine.
You know this is a bug that is going to bite you! Next is a trip to the Y-Block Nationals in Columbus, Ohio Labor Day weekend. After you see what these guys are doing with their Y's I expect you to suffer a bite or too from the speed bug.
We are having more fun with Y-Blocks than ever before and it just keeps getting better! Chuck
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By joey - 12 Years Ago
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Lex (5/6/2013)
I'm thinking about putting on a John Mummert aluminum intake on my stock 312 and maybe a 600 vaccum secondary Holley. Question is do you think I would notice any performance gains and would the 600 be too much carb for that engine?
There are many opinions on a question like this, and so I'll throw mine into the ring. When you say stock 312 I assume the heads are untouched. Do you know which heads you have? Obviously some flow better than others, and that's a big factor when considering carb size. But in my opinion a lot depends on how you plan to drive the car. If it's for street cruising (which is what I infer from the "stock" description) then more often you'd be interested in low-end torque, nice pickup from stop, rpms up to 3000 or 3500 most of the time. In that case I'm not sure if all 600 cfms would come into play very often, and a smaller carb might be more efficient and actually perform better (not to mention more gas-friendly). My own 312 is set up with stock manifolds, but it has a mild cam and ported "C" heads. I elected to put a 575 cfm Demon carb on it. It runs great, but I certainly wouldn't be looking for a bigger carb, as the 312 is only going to create a certain amount of vacuum anyway under most driving conditions. But if your goal is high rpms and going fast, then your demands will obviously be different. In that case you might want to supplement the Mummert and new Holley with better flowing heads and exhaust. Limiting the changes to only the carb and intake kind of puts you halfway in between (not that such a setup isn't viable). To refine your mechanicals to best advantage one needs to define the driving goal (you probably already have, it's just that I don't know). Of course making more modifications would mean more work, more money, and further deviation from original.
As I said, just my 2 cents.
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By Ted - 12 Years Ago
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Lex (5/6/2013)
I'm thinking about putting on a John Mummert aluminum intake on my stock 312 and maybe a 600 vaccum secondary Holley. Question is do you think I would notice any performance gains and would the 600 be too much carb for that engine?See if this past thread helps. http://forums.y-blocksforever.com/Topic77765.aspx
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By NoShortcuts - 12 Years Ago
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Hi Joey,
I very much like your input on Lex's question. -Well put... and worth far more than two cents in my view.
Salute!
Regards,
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By joey - 12 Years Ago
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Thanks. I am always struck by how the gentlemen on this board are so generous with their time and advice. The expertise shared here is a great asset to Y-Blockers. Just trying to contribute whatever little I can.
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