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By jimcar-9 - 10 Years Ago
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Hi
I am planing on rebuilding my 272 eventually, (Not right now, just collecting parts) It pretty much goes like this
272 0.040 over (278ci)
-B intake
-G heads
+10 cc dome pistons
Mummert ram horns
Mummert 270 cam (max 5800)
If I make some number crunching it says that the carb should be at 378 cfm at 83% volumetric efficency and 466 cfm at 100% but I guess this setup would never come near 100%
This is going to be stock(ish) looking/handling truck with some grunt under the hood. So I prefere some streethandling caracteristic like low end torque instead of dragstrip ET performance
So I have been hesitating between the Holley vac 2:nd 4160 model 390 cfm or 465 cfm......
Put out a question in a facebook group and got replies everywhere from "390 is perfect" to " 390 is WAY to small" " 465 is the absolutley minimum" "you could use a 650 at least"
I am at the moment leaning towards the 390 (as the numbers tells me), as I have a hard time understanding that the vac secondary would really be much use on a 650 carb when the numbers says the engine setup only needs abput 390 at the top end??
I know the are some gurus on here that might lead me in the correct way.
Thanks in advance
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By PF Arcand - 10 Years Ago
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First, is the vehicle actually going to be used normally as a truck?
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By jimcar-9 - 10 Years Ago
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Sure, I will be towing stuff up to 3300 lbs once and a while and the bed will see the city dump more than once.
Not a streetrod of any kind more of a truck. And maybe a redlight race when I feel for it (not very often)
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By charliemccraney - 10 Years Ago
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I don't think you're going to be towing 3300lbs with the 270 cam. That cam is getting closer to the street rod / hot rod end of things and your low end will not be as strong. The rpm range for it is 2000-5800. You need a cam that works from idle for towing.
I stand by my recommendation that a 465 is the minimum and a 570 will probably work well for you. Err on being a little bigger than necessary with a vacuum secondary carb.
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By jimcar-9 - 10 Years Ago
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I am open to suggestions would the 265 cam be more appropriate.
Or is it the stock cam that is need?
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By jimcar-9 - 10 Years Ago
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Or are there any other cam manufacturer and grind you could recomend?
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By jimcar-9 - 10 Years Ago
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charliemccraney (10/7/2015)
I don't think you're going to be towing 3300lbs with the 270 cam. That cam is getting closer to the street rod / hot rod end of things and your low end will not be as strong. The rpm range for it is 2000-5800. You need a cam that works from idle for towing. I stand by my recommendation that a 465 is the minimum and a 570 will probably work well for you. Err on being a little bigger than necessary with a vacuum secondary carb.
The rear axle has a ratio of 4,89. That should effect the towing as well to the positive....
Its also a manual trans, alot more formgivning than an auto when towing
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By 57RancheroJim - 10 Years Ago
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Are you sure the rear ratio is 4.89 and not 3.89?
I have a 3.89 rear with a 3 speed OD, 292 with a Isky E4 cam and use a 390 Holley and have no complaints, runs great in town and on the hiway. I did go to a larger squirter and upped the main jets a little..
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By speedpro56 - 10 Years Ago
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I think with the rear end ratio the 270 should be fine and I'm with Charlie on the 465 cfms Holley, even the 570 would work. I'm running around a 265 duration in my stock built 292 in my 56 convertible and feel like it needs to be a 270 duration cam at least. We tend to forget with our solid lifter engines we lose a little duration and lift with our lash adjustment which lowers the cam profile some from what I've read.
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By chris70 - 10 Years Ago
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Hi,my truck has an Isky E4 cam G heads and the 3.89 rear axle and i use a 390 vacuum secondary and 1 inch spacer and it is a pleasure to drive even in traffic with really good low end torque,with manual trasmission you should have no problems with this set up.
Smaller carburetors have a better signal at the Venturi by lower rpm than larger,on the othe other end you loose power on higher rpm range.
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By charliemccraney - 10 Years Ago
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You might get away with it with a 4.89 gear.
Chris, the E4 is a little smaller than the 270, which may make it stronger on the low end. Do you also tow 3300lbs with it and haul stuff to the dump? There is a big difference between cruising around with no load, versus towing.
My cam is a hair bigger than the 270, with more displacement and the low end is noticeably lacking for towing. This is in conjunction with a 3.70 gear. I have hauled probably about 1000lbs in the bed, an assembled Y, the automatic transmission and an engine hoist. While it did it, I wouldn't want to do it for anything that is even remotely regular. It's absolutely fine if not hauling anything of significant weight. If anything, the cam is a bit small for me and the way I currently use it.
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By 2721955meteor - 10 Years Ago
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I have a 1957ranchero,.040 over bore,bone stock cam,g heads 3.25 gears,3speed trans,570 holley vac. sec.it works well, good lift frome a stop on a hill,
i have instaled ford dura spark ign in the dist with 45gaped plugs.will install a 57 312 regrind cam in the future,to get some more high end grunt..tho my present resto takes most of my time,1948 merc f47 cnadian (f1),power will be 292 y with c heads modified to 190 intake valves,4speed manual,with 4th od.wondering about going to a 3.50 gears. still looking for 9in diff
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By jimcar-9 - 10 Years Ago
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Of course, my misstake 3,89 and nothing else.....ops
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By jimcar-9 - 10 Years Ago
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I will check out the isky E4 and look at the spets for that.
Thanks for the feedback guys
Keep em comming
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