Can anyone recommend a good 4 BBL manifold and carb set-up for my 72 351 C. I want ECONOMY not speed...... Will Ford products work well enough? It'd be nice to stick with Ford products... Thanks for any info....
Go for an Edelbrock 600cfm carb. There are similar size Holleys, but the Edelbrock has vacuum operated needles in the main jets -- reduces the size of the main jets when running at light loads, e.g., cruising. Hook your distributor vacuum to the manifold -- that'll improve slow speed mpg a bit. Run as much advance as you can without pinging on whatever grade gasoline you run. There will be others here who know the best manifold.
I agree with bb on the carb selection and if you are only looking for a cruiser stick with the stock cast iron manifold. If you have the money to spend and want a little better economy go with a different gear in the back (I.E. 2.75) that will bring your rpms down and that too will save some fuel.
mucho thanks Great, MORE stuff on my To Do List!!!! I also have long range plans for an overdrive tranny....... I found an inexpensive 4BBL Ford manifold just today.... I'll look at the Edelbrock carb next.....
4BBL economy Well, I've been told by several "car guys" that the smaller 4bbl carbs have primaries smaller than the 2bbl carbs, and that, if you keep off the pedal, your mileage "should" be better.... I'm no scientist, but I think that sounds reasonable......
Actually if you improve the intake with a 'performer' type aluminum manifold and a 600cfm carb ALONG with a large free flow exhaust, you should see better mileage. It produces horsepower at a lower rpm and therefore you accelerate just as fast with less throttle pressure. This raises the around town mileage somewhat. On the open road, you are running as efficiently as possible and should see the biggest gain in mileage there. My 79 went from 15.5 to 18 by going from a single exhaust to a 1.75 dia. dual exhaust, with an 'H' pipe. I'll be installing a performer RPM and a 600 holley this winter. Since it will improve intake air flow and mostly run on the primaries, it will lightnen the car a liitle and should improve mileage on the open road. Those changes took my son's 66 mstang from 14 mpg to 21 mpg open road when we did the same 3 years ago. Around town didn't change more than 1 mpg, but then we tend to use all 4 openings in the carb once it warms up..... Lance
Just a thought here, does your 351 C have 2v or 4v heads? BIG BIG DIFFERENCE that needs to be specified when you're talking to the parts house or online folks where you buy your intake. If you have 2V heads, the Edelbrock Performer intake will work well, and I agree with the 600CFM carb. More than that is a waste of money, especially for economy. Good Luck Bob Jones
Got a new Summit Racing Equipment catalog the other day. In it was a tech tip for calculating CFM. Here's what it says. Engine Size (c.i.d.) X Maximum rpm/3,456=cfm@100 percent Volumetric Efficiency (VE) Example: 350 c.i.d. X 6,000 rpm=2,100,000/3,456=608 cfm Approximately 608 cfm would be required for this engine. However, most street engines are capable of achieving only about 80 percent VE; a modified street engine with ported heads, headers, good intake, and carburetor can achieve about 85 percent VE; a fully modified race engine can achieve 95 percent or greater VE. The cfm number arrived at with this formula must be factored by this percentage. So I did some calculations based on my motor figuring, at best, it might make 85% VE. Here's what I came up with. 100% VE 85% VE 3000RPM 305CFM 259CFM 4000RPM 406CFM 345CFM 5000RPM 508CFM 432CFM 6000RPM 609CFM 518CFM Considering we have no way of knowing what the VE of our engines is, this is an interesting chart in that it shows we don't need as much carburetor as we think. Which leads me to think back over my years in the industry where guys would take a small block motor, drop a 750 double pumper on it and wonder why their car ran like shit. WAY TO MUCH CARBURETOR! All this is not to say you can't run bigger. Just don't go too big. I'm considering an upgrade and think my best option would be an Edelbrock Performer Dual Plane manifold with a Holley Street Avenger 570CFM. A good package that can be had at a reasonable price.
Assume??? Thanks for all the info guys... I have to assume I have the factory intake(it looks like 35 years of gunk) So, some manifolds hook up OK to the 2bbl heads, and others do not.. More pondering to do.... David
Jax, ya I agree to a certain point, 586-593cfm is what a 351ci engine requires. But a 351C is a different animal. Heads make so much of a difference on a Clevo, a 351C is not a generic GM engine, Clevelands like to Breath. His setup and good intake and a 650, good to go...
2-seater has it right, if you NEVER go to WOT then 600 is probably ok. Otherwise a little small for a 351. When I played with that 'other' brand of car...... The motor that is only 1 CI smaller ran best with a 650 and vacuum secondaries. A 600 worked for most street but when you went to pass, the car felt like it had asthma. Swapped it to a 650 and it ran like a goosed moose!! Just a thought. OR.... You could just stick a 500CFM Holley 2-bbl on your manifold and drive it!! Lance
Good info, guys. Thanx. The reason I picked a 570 was for torque. I was told a decrease in CFM would give me more. I'm presently running an Edelbrock #1406 "economy" model 600CFM. To get the best of both worlds I should go with the Holley 670?
