this sound like a deal?
Hedman long tube headers 1968 Mustang 289-302 - $60
[hr]
Reply to: sale-532830542@craigslist.org
Date: 2008-01-08, 6:50PM EST


This is a pair of Hedman headers removed from a 1968 Mustang I parted out recently. They have ZERO miles on them. They have ZERO scrapes, bends, or dents. They were run long enough to burn the paint off and have a coating of light surface rust but would blast and ceramic coat or hi temp paint nicely! They may fit other year Mustangs as well but they were on a 68 with power steering and fit perfectly! Will fit 289 and 302 and maybe 351W You Ford guys ought to know. Price is 60 bucks firm. Call 248 542 3039 to inspect or purchase. Thanx

 

I don't see how a 480cfm carb could be too small on a STOCK 289, when Busch cars are turning almost twice the rpm and making 3 times the power with only 390cfm. People get way too much intoCFM on carbs, but in all realityCFM doesn't mean dick. It's fuel mixing that matters, you can have all the carb in the world, but if it can't meter fuel accurately and it can't atomise and shearfuel correctly, you lose power. Period. You can take a Holley carb that's the right CFM and tuned for an engine with downleg boosters, and replace them with annular boosters and make more power(not always, but often). The annular boosters arelarger so they reduce CFM,but atomise better, so even though theCFM went DOWN, power went up, because metering was improved. The purpose of the carburetor is NOT to get air into the engine, that's what the rest of the parts do. The purpose of the carb is to control fuel metering and atomisation/shear.

Carb CFM is also a VERY arbitrary rating system. 4bbls are rated at 1.5" Hg of depression and 2bbls are rated at 3.0". That means that a 450cfm 2v is NOT flowing the same as a 450cfm 4v, because the flow rates are based on different pressure differentials. TheCFM rating is just what it flows at the TESTED pressure differential. The higher the manifold vacuum the more CFM the carb will flow. That means if you flowed a 600cfm 4vcarb under the same rating standard as a 2v carb, it would have a rating of 850cfm rather than 600. You need to understand that the CFM rating of a carb isNOT the ABSOLUTE MAXIMUM it will flow, but ONLY what it flows AT THE PRESSURE DIFFERENTIAL FOR WHICH IT WAS TESTED! Put that same 600cfm 4v on an enginethat you're only pulling 0.5" Hg of manifold vacuum with, and you're only moving about 350cfm, NOT 600.

So what does that mean? It means if you run a "smaller" carburetor than what the engine "needs" that it WILL be a restriction to flow, but not nearly as much as you think it will(ie running a 500cfm carb on an engine that wants to move 600cfm, it will draw something like 580cfm through the 500cfm carb). You end up pulling more manifold vacuum in the process, so you move MORE CFM than the carburetor is rated for(cuz the vacuum/pressure differential/depression is different), but not quite as much CFM as the engine would pull with a totally unrestricted induction. But you NEED restriction to generate the velocity in the venturis to make the boosters work, that's the WHOLE POINT of a carburetor. Slightly less airflow traded out for increased metering means MORE power, not less, up to a point. Obviously if the carb is just insalely too small, like a 1bbl 150cfm carb on a 600 inch 10,000rpm race engine, you have a problem. But slightly increased shear/atomisation will make more power than slightly increased CFM will.

There's a reason the factory cars that ran well with carbs used "too small" a carb, and there's a reason that the NHRA Pro Stock guys are using ONLY as much carb as they need, and not more. And there's a reason that NASCAR engines can use "too small" of a carb and still make assloads of power(and they're running SMALL carbs for their setups). It's atomisation and shear, NOT CFM that makes power(again, up to a point). And even if you make slightly less PEAK power with a smaller carb, you'll make better overall AVERAGE power due to increased shear/atomisation at the rpms lower than peak hp. Plus on a street car the better shear means better mileage and throttle response, which are far more important than an extra 5-10 peak horsepower.

And btw, I'm not bashing on anyone's views here, it's just that there's so much misunderstanding and misinformation about carburetors out there that's been propogated and accepted as gospel truth, and a lot of it is wrong. When anyone talks about carbs it always turns to CFM ratings, but you never hear people talk about shear oratomisation, and only occasionaly is metering signal even mentioned. You can suck all the air into an engine you want, but if the fuel isn't metered properly it's not burned properly, and power is lost. That's why EFI VERY OFTEN makes more power than carbs do, NOT because EFI is better(in terms of power aPROPERLY setup carb often makes more), but because the carbs are often setup wrong and as a result the EFI is metering properly, and the carb is not. ANY system will make more power than another if it can burn fuel better. Remember, the whole point of an engine is to burn fuel to make power. It's air + fuel, not just air.

 

2" exhaust is too small. You need that motor to breath as much as possible, taht's why I'm saying 2.5". 3" is too big as wel because you will lose torque with a bigger exhaust. I only say Edelbrock carbs suck because all the old time gear heads here in CT do not like them. So again it's totally up to you what you choose.

 

You just said it yourself.

I'll probably think about switching to a 625 or 650 Holley design (Holley, Demon, Proformer, etc) when I upgrade heads.

 

I run an original Autolite 4100 on mine with absolutely no problems at all!!

 

well here go's i'am running two Edelbrock 500's on a Edelbrock F-28 intake Edelbrock heads TFS stage1 cam and shorties right now till i get car back from paint in a 65 FB 5 speed tremec seens to run fine would probably run better with 1 4B but dang it sure looks good with 2 4's tucked under that hood

 

That doesn't mean Edelbrocks suck, just that I'd like to upgrade to a slightly larger carb when I get some heads that will actually flow well, and I've heard good things about Demon and Proformer stuff. I like the Edelbrock/Carter design for simplicity, ease of tuning, and reliability. Holley can't touch it in those areas. But I'd like to see how well I can get a Holley design tuned to my engine. I see it as a challenge

 

Autolite 4100 that I purchased from Pony Carbs. Installation and adjusting was very straightforward.

 

Holley 700 DP on a 351C 4V.

 

4V Cleve's are so sexy