quote:
Originally posted by "72 GTS:
Hello
Same question for me please, I would need a 4150 style Holley carburetor, to run the 351C engine
Here's the camshaft
http://www.compperformancegrou...egory_Code=F351MFTCMThis is going to be a Fia approved engine 351ci, Holley dominator intake, gts headers, 4 barrels (Holley) carburetor, points distributor,
First step before the webers, who knows ?...
Kind regards
Philippe
Years ago Ford Muscle Parts (John Vermersch was the engineer then and still is head of Ford Racing Parts Division) recommended a Holley 850 cfm "double-pumper". The old number was R-4781.
There testing showed it made 15hp more than any other carb.
I personally ran a Holley r-4779. That is a 750cfm double pumper. It ran best on an Edelbrock Torker.
It was calabrated out of the box, to have a much heavier idle then say, and 1850 would.
Holly's explanation was that was needed because it was anticipated to be used on a car with race size headers and collectors.
They said that the heavier idle was to eliminate leaning out caused by the scavenging effect of the headers.
I can tell you that the idle is heavy and is annoying. It will smart your eyes because of that BUT the car ran like a frightened cat.
The 48 ida Webers in fact have a reputation for being heavy at idle. The 4779 Holley is worse.
The Webers with this cam,
http://www.compcams.com/Compan...s.aspx?csid=861&sb=2and the Hall 180 headers idle surprisingly clean.
This I am convinced is because of the header scavenging effect. What that simply means is the headers are doing what they are supposed to and the size and length of the tubes and collectors are matched well.
I know you don't need the 850 (4781) but the engine likes very much the mechanical secondaries with the secondary accelerator pump.
To run the Holley double pumpers which work very very well on a track car, you really need to be able to adjust both the idle air bleeds and the main air bleeds to get the air fuel mixture where you want it for a street car.
For a track car though, out of the box, they are fine.
For strictly performance, i.e., get up and go, you will be much happier with a Holley double pumper on a hot Cleveland then any of the vacuum secondary carbs. 750 is about the size that you need.
An 1850, vacuum secondary 600cfm is all any 351 needs ON THE STREET. It is clean and crisp but really will not give you the top end that you want on the track. No where near it.
I aslo tried on both my 427 and 351c, a 69 428 cj carb (735cfm), a 69 Boss 302 carb (780cfm), and a generic 3310 (780 z28 Camaro carb).
The three vacuum carbs were all very flat and clean at idle which is to be expected because they were not calibrated for headers.
You are going to get a lot of different recommendations and with the difficulty of accessing them on a Pantera you want to be close to start with.
With that camshaft Mikael is correct with the 600cfm recommendation. The problem is, and this is from personal experience, it is way to small for a track car.
Neither is a 6700 rpm redline reality on the track. Try 8,000 rpm, and the engine better have been built for that consideration.
At 6700rpm you are going to feel like the track workers look in their electric golf carts.
I would go with the hotter cam (and have) and stay away from the special "Weber cams" for your purpose, when you get to them that is.
In my opinion, those are to make the reversion more acceptable for street use so the guys in their Gucci loafers and heavy gold dog collar necklaces don't get their noses all out of joint needlessly. You do not want them for track cams. For that purpose, they just plain suck.
I saw a before and after with a Boss 351 with 48 ida's. On the track it was easily down 100 hp with the special "Weber cam". You could clearly feel the difference in the car and see the difference on the track from a distance.
The car had no top end get up and go and was just plain flat.
Wave you dyno numbers at me that show the cams work. I don't believe it. I saw the difference for my self. You LOOSE power. A lot of it.
I would say a 4779 Holley, out of the box and just adjust the idle. The 427 likes the 750 also, but is difficult to compare directly since there are too many differences in parameters caused by the cubic inches. There are similarities in some respects but too many differences in others.
With that cam your car will idle around 850 hot, but there isn't enough overlap for a track car. That's a hot street cam that you have.
My personal opinion is that the best overall set up would be a 2x4 Holley carb set up with two 1850 carbs on a 180 degree manifold like Ford ran with the 67-68-69 Trans Am race Mustangs.
That set up just plain works and no need to look further. The Wizard may have stumbled upon that set up purely by accident but it is one of the best kept secrets ever with a street/strip set up.
It certainly ran exceptionally well under race conditions which is fact, not conjecture on a pitifully bad head design.
It would run as if you had a single 600cfm on the street but give you the top end that you need.
I have this on my 347. That is running vintage 302 Windsor heads.
They are race ported but they aren't even a close comparison to my A3 circle track heads.
Unfortunately no one ever made this combination manifold for the Cleveland.
And before anyone chimes in that a single Holley makes more power and is better, all I can say is that is just not true and you have to drive one to understand.
There is a very funny thing that happens with engine dynomometers and air flow benches, they really are lousy on the track. They don't handle for crap either!
Of course this is all my opinion based upon my experiences and is not a rehash of what a car magazine has written for the sake of sensationalizing their magazine sales.
I simply am not going to argue with a dyno. All I will say is put the engine in the car and see if it is faster.
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