kirkallen143
Famous Member
Are they the same? The metering blocks for the 7448 and 4412 holleys, just wondering if they are the same and are interchangeable.
Kirk
Kirk
metering blocks: 350 vs. 500 cfm Holley
- Thread starter kirkallen143
- Start date
Howdy Back Kirk:
I don't have a #7448 to compare to my #4412, but I can tell you that by the "Holley Carb" book they have different main jets and a different rated power valve. Of course these items are replaceable. The differences that are more difficult to tune and/or adjust are the air bleeds and internal channel restrictions. Hopefully William, aka WSA11, will be along with more information soon.
Main Jet, Power Valve rating, Primary discharge nozzle
#4412- 73 125-50 .028"
#7448- 61 125-85 .031"
Since so many other parts are interchangeable I'm guessing the metering blocks are too. The metering block gaskets have the same number for both. I'm fairly certain the differences will be internal.
Adios, David
I don't have a #7448 to compare to my #4412, but I can tell you that by the "Holley Carb" book they have different main jets and a different rated power valve. Of course these items are replaceable. The differences that are more difficult to tune and/or adjust are the air bleeds and internal channel restrictions. Hopefully William, aka WSA11, will be along with more information soon.
Main Jet, Power Valve rating, Primary discharge nozzle
#4412- 73 125-50 .028"
#7448- 61 125-85 .031"
Since so many other parts are interchangeable I'm guessing the metering blocks are too. The metering block gaskets have the same number for both. I'm fairly certain the differences will be internal.
Adios, David
kirkallen143
Famous Member
CZLN6":3dvr15d2 said:
I was thinking the same thing, most use the same part no. and gaskets are the same. I finally got the 7448, and the only full vacuum sorce is the 1/2" line for the pcv port, and I did not need the timed vacuum port from the metering block that it has. That is why I ask, to see if I can replace the throttle base and metering block...I'll give it a try anyways.
I am also going to play with the autolite 2100 for boost application, such as Linc is doing (got one at the JY for $10.00). There is a feller over at TurboMustang.com doing this very same thing, yet he will run alcohol in his. Linc has been talking to him lately. First thing is to drill/tap the jet orfice to 1/4"-32 extra fine to accecpt holley jets. I'll keep you updated. Have a good one.
Kirk
Kirk, the metering blocks are not interchangeable as produced from holley.
The power valve restriction under the power valve is different, the 7448 I think has a .059 orifice, which is right on at full throttle with our small engines. The main jet can be brought down to a 59, & a 8.5 power valve will cover the lean holes on part throttle acceration.
The 4412 was designed for a V8 & is way too rich.
Go to a 68 main jet, 8.5 power valve & the PVRC needs to be reduced down to .055 or .052 depending on your engine.
The idle restriction in the metering block needs to go from .034 to at least .033 or lower on a small engine.
The hole in the throttle blade should be replaced with a plate from holley with no hole or you can braze this hole shut. The reason for this is so when you set your curb idle the throttle plate uncovers a little more of the transfer slot which is needed for proper transition.
There are many more mods to perform on the block for perfection, but I'll cover that in another post. Hope that answers your question. William
The power valve restriction under the power valve is different, the 7448 I think has a .059 orifice, which is right on at full throttle with our small engines. The main jet can be brought down to a 59, & a 8.5 power valve will cover the lean holes on part throttle acceration.
The 4412 was designed for a V8 & is way too rich.
Go to a 68 main jet, 8.5 power valve & the PVRC needs to be reduced down to .055 or .052 depending on your engine.
The idle restriction in the metering block needs to go from .034 to at least .033 or lower on a small engine.
The hole in the throttle blade should be replaced with a plate from holley with no hole or you can braze this hole shut. The reason for this is so when you set your curb idle the throttle plate uncovers a little more of the transfer slot which is needed for proper transition.
There are many more mods to perform on the block for perfection, but I'll cover that in another post. Hope that answers your question. William
The variance between any 350 and 500 is h-u-g-e. The little 350 was a Ford 289 replacement, the 500 designed for 396 and 390's.
The ported vaccum differs between the 350 and 500, some older pre 1976 350 cfm carbs ran 4150 style float bowls, there were some truck versions which had vaccum vents for emissions. Check valves, picture window power valves, some were reverse idle, some 350's got Economaster 8 slot venturi boosters which made it a 320 cfm version.
Originally, Holley designed the 2300 series carb for AMC and International Havester in 1963 as a 280 cfm 2-bbl carb. In about 1966 (Ford Total Performance), and again in 1969 (Mopars Mass Transit System and Chevrolet Pefromance part numbers), a string of Tripower variants used hacked up versions of the 280 and 350 Holley with vaccum vents and 4150 float bowls, and cut down ait horns and even vaccum operations.
Then Holley sort of sold out lots of the tri-power float bowls in the 1970's on the 350 and 500 cfm 2-bbl. It was now an economy upgrade on the Rochester 2 jet, Autolite 2100 or Motorcraft 2150. 350 was for a 221/260/289/302, the 500 for the 3512v, 352-390 FE Despite its popularity, the 7448 and 4412 has never been an emissions legal carb, but there are a heap of them sold each year for econo oval track V8's.
Last week, I got two 9117 350 versions which were exactly the same, what the odds were of that happening, I don't know.
The ported vaccum differs between the 350 and 500, some older pre 1976 350 cfm carbs ran 4150 style float bowls, there were some truck versions which had vaccum vents for emissions. Check valves, picture window power valves, some were reverse idle, some 350's got Economaster 8 slot venturi boosters which made it a 320 cfm version.
Originally, Holley designed the 2300 series carb for AMC and International Havester in 1963 as a 280 cfm 2-bbl carb. In about 1966 (Ford Total Performance), and again in 1969 (Mopars Mass Transit System and Chevrolet Pefromance part numbers), a string of Tripower variants used hacked up versions of the 280 and 350 Holley with vaccum vents and 4150 float bowls, and cut down ait horns and even vaccum operations.
Then Holley sort of sold out lots of the tri-power float bowls in the 1970's on the 350 and 500 cfm 2-bbl. It was now an economy upgrade on the Rochester 2 jet, Autolite 2100 or Motorcraft 2150. 350 was for a 221/260/289/302, the 500 for the 3512v, 352-390 FE Despite its popularity, the 7448 and 4412 has never been an emissions legal carb, but there are a heap of them sold each year for econo oval track V8's.
Last week, I got two 9117 350 versions which were exactly the same, what the odds were of that happening, I don't know.
kirkallen143
Famous Member
Yes, upon further inspection (and answering my own ?'s) the throttle bases are NOT interchangeable, bigger venturi's on the 4412. As for the metering blocks I only saw where some of the metering circuits where in different locations (by what I mean is, the tiny holes where the fuel flows), some were higher in the grove next the PV circuit (not the pvcr's). Pics would be a whole lot better at explaining than I can do.
I plan on trying these different metering blocks to see what I can come up with. I will let ya know.
Kirk
I plan on trying these different metering blocks to see what I can come up with. I will let ya know.
Kirk
Kirk, if you want to update the metering block, which includes all the proper upgrades to the idle & transfer mode, Quickfuel Technologies makes a metering block.
This block still needs modifications to the emulsion bleeds & the PVCR still has to be drilled & tapped for a 6-32 screw in adjustable orifices.
You cannot just bolt on the metering block as received.
This block saves you several hours of trying to modify the stock metering block. William
This block still needs modifications to the emulsion bleeds & the PVCR still has to be drilled & tapped for a 6-32 screw in adjustable orifices.
You cannot just bolt on the metering block as received.
This block saves you several hours of trying to modify the stock metering block. William
kirkallen143
Famous Member
Hey, I sure do appreciate the suggestion, but now it is what money can afford.
I did put the 4412 metering block on the 7448 and it started and ran pretty good. The rich exhaust smell is not as bad (I mean doesn't burn your eyes) and the only thing I can see now is that you have to pump the accelerator a couple of times for start-up, even when it is warm, the 4412 you did not. Of course I am running 68 jets and the A/F meter is showing rich, but not real rich. I put the 8.5 PV back in since at idle I have @ 18"Hg. I need to play with the timing. I had the vacuum adv hooked up, but had to set my initial timing so retard, 14* ATDC, off the line was bad. I will try no vacuum adv and run the mech only (limited to 12*) and set my initial from there. The 7448 runs real good, very, very crisp throttle response with the orange cam in #2 position and a 0.028" squirter. The smaller venturi's really seem to work better on this almost stock, boosted engine (from what I have seen so far). More updates to come, thanks for listening.
Kirk
I did put the 4412 metering block on the 7448 and it started and ran pretty good. The rich exhaust smell is not as bad (I mean doesn't burn your eyes) and the only thing I can see now is that you have to pump the accelerator a couple of times for start-up, even when it is warm, the 4412 you did not. Of course I am running 68 jets and the A/F meter is showing rich, but not real rich. I put the 8.5 PV back in since at idle I have @ 18"Hg. I need to play with the timing. I had the vacuum adv hooked up, but had to set my initial timing so retard, 14* ATDC, off the line was bad. I will try no vacuum adv and run the mech only (limited to 12*) and set my initial from there. The 7448 runs real good, very, very crisp throttle response with the orange cam in #2 position and a 0.028" squirter. The smaller venturi's really seem to work better on this almost stock, boosted engine (from what I have seen so far). More updates to come, thanks for listening.
Kirk
