I purchased a brand new Holley 2300 series 350 cfm 2-bbl. street performance carburetor (#7448) for the car from Speed Unlimited off eBay for $290.83 shipped.
The Holley 2300 series carburetors are basically the front half of their infamous 4150 double pumper carburetors. They share the same primary metering blocks, center hung floats, 'V' fuel bowl, metering block & fuel bowl gaskets, same needle & seat(s), and the same jets as the 4-bbl carbs.
Out of the box the 350 cfm unit comes with manual choke, a 61 jet, and a 30cc accelerator pump. Both stock butterflies are 1.690" (11/16") which are the same size as a standard Holley 650/750 cfm double pumper carburetor.
They also have the standard 5-1/8" air cleaner flange so it will fit any standard 4-bbl. air cleaner, factory or aftermarket, which is a huge plus.
Holley rates the cfm of it's 4-bbl. carburetors @ 1.5" Hg pressure drop and their 2-bbl. carburetors @ 3.0" Hg pressure drop, so they are not an equal comparison when looking directly at the numbers.
Here is a breakdown showing the flow ratings of the original slant six carburetors compared against the Holley 2300 series #7448:
.......
Carburetor.............................
cfm @ 3.0" Hg...............
cfm @ 1.5" Hg
Carter BBS (/6 1-bbl.)..............................200..............................141
Carter BBD ('Super Six' model)................285..............................202
Holley 1920 (/6 model)............................185..............................131
Holley 1945 (/6 1-bbl.)............................170..............................120
Holley 2300 (#7448)...............................350..............................248
As you can see upgrading from my stock Holley 1945 single barrel carburetor to this unit I gained an amazing ~105.5% increase in cfm.
This carburetor also bests the factory Carter BBD 'Super Six' piece with a cfm increase of ~22.5%!
In order to install my AussieSpeed Hurricane aluminum intake manifold I need new gaskets. I ordered intake/exhaust manifold gasket and a hot box gasket. I went with the premium performance graphite gaskets for both places from HEMI Performance.
These gaskets have optimum "crush" value ensuring a tight seal for flawless results.
The gasket material is a perforated stainless steel insert sandwiched between two layers of flexible graphite to ensure that they have a super high heat tolerance like no other replacement gasket.
~$50.00 shipped from Australia. Shipping ended up costing the same amount as both gaskets did.
I also picked up this Hughes Engines slant six double row true roller timing set. They had the best price, had them in stock, and they had a free UPS shipping deal which brought the total to $49.50 shipped. I got the last one and they are not going to carry them anymore.
I came across a few sets of flow numbers for the factory slant six head.
This was what I felt the most accurate representation of a completely stock slant six head and was done on a quality bench by a very experienced tech.
Stock valve, stock ports, stock runners, and the spark plug was in.
@ 62.5 degrees and 28" water; performed on a calibrated Superflow 600.
Lift.........
Intake CFM.......
Exhaust CFM
.100"............
51...................
31
.200"............
99...................
52
.300"...........
131...................
65
.400"...........
140..................
109
.500"...........
146..................
114
.600"...........
147..................
115
It's a wonder these poor engines can make any power at all. Oversized valves and quality head work are a necessity to make any power at all on a n/a slant six.
With this in mind I decided to purchase an oversized valve kit for my little 225 leaning tower of power. There are no aftermarket head offerings for this engine and even if there were I sure wouldn't want to shell out that kind of cash for one anyways. There are a few slant six performance shops that can port your factory head, however they charge $600.00-1,500.00 depending on how much flow you want. As neat as these slants are I am not that dedicated and could have some awfullly nice SB or BB heads for that much coin. I decided to just do a simple port match, have my local machine shop install a set of over-sized valves (1.70" intake & 1.44" exhaust), and blend the bowls to match. Mopar used to make these same size valves but quite selling them back in the early 90's as demand was just not there anymore. My Mopar Performance engine guide states they showed a 23% increase in intake port flow and a 34% increase in exhaust port flow simply by using their O/S valves and having them backcut. The valves I purchased already come with a backcut which saves a little machine work ($$$) on my end. They are stainless steel and CNC machined. They came with heavy duty locks and maganese bronze guides. They are very nice, and I have ordered from this manufacture for other V8 head/engine builds.
Since the head will be coming off now is the time to get it shaved (~.065").
The slant sixers say the valves, port matching/bowl blending, and shaved head makes a massive difference, but I'm not expecting any miracles.
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