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327F Intake Manifold Documentation ( and aftermarket intake commentary )

May 13 2014 at 3:09 PM
Paul  (no login)

Hi guys,

One of the things about owning any sort of vintage device that was intended to move, is the desire to make improvements along the way. Thus is the case now with my 327F-powered 1966 20-foot Sea Skiff, so I did a little research before spending any money and found some interesting things.

[linked image]
This is what my 327F looked like when it arrived in Nashville. I bought the boat without knowing if it would run or not, and guys I really didn't care. As it turns out it did run with a carb transplant, but with very little extra, such as new exhaust logs, new brass freeze plugs (they were steel), distributor job, new carb, and a nice tune-up, this thing has proven to run like a champ. I have no idea how many hours are on the motor, especially due to the fact that this block once ran on the highways too.

Although I never pulled the motor I did have to rotate it in order to fix a cracked fiberglass crossmember, but hey, that's just an inconvenience. The photo is optically distorted at the bottom, those frames are actually straight.
[linked image]

After a little TLC it proved it was strong and ready to run.
[linked image]

Since I have already done the intake swap on a few motors in the past, including a very rapid 17-foot Chris-Craft (1956) V8, I know the difference a high performance intake can make and it can be pretty significant.

On the 327F, however, I am wondering a bit, because the intake that came on this motor is a good one to begin with.

[linked image]
[linked image]
[linked image]
[linked image]

You can see the numbers here, and guys, I don't know for sure if this is a stock 327F intake or not, because my motor block has been replaced in the past unless somewhere along the line CC also painted them organge, lol (found organge paint under the blue).

The number on my intake is 3844459.
[linked image]
(the letter X in the application section stands for Corvette).

Upon searching the numbers I understand the GM 327 of the era came in two stages of tune.

1). 250-hp at 4500-4800 rpm, single exhaust, somewhat restrictive exhaust manifolds, and 4-jet Rochester carb on a Rochester specified intake manifold. (The Rochester intakes were used on the early 283 CC motors, and these will not accept the Carter AFB or #1409 Edelbrock clone without an adapter).

20. 300-hp at 5300 rpm, dual exhaust, better exhaust manifold, and Carter AFB carb on the Carter specified intake manifold.

Other than that I understand the two motors are identical with the same cam, heads, compression, etc. Since there are so many heads used on these motors, I'll await further info to really make the final call on that one, although I'm told the 250 and 300 engines did get the same heads.

Chris-Craft 327F motors apparently got the 3844459 Corvette intake due to the fact that it was set up for the Carter AFB carb.

The difference in carb, intake, and exhaust side was worth fifty (50) horsepower according to GM. One only wonders why (with the use of the same general amount of liquid metal) GM just didn't cast a "good" intake for everyone instead of using that crappy Rochester intake. Of course, adding the dual exhaust would run the cost up a bit, but hey for 50 more horses ALL 327 automotive motors should have been 300 horsepower rated.

While I think the stock iron intake is probably a very good design, it is not the one GM used for the 340 and 360-horsepower 327 motors and those power numbers were probably obtained at much higher compression ratios and engine speeds than we would generally use in our classic boats. Another thing to consider, look at the photos and you will see a DEDICATED oil fill tube. Therefore, if you are thinking about swapping to an Edelbrock intake, for instance, better check and see if they offer the flat plate section that can be drilled for that filler tube, or you'll have to use a valve cover that has a oil filler cap. I drilled the high performance aluminum intake I put onto my 1956 17-foot Chis Craft Sportsman Utility in order to use the old style oil filler tube and also use some nice finned aluminum valve covers without any filler caps. That stock oil filler tub also ventilates the sump allowing the PCV system to work properly. Last time I checked, the Performer RPM came with the boss provided to drill out for the oil filler tube and the Performer RPM Air Gap did not.

Even with the good iron intake, I think the addition of the #1409 and a Performer RPM intake manifold would produce another 10 to 20 horsepower. Is it worth it? (No), but it would be fun (boatitis)!

Regards,

Paul














    
This message has been edited by FEfinaticP on May 13, 2014 4:08 PM


 
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AuthorReply
Paul
(no login)

Oil filler tube on the older SBC motors

May 14 2014, 5:56 PM 

Note the tall oil filler tube to the right of the thermostat, it also doubles as a vent to allow make-up air into the sump that is drawn out the other end by the PCV system.
[linked image]

Edelbrock makes three nice aluminum intakes that will fit the small block GM motor and work in our marine context.

1). Performer EPS
2). Performer RPM
3). Performer RPM Air Gap

Items 2 and 3 offer basically the same performance, with the Air Gap being a teeny bit better. Item 1 works better than a stock iron intake but not as well as items 2 and 3, which both offer better higher rpm power and a little bit better rating all up and down the rpm range.

The Performer EPS can be ordered with or without the filler tube, here is the #2703 with filler tube millina and tube ready to insert.
[linked image]

The Edelbrock Performer RPM intake manifold has a flat piece of metal (a boss) dedicated for this, and it is located where it can be drilled out to install the old style oil filler tube. You can either buy a new filler tube to replicate the old system or pull the old one off the iron manifold (like I did with my 17-foot Sportsman) and re-use it on the aluminum intake. The whole idea of the oil filler tube is to retain the old style valve covers that don't have filler caps.
[linked image]

However, the Performer RPM Air Gap intake does not have this boss, and there would be a need to find another way to admit make-up air into the crankcase. Can be done, just a point of information. Personally I like the valve covers without filler caps on these old engines, but a filler cap valve cover would be an easy solution.
[linked image]

Interesting to note the RPM and the RPM Air Gap are using identical internal port dimensions, but the RPM Air Gap has the divider plate cut down and the RPM does not. This is commonly done to enhance higher RPM power performance because it equalizes the flow a bit at higher speeds. Apparently the base RPM did not need that.

Despite what the photos might suggest, all of these aluminum intakes are NON EGR.

regards,

Paul

 
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Paul
(no login)

Small Block Chevrolet Intake Performance Charts (23 different models tested)

May 15 2014, 11:24 AM 


Here is a GREAT reference piece compliments of CAR CRAFT. This article will help us weed through the marketing pitches and see actual dyno results (AND PRICES TOO !).
http://www.carcraft.com/techarticles/1309_dual_plane_intake_manifold_comparisons/

It is an in-depth tech review with actual testing of 23 different dual plane intake manifolds of the style we would potentially use on our Chris-Craft boats. Of course for all out racing or offshore high performance use, some would opt for the single plane intakes but those are not considered in this particular test because they are basically for "racing only" and very high horsepower and rpm use.


Here is the good stuff just looking at performance, and I'll tell you now just forget about the one at the top, AFR (Air Flow Research). AFR is always better than anyone else when it comes to air flowing through an intake and a cylinder heat, but they are always far more expensive than anyone else as a result, and this intake is a composite, and OUCH, it is way expensive.

[linked image]


Interesting thing about the chart, when it comes to TORQUE, certain Edelbrocks fare well.
However, the delta between the top performing intake and the worst is 23 footpounds, and that is a unit of measure you would actually be able to feel in the boat (ability to spin a bigger prop, or cruise more comfortably at a given speed, etc.).

Then quite astounding, we see the delta between biggest and lowest horsepower is a whopping 48 horsepower. So guys, don't anyone buy a Professional Products Intake, they're at the bottom of horsepower and torque curves, but most likely they are better than the generic iron production intake we have on the boats.

If you have the clearance in your engine compartment or engine box, a 1" or 2" phenolic 4-hole carb spacer will provide even more torque to any of the intakes noted above. It will also help a bit in keeping the carb from cooking during operation and when the motor is shut down. Don't make the mistake and use an open spacer for your marine appliction, use the 4-hole in the rpm ranges we'll see.

So maybe I'll make a swap here sometime on my 327F, but I will probably grind off the brand identification and paint it to match the rest of the motor happy.gif We'll see.

Regards,

Paul

 
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XK-Mike
(Login XK-Mike)

Edelbrock 7101 Thoughts/opinons?

June 3 2014, 1:16 AM 

I was thinking of swapping my iron manifold for an Edelbrock 7101 Performer RPM. I will only be in fresh water so the automotive one should suffice. Any thoughts on the topic? I would love to hear them.

XK-Mike


    
This message has been edited by XK-Mike on Jun 4, 2014 1:27 PM


 
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Paul
(no login)

Intake clearance issues to check, more than just the carb height in the motor box

June 3 2014, 9:32 AM 

These intakes can (and will) make a difference, and with some of the lower powered motors it will potentially make more difference than the high performance motors because the latter may have already come with a performance intake.

Here is an example of what to beware of...........not sure this applies to your motor but I think you'll get the idea.

Note this FLV and pay special attention to the thermostat casting. See how it fits nicely within the limits of the intake casting?
[linked image]

Now look at what I think it an aftermarket intake with taller dimensions, note the same thermostat casting.
[linked image]
[linked image]

It appears to me that the thermostat has been placed on a (custom made?) pedestal in order for the cooling hose routing to still work with the higher rise intake runners.
I don't know this for a fact, but these are the sorts of things to watch out for if you do make a swap for an intake, and also beware if you go for the DUI ignition system
too, those are big and need a lot of side clearance. This may be a GM performance intake, but the Edelbrock RPM would be very similar. I don't know if those thermostat
lift castings are something of a CC part or whether the guy made his own, both are possible.

Other than the fit and clearance issue, also beware if your motor is a Q series because then all bets are off as you'll need a lot of hose and water pump adaptation work,
but once done the motor would probably love the intake. After installation I would watch plugs to be sure you have not created a lean condition, but probably will be good
to go !!

Regards,

Paul

 
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Verne
(no login)

250 vs 300 horse power

June 3 2014, 9:57 AM 

Paul, the 300hp did have the same bottom end as the 250hp (cam and all) but it also had different heads. The casting number ended in 461 and they are identified on the outside by the 2 "camel humps" cast into the front of the head. These are the heads everyone calls "fuellie heads' because they first appeared on Corvettes with F.I.
The entire top end (the breathing part) of the motor is what made the 50hp difference. Carb, intake, heads and exhaust manifolds. Without those heads (bigger valves) you won't see the 50hp increase.
BTW, the iron intake that was on your motor was cast on Dec, 5th 1965 at Flint.

Verne

 
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Craig J
(Login craigjudge)

SBC Heads

June 3 2014, 10:48 AM 

I take this chart with me when I go to swap meets. The good guys can spot good heads from 40'. I need a cheat sheet
http://www.fastnuf.com/Headguide.html

 
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Paul
(no login)

Guys.........just a bit of info here for ya..............about the SBC motors

June 4 2014, 9:32 AM 

When it comes to the SBC, realize every man, woman, grandparent, and child over the age of 12 can disassemble one of those blindfolded, and those who have stayed in a Holiday Inn Express can even rebuild them blindfolded.

As some people get older they even do this with fancy clothing to add another element of challenge.
[linked image]

The 327F motor remains my favorite of the series, due to a great marine format and the ability to add power in increments according to what's in your wallet. We've had some good reports on intake swaps. I may be giving one by the end of the season too happy.gif

regards,

Paul

 
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Paul
(no login)

I've heard that story with variations .......

June 3 2014, 4:15 PM 

.....depending who is telling the story, the heads do and do not come into play. The story I got was the dual exhaust and intake were the issue, and no mention of the heads being different.

I know this is so becuase I read it on the internet, lol, and stayed in a Holiday Inn Express, performed open-heart surgery at the age of 12 (with a ballpoint pen) and communicated in Italian when I did it.

regards,

Paul

 
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Paul
(no login)

Here is the intake manifold I selected for my SBC repower motor

April 5 2018, 4:21 PM 


 
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