Intake performance modifications.

[LaVelle]

I have a moderately built 454 running a Eddy Performer 2-o w/open adapter plate and Holley 800dp.
I think the 2-o intake is limiting the engine and it would like a RPM. ( opened ports on the 2-o to match the heads, from the cast peanut openings )

I was looking at the factory 3931067 high rise intake and 800cfm Q-jet I have, and that buy runner shape it looks a lot like the RPM and is almost the same height.

So the question is would the 3931067 and a 800cfm Q-jet out perform the 2-o, if I removed the plenum material between the primary's and secondary's and smoothed the turns from the plenums to runners? ( leaving the divider wall to maintain the dual plane)

[Walter R. Malik]

I have a moderately built 454 running a Eddy Performer 2-o w/open adapter plate and Holley 800dp.
I think the 2-o intake is limiting the engine and it would like a RPM. ( opened ports on the 2-o to match the heads, from the cast peanut openings )

I was looking at the factory 3931067 high rise intake and 800cfm Q-jet I have, and that buy runner shape it looks a lot like the RPM and is almost the same height.

So the question is would the 3931067 and a 800cfm Q-jet out perform the 2-o, if I removed the plenum material between the primary's and secondary's and smoothed the turns from the plenums to runners? ( leaving the divider wall to maintain the dual plane)

IF the weight is not a problem, the tall, late 60's cast iron factory Quadrajet carb base manifold will probably make the most overall power.
Putting the factory aluminum manifold for rectangle ports will be about the same but, lighter. Just like the marine engines.

EDIT: Holley used to offered a couple oval port, two plane manifolds based upon the Chevrolet aluminum rectangle port manifold which worked even a bit better; square 4150 carb flange and Dominator flange.

[mag2555]

Cutting down the divider will help WOT power, but with these type of shallow Plenum Intakes it can really screw with the part and mid throttle metering!
It cost more then grinding work , but a bigger size Carb is the best way to go on average.
You would be surprised how big of a Carb you can get away with on a duel plane Manifold and 454 cid!

[Newold1]

Can you give a little more information on your build such as camshaft and cylinder heads and such?

Just changing a moderate manifold change like this may not yield anymore if the whole induction system and camshaft specs. are not taken into consideration.

[LaVelle]

Can you give a little more information on your build such as camshaft and cylinder heads and such?

Just changing a moderate manifold change like this may not yield anymore if the whole induction system and camshaft specs. are not taken into consideration.

454 .030 oversize.
L2399 pistons (8.8-1 )
781's w/ 2.19-1.88 valves, pocket ported and casting buggers removed from runners.
230/236 @ .050 .552/.555 lift Hyd. flat tappet.
Eddy Performer 2-o, w/ Holley 800dp.
1 3/4" headers.

[LaVelle]

Cutting down the divider will help WOT power, but with these type of shallow Plenum Intakes it can really screw with the part and mid throttle metering!
It cost more then grinding work , but a bigger size Carb is the best way to go on average.
You would be surprised how big of a Carb you can get away with on a duel plane Manifold and 454 cid!

I planed on leaving the plenum divider intact, and adding a 5/8" open spread bore spacer to join the plenums, and to help the short side plenum air turn the corner after exiting the throttle blades

[Newold1]

My opinion:

With your engine that size camshaft, your heads, the cubic inches and compression I think you might be close to being slightly oversize on the carb, but proper jetting and tune it will work fine. I don't believe an intake change is needed as with those specs the engine is probably all done at 5500-6000rpms. Nice mild 454 engine that should perform nicely on the street. Unless you have some real issues or problems, get a nice tune both carb and ignition and leave it alone beyond that. JMHO

[LaVelle]

Your correct in it being a nicely performing street engine. ( To which there are no complaints.)
The 2-o intake and 800dp was what Pat had to use.

It's just that I did an 454 for someone else that had the same heads w/o the pocket porting and a 230/230 .050 .520/.520 cam and a Performer RPM intake that noses over at about 5800 rpm and is done, where this engine seems to plateau on power about 5500 rpm but still rpm to 6200 rpm without the power falling off got me wondering.

The hacked iron manifold and Q-jet are an experiment in stealth and deception, (without power loss) more that anything.
I ran across a article on Brzezinski intakes for SBC's, and wondered how that principle would work with a early high rise BBC intake.

[427dart]

Sounds like you want to get the most out of the stock type iron intake and look stock from the outside.
See if you can read up on what the F.A.S.T. ( Factory Appearing Stock Tire) guys are doing. I believe there are several running the 396/ 350 type setups in Chevelles.

[Newold1]

You should understand that neither factory iron manifold will even with some port and matching work never quite flow what the Edelbrock 2161 will flow.
The port volumes on the Edelbrock are just bigger.

If you take the GM iron 350-360 HP Holley carb version 3866948 and open the carb flange openings to match up with the openings on a GMHPP #12363407 aluminum intake manifold with your Holley 800 DP hardware'd like the GM factory Holley you would have a stock GM 396 -350-360HP looking intake system that will flow close to more than what your heads and cam will need. Your camshaft is probably where you are short on the 5800-5900 rpms you are looking for power at. Just my thoughts here.

[LaVelle]

Sounds like you want to get the most out of the stock type iron intake and look stock from the outside.
See if you can read up on what the F.A.S.T. ( Factory Appearing Stock Tire) guys are doing. I believe there are several running the 396/ 350 type setups in Chevelles.

Thanks, I'll look into F.A.S.T.. I was thinking of going to PIR. and talking with some of the super stock guys

[LaVelle]

You should understand that neither factory iron manifold will even with some port and matching work never quite flow what the Edelbrock 2161 will flow.
The port volumes on the Edelbrock are just bigger.

If you take the GM iron 350-360 HP Holley carb version 3866948 and open the carb flange openings to match up with the openings on a GMHPP #12363407 aluminum intake manifold with your Holley 800 DP hardware'd like the GM factory Holley you would have a stock GM 396 -350-360HP looking intake system that will flow close to more than what your heads and cam will need. Your camshaft is probably where you are short on the 5800-5900 rpms you are looking for power at. Just my thoughts here.

I don't have any flow numbers to argue or verify which will flow more air, but bigger runners and peak flow numbers aren't everything either.
A lot can be said for port velocity, and its effects on shift recovery

I'm wanting to get away from the Holley, as I said earlier this is an experiment in stealth and deception.
( I'll be putting the 2-o and the 800dp back on this engine after all is said and done.)
I'm just forward thinking on a deceptive peanut port 454 build for my 65 3/4 ton GMC. ( for sand bagging in a game of "who has the faster tow rig" )