I DID SOME SEARCH AND FOUND THAT THE RECT. PORT INTAKE CAN BE USE WITH OVAL PORT HEADS ,AND IN (SOME CASES THERE HAS BEEN A BETTER E/T ??),BUT I WANT TO FIND OUT MY SELF .
I NEED TO KNOW IF SOMEONE HAD DONE THIS AND IF THERE IS A NEED TO TRY TO MACH THE OVAL PORT EDGE TO GET MORE FLOW AND NOT LET THE AIR TO CRASH AGAINST THE OVAL PORT WALL THAT IS FORM WENT THE RECT.PORT INTAKE IS USED .

While its probably better to smooth the transition, it is not entirely necessary.

The engine is sucking the air down the ports due to vacuum, not pushing air in, so the air doesn't really "crash." the mismatch is not as bad as it sounds, although there are probably inefficiencies due to the abrupt change...

IT IS GOOD TO HEAR THIS ,BUT FOR EXAMPLE SOMEONE OUT THERE USES A TURBO THIS IS NOT A GOOD THING TO DO . :confused:

Actually, some porting could be done on the intake manifold for a better match. At least that was the situation in my case. You'll probably find the port floor of the rect manifold port is higher the the oval head port. Also you'll probably find the rect intake port is narrower than the oval head port. The only place that grinding on the head will help is the roof of the oval port, which is much lower than the roof of the rect manifold port. But you can't grind enough out of the head port roof for a perfect match.

Do NOT lower the port floor on ethier the manfold or the heads!
Just leave it alone, the rectangular manifold is used basically to reduce the restriction the motor sees. creating a transistion wont help, IMO.

rcatala,

Just an FYI: When you use ALL capital letters on the internet that means you are SHOUTING (YELLING) in internet-ese.

Rod

You can install a rectangle intake on an oval port manifold - do NO porting, or matching. What this gains you over the typical old style oval port dual plane intake is plenum volume.

This rectangle intake to oval head swap has been completely obsoleted by the Edelbrock RPM Air-Gap intake.

The problem with many of the older design aftermarket oval port dual plane manifolds is that they were out flowed by the factory L78/LS6 (rectangle port) casting. The L78 intake flows quite well - it was my manifold of choice on my centrifugally supercharged 468.

...and if you happen to be one of those unfortunate souls with a really crappy oval port single plane intake like the Torker - you will be flat out amazed what a good intake will do power wise.

Thomas

Sorry about the capital letters and thanks for the advice Rod.
Thomas I got a Victor TD-454 installed but it is to much for my combo ,I just got a used Edelbrock rect.port RPM AIR gap intake vey,very cheap .

If you DON'T do any port matching on the bottom or sides you'll be amazed at the bottleneck created at the gasket surface. Do a trial fit with an oval gasket (just for experiment- must use rect gasket to run) and look at the impressions. The cross section of the port opening at the mating point will be smaller than the oval head port.

I've been reading the posts on this site for a while now with great interest. I come from the Camaro side, but my car is a factory BB and there seems to be much more info floatin around on this site pertaining to THE RAT.Anyway sorry for the ramble but this thread prompted me to join up and post.
I'm considering an intake manifold swap, I now have a Torqer 2 on my 427 and I wonder how much performance is to be gained by trying to shoehorn a performer or similar dual plane intake under my SS hood. My engine has oval port heads but I own a GM aluminum rec port intake. Will it be better? I think I have a bit of a mis match going with the single plane and the cam I have. Any comments are welcome.

Thanks, Harlan.

I believe one of the basics of porting:
DO NOT LOWER THE PORT FLOOR. It applys to the manifold as well!

You're trying to make an aerodynamic port, lowering the floor will NOT accomplish this.

If anything "raise the roof" but IMO dont touch it.

These look pretty good:

http://kjett.home.mindspring.com/Images/rectoval/

What testing did you do to back up those looks?
Interesting, becuase my thoughs are to fallow the ideas of "raise the roof" not lower the floor.

If i'm wrong i will apologize, i'm trying to prevent someone from possibly ruining a good manifold.

Originally posted by UnderPressure:
What testing did you do to back up those looks?
Interesting, becuase my thoughs are to fallow the ideas of "raise the roof" not lower the floor.

If i'm wrong i will apologize, i'm trying to prevent someone from possibly ruining a good manifold. I don't run oval port heads. I provided a link with pictures so people could see the differences in the port shape and what could be done to rectify the difference. I didn't provide any advise to do anything.

<being a nice guy to a new user>

hgerrick
post some more info on your car. are you working on a camaro? I ran into a problem with installing a performer on my big block, I had to change to a drop base air cleaner. If your working on a camaro then this may not be a problem.
Post what your car is (weight)
man. or auto.(stall convert.)
rear gear
cam you have now
what has been done to the motor.
I have a Torker on my BB and it responds nicely to my combo. graemlins/thumbsup.gif

Originally posted by 1966_L78:

The engine is sucking the air down the ports due to vacuum, not pushing air in, so the air doesn't really "crash." the mismatch is not as bad as it sounds, although there are probably inefficiencies due to the abrupt change... Tony,
Actually this is a common misconception but not factually correct. smile.gif
Old Ma Nature does not like pressure differences so when you have a low pressure area she tries to fill it.
Consider the atmosphere as "natures blower" with 14.7psi of boost at sea level & it will sort of make sense.
When you add a blower & it is showing 15lbs of boost what you actually have is about 30 lbs as you are adding 15 to atmospheric pressure.
Hi pressure air is just trying to fill the low pressure area the piston has created. It is the air pressure rushing in to fill a void not a vacuum pulling it in.
This is why you can have over 100% VE under certain circumstances, because a body in motion (air pressure in this case) tends to stay in motion so even though the cylinder should only hold it's measured volume say 50 cu in you can end up with say,, 55 cu in of air in the cylinder. Walla,,,,,110% VE :D
If this is confusing some of the blower guys here may be able explain it clearer.

kjett, Where did those pictures come from? It looks exactly like what I did to my rect port intake, but I know the pictures didn't come from me.

Yes, Im working on a 68 SS Camaro with the stock SS hood. Yes, clearence is a definate problem. That's why I bought the torquer. I think a BB Camaro weights around 3600#. Honestly, I've never weighed the car in the 25 years I've owned it. The car is a 427 with 400 Turbo and 373 12 bolt posi rear. The torque converter is a custom built 12" with about a 2500 stall and a positive vane angle to get a raised stall but still not be to slippy in the upper RPMS. It works great on the street. I built the motor in 1990. The basics are 9.5 to 1 static comp. ratio.Zero deck. Small port open chamber heads, 2.19-1.88 valves installed, valves unshrouded, bowl clean up, nice heads. It's a Cam Dynamics "high lift about-.540" short duration" hyd. flat tappet cam. The cam has a definate lope and I have 12" vacuum at idle. I have lost the cam card I just don't have more details. I remember the guy told me the cam was done at 5500 RPM unless I retarded the cam 3 degrees. The car goes like stink when you have your foot into it. What I would like to have more of is, tire shredding low end power without doing it with a slippy torque converter, also to clean up the just off idle smoothness of the engine. I"m trying to decide if a dual plane helps do this, or if I want to much, and need to change the cam to get this. I think an original performer fits, Anything higher is probably out. Is it worth the switch? Sorry for the long post.

Harlan.

I stand corrected, I asked two reputable sources today, and each mentioned that it was not detrimental.
See, you learn something every day!

I did some more searching graemlins/clonk.gif and I understand that almost everyone is keeping the ports untouch ,maybe because they try it for the first time and see some difference and keep it that way without trying any other modification . :confused:
Jules maybe i will keep them untouch ,There is allways something new to learn here in TC ,THANKS to TC MEMBERS graemlins/thumbsup.gif

Hey wolfplace...if its not a vacuum then why do you get a vacuum reading off the intake manifold? The cam,heads and exhaust also plays a part in overfilling a cylinder. correct? Learn me something, but hey I'm from Missouri so ya gotta "show me"

Wolfplace,
Overfilling the cylinder involves pressure waves and inertia super charging.
As well as correct valve timing, and an intake that is aerodynamic and promotes a high velocity charge.

Harlan, guaranteed that an oval port Edelbrock Performer RPM or Air-Gap will definately wake up your combo.

I understand that tens of thousands of Torker manifolds have been sold for space limited applications not using a drop base air cleaner assembly - but it flows absolutely terible.

Thomas

Originally posted by UnderPressure:
Wolfplace,
Overfilling the cylinder involves pressure waves and inertia super charging.
As well as correct valve timing, and an intake that is aerodynamic and promotes a high velocity charge. That's all part of the "certain circumstances" I was referring too. :D
But it starts with a pressure differential otherwise you have zero movement of air smile.gif

Bob,
Didn't say there wasn't a vacuum, I said the vacuum doesn't pull the air in

Thank You!!!!!!! That's what I'm looking for. Somebody that has some kind of idea if the Torquer works or not. I bought it solely for height considerations. Maybe this is the wrong site but does anybody know what will fit under the hood of my car? 68 Camaro BB with an SS fake louvre hood.

Thanks, Harlan

hgerrick, my '67 Camaro with 454, iron heads, alum. intake, M21 4 speed, 12 bolt, all steel body, full interior complete with am radio weighs 3280 with 1/3 tank of gas.

Bob,
Didn't say there wasn't a vacuum, I said the vacuum doesn't pull the air in
I'm still lost,,,if the vacuum does not pull air in,then why when you are under the hood,,,if you crack open the throttle,you can feel the increase of air flow into the carburetors throat. I know its not an immediate increase in barometric pressure. The piston going down in the cylinder is most certainly creating the vacuum on the intake stroke,afterall the internal combustion engine is just an air pump,pulls it in thru the carburetor,pumps it out the exhaust after it has been compressed,heated and made its horsepower. heat=power and vice versa

Bob, I think it's easier to visualize if you think of air being like water although less dense. Air molecules have weight just like water molecules. The deeper you go in the ocean, the more water molecules above you and higher the pressure exerted by the water. Same with air-we live on the bottom of the "ocean" of air. The higher you go in the atmosphere, the less air molecules, and therefore less weight or pressure.

Now, just like in a bathtub when you open the drain plug. There's no water in the drainpipe so the weight of the water makes it try to flow down the drain.
When the piston moves down on the intake stroke, the cylinder volume suddenly increases (negative pressure or "vacuum") and because the pressure in the cylinder is now lower than the 14.7psi atmospheric, the air tries to "go down the drain" into the cylinder.
Any object that is moving has inertia-its resistance to change from its present course or state. When the air molecules are moving at high velocities, they become more difficult to stop. They are elastic and compressible. As they move at high speed down the intake runner, the intake valve closes and they smack into the backside of the valve. Like a slinky, the rearmost molecules keep moving and "pack" into the area which raises the pressure in the valve pocket area just slightly higher than atmosphere. More air molecules are then present. When the valve reopens, that higher pressure present behind the valve allows a greater amount of air molecules to push their way into the cylinder. Same when the piston changes direction at the bottom of the stroke-the air can't immediately stop and has enough inertia to keep moving in its original direction (inward) against the now upcoming piston. These are the inertia waves which you referred to.
This is how inertia "supercharging" works- it uses the weight and speed of the air molecules and their resistance to changes to pack more of them into the cylinder.

I don't know if I explained it well enough but this is just a simplistic overview of the situation and I'm NOT a scientist.

Randy

Thanks, Wooderson

Sounds like my weight estimate was a little high.

What kind of intake-hood combination do you have?

Thanks, Harlan.

GM factory high rise intake and GM cowl induction hood. The intake is actually a "marine" intake which was used by Mercury Marine from GM. It looks identical in height to the 60's style factory high rise except it can use either a square or spread bore carb. I use a spread bore Holley and '67 Olds Toronado dual snorkel air cleaner. It's a drop base air cleaner that sits low. The frame mounts are for a '67 327 and the engine mounts were from a '68 350 Camaro if it makes a difference in height. Don't know for sure.