I have done a search on this, and still cant find a definitive answer. Im an going to be using my rect. port heads on the engine Im building. I have an old GM (winters casting) rect. port intake, aluminum. It came on the car back when I bought it. My RPM air gap oval port intake is sitting on the bench...that's the one I really want to use. I dont want to have to buy another rect. port intake. Can I, or can I not use the oval port intake on rect. port heads?? I was told by an engine shop that it should be done that way, it speeds up the intake charge due to the smaller runners....but the previous posts indicate a rect. port intake on oval heads, just the opposite of what I need. Or should I just use the old low rise intake that matches? How much of a performer is that type on intake?? John

Won't work...oval intake won't cover rectal port heads....rectal intake on oval heads is the way to go.

Some oval intakes will cover the rec port openings. You have to check the flange side of the manifold. Lay the rec port intake gasket on the manifold. If it sits correctly and covers the sealing area it would work. DOn't know about the RPM, but most of the single plane intakes will work on both.

"I have done a search on this, and still cant find a definitive answer"

The definite answer is it definitely won't work.

Robert this is not a flame at you but it is amazing to me that this topic just goes on and on. Set your oval manifold on the car with out any gaskets. The hole is HUGE at the top of the Rectangle head portss.

Ya cannot use oval port intake gaskets...you end up with a gasket material covering over the mismatched area...nothin but gasket material. If you try the Rect. port intake gasket under an oval port manifold on rectangle heads you end up with daylight between the port roof in the head and the manifold.

The definite answer is it definately will not work with any GM intake and most aftermarket intakes. I should add I have never seen an aftermarket Oval manifold with enough Meat in that port area to seal against a rectangle head. Now it might be that there are some..never been a big fan of aftermarket stuff.

Hopefully as other folks search this topic they will see the answer here. Got my ass kicked once for jumping somebody on this and I don't mean to jump you. I just cannot understand why a simple test like outlined about is not done.

There is also endless, sometimes mindless, discussion of the relative merits of Rectangle intakes on OVal heads. Suffice to say it works. I have driven a car set up that way and seen more than a few at shows..guys just like the high riser look aside form any perf gain / loss. Is it .001 faster at 60 ft. due to turbulence (somebody with a degree in fluid dynamics not people who wish they had one should look into this with a dyno) or is it 2 mph slower in the quarter? I have no idea, not interested in drag racing. Can you operate such a combo on the street ....yes..Rectangle manifold on oval heads it is a functional combo. Is it an optimized combo...beats me. Oval manifold on rectangle heads...not gonna happen.

Oman,

Your information is partly correct. But I know for a fact that many of the single plane oval port manifolds will work on rec port heads. Personally don't see what you would gain from this. In theory you would have a high velocity area stepped down to a low velocity area as soon as it enters the head port, quite contrary to the current thought on cyclinder head performance and max flow velocity. Most of these are cast from the same molds with the difference being the port entry area. The only way to know for sure is to match the rec port gasket against the oval intake and see if it covers the sealing area.

The last two aftermarket manifolds that I have used would definitely seal a square port head.
Eddy Vic Junior O
Weiand Action Plus
The manifold flange is brought right up to the valve cover mating surface. You'll just have to lay the manifold on to see for sure.
I really don't see the problem doing this. You would use a square port gasket.

Well I will stand corrected....I know ya cannot do this with stock manifolds made by GM and honestly I just don't fool around with aftermarket stuff. Little things like thermostat angles that make it impossible to use a stock hose or ood location of temp sender bosses and what not just leave me flat.

My buddy went recently went NUTS trying to put some sorta speed part goodie manifold on his 65 Chevelle. Hadda buy one of those rotateable t-stat housings in order to use a formed factory upper hose. EXPENSIVE band aid indeed.

I only do street driving and frankly can't say I ever saw a difference in a street vehicle with a manifold swap. More or less summarized by: a 4 bbl is a 4 bbl is a 4 bbl regardless of the intake unless you start the single plain dual plain debate. Single plain just makes no sense on the street for my driving style so I am back to "Ya seen one dual plain ya seen em all" I just stay with GM stuff on my cars and as a result I have no point of ref on aftermarket stuff.

All this theory on velocity and atomization and pooling and all that "wanna be an engineer stuff" simply has to be proved or disproven on the track. Somebody someday will run some of these combos and the numbers will tell the tale.

I worked as an aircraft engine test engineer many years ago and I saw more "In theory...." ideas blown out of the water when subjected to analytic test stand evaluation than I care to recall. "In theory it will last forever with this new ....." sometimes blew up almost instantly. "In theory this part will never stand up to operation at ____degrees temp"...lasted forever. Sometimes ya just gotta try it...trouble is that takes time and money.

This controversey is one of fit and functionality. Just cause it fits don't mean it is better and if it won't fit well that says it all doesn't it.

Johnny, the Winters casting is just as good as a standard RPM, just use it.

And BTW, never done a bass-akwards mani/head deal, but anyone who thinks that smaller intake runners opening to a bigger intake port is a good idea really should think about doing something else for a living. I'm a numbers guy, and even I know you lose velocity when you increase size. THat's why funneling down from large intake runners to smaller intake ports just above the valve makes intuitive sense. Velocity will be increasing just above the vavle. Can't be a bad thing.

Anyway, run the Winters. Oman, glad to hear that the rect on oval heads works. Have a few rect intakes and a set of oval heads and guess I'll try the mismatch first - although it just don't 'feel' right.

Some may actually argue that the factory manifold (if the devider is still in) is better. Personally I like the factory one.

I will do some surfing tonight at both Dart/W/P's and Brodix's sites and read up on this more before I open my "mouthy" mouth..

pdq67

Thanks...I thought about the velocity thing, and it didnt make sense to me either...going from larger to smaller, in the direction of flow, makes sense, not the other way around. OK, I think I"ll use the GM intake for now. Gene, I know what you mean, matching up the square to round just doesnt "feel right"....but give it a shot and see what happens. I have to stop selling my stuff on ebay as soon as Im done with it. I had two different rect. port intakes that I could use, but sold them both.....who'da thought!!!

I run a Dart single plane oval port intake on my engine that has 310cc Canfield rectangle port heads. The Dart manifold was opened up to a Mr. Gasket 101/FelPro 1275 gasket. The port alignment is perfect. I'm still getting this new manifold dialed in but so far my car has picked up over ~.25 in ET and 3-4MPH over the old setup (Edelbrock Performer RPM and Wilson tapared spacer). The ET/MPH gain was measured using meticulous records that I keep including launch RPM, shift RPM, fluid temps, tire pressure, jetting, timing, etc, etc, etc... Initially the oval port intake was slower in 60' and faster at every other increment in the 1/4 (60-330, 330-660, 660-1,000 and 1,000-1,320). What I learned over a few track outings was that the new intake needed more pump shot to get the car off the line due to the increased plenum area. I went from .035 f/r squirters to .041f and .045 rear, and I also added a 50cc pump in the rear of my HP950. Once I got the 60' times back around to where they were with the old setup the car's performance blows away that of the dual plane/rect port RPM (which was also ported to the same gasket). My shift RPM has been increased by 200RPM and I'm trapping around that same amount higher due to the increase in 1/4 MPH. Last time at the track in 3,500' air my car ran 10.77@124.95 with a 1.54 60'. The last data I had on my car with the old intake was taken in 3,851' air and the car ran 11.06@120.90 with a 1.53 60'.

You be the judge if it works or not.

Sell the two you have and buy the "right one"

427L88

Hey Gene

How goes it???? Snow melt YET? I said it works I have no idea if it is faster slower or the same as far as performance. The car I drove was nothing special just a BBC with ovals. It ran OK from a driveability point of view.

Kjett is living in a world I never go into. All those numbers and such.....never had the fever that bad. Did a little racing: broke some parts won a few races when I was a kid at Lebanon Valley (sorta near you I guess) but I just never went to the level these guys are workin.

I supppose when you start tuning at those levels a lot of the generalizations I made about street engines with stock parts become pointless. I just never did that real nats ass tuning stuff diggin for that last 2 or 3 horsepower....lazy I guess. Bolt it together, check the timing take a look at the plugs after a few miles...done.

I knew guys who bough new 67 GTO's and swapped on 66 3x2 systems just to see what would happen. They flailed and flogged and tuned away and then tuned the daylights outta the Q-jet after re-installing it. Low and behold it was almost a wash. Lots of hours, $$$$$$ and midnight oil poured into optimizing each induction system....not me gotta take a nap, got a date, goin down to the tavern, going up to the lake.

Oman, no snow yet, but summer's been slight, and also " all work no play" :mad: It doesnt seem likely I'll get my chance to really 'air out' this ol rect port hp-mill with "lotsAgear" and show the "torque boys" that hp-built street mills can run 11's too! smile.gif

All goes well Sir! I was glad to see your reply here. Nice to see you stop by. How've ya been? Hope all is 110% A-OK.

Johnny, I have two rect dual planes ( one a marine with QJ flange), and of course, the rect 3X2.( which I don't think I'd 'mismatch' for a 5500 496 thumper. The trips are meant for R's. Should think flow would be too bumpy at those vels - least'n at 500 c.i. or so) One will be used for the next 396-325hp clone project for sure.

BTW, I should not have said the Winters is just as good as the Edel RPM. I have no reasonable basis for that, just that the Winters/GM that used to sit on the 427 'seemed quite right' to me. Good rip to, some silly, 7300- sh rpm. WITH A PLENUM DIVIDER! ( as Mike indicates. It SUCKED without one. Even at 7000+ it seemed, and certainly on the way there).

Slap the Winters/GM and get to cruisin'! You and me both are wishing for an Indian summer!

graemlins/hurray.gif

( that's me jumping and praying my Seneca Indian summer prayer!)