My 454 has a GM intake (#3933163) and cylinder heads (#3964290). I have not had the engine apart yet. When I researched the part no.'s, the intake was listed for use with rect. port heads. My heads are listed as oval port.

Did I read something wrong or are these part desciptions correct?

If so are these parts matched incorrectly?

As far as I know both items are stock and unmodified.
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Jeff
70 SS 454
4 Speed

[This message has been edited by Jeff_70SS454 (edited 11-11-2002).]

More information required?

If thats the case,Yes,they are mismatched,but there is a guy in New Jersey that does it on purpose,and he runs in the mid 10's http://www.chevelles.com/forum/biggrin.gif

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Bob West 1972 Malibu
454+.030/3900 lbs.
TH350-3.73's
1.72 60 ft. 11.97 @ 113.37
1/8th 1.66 7.46@91.70

I'm a small block guy, but I've read some posts where the some big blocks have a situation where the intake ports are larger than the head ports where they meet at the intake gasket. It defies reason etc, but these things run very well. I don't know which big blocks they were talking about, but some searches should make it clear for you. I think that's what Bob was talking about.

Yes it will work but in most cases you loose some bottom end torque.

In years past, there have been numerous articles in the performance magazines (HOTROD, etc) which say that a condition called reversion will be the result of this kind of a mismatched situation, But, so far EVERYONE here who has actually done it reports that this combo works fine. So, based on reports from this forum, I'd say go for it! At a swap meet a few years ago, I saw a set of oval port heads which had had the roof of the intake port contoured to help improve the transisition from the rect port manifold to the oval port head.

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Tom Parsons

One of these days I am going to drag some pieces down to the head porter and put them on the flow bench. You would think it must do something bad but I gave a friend a big port manifold and he put it on a 350HP 396. Says the thing runs fine but it a street only car.

Running the big port manifold on oval port heads works okay because your engine is working on a vacuum... Think of it like a vacuum, and not like your are pouring fuel into the head from the intake... It is sucking in the air through the head ports, and therefore, doesn't really "see" the mismatch. There will be some turbulence at the interface, but not too bad...

The larger intake reduces the restrictions, especially at any bends in the intake ports... But while it works okay, I can't see how it actually makes an improvement... The engine can only pull in the amount of air that can flow through the head...

This might cause slight problems with the signal the carb receives, but usually not significant.

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"Once you go RAT, you never go back..."
TC #1366
Tony
The Chevelle (http://www.chevelles.com/showroom/1966_L78/ChevelleA.jpg)
Dual Quad 396 (http://www.chevelles.com/showroom/1966_L78/ChevelleC.jpg)
Side View (http://www.chevelles.com/showroom/1966_L78/ChevelleD.jpg)

[This message has been edited by 1966_L78 (edited 11-14-2002).]

Kind of blows the theory of gasket matching right out the window. Doesn't it???

Cam

Yeah it does.

<BLOCKQUOTE>quote:</font><HR>Originally posted by Cam Sweet:
Kind of blows the theory of gasket matching right out the window. Doesn't it???

Cam<HR></BLOCKQUOTE>


IMO,gasket matching an intake is a waste of time.Someone show me a timeslip documenting the difference http://www.chevelles.com/forum/biggrin.gif


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My 70 SS396 (http://www.chevelles.com/showroom/mr4speed70SS1)
Engine pic (http://chevelles.com/showroom/mr4speed70SSengine2)
My Black Cherry 70 SS454 (http://www.chevelles.com/showroom/Photo0031.jpg)
The launch (http://www.chevelles.com/showroom/CClaunch.jpg) 13.13 @ 101.490/1.92 60 ft. with radials,2.73's,and thru the mufflers
1.90 Best 60 ft.
101.84 Best MPH
1968 Oldsmobile Cutlass convertible
1973 GMC Sierra 454 p/u
1985 Cadillac Eldorado (daily driver)
Chris Corwel,TC Member # 785
Member # 141 AMCA

I think the turbulence from a little mismatch might be a good thing, keeping the fuel atomized, etc...

I ran the rect port intake (163) with 750 Holley (2 different similar carbs)on my oval port heads for awhile but the stock iron oval intake with Qjet ran noticably stronger. I don't have timeslips but the difference was very obvious, especially on the bottom end. Then I epoxied and ported the rect port intake to match oval port gaskets. The blending (mostly in the roof of the ports) goes about 2" into the port. I used Moroso A+B epoxy and a regular stone bit on a die grinder to shape it. I used an aluminum cutting bit to match the bottom half of the port. This made it run better, about on a par with the oval intake on the bottom end, hard to tell on the top end if it was better. The rect port intake bottom of port is higher than the oval port bottom. The top of of the rect port is MUCH higher than than the oval port top. You can see it on the gasket impressions after disassembly. This makes an opening between the two that is smaller in area than the oval port. IMO it hurts flow and hp. Others may have different results but I know what worked for me.

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von '69 300 Dlx SS TC #15 ACES #1575 HSCA #5
My '69 SS (http://mywebpage.netscape.com/jerryacheson/vons69.html)