[steve25]

I have one of these I am starting to go over and here’s the first big problem I see.

The entrance to the water crossover is way smaller than a factory gasket as my photo shows, but there’s more to this restriction then first meets the eye.

The internal area is way smaller then a factory iron intake .

Here’s what I found.

The speedmaster

On the drivers side of the crossover the minimum width is .995” with a minimum height of 1.148”.
The shape is basically oval.

The passenger side shows .918” in width and 1.230” in height, once again with more or less an oval shape.

On my 1968 iron intake here’s how these two water passages check out.

Drivers side.
Width 1.215”
Height 1.175.

Passenger side.
Width 1.175”
Height 1.188”
Both passages are basically square overall.

If you want to see the ruff flow area difference here ya go.
Speedmaster driver 1.14 sq in
Passenger 1.078 sq in

1968 iron intake.
Drivers 1.427” sq in
Passenger 1.39” sq in.
A substantial difference in flow area .

I am going to try a hold onto this intake long enough to air flow test it during the week.

[joes455]

I thought you were going to compare the speedmaster rpm to an original edelbrock rpm?

[steve25]

I did want to a number of months ago, but could not hold onto the Edelbrock manifold long enough.

[Nobuddy]

Easily fixed if it creates doubts. Why anyone makes a performance manifold with the water manifold attached is beyond me.

An accurate measurement of the carb flange height and angle compared to an original iron would be nice to have.

[Steve C.]

" Why anyone makes a performance manifold with the water manifold attached is beyond me."

???

https://www.edelbrock.com/performer-...1Qtcu0ayLZdu9c


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[steve25]

After taking these measurements if I was to run this intake and had an unused cast iron intake I would cut off both crossovers and use the cast iron one on my motor with the aftermarket intake.

[Steve C.]

Related tid bits from the past....

"... the major reason to remove the water crossover from the actual intake is to allow the intake portion to be correctly located over the head ports. Sometimes more attention is often paid to stopping coolant leaks than matching up the intake ports. If you install the intake incorrectly, all your port-matching can go out the window. If your manifold is even 1/16 inch off front to back, those sharp steps between the intake and the head will create eddys, causing your flow numbers to deteriorate."
Jim Hand

Further comments made.....

.. And with the crossover having to be drawn up against the timing cover, the ports will not match up.
So, cutting the crossover off allows the crossover to be drawn up and tightened. (No water leaks)
Then you can position the intake/ports where they need to be.
johnta1



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[steve25]

Simple fix with no down side.

Never gasket match the flange of the intake manifold 100% up to the gasket , leave it .050” smaller all around its perimeter.
This is what I always do if I am not going to be the one bolting on the manifold.

[1969GTO]

Speedmaster parts...........Made in China?????????

[steve25]

Yes, made in China, or at least cast in China.

Is it machined in China, I don’t know, so maybe someone on this board can answer that.?

[LStathas]

Millions of 2 barrel intake water crossovers just threw their hands in the sky! Pick me! I love the design of the blocked exhaust crossover. My heads are filled but this intake still gives a great look, IMO

[LStathas]

I went thru all the work to grind out the entire exhaust crossover on an RPM. The China unit eliminates that work if a person decides to go that route.

[Half-Inch Stud]

I got the Speedmaster dualplane because of the fuel injection bosses. 421 engine build on slow role as we work the home and yard, then the garage.

[HWYSTR455]

You can muck with the crossover/timing cover seal to compensate port alignment without having to cut the crossover off.

I take a triangular file and cut a groove at the top/center of each port on the intake, and do a small dimple just below the valve cover rail on head for the center of each port.

You can sight the intake and head port centerlines to line the intake up.

If the intake needs to go more forward, file the intake pad where the O gasket sits. If it needs to go the other way, glue 2 O gaskets together and sand it down to the size you need. Or buy gasket stock and cut your own.

I understand that by separating the crossover from the intake makes it easier to R&R the intake, but how often will you really do that?

When the crossover is separated, it can be a challenge to get it to seat squarely to the timing cover. The timing cover to crossover bolt will pull the top more than the bottom. I've seen folks with leaks at the bottom of the O gasket. So I stopped separating them.

You can port the crossover to match the gasket, but can't go too far unless you separate the crossover, or there won't be enough meat to compress the intake gasket.

If you consider the size of the passages in the head, the crossover really doesn't need to be bigger than they come shipped.

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[PAUL K]

If possible we prefer to leave the water crossover attached, it acts as a locating stop so the ports are always in the same position. Back in the day when manifold gaskets could be re-used and we did a lot of manifold testing, separating the crossover was the "hot set-up". We could change a manifold and carb out in nine minutes at the track and quicker on the dyno.


Pontiac engines are usually short on crossection and need as much area as possible at the manifold to head transition. I posted a couple of pictures of our preferred gasket match. If the pushrod pinch is the restriction there are better ways the match the manifold ports.

[Squidward]

I divorced my crossover. I had no idea about the cooling port diameter. I used to use a 2bbl iron crossover, until I went efi. That required 1 threaded port for gauge temp, 1 port for efi.

Good to know, because I had to take a cooling journey a while back, and I was trying to determine the constraint. I did determine that there was a coolant flow constraint with a standard tstat, and that 1st gen radiators are stupid small. But all these items can stack to make a marginal cooling performer.

I really love the lack of crossover and air gap. It makes a great place to hide wiring and hoses.

[HWYSTR455]

Agreed, there's tons of room under there wo the exhaust crossover to hide stuff!

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