How to tell if my 454 is oval, round, or square port....

[MERC1000]

I have a Mercruiser 7.4L non-Mag I want to put an alum. intake on. Is there anyway to tell what ports it has without taking the intake off? Oval port intakes seem to be easier to get. Oh yea its a 1990.

[rockyone]

Non Mag are all oval port the bolt holes on rec port between the runers are almost even with the top of the runners holes on oval port are higher then the runners.

[laser380]

There are actually three types of head for a BBC. Peanut port....looks oval, but small. Large oval ports...looks just like the peanut port, but larger. Then the rectangular port.....Large part rectangular in shape.

I would think if you are running a non-mag motor, you would be running the peanut port head. Not sure though. Best way is to pull the intake you have off and take it in to a speed shop and see what they tell you, or post a picture of the ports in the heads after you pull the intake, and I can tell you. You may also look up the head casting number on the heads under the valve covers. That will also tell you the CC's they have. See if you can get the casting number first and post it and I will see what I can find out for you.

Large oval port intakes will fit over peanut port heads, but a peanut port intake or large oval port intake will not fit a rectangular port head. Its all going to depend on what head they used. Sorry cannot help more unless you can get a casting number for me.

[MERC1000]

Ok thanks. What I was trying to avoid was taking the intake off then finding out I have the heads that require a $600 intake, it would be just my luck. I would like to avoid breaking the seal on the engine until I have everything right there to swap it out.

[audiobill5]

The Mor-tec web site is a great reference for all that are GM casting numbers! http://www.vetteclub.org/warehouse/t...ortec.com.html Bill

[mach1magnum]

pull a valve cover get the head casting numbers