Thread: BBC heads, I have a question.

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I didnt notice that the ports on my tunnel ram were different sizes till this morning and its been bugging me all day.
I was planing to use this intake on my 454 but I have not yet taken the intake off the motor so I dont know what the ports look like on the heads.
I also have another pair of heads from a 396 or 427 that have all the same size ports.

I am confused. Why are the ports different sizes?
Is this some kind of special manifold?

Thanks

sell it on e-bay that thing is very old and not the best ? ask jerry C that thing is as old as me they played with the runner size the short and long port on the big block head or what some say left and right ports runner i am thinking just old news they did alot of things like this edelbrock made a old tunnel ram the top look like a shoe box they if your floats were off they would fill up with fuel and if it back fired then you had a moon shot

Thanks Pat. Are you saying that the ports just didnt match up and that was the intended result? Or did some porting have to happen?

Thats kooky.

I have seen a lot of them for sale and in use.

Is it ok to run in the short term?
I can replace it when I find another better one.

BBC's had a problem with certain cylinders leaning out under some conditions. That's why some 4bbl manifolds sat the carb crooked. Your odd size ports look like an attempt to rectify this by feeding more mix to these cylinders. It's too much difference to be accidental, it was done deliberately for some reason.

Originally Posted by maddddog

Thanks Pat. Are you saying that the ports just didnt match up and that was the intended result? Or did some porting have to happen?

Thats kooky.

I have seen a lot of them for sale and in use.

Is it ok to run in the short term?
I can replace it when I find another better one.

yes it was made this way there is some fuel robbing going on in a intake but alot of times it not to big of a deal you just cross jet it by jumping up on the jets could be for this.i have used some tunnel rams and never played with port velocity by closing down the port runner in the tunnle ram i used the older weilands for the bbc and work very good . like R Pope said looking at the intake thats what they did stock. i can not you how good it work JERRY C could tell you better then me . they made the intake like this or if the rigth and left port runner of the head was in play in could add to the robbing to ? any time if it can be done you want the barrels of the carb to lay in line with the ports of the intake and different plenums shapes to . so carbs you will see on some intakes do have a twist or they cut the 4500 holleys in 1/2 to lay them over the intake ports more done with the big chief heads or big dukes /pro stock symmertrical port heads

The manifold is satisfactory for a street, or occasional, street/strip motor. If tou're looking for maximum power it's seriously outdated. If it's going to be used on a street cruiser, put it on and enjoy.

If the port sizes difference is bugging you, break out the grinder and make the little ones match the big ones!

Thanks everyone.

I think I will just put it on and see what happens.
It will be a street car, so I guess its ok for now.

Ya gotta love this place!!

Be careful, like Pat said above this shoe box design has a tendency to pool fuel up top and can grenade on you!

Kitz

Originally Posted by kitz

Be careful, like Pat said above this shoe box design has a tendency to pool fuel up top and can grenade on you!

Kitz

This I never knew. I have seen blowers go, but didnt know that can happen with a tunnel ram too.

What steps can I take to make sure this doesnt happen?

take a look in side .yours looks ok. the box bomb was used on the sbc and had sharp edges and flat plenum were fuel would lay .yours not so much see how your plenum bottom slopes to the ports and corners to this helps with the fuel from pooling