BBC Square Port Intake Manifold on Oval Port Heads

[Jim]

I am planning on installing a square port blower intake manifold on oval port heads for my BBC? I could not find an oval port blower manifold so I bought one with square ports. The oval port heads came with the motor and are reconditioned. I have read pros and cons about this setup. Does anyone have experience with this combination and does it work ok for a street motor?

[Bill Cleveland]

Jim -

I don't have much experience with big blocks, but . . . I have heard some pretty knowledgeable Chevy experts say that port matching between intakes and heads is a waste of time, and as far as porting goes, more time should be spent in the bowl area nearer the valves; that said, I would think some smoothing might be in order, but I am just guessing. Surely someone in this audience has a clue about this . . .

[chasracer]

What you end up with is a lot of fuel falling out of suspension where it hits the sides of the peanut ports on those heads. It's going to run and it's going to be fun, but odds are you will discover a lot of cylinder to cylinder fuel distribution issues. Plugs will probably foul a bit more often and of course the cylinders themselves will have to endure some additional fuel wash. Plan on checking plugs and keeping the oil/filter changed more often than normal.

AS to cylinder head/intake port matching - yes it is very important if you are looking for every HP you can get out of your combination. On a street motor, I am not sure it is something you could really measure, but I am talking just a regular minor mismatch here. The mismatch you are considering is pretty sizable.

Good luck.