I have a 400 cu.in. and am using a edelbrock p4b intake but the crossflow port on my 4x heads are too large for the intake to cover completely. Yet the intake fits pontiacs from 350-455, what gives, is there anyone that has run into this problem??

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I have a 400 cu.in. and am using a edelbrock p4b intake but the crossflow port on my 4x heads are too large for the intake to cover completely. Yet the intake fits pontiacs from 350-455, what gives, is there anyone that has run into this problem??

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Pontiac made two different height crossovers. I believe the split was in 1971, i don't remember for sure. There was just enough difference to make the intake not seal.Did the intake list a specific year when you bought it or was it just all 350 - 455 pontiacs? I'm sure that someone has a book with the exact date of the change. Short of changing the heads or welding the hole in the head up i don't know of any solution to your problem. mike

The exhaust crossover changed in 1972. Pontiac placed a heat sink above the crossover making the hole smaller than 71 and older(it looks like there is 2 holes). There are 2 easy solutions to fix this. The first is a intake gasket I sell by Mr. Gasket that has no hole for the crossover. The second is to use the 72-79 intake gasket (stock) and to place a thin metal plate(stainless steel is best)on top of the gasket and have the intake hold it in place. The plate embeds itself in the gasket. The first solution allows a hole to be "blown" through the gasket allowing a heated manifold. It also will eventually cause an exhaust leak. The second solution blocks the heat altogether which is a plus for warm weather driving. You can also use the plates on the Mr Gasket gasket (solution 1)

thanks for the help, I'm going go with Paul on this one and see how it goes. thanks again

Here is the simple and most effective way to solve the exhaust crossover miss-match when using a 71-earlier intake on 72-later heads:



[This message has been edited by Todd (edited 07-18-2000).]