472/425 intake swap: which gasket set?

[bicentennialcadillac]

I'm nearing time to put the '68 472 intake on my '79 425. I haven't seen this covered elsewhere - which gasket set should I use, the '68 or the '79?

The gasket sets look identical, but partsamerica.com insists that they're different. Thanks in advance for any guidance provided.

[caddydaddy]

The 472 has larger ports, so with either gasket set, you're not going to match up perfect. If you open the ports to match on the 425 heads, then I'd use the 472 gaskets.

[Night Wolf]

IIRC I used the '68 472 intake manifold gasket set when I swapped it over on my stock 425... I never had problems with it, we did RTV the 2 rubber gasket things tho.

[Finalman]

How much of a difference does just the 472 manifold make, and, does it have to be an older style manifold?

[Night Wolf]

it made a very noticeable difference, my carb was also rebuilt at the same time.

I know the '68 472 intake manifold is the best flowing of factory manifolds, and with it opened up as mentioned, it'll match the Edelbrock intake manifold for flow until 5,500-6,000RPM or so, well beyond even a mildly modded BB Cad (factory redline is around 4,000RPM) But there is no hood clearance issues, you can keep A/C, it's alot cheaper and looks stock

[caddydaddy]

Originally Posted by Night Wolf

(factory redline is around 4,000RPM)

More like 5,000 RPMs. Even the HP peak of the 472 is at 4,400 RPMs. The rocker arm retainer clips of the T pedestal valvetrain is what fails at high RPMs. That occurs when you try and rev them over 5,000 RPMs.