400 1971-79

Pontiac V8 400 1971-79

The Later Castings — 400 1971-79 for Pontiac V8s

The 1971-79 400 ran through the low-compression years, and its heads are a different group from the 1967-70 castings. Butler lists the 1971 heads including 96, 7K3, 197 and 7F6 together with the 4X, 6X and 5C castings on the 4.980" valve length, generally with a smaller factory exhaust valve than the earlier heads.

A rebuild is built from Butler's cast iron head parts: Ferrea stainless valves in the 4.980" length including the common 1.77" exhaust upgrade, cast or bronze guides, seats, seals, springs matched to the cam, retainers, locks and shims.

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More About 400 1971-79

1. A Different Valve Length Than 1967-70

This is where the 1971-up 400 separates from the earlier engine, and it decides every valve you order.

The 4.980" group	Butler lists the 1971 castings 96, 7K3, 197 and 7F6 along with 4X, 6X and 5C heads on the 4.980" valve length, where the 1967-70 group uses 5.095" and 5.110".
Sizes in that length	Ferrea offers a 2.11" by 4.980" 30 degree intake and a 1.77" by 4.980" 45 degree exhaust for this group, sold as matched kits against those casting numbers.
The exhaust upgrade	many of these castings left the factory with a smaller exhaust valve, and Butler lists kits both ways, with the stock size exhaust and with the 1.77" upgrade.

2. Buying Spring Height With A Longer Valve

If you are putting a big cam in a 1971-up casting, this is the note that matters.

What Butler says	the 1.77" by 5.110" exhaust and 2.11" by 5.095" intake may be used in 4X, 6X, 96, 7K3 and 5C heads for taller spring height, but you must use a longer pushrod.
Why you would	the taller retainer position gives you the installed height a bigger dual spring needs without cutting the casting to pieces.
What it costs	a pushrod length check with an adjustable checker, fresh rocker geometry, and a look at retainer-to-seal clearance at full lift.

3. Rebuilding A Low-Compression Era Head

Exhaust seats	heads from the unleaded years deserve a hard look at the exhaust seats. Let your machinist decide between cutting and inserts.
Guides	11/32" cast or bronze guides for Pontiac cast iron heads. Bronze if the engine is going to see stiff springs and a high rocker ratio.
Springs	rated around a 1.600" installed height, chosen against your cam and checked for coil bind at your actual lift.
Let Butler spec it	the cast iron Head Builder Kit matches valves, springs, chromoly retainers and locks, seals for machined guides and a shim kit to your casting and your cam specs.

Pull a valve cover, find the casting number and call with it. The 1971-up 400 heads look like the earlier ones from three feet away and take different valves.

Not sure what your Pontiac needs?

Call our tech team at 866-762-7527. Tell us your engine, heads, car, and power goal, and we will put the parts together as one combination that works.