Hardened Locks, 351M/400

Half Four Groove, Half Single Groove to suit 341/400M

Though the years, Ford 351M/400 used three valve lock variations. Early engines used all four groove valves followed by engines using half four groove and half single and then they went to all single groove.

From what we've seen, the 400 engine was in service between 1971-1979 in cars but remained in service in trucks until 1982 while 351M engines started in 1975 and ended in 1979 in cars but remained in service in trucks until 1982.

The main difference is the 400 engine started in 1971 which the 351M starting in 1975, both ending in 1982.

If you're going through a 351M/400 engine and want to replace the locks, you'll want to verify which locks your engine actually has before ordering.

We offer the following as a basic guide with no guarantee the information is 100% accurate.

• In cars- 1971-1978 400 engines had multi groove intake valves. (also 1975-1978 351M)
• In cars- 1971-1977 400 engines had multi groove exhaust valves. (also 1975-1978 351M)
• In cars- 1979 351M/400 engines had single groove intake valves.
• In cars- 1978-1979 351M/400 engines single groove exhaust valves.
• In trucks- 1977 351M used multi groove exhaust valves
• In trucks- up to serial number CGO,001 used multi groove intake valves.
• In trucks- serial number CGO,001 and up used single groove intake valves.
• In trucks- 1978 and up used single groove exhaust valves.

Since there is so much variation for 351M/400 engines in cars and trucks, it makes sense to check before ordering as valve locks are not refundable.

All 351/400M engines used 11/32" Valves.

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