| Also known as | E4221 |
| Diagram | Fig. 5 — CYLINDER BLOCK AND HEAD TR7RV · ref 19 |
| Subsystem | engine top |
| Listed in parts books | 1964–1965, 1967–1968, 1970–1971, 1974, 1976–1980, 1985 |
Inner valve spring (red spot)
Inner valve spring (red spot) for the cylinder head, works with the outer spring to close the valve, PN 70-4221.
70-4221 is the inner valve spring, marked with a red spot for identification, that sits inside the cylinder head on the top end of the engine. It works alongside the outer valve spring to close the valve and keep it seated against the seat once the cam has finished lifting it. The red spot is how Triumph identified this particular spring rate on the parts counter, and it's worth keeping that marking straight when you're sorting springs during a rebuild.
Read more
This number shows up across a long run of cylinder block and head figures in the parts books, covering 6T, TR6, TR6R, TR6C, T120, T120R, T140E, T140V, and TR7RV listings, so it's a part that carried forward through a lot of different head castings over the years. It also carries forward from two earlier factory numbers, 70-4222 and 70-7400, meaning if your parts book or an old box of parts shows either of those, you're looking at the same physical spring.
When you're doing valve work, inner and outer springs get inspected together for free length and squareness — a tired inner spring is easy to overlook since the outer one masks a lot of the visual cues. If you're rebuilding a head, it's a good idea to check both springs' condition side by side rather than just eyeballing them separately.
Sorry if we got something wrong here. If you think this information isn't correct, .