Tight Valve Spring Seat

jluetjen · jluetjen's Garage

I've got some new competition valve springs which include the lower seats. When I try to install them in my heads, most of the new seats seem to be interfereing with the heads, as if they are too large. How tight are they supposed to be? I can't seem to find anything in the manual that mentions this.

Grady Clay · 03-24-2007, 12:57 PM

John,

Measure and see. Compare to your OE spring seats.

I don’t think an interference fit is desirable with the spring seat. Call the manufacturer and ask. I would be concerned that an interference fit of the spring seat might add to the stress in the head from the interference fit of the valve guide and valve seat.

Yes, the spring seat shouldn’t be able to have lateral movement. If it does, there is the risk of wearing the head where the spring seat sits.

Best,
Grady

camgrinder · 03-24-2007, 01:43 PM

I had a small batch of spring seats about 2 or 2 1/2 years ago that were a little tight in the head. If they are mine, I can swap you out for some new ones.

jluetjen · jluetjen's Garage

Thanks John -- yes they are. I'll send them back to you. Thanks for the support!

jluetjen · jluetjen's Garage

Just for future reference I measured both the set of "factory" spring seats, and for comparison the "bad" lot so that people will be able to check theirs in the future. In the case of the factory seats, I had 15 of them, and obviously 12 of the defective set.

Factory set: Avg. diameter = 34.09 mm with 6 standard deviation range from 34.00 - 34.18. So chances are if your set measures within that range, they're consistant with the factory set that I measured, and should be good.

Bad set: Avg. diameter = 34.33 with a 6S range from 34.19 - 34.47.

The ID of the seat area on the heads had an avg. inside diameter = 34.27 with a 6S range of 34.06 - 34.48. (I suspect that some of the extra variation on the heads was due to my measurement accuracy since it was kind of awkward getting a square reading.)

Note that these measurements all apply to the 2.2-2.7 engine series since that's what I'm building up. I don't know if the earlier 2.0's, or the later 3.0 - 3.6's are different.