I have a couple of modified smallport cylinder heads, one came on an engine fully assembled and working.
Not knowing any details about the head l decided to fit the springs and cams to another head that l had professionally modified.
When l went to fit the springs (unknown make but probably CatCams) they were slightly too big for the head side spring seat, l was not using the seat inserts as this is how they were on the head l removed them from.
The springs are the same diameter top and bottom.
Does anyone know if the spring seat diameters are somehow different over the production Years?

First, do not run without the valve spring seat. The spring rotates while running and will wear away the alloy surface. If it was my head, I would take a Dremel tool with a sanding drum and open the bottom of the coil spring, just enough to fit over the seat. You MUST polish the reworked surface on the coil spring. The valve spring is highly stressed, and any rough surface will lead to failure. The other option is to take the seats to a machine shop and see if it would be possible to turn down the small lip on the seat.

Fair point about spring rotation.
l think the best way to approach this is to replace the valve springs with some that will allow 10.5mm lift and will fit with the original bottom retainer.
lncidently Catcams suggest the removal of the bottom spring retainer for their springs.
Any ideas for springs to the above spec?
Thanks

BC springs are good for 11mm of lift and fit in the stock spring seats.

I've checked - viewtopic.php?t=15683&start=30#p104740

oldeskewltoy wrote:BC springs are good for 11mm of lift and fit in the stock spring seats.

I've checked - viewtopic.php?t=15683&start=30#p104740

I don't run the engine past 8200 rpm do you think those springs would cope ok? (Re. the comment about 7MG quality in the post)
Engine uses standard valves, lightweight followers, titanium caps and underbucket 13mm diameter shims.

totta crolla wrote:

oldeskewltoy wrote:BC springs are good for 11mm of lift and fit in the stock spring seats.

I've checked - viewtopic.php?t=15683&start=30#p104740

I don't run the engine past 8200 rpm do you think those springs would cope ok? (Re. the comment about 7MG quality in the post)
Engine uses standard valves, lightweight followers, titanium caps and underbucket 13mm diameter shims.

When I was looking for the inner valve springs for the 5VEU, I got to talking to the tech @ Pac Racing Springs(https://www.racingsprings.com/), and I was informed that the BC springs, the old Kelford springs(NLA), and the Ferrea springs are all extremely similar, with the only differences essentially being only finish. So I'd say they are good to go......

Thank you.