4 replies to this topic

[dotmatrix]

so I am putting my race engine back together and I have gotten to the cylinder head, and I have been reading the valve spring fitting article on minispares on the subject which basically says that the springs I use (C-AEA526) should be fitted at about 1.375" in fitted length, not more than 1.4 and no less than 1.35.

the fitted length of mine vary between 1.402" and 1.358"

 

I realise that they are all sort of within the spec, but I am going to put shims under the ones that are too long to bring them down under or at 1.375". I am not going to have the head machined to bring the ones at or close to 1.358" up to 1.375"

 

so my question is: is it important to get them close together all of them or is it good enough to just tighten to most loose ones up to get them bellow 1.375"?

I rev this engine to close to 8000rpm maybe that helps you determine the needed length.

 

thanks in advance

Martin.

 

[Spider]

the fitted length of mine vary between 1.402" and 1.358"

 

That's a fair bit of variation. What's the cause of that ? Is it the way the seats in the head have been dressed or the seats in the head all over the shop ?
 

[dotmatrix]

the fitted length of mine vary between 1.402" and 1.358"

That's a fair bit of variation. What's the cause of that ? Is it the way the seats in the head have been dressed or the seats in the head all over the shop ?

i dont know. the head has the valves minispares calles rimflow, it has 8 seat inserts, and the have been cut and lapped in multiple times, i think it has also had a seat or two changed again. the exhaust seats are generally much wider than the inlets and the exhaust valves generally sit further out in the chamber. i have been using it for racing for more than 10 years.

Edited by dotmatrix, 14 April 2021 - 06:13 AM.

[Spider]

It sounds like it's the Valves that are the reason for this variation.

 

Those that are recessed would do better in terms of flow to have them addressed, which likely means new seats.

 

Apart from likely reduced flow from the recessed valves, you'll also be missing out with the valve tips not all being at the same height as you can't set the rocker shaft at an optimum height, relative to the valves.

I'd suggest sorting the valve seats first, then look at the spring heights. If they are too long, they can be shimmed, if too short, to a point, the spring seats can be lowered. Usually, if you can get the longest fitted length, then if it were me, I'd be checking at full valve lift that I had no less than 0.050" between coils.

[dotmatrix]

It sounds like it's the Valves that are the reason for this variation.

Those that are recessed would do better in terms of flow to have them addressed, which likely means new seats.

Apart from likely reduced flow from the recessed valves, you'll also be missing out with the valve tips not all being at the same height as you can't set the rocker shaft at an optimum height, relative to the valves.

I'd suggest sorting the valve seats first, then look at the spring heights. If they are too long, they can be shimmed, if too short, to a point, the spring seats can be lowered. Usually, if you can get the longest fitted length, then if it were me, I'd be checking at full valve lift that I had no less than 0.050" between coils.

yes. i get it. i should fix that. its a pretty big variation. thanks