Installing Valve Spings < Shimming

[to4garret]

Hey Guys,

i got a set of BC Valve Springs that i want to install.

now, i know how to change the stock ones over, thats not the problem, in fact i will do it on the car if i can get away with it.

but i've heard when installing new springs you may need to shim a few of them to get them to apply equal pressure when closed and too keep their oscillation freq in spec for high reving engines. :?

should i take the head to a pro so they can test each spring individually and charge an arm and a legg?

or should i take one for the team and just do a straight swap and post pic's of ensuing carnage?

 

[mattrat]

straight swap, ive just bought some aswell..
think many peeps have done it straight in straight out..
no trubs?

 

[to4garret]

no trubs?

sorry dont understand that bit? :?

 

[DOUGMO]

translation=with no troubles

 

[EVO-00X]

It depends on what else you have done to your head and whether there is any variance in the BC spring heights. Basically if you had any work done to your valve seats or valve face and/or installing new valve stems and springs then the heights need checking to ensure good pressure at the installed height. If you add too much shim height then you're risking spring compression to near coil bind (weakens the spring) or full coil bind (bye bye valvetrain) :roll: I left mine to the professionals :wink: I'll send you a PM.

 

[rob323]

Are they dual valve springs (with the little inner springs)?

When I rebuilt my rally car motor, a mate showed me how to measure the springs. You simply put a set of bathroom scales on a drill press, put the spring on that and them put something flat on top of the spring. Pull the handles down on the drill press and set the stop at about when the spring in compressed to how it would sit in the head when built (but not compressed by the cam). This will give a rough seat pressure.

On my gemini head, it used dual valve springs, I measured and recorded the values from the scales for each spring, and then matched inner and outer springs to give the minimum variation when the values of both inner and outer springs were added. It allowed it to rev cleanly for another 500-1000 rpm (which took it up near 9000 rpm, only went there a few times though).

 

[to4garret]

na they are just plain BC Heavy duty springs.

i like the scale and drill press idea

 

[rob323]

Well, if they are not duals, you can't really balance the springs out, but you can check them all for consistency. It's surprisingly quick and easy to do.

 

[rob323]

Oh, if you have valve seat washers (called "seat savers" by one mob I spoke to) that look like copper or brass plated steel, don't use them. I had to rebuild the motor in my rally car solely because of them. The valve springs chewed the plating off and it went through every orifice in the motor, destroyed every bearing, the oil pump and the crank.

 

[mattrat]

howd you go with this.
i seated all my valves and installed the bc springs n retainers today.
they were all perfect height, like exactly.
was a solid 9-5 day tho
man those little semi circle things are C*&TS of things.
i literally hate them.
lol matt

 

[to4garret]

man those little semi circle things are C*&TS of things.

collets

yea they are fun.

i ended up get a local performance engine/head machinist to do it, cost around $130 just for the springs, he did mention that 3 springs needed new shimms to provide the correct tension.

apparently.

 

[WindeX]

I have read that if you grease them up alot they tend to stick a bit more and you dont have the problem of them falling out.