Valve spring question... Buying the BC kit... - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

UNITEDMASTER · 05-25-2012, 10:41 AM

Tomie make different spring seat shims.Here is how I go about equalizing seat presures. First take all the neww springs and test them in the spring pressure tester ,i do it at 1" and at 1/2", this is to get an idea how consistant the springs are,taking note of the heavy ones,mark them & keep track of their placement .

Now it is highly important that whoever did the valve job was not a screw ball. Because if the cut the hell out of the the actual valve seat this may affect installed spring height.Also if they did a shit jod grinding the valve tips this will affect max lift values accross the head also. Quality vale job is highly critical if your gonna go this far with a cylinder head.

Now put the head together(keep track of the heavy springs location) .Check what all the installed spring heights are.Take notes of all . On some engines you can use different thickness spring seats &/or shims some heads you can actually machine the head where the spring sits.

Do the math & adj/shim accordingly. Once you have the heights all equal now you need to make a rig of some sort with a dial indicator on it & a helper is good. It REALLY helps if you have a rig to bolt/clamp head to with the chambers open on bottom

Look at your cam card find what your max lift is, have your helper using the rig with dial indicator or turn the cam to compress the spring to the max lift value,then with your machinist rule & flash light measure the compressed height. NOW if you did all the other stuff correct then the all should be verry close

The installed height plays a big part in actual seat pres. closed & coil bind .open.

Now to equalize seat pressure closed,then you will need to shim the actual spring.Now you gotta measure their pres. at the correct installed height,then shim sprigs up(more coil tension) This process is kinda a trial & error hit or miss deal, and take time. Thats why it important to start with a good set of" MATCHED" springs that are all very close to each other from the begining at the 1" & .500 test.

Hope this makes sence, this is just a vauge idea of whats involved in blueprinting a head

05-25-2012, 10:41 AM	#1
UNITEDMASTER Nissanaholic! Join Date: Apr 2006 Location: Anaheim Posts: 1,626 Trader Rating: (10) Feedback Score: 10 reviews	Tomie make different spring seat shims.Here is how I go about equalizing seat presures. First take all the neww springs and test them in the spring pressure tester ,i do it at 1" and at 1/2", this is to get an idea how consistant the springs are,taking note of the heavy ones,mark them & keep track of their placement . Now it is highly important that whoever did the valve job was not a screw ball. Because if the cut the hell out of the the actual valve seat this may affect installed spring height.Also if they did a shit jod grinding the valve tips this will affect max lift values accross the head also. Quality vale job is highly critical if your gonna go this far with a cylinder head. Now put the head together(keep track of the heavy springs location) .Check what all the installed spring heights are.Take notes of all . On some engines you can use different thickness spring seats &/or shims some heads you can actually machine the head where the spring sits. Do the math & adj/shim accordingly. Once you have the heights all equal now you need to make a rig of some sort with a dial indicator on it & a helper is good. It REALLY helps if you have a rig to bolt/clamp head to with the chambers open on bottom Look at your cam card find what your max lift is, have your helper using the rig with dial indicator or turn the cam to compress the spring to the max lift value,then with your machinist rule & flash light measure the compressed height. NOW if you did all the other stuff correct then the all should be verry close The installed height plays a big part in actual seat pres. closed & coil bind .open. Now to equalize seat pressure closed,then you will need to shim the actual spring.Now you gotta measure their pres. at the correct installed height,then shim sprigs up(more coil tension) This process is kinda a trial & error hit or miss deal, and take time. Thats why it important to start with a good set of" MATCHED" springs that are all very close to each other from the begining at the 1" & .500 test. Hope this makes sence, this is just a vauge idea of whats involved in blueprinting a head __________________ MR JACKSON.