rocker shaft shims???

[dodgefreak8]

I had my machine shop deck my block on my 318 .015" and my heads .020" for a total of .035".. My question is, Do I need to shim my rocker shafts .035" to correct the geometry or is this to little to worry about?? Also is it absolutely necessary to mill the intake side of the head when this is done if I don't use the intake end gaskets and use RTV instead?? thanks

 

[72demon]

I woudnt worry about your rockers as much as your intake you'll need to get different head gaskets at least 30th over or mill your intake your lifters can take the underage it's the intake that cant

 

[dodgefreak8]

I'm running the felpro permatorque gaskets and I think they are .039" compressed. Should I still mill the intake side??

 

[GoodysGotaCuda]

Absolutely mill the intake side of the head

 

[dodgefreak8]

so do I figure for the total .035" that was taken off or just the amount taken off the heads when I figure how much to mill off the intake side??

 

[dusterdon]

when they said they took .015 off of the decks, was that below factory blueprint specs, or just a plain old .015 off. It makes a difference. If you go to a .040 head gasket, you don't need to cut the intake side, because the gasket is making up what was taken off. find out about the deck height and go from there.

 

[fishy68]

Measure it like Don said and if you do need to take some off take off .0095 on the intake side for every .010 needed on the deck side. Don't just use RTV to seal the intake. The only time I ever saw it used on an application where gas ran through it turned to jelly. I don't know if this happens every time or it was just a fluke thing I saw but I don't use it to be safe.

Rocker arm shims are only to correct for valves that are higher than their stock installed height. If you change anything to make up for the deck height difference you'd change the pushrods to shorter ones. To find out what change is needed for the geometry you need to install checking springs on a set of valves and run the rocker arm through the lift cycle. If it starts out slightly on the intake side, rolls through to the exhaust side of the stem at mid lift then back towards the intake side at full lift the geometry is correct and you don't need shaft shims. Shiming causes the rocker arm during the lift cycle to start closer to center of the stem so the only time you use shaft shims is if the rocker arm starts too close on the intake side. Hope that makes sense.

 

[dodgefreak8]

it was just .015" off what was there. Here is my big problem. I ordered pistons from mancini that have a compression height of 1.720".. the factory pistons were 1.760. I have no idea why anyone would make that low of a compression piston for a rebuild kit when the factory never even used that low compression piston in the first place. So I am trying to get my compression up to the 9.0:1 range but I keep shooting myself in the foot here. I had him take .015 off the block and now I am thinking of having him take .035" off the heads for a grand total of .050" off which will probably only get me back to where I was from the start if I use the felpro gaskets I have. I should have just got KB167's dang it!!!

 

[fishy68]

I don't know why they make stuff like that either. You really have to watch pistons because they vary like that and it affects the compression ratio allot. Will they return them and give you the ones you want? I know sending stuff back is a PITA but it would be better to have the right pistons than take that much off of the block and heads. If you do take .035 off the heads I'm sure you'd need to take some off the intake side of the heads also. And you'll most likely need shorter pushrods. So all in all the cost will probably be pretty close to the same.

 

[NorwayCuda69]

hmmm loads of interesting replys.. i took of 1 mm on an LA engine.. actualy it was a 340. we also milled the head 1,5 mm dont know what that would make in inches but 25,4 = 1" anyways it was no problem for intake or lifters.. it was crane flat tappet and original pushrods.. heads was ported early J, intake was edebrock performer rpm. The problem u could face is that the gasket under the intake front and rear dont get the needed presure so it would leak..