shims on valve springs

Topic: shims on valve springs (Read 2351 times) previous topic - next topic

shims on valve springs

December 24, 2004, 11:35:02 AM

well ,, things to do today...

do dishes for the wife
get the boys to get rid of the mess in the living room
pull out the ham from the freezer for tomorrows dinner
start a fire in the garage
clean out the fireplace in the house
start a fire in the house fireplace

then some fun

im gonna shim up my valve springs on my 6cyl. ill let you all know what happens after i test drive it.

I plan on using a home made tool to pry up on the lower part of the spring then slip in my horse shoe shaped shims i need to finish making. they MIC out at about .035'' thick.

any advice , it will be a while before i get to my fun but in the meantime, if anyone has a input, id appreciate it.

Re: shims on valve springs

Reply #1 – December 24, 2004, 01:47:16 PM

I would def not use shoe horn shaped shims. THey make them round for a reason, id keep them that way. Why are you shimming them? Do you have a high lift cam, are you experiencing valve float at high rpms, high mile springs. In that instance I would simply replace the springs, theyre cheap.

To do it right I would pressurize the cylinder to keep the valves in place, use a valve spring tool to compress the spring to remove the keepers. Then replace the spring and valve seal and compress the spring to replace the keepers. Just my advice. Ive done it before on my TC and just about to do it again on my 351W Lightning. Except I will be replacing the rockers with crane 1.7 rockers and crane springs. Good Luck.

Ronnie

Re: shims on valve springs

Reply #2 – December 24, 2004, 08:33:43 PM

reason why ...
springs spin fairly easy with some effort while not under a load. They are weak and should have been replaced when i rebuilt. This is my first and only experience with a car that has this many miles. I dont think anyone here has as many as i do. I notice so many little things that are wearing out just because of age and there are a lot of "for instance" examples i could list but thats another story.

I should have replaced the
springs/keepers/valves/pistons/piston pins but i did not.

This is a 3.8l cfi so no fancy mods here. It would be a one a million chance my shims ever come out cause they sit in the lower cup anyway. I agree with you though, i should have replaced them way back then.

I also have a second question,, i think i touched on this a while back on the other board
the fulcrum on the rocker,,,,,, my fulcrum height is .0775'' which i just mic'd out.
Could'nt i remove about .002 of the fulcrum where is mates to the head. Would'nt this force the valve to open more? seems logical to me.
this in combo with my shims,, might tighten up the valves> yeh or nay?

btw,, valve covers off and valve springs inspected as well as one rocker off. I must have been on crack to think i **just might be able to** pry up on the lower end of the spring to slip a shim in.
ill have to hook my air up on sunday and do this,, maybe tomorrow night after christmas has simmered down around here.

Re: shims on valve springs

Reply #3 – December 25, 2004, 01:50:57 AM

How many miles are on the motor? I just figured since you were gonna have the valve covers off and worry with shimming the valves, it would make sense to go ahead and replace the springs and definately the valve seals for sure. If you must shim the valves say .030, which is the norm, then atleast replace the valve seals to prevent oil from entering the cylinder through the guides. THese are very cheap also.

Dont worry about replacing the keepers, and usually the old valves can be ground to a like new surface when performing a valve job on the heads. Just FYI.

I forgot about the spring cups on the alum 3.8 heads. However, you will need to completely remove the spring in order to install them. This prying up on the bottom of the spring thing will be nearly impossible.

WHy are you trying to tighten up the valves? The bolt down rockers need to be torque to 22ftlbs preload. THis is stock application and from what I understand you are stock. THere is no need to tighten the valves. The springs keep them "tight". If the rockers seem loose when torqued down, aka they dont press down on the valve stem as they should then you have other problems. THis could include valve stem wear, which I highly doubt. The other possibility is cam/lifter wear which I doubt also b/c roller cams do not typically wear out. So you should be fine.

If the springs are loose as you described then either shim them say .030 or replace the springs. Either way replace the valve seals. Good luck..

Ronnie

Re: shims on valve springs

Reply #4 – December 25, 2004, 01:31:47 PM

""""How many miles are on the motor?""
about 335,000 miles now

""WHy are you trying to tighten up the valves? """
because the spin fairly easy when you grasp the spring and turn it.
sorry if i forgot to mention that in the previous post. :dunno:

I also found a rocker arm that is cracked right where it rubs the valve stem. its on the opposite side of where the "W" is stamped in the rocker that you never see cause its always full of oil. Hmmmm, maybe its an "M" for motorcraft,, but anyways the crack is right there. why cracked, i dont know.

like i said,, i find so many things just because of age.

anyways ronnie, i lapped the valves when i did the rebuild and the valve angle seemed to be present and not too worn. There might be some excessive wear on the seat which actually means new heads since they are aluminum. like i said,, lots of little things here to consider. Im almost wondering if .030 is enough but anything must be better. Im not sure what you mean by roller cams and the odds of valve stem wear,, you might not understand what motor im talking about here.

Now,, anyone think cutting down the fulcrums along with shims is an ok idea for the 3.8?

Re: shims on valve springs

Reply #5 – December 26, 2004, 05:55:52 AM

Quote

because the spin fairly easy when you grasp the spring and turn it.

Well, the proper way to check springs is by measuring the pressure needed to compress them to specified lengths. My manual says an 87 V6's springs should be:
190lbs @ 1.28" (valve open)
73lbs @ 1.70" (valve closed)

Here's a (Chevy) page that shows the spring checker gadget:

http://www.supercarsunlimited.com/tech/springs/springs.htm

Quote

Could'nt i remove about .002 of the fulcrum

Besides very slightly changing the angle of the arc that the rockers sweep against the valve stem tips (could create more side force, wearing the guides faster), the hydraulic lifters will happily compensate by having their internal workings .002 away from their "normal" place, so you won't get any more lift, unless you grind the fulcrums so far that the lifters bottom out, at which time you're looking at possible coil bind and many broken parts.

Re: shims on valve springs

Reply #6 – December 26, 2004, 10:51:17 PM

I decided to not mill the fulcrums,, i got to thinking i better not get carried away. I ended up making a valve spring compressor but its not like the ones that allow you to remove the keepers. It binds the top of the valve while pulling up on the lower part of the spring. Pretty simple of a diy for the most part.
ill try to post a pic of it if anyone would like, it worked great for my situation. I ended up not using my original shims cause they just seemed too thin. I ended up giving some "C" shaped snap rings a try cause they fit perfect **under** the lower cup. These mic'd out at about .055 which some of you may think is a bit much. Im compensating for a lot of wear here on the fulcrums/ rockers/ valve seats and worn springs not to mention the fact i did lap the valves during the rebuild with a cordless drill. Theres lots of new room here above and beyond the typical 100k mile engine that a .020 shim might work for.

i used my made up spring compressor till the lower cup was loose. I layed the snap ring under the cup and used a long flat head screwdriver to snap/slide them in place under the cup. When i lower the spring back in place, the spring was much more tight.

I dont see anything incorrect about shimming in this manner, the valves sit nice and flat.
I left both valve covers off and started the car just to make sure i did not need to tweek on the rockers anymore. I have to say, its running much smoother than before. I took it out for a drive and there seems to be less of a damand on downshifting when climbing hills. Not too sure on actual power cause i have not pushed it yet.
still waiting for the smoke or kaabammmm :dunno:

Im not gonna mention what these "C" shaped snap rings are actually used for unless someone really wants to know. Lost of people here will probably think im crazy so we'll leave it at that. You actually have to modify these snap rings a little till they look like a "C" then they will slip right in. All ill say for now is that they are actual car parts but more specifically, they are drive train parts.

Differences so far
Seems to have more power for going up hill (less demand to hit passing gear)
Idle? well, i pretty much sat a mug of coffee on the air cleaner and the engine barely rippled the fluid. Im very pleased with the smoothness i end up with.

to be continued, only if i end up regreting this.

BTW<< i forgot to moan and groan about what i found back during my rebuild. It appears that when the engine was put together by FoMoCo, a few of the rocker fulcrums were put in backwards. **YES this can be done if you look at the oil valley milled where the fulcrum and the rocker meet. It was very apparent that this was a mistake cause the ones that were incorrect had this wierd "X" patern worn at the mating surfuce. Be aware of that when you those of you consider lubrication surfaces on the valve train, THE FULCRUMS CAN BE INSTALLED BACKWARDS!. They should mate up to each by comparing the oil valley lines. There is a "minus" sign in the upper right and lower left but flip the fucrum around 180deg and you will still end up with the same but the oil valley may not be lined on the fulcum to rocker.