I have a question for you guys changing valve springs. I was discussing this the other day with a guy. When you buy new springs, rated by the mfg for the cam being used, do you still have to check and shim them? Or are they a direct replacement.I'm thinking they should be checked for height and coil bind regardless if they are the specified spring.
Thanks,
Gary

 

yes, always check the installed height as the spring pressures are only accurate for the proper inst. height. The stiffer the springs you use the more it will be off the proper closed pressure when the installed height is off (rate = #/dh so if rate goes up the more error in dh the more error in #)

When installed w/ the proper installed height you can be sure the bind is no problem if you compare the specs of the springs w/ the lobe lift however it's never a sin to check it anyway.

 

Thanks TT, now another that might help others as well. What is the proper procedure? Without the spring,pull up on the valve with the retainer and locks in place. Use a snap gauge under the retainer and at the base and check the height. What is the proper shim determination?
Thanks
Gary

 

Get one of these, makes life a lot easier


Use that to measure the total height from seat to retainer w/ valve closed and then check that against the installed height specs deliverd w/ the spring, that will give you the shim amount you need.

 

TT, I agree and of course I don't have a spring mic in my mass of of tools! I tried to do a quick check on a set of heads here but my snap gauges don't fit too good!
I have to look a little closer at these heads.
Gary

 

TT
What you are saying is bacially true; however, the springs should be checked first before installing them. What sense would it make to set them at the correct height if the springs are not at the rating the manufacture puts on the box. Those valve spring checkers are not all that expensive but the cost just keeps going up and up when doing a job right. At times it's hard to justify the cost when the tool is going to be used once or twice. The only valve springs we checked for the rating and setting the height was on the garage's modified and sprint cars (and my street engine). They were checked every time before the heads were put back on the car. I would not be all that concerned with a daily driver. When racing, things change and more precesion is needed. There is less room for error and repeatabilty is also a concern.

 

Gary I did a post on how to check springs and shim along with checking spring bind. I was actually looking at the homemade gage I recommend and you can whip one up too. It is installed height and working height. I will post the picture tomorrow from work and try to find the post.
I check each and every installed height, open clearance and that includes valve seals and coil bind. It is easy.
I have often found one guide a touch long and with the valve seal installed the retainer hits the seal and will destroy that valve train.
I will have more information tomorrow

 

Gary I found the picture of the little gage I make. I use bronze welding rod. Cut and smooth one piece the installed height say 1 7/8th, a very common size. Make one wire as close as possible to 1 .875 If the lift is say 600 for example and you want .060 before touching the seal with the underside of the retainer take 1.875 minus lift of .600 and .060 safety or .660 from 1 .875 Make the other wire in this case 1.215 This is the installed height and the working height. Join them together like in the picture on a slant using normal soft solder.
This is the checking tool.
For each and every valve check. I install the valve without a spring, the valve seal the retainer and keepers in place and pull up on the valve and insert the big rod of the gage. It must fit and if too loose install a shim. try again until when the proper spring shim is installed and the 1.875 wire fits nicely under the retainer and on top of the spring shim. This is your installed height. Now one more check for the valve. Let it drop down on the valve seal. The small gage should not go in. It should be too long to fit between the spring shim and the retainer. If it fits your retainer to valve seal is too short. It it doesn't fit you have more then enough clearance.
The last thing is take a spring, put a retainer on it and squash it in the vise. Measure from under the retainer to the jaw of the vise. It should be less by at least .040 then the short wire you made.
If so that valve is safe to assemble. Once you get use to it it takes only a hour as check and assemble a head and you know all clearances are fine.
If your valve retainer hits the valve seal and this often happens shorten the retainer a small amount on the lathe. It doesn't hurt the retain, increases clearance and that part of the retainer hangs below the keepers anyway.
Good luck and don't hesitate to ask if I didn't explain this right.
Gary this is for you

 

Thanks TT and Norval. I haven't had time to really look at these springs yet but something doesn't look right. I probably won't get to them until next week when I get back from carlisle. I have to load up the truck tonight afterwork so that kills today.
Thanks for the advice.
Gary

 

I don't have the mic. All I use is my digital calipers. The center slide rod is a depth gauge.

Comp Cams has spring charts about how to set their springs to get the desired pounds by shimming or unshimming. I buy the springs after figuring out the installed height I need for the pounds of spring pressure and the desired max lift.

Not running springs anywhere near the max valve open height makes them last allot longer. When i had low .500 lift cams I had .600 max lift springs. When i went to over .600 lift cams I went to over .700 max lift springs. I don't even have to think about coil bind or seal smashing or valve float

 

I use an old discarded pencil to make my "go-no go" gauge. Cut it down to a hair longer than the installed spring ht. Use a file to square off the ends and to cut off any extra. Use calipers to check the final length.

Then you assemble the valve/retainers in the guide without the spring and use the "go-no go" gauge (pencil stubb) to determine if shims are required. If there is any slack, you can use feeler gauges to determine the number of shims required.

You could also make another gauge to check for valvetrain interfearance at full lift.

Not aerospace tech here, just shade tree bubba blueprinting.

-Mark.