instaling valve springs on bbc

i know alot of people go to the machine shop but i really want to know how i changed spring before but not on high peformance. i know my current springs are 1.950 installed height. with the cam swap comp says to have 1.900. so all i have to do is install the spring and use a valve spring height micromter to make sure im at 1.900 and do simple math right? but do you measure from the seat to the retainer or under the retainer do you have to measure from the retainer to the tip also. i also heard you lose spring height after brake in so would 1.910 be fine how much over or under is acceptable. if i come in at 1.950 with new spring i would have to have the head seat ground right. if anyone knows can it be explained idot proof. i am mechanicly inclined but not book smart.

Use a valve spring micrometer, they are available inexpensively from Comp Cams.

Measure from the bottom of the spring pocket in the head to the underside of the retainer. You then add shims to correct the spring height.

DON'T get worried about getting everyone exact if this is a street engine. If you get them within .005 (five thousands) of an inch they will be fine.

It's really that simple.

Good Luck!:cool:

i did tell you ? or not if your all at 1.950 that alot for a stock head that hard to get some times with race head s??? but any ways if they are are that hi 1.950 get some -050 less keepers or throw a 060 shim under the spring and call it good. your valves should not need to be ground only if ther not sealing or beat in you should never sink your valves to get more spring set up there is longer valves +050 keepers new retainers with more set up and you can cut spring pockets but you need less set up right?

pat just curious what shop are you ought of. i ordered a comp micromter today about to pull engine clean up and put togethr. so to make sure im on the right page my current height is 1.950. comp springs are a 1.900 so ading a .060 shim would take me to 1.960 or -.050 keeper would highen up the spring to 1.950. no matter what i want a 1.950 installed height right. thank you for your help

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Originally Posted by 6801

pat just curious what shop are you ought of. I ordered a comp micromter today about to pull engine clean up and put togethr. So to make sure im on the right page my current height is 1.950. Comp springs are a 1.900 so ading a .060 shim would take me to 1.960 or -.050 keeper would highen up the spring to 1.950. No matter what i want a 1.950 installed height right. Thank you for your help

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mccarthy performance
mi 989-667-4071 no if you added a 060 shim under the spring that s 060 less 1.890 or a 015 shim and a 030 shim gets 045 1.995.a - 050 valves locks / keepers that - is less so with valve locks so that would be 1.900 there more then one way to Go. shims would be cheaper and not to hard to find

Working from your 1.900, adding a .060 shim will make it 1.840. Measure the spring without including the shim. Lunati says that + or - .020 is acceptable.

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Originally Posted by roofcam

Working from your 1.900, adding a .060 shim will make it 1.840. Measure the spring without including the shim. Lunati says that + or - .020 is acceptable.

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no HE IS STARTING AT 1.950

Okay...I thought he was trying to work from the 1.900 of the Comp springs.

What is the setup height from spring cup to under the retainer NOW ? If it is 1.950 rigth now and you need 1.900 less height you need to shim to get to 1.900 setup height or a -050 valve locks .less set up height . If you have only 1.900 setup height then you can use a + 050 that give you more set up heigth to get FROM 1.900 TO 1.950

maybe im a complete tard so i want my new installed height to be 1.900 for example if my current springs are 1.950 adding a 60 shim would take me to 1.890. so i would want my new springs to have a height of 1.900 comp spec and if i get an installed height of1.920 i would want to add a 20 shim to bring to 1.900.

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Originally Posted by 6801

maybe im a complete tard so i want my new installed height to be 1.900 for example if my current springs are 1.950 adding a 60 shim would take me to 1.890. So i would want my new springs to have a height of 1.900 comp spec and if i get an installed height of1.920 i would want to add a 20 shim to bring to 1.900.

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yep that is it

im also assuming the valve seal should at no point touch the valve spring?

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Originally Posted by 6801

im also assuming the valve seal should at no point touch the valve spring?

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that would be very good you want them not to get crush you should check that by measuring the bottom of the retainer to the top of the seal so lets say if your cam is 700 lift the add 060 to that so you would need 760 so you do not beat the seals to death any size your cam is you need to add 060. for room ok ?

that im ok with but should there be room from the inside diamter of the spring to the seal. i only took out 2 springs. the seal has about .005 side cleareance between the seal and the spring. with the new spring the seal sits flush not forced in the inside diamter of the spring.

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Originally Posted by 6801

that im ok with but should there be room from the inside diamter of the spring to the seal. i only took out 2 springs. the seal has about .005 side cleareance between the seal and the spring. with the new spring the seal sits flush not forced in the inside diamter of the spring.

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if you have PC seal s you may have 531 od you can buy now a elastomer hi rigid chimney thin wall small O.D.valve seal for only 11/32 stems valves if you have 3/8 stems you will have to go 500 OD and the white PC seals cut for a 500 PC seal