3970627 valve spring measurements

[Duke W.]

Re: 3970627 valve spring measurements

The test data was 347 pounds at something approximating .500 lift depending on installed height.

Duke

[Clem Z.]

Re: 3970627 valve spring measurements

The test data was 347 pounds at something approximating .500 lift depending on installed height.

Duke

sorry i forgot to add the 105# install height pressure so the total of over the nose is 339#

[Bill M.]

Re: 3970627 valve spring measurements

sorry i forgot to add the 105# install height pressure so the total of over the nose is 339#

My Chevy Power lists the 3916164 (L-88) at 125 lb. installed and at 310 lb. at 0.560 lift.

I calculate the L-88 (164) at 297 lb. over the nose at 0.520 lift...

[Duke W.]

Re: 3970627 valve spring measurements

sorry i forgot to add the 105# install height pressure so the total of over the nose is 339#

To repeat the calculation that I provided earlier using the supplied data.

Average rate = (347-120)/0.5 = 454 lbs/in

120 lbs was the average force at 1.88" and 347 lbs at 0.5 valve lift.

Duke

[Joe R.]

Re: 3970627 valve spring measurements

In another thread, Clem mentioned that he had a valve spring tester but no springs. So I asked him to test mine. I sent two of my 3970627 springs to him. Here's what he said:

i can test them for seat pressure and # / inch but i can not test them at full lift as my tester only goes to 250 #. i have a dial indicator on the tester so i can read pressure at every .100 of a inch.

I CHECKED THEM AND IT LOOKS LIKE THE 7TH EDITION OF THE POWER MANUAL IS CORRECT. 450 # PER INCH. THE 267 # FIGURE IN THE PERFORMANCE PARTS CATALOG MUST BE THE OVER THE NOSE PRESSURE AT FULL CAM LIFT.

I STARTED OUT AT 1.880 " SPRING HEIGHT USING THE RETAINER AND THEN I COMPRESSED THE SPRING .100 " AT A TIME AND TOOK A READING. SINCE THERE IS NO INTERFERENCE FIT BETWEEN THE INNER AND OUTER SPRINGS THERE IS NO FRICTION INVOLVED TO CAUSE A FALSE READING. SO DOING BOTH SPRINGS TOGETHER GETS YOU A TRUER READING. AFTER MARKET SPRINGS HAVE AN INTERFERENCE FIT SO THEY MUST BE DONE SEPARATELY TO MAKE SURE FRICTION DOES NOT ENTER INTO THE READING. I CHECKED BOTH SPRINGS AND EVERY READING WAS WITHIN 5 #, WHICH I AM SURE IS WITHIN THE ACCURACY OF THE CHECKER. BOTH SPRINGS SHOWED BETWEEN 110 / 115 # AT 1.880 " INSTALLED HEIGHT. EVERY .100 " MOVE SHOWED BETWEEN 40 # AND 45 # INCREASE IN PRESSURE. I WISH MY TESTER WENT ABOVE 250 # SO I COULD HAVE CHECKED THE PRESSURE AT .500 " LIFT WHICH WOULD BE CLOSE TO THE STOCK CORVETTE CAM.

remember the the L-88 / ZL-1 cams have more lift so they need a less # / inch spring to keep the over the nose pressure under 300 #. i bet that 267 # spec is over the nose pressure.

Clem, a big THANK YOU for testing the springs!

Does this answer some or all of the nagging questions about these springs?

Joe

[Duke W.]

Re: 3970627 valve spring measurements

Readings of 40 to 45 pounds per 0.1" indicates a rate of 400-450 lbs/in, so I guess the 450 lb/in rate quoted in some sources is correct.

I still find it amazing that this spring which was used in non-HD big blocks from about 1969 is signicantly stiffer than the HD spring, but that's what the test data says.

Duke

[Clem Z.]

Re: 3970627 valve spring measurements

Readings of 40 to 45 pounds per 0.1" indicates a rate of 400-450 lbs/in, so I guess the 450 lb/in rate quoted in some sources is correct.

I still find it amazing that this spring which was used in non-HD big blocks from about 1969 is signicantly stiffer than the HD spring, but that's what the test data says.

Duke

i believe it is because of the HD engines cams have higher lifts so they need less #/inch to prevent too high a pressure at max cam lift. they do have higher installed pressure which would control valve float. i have a L-88 spring here that i have used to calibrate my tester as i had it checked on a spring tester in a standards lab. if i can find a L-88 retainer i will run a test.

[Clem Z.]

Re: 3970627 valve spring measurements

i believe it is because of the HD engines cams have higher lifts so they need less #/inch to prevent too high a pressure at max cam lift. they do have higher installed pressure which would control valve float. i have a L-88 spring here that i have used to calibrate my tester as i had it checked on a spring tester in a standards lab. if i can find a L-88 retainer i will run a test.

i just did the L-88 spring(3916164) which is used and guess what it came out the same 40#/45#/ .100" movement. i did a new small block after market spring and it came out 30/35#/.100 movement. very interesting. below is a picture of my setup.

[Bill M.]

Re: 3970627 valve spring measurements

i just did the L-88 spring(3916164) which is used and guess what it came out the same 40#/45#/ .100" movement. i did a new small block after market spring and it came out 30/35#/.100 movement. very interesting. below is a picture of my setup.

Thanks, Clem.

I have 3916164s in my 396, I was thinking that I should replace them with 3970627 to reduce the load on the cam. Scratch that off the to-do list...

Bill