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Valve spring question for cam break in

Napoleon1991

Napoleon1991

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I have a question about breaking in my comp xe268h cam in my 440. I purchased the recommended comp 911-16 springs but the open pressure of 309lbs worries me during the break in period. The manual that came with the cam said that there should be no more than 260-270 lbs open pressure during break in. Where can i buy short ratio rocker arms or light weight springs? My springs are single with a damper so i have no inner springs to remove. Any advice would be appreciated.
 
You might want to consider a lighter spring. Whats your installed height ?

When I was doing the numbers installing a Sum6401 and the recommended spring was the 911, I checked the installed height and it was less than the rated height they use on the 911 at 309lbs. It would have been a lot more weight than was recomended. I ordered a lighter set that worked out better for my installed height.

I'm sure plenty have used the 911 without any problems. I've also read where some were wiping lobes and thought to myself maybe this was the reason.

I'll report back with my numbers and spring.
 
I broke in a set of new Comp Cams hydraulic lifters on my existing 292°/.509 cam with those springs. I don't know how long or how much wear the cam had, but I installed the lifters and springs and did a break in like it was a new cam.
Having said that, I recommend you follow the manufacturer's instructions.
Surely someone on the forum must have some weaker or worn springs. I held on to the worn, stock springs in case I need them in the future.
 
By the way, I changed my springs because of "intuition" based on my motor power falling off quickly at higher (over 5,200) RPMs. I had the pressure tested and I was right. With the new 911-16 springs and new lifters my 440+6 pulls like a monster to at least 6,200.
 
biomedtechguy said:
I broke in a set of new Comp Cams hydraulic lifters on my existing 292°/.509 cam with those springs. I don't know how long or how much wear the cam had, but I installed the lifters and springs and did a break in like it was a new cam.
Having said that, I recommend you follow the manufacturer's instructions.
Surely someone on the forum must have some weaker or worn springs. I held on to the worn, stock springs in case I need them in the future.
Click to expand...

I do still have the original valve springs. Will they be ok to use with this cam for break in?
 
My installed height was 1.850 and I ended up going with Crane 99839 springs.

911 open 309 lbs @ 1400 rated 373 lbs
911 seat 122 lbs @ 1900

99839 open 298 lbs @ 1300 rated 354 lbs
99839 seat 121 lbs @ 1800

Difference being the height of the open and seat numbers. The Crane 99839 just fell into the recommended numbers for my installed height.
 
khryslerkid said:
My installed height was 1.850 and I ended up going with Crane 99839 springs.

911 open 309 lbs @ 1400 rated 373 lbs
911 seat 122 lbs @ 1900

99839 open 298 lbs @ 1300 rated 354 lbs
99839 seat 121 lbs @ 1800

Difference being the height of the open and seat numbers. The Crane 99839 just fell into the recommended numbers for my installed height.
Click to expand...
So you eliminated any possible chance of coil bind that the heavier and longer spring may have encountered. All the lift in the world accomplishes nothing if the spring holds the valve closed.
 
Just for comparison look at the valve spring dimensions and installed loads on the Edelbrock Performer BB cyl. heads.
 
You didn't say which heads or if you know the installed height range for your heads. You indicate 309# open pressure. That corresponds to the 1.900 installed height with a .500 lift. If you have "stock" heads, you will have an installed height much less than 1.900. That makes your open pressure concerns even worse. Check what installed height you actually have. Then decide if the 911 spring is really what you want for your application. Break in with stock spring would be a pretty good idea, no matter if you stick with the 911's or go lighter.
 
66Satellite47 said:
You didn't say which heads or if you know the installed height range for your heads. You indicate 309# open pressure. That corresponds to the 1.900 installed height with a .500 lift. If you have "stock" heads, you will have an installed height much less than 1.900. That makes your open pressure concerns even worse. Check what installed height you actually have. Then decide if the 911 spring is really what you want for your application. Break in with stock spring would be a pretty good idea, no matter if you stick with the 911's or go lighter.
Click to expand...

This is what I was trying to convey. You said it better.
 
Just measured my installed height. Its 1.850. Also checked the original springs and it looks like the coils would be very close to binding, so that rules out using them. Anyone know where i can get short ratio break in rockers? Ive searched for them, but can only find chevy stuff.
 
The 911-16 spring is the milder choice for that camshaft. I do not believe the stock springs will work, but applaud you for considering spring pressures. I don't think you have to worry about it. I've used at least 1/2 dozen of these over the years and as long as the lifters rotate, the engine fires immediately, and you can run it straight through the full break-in period above 1800rpm, you should be fine.
 
Check it, if you don't you have no idea what you are working with. Height mikes are cheap. Mine is a cheap JC Whitney modified for a Mopar spring dimension, checked by quality measuring devices (dial caliper or mic). Good ones are not too expensive. Simple to do the height checking. Your 452's are 1.830-+/- to 1.87 depending on the valve wear/valve job. Valve spring set up is critical not only for the break in, mainly for normal driving(whatever that is).
Sorry this post is 7 hours old. My computer seems to have failed me again..
 
Napoleon1991 said:
Just measured my installed height. Its 1.850. Also checked the original springs and it looks like the coils would be very close to binding, so that rules out using them. Anyone know where i can get short ratio break in rockers? Ive searched for them, but can only find chevy stuff.
Click to expand...

With the XE268H cam it's hard to believe stock springs would be be near coil bind. That cam has approximately the same lift as a magnum cam. Put one in the vise with a retainer that you plan to run, tighten it to coil bind & measure it. I bet you still have .100 before coil bind with that cam & the stock springs.
 
66Satellite47 said:
With the XE268H cam it's hard to believe stock springs would be be near coil bind. That cam has approximately the same lift as a magnum cam. Put one in the vise with a retainer that you plan to run, tighten it to coil bind & measure it. I bet you still have .100 before coil bind with that cam & the stock springs.
Click to expand...
Havent measured the old springs in the vice yet, but i did measure between the coils when it was installed on the engine with the valve opened and there was less than .050 between coils.
 
You guys that do not have the correct tools can us a drill press and a bolt chucked up in the drill, then set the valve spring on the drill table with the top retainer sitting top and use a $20 dial indicator jigged up to get a good reading at the particular Dims. you are shooting for. Write both Dims. down for each spring, installed height, coil bind. If all springs are pretty much the same then take them to the shop and have them tested to see if the number values are correct if not then shim a little plus then you can figure the all important spring rate. Aint that bigga deal with a good drill press and then YOU know the values of YOUR heads.
 
I have those springs on my 452 heads. I had a local machine shop install them. Same place that told me what I suspected about the springs that were on the heads being way low on pressure open and closed.
 
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