rcsb4.8to6.0

what exactly is spring preload, and how do you check spring preload "valvespring." i was told that the spring preload needs to be set at .060 just wondering how to check thatbecause i never did when i put the cam and the 918's in the 6.0. just thought that could resolve some of the valvetraine noise i was hearing.

PREDATOR-Z

If you are running stock rockers, there is 2 ways of adjusting preload
1- Custom length pushrods (quasi impossible as you would require a different lenghth on every valve to achieve optimum)
2- shimming the springs.

rcsb4.8to6.0

how do you go about checking the preload.

kemmert

Spring preload is what the specs say the height the spring needs to be shimmed to for the correct seat pressure. Seat pressure is basically how much pressure the cam manufacturer wants the valve to be held closed with.

If'n you used pushrods to adjust valve spring preload, to raise preload, you would have the valves open. Different length pushrods are used to correct valve train geometry problems.

Shimming the springs is the generally accepted way of adjusting seat pressure. In order to do this, you need a spring tester and you can get by with a snap gauge, preferably a height micrometer, though. For example, say the cam company wants 114 lbs of seat pressure, compress the spring in the spring tester until it reads 114 lbs, then measure the height of the spring while it is compressed. You then add or remove shims at the spring seat until the distance from the shim to the underside of the retainer matches the length of the spring when compressed to the 114 lbs.

PREDATOR-Z

Thank you for elaborating, I was short on words. LOL

gollum

iTrader: (1)

Here's my method for figuring hydraulic lifter preload:

Oem LS1 cam base circle diameter 1.550", subtracting new cams smaller base circle diameter (specs on cam card), divided by 2. Now subtract your answer from the 0.090" factory preload setting. This will be your preload using stock length pushrods and stock rockers. Everything else being stock specs.

Oscar Will

......and don't "over-shim" a spring so that it binds at full lift. If you have to adjust too far something is wrong anyway.

Cstraub

iTrader: (1)

Valvespring pre-load. . .I'm going to have to ponder this one. On another note, adjusting lifter pre-load with bolt down non-adjustable rockers is done with shims and/or pushrods, either non adjustable or adjustable length pushrods.

Chris

Unaffliated Racing

iTrader: (15)

Chris...I'm with ya on this one. I've been scratching my head all day looking at this topic. I think they have two different things confused together.

Squintz Palladoris

iTrader: (1)

Yes they do and Chris is correct. If you shim the valvespring the you are not going to change anything but the pressure the spring exherts on the valve itself. And installed height of the valvespring.

Just a bad choice of words. What you were looking for was lifter preload.

Brad

Cstraub

iTrader: (1)

Un,
Yeah, I thought at first we were pre-loading the inner spring to simulate a retainer step so we could check pressure on the Rimac, but this thread didn't go there.

Chris

PREDATOR-Z

Did I say something wrong?? Above post

kemmert

Ya know, I got to thinking about this at work today, and I believe he was originally meaning lifter preload, like ya'll are saying... The .060" valvespring preload didn't make a whole lot of sense to me, and I forgot about the LS1 not having adjustable rockers, so that didn't occur to me until later. Used to working on the 'old' engines.

PREDATOR-Z

Now that I read the first post I see what you guys are talking about. I didn't pay attention to the "spring preload" comment.
My reply was assuming we are talking about lifters and ways to adjust preload with stock rockers.

DaleMX

iTrader: (4)

Yea, I think a spring is compressed a little more than 60 thousands at installed height. Your preload is fine if you did the install correctly and you dont have any bad lifters, these fast ramp cams just make alot of racket. I like the sound personally.

One question. Did you also install hardened pushrods or did you stay stock.

Gman2002Z06

I don't think they are saying the .06" shim is only compressing the spring a total of .06"...What they are saying is that when the spring is installed normally, it may show 120# seat pressure...By adding .06" shim under the spring, you could in essence bring the seat pressure up to say, 140#...

Noisey valvetrain sounds like lifter preload being too light...At least in my case, after my cam install, the valvetrain tapped like crazy when the engine warmed up...Added a set of adjustable roller rockers and now the valvetrain is business like, but quite and no...TAP, TAP, TAP...

Peace...Gman

DaleMX

iTrader: (4)

Yea I know, I was kidding in that part Jeezz do I half to explain everything. I went with YT's and shimmed them up to the specified preload and it does quiet it down some, but I believe that is just the effect of the added mass of the YT's. If the lifter pumps up good it wont make any racket at .040 preload. At least that's my take of it all.

Anyway he could have a bent pushrod, a bad lifter, or any other number of valvetrain problems that would cause the tap that should be ruled out before cashing out on aftermarket rockers. That's why I asked about the pushrods.

Gman2002Z06

Well, from what I have been reading and finding is this...Regarding preload on all aluminum engines...If you do not have enough initial preload, as the engine warms up and expands at a greater rate than all the steel valvetrain components...You start to loose that light preload that you had to start with...Which, again, is why I just added the adj. rockers last weekend...When I started the engine cold...It was totally quite in the valvetrain...Then, as it warmed up, you could hear the tapping begin...Very quite at first, then louder and louder and louder...So, I took the chance on the rockers and it paid off...Very quite valvetrain with the proper LS1 lifter preload of 0.09"...

Peace...Gman

DaleMX

iTrader: (4)

Dont get me wrong, I just wouldn't spend money on the rockers until I was sure nothing else was wrong.

There is another thread about the ticking that bring up the point of oil pressure, What is it like at idle?

Gman2002Z06

My oil pressure is fine...37psi at idle, about 43psi at 1500rpm, and up to 60+ psi when the rpms rise about 4000 or so...

Besides...If it was an oil pressure problem, when the engine was reved up, the ticking would dissappear...In my case the ticking was always present, at all rpms...But, it was not present when the engine was cold...I'm not sure what the base circle diameter of the G5x3 cam is vs. the stock LS6 cam, but I know that they put 7.35" long pushrods in with the cam swap...This is when the ticking really got loud...When I swapped the rockers out...I can tell you that the rockers were extremely loose, some of them had no preload pressure from the spring in the lifter whatsoever...

It's easy enough to check the preload...Take one rocker that the valve is totally closed, loosen the rocker bolt up until there is no pressure on the spring, then finger tighten the bolt to take up the slack...Then count the total number of turns it takes until the bolt seats the rocker in it's cradle...Remove the bolt and measure the thread spacing, multiply this by the number of turns it took to tighten the bolt, and there you have your preload measurement...

Peace...Gman