IHADAV8.com - Turbo Buick Tech, and Nonsense
Tech Area => General Buick Tech => Topic started by: phil_long on December 06 2012, 05:52:27 PM
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I've been doing a LOT of reading, but I have yet to find any material as to how the valve springs work and why it seems to be one of the first mods. I've read a couple threads after searching and searching, and seen someone say if your car accelerates hard, then seems to hit a wall, then it could potentially be valve springs. Im not interested in throwing parts at the car, but I seem have an issue with my car pulling at higher RPM's. Thanks for any input fellas
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Valve springs do two things. They hold the valve closed so it can make a seal and they keep the lifter in contact with the cam. (Imagine the damage a hammer will do pushing down on a nail as opposed to a hammer bouncing off the nail and slamming down on it).
If the springs don't have enough poundage to keep the valvetrain stable then all hell breaks loose and power pretty much ceases to be made at that point. If you hop in my time machine, go back to '87 and get one of these cars brand new, the springs are too weak. Years of age and/or use just make the problem worse.
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Valve springs do two things. They hold the valve closed so it can make a seal and they keep the lifter in contact with the cam. (Imagine the damage a hammer will do pushing down on a nail as opposed to a hammer bouncing off the nail and slamming down on it).
If the springs don't have enough poundage to keep the valvetrain stable then all hell breaks loose and power pretty much ceases to be made at that point. If you hop in my time machine, go back to '87 and get one of these cars brand new, the springs are too weak. Years of age and/or use just make the problem worse.
Thats a great analogy. Hopefully im not reading TOO much into the analogy, but, would you say that the healthy valve spring would represent the hammer NOT bouncing off the nail, and actually supply the pressure upon the nail until lifting off the throttle? Sorry if i sound dumb
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And, the reason i mention this is because I ORIGINALLY thought it was the tranny, but after a certain RPM, my foot could be through the floor, and the car doesn't pull again until after shifting. My trans shifts completely fine and firm, and the car pulls pretty good when im NOTat WOT, but its when it holds in gear longer at WOT that the car falls flat on its face.
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And, you can actually feel the springs being too weak throughout a WOT pull? Thanks again
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The cam profile ultimately limits the rpm IF the valve springs are in good condition.
If the valve springs are tired (any car that has the factory original springs was probably tired at 50,000 miles) then the lifters will not have enuf pressure exerted on them to stay in contact with the lobes before the engine reaches the end of its power band. Stock cam with stock turbo was usually done around 4800 because it ran out of air flow. With a bigger turbo, it would usually start dropping off around 5200 rpm but the engine might rev to 5400 or so but with less power. Engine combo will have a lot of affect on this.
Putting stiffer springs on will not do much for power because the cam was not designed for high rpm output being its a turbo but they will allow all the performance originally in the car plus a little more if they are a bit stiffer..
I have seen many a Regal that dropped on its face at 4000 rpm because the springs did not have enuf pressure to close the valves under boost.
Replacing the springs with new ones makes all the difference in the world. No need to go too radical because the cam lobes were made for relatively low rpm-
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Ok, thanks for the info. Trying to understand the operation to know what im looking for. As mentioned before, the car is SUPER strong at low RPM's. Its not like it slowly fades away as RPM increases, it literally feels like it stops pulling and waits to shift and then i get hit with a load of power once again. Its consistent throughout all gears. Guess this might also explain why my 3rd gear pull feels like shit. Under part throttle to maybe half throttle, the pull is consistently strong, but of course this isn't WOT at the 17 lbs of boost i need to get a stiffy!! :D
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But, i have still been researching and read a few people complaining about wiping out their stock cam(which is where i dont want to be). Seen some folks going with the comp 980's, but i dont want to throw parts at my car anymore.
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so, do you want to have it run properly, or, are you satisfied with it as it is? You confuse me.
If you put a too stiff spring on an old cam, you might have a problem, but putting something equivalent to the 980s which are only slightly stiffer than the factory springs is not much risk. You can always put some Joe Gibbs break in oil, or one of the additives and run it for a few miles for added insurance...I generally do.
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Keep in mind that putting "stiffer" springs that are in spec isn't really a bad thing. Yes, they have more poundage but the extra stiffness brings them up to spec most of the time.
Also, adding stiff springs to an old cam and lifters is actually much preferable to stiff springs on new units. New parts are are made of crappy cam blanks with crappy lifters that don't have tougher stellite feet. When cams and lifters bed-in they work harden as they marry together. After running the stock parts for years and many many miles they're set up for stiff springs much better than new parts.
What RPM is you car shifting at? And can you tell what RPM the car falls on it's face before the shift?
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Not my intent to confuse. I want the car to run properly. Im only researching to get an idea of what it is I'm up against. Thats all! :cheers:
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And Earl, Im going to check into that today. I hadnt had any intent to pay attention to RPM's until after researching last night. I mainly watched KR and O2 count. I revved it in park and the RPM's got as high as 3733, but due to how slow the SM monitoring is, i didn't trust it. :chin:
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Might have to buy a tach?
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why do you need a tach? You have a scanmaster. It reads plenty fast for what you are doing.
Earl summed it up well in his last post
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ok
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The reason I ask is because if your car loses power at 3500 and shifts at 5200 it might just be valvesprings.
If you're shifting at 10,000 and loose valvetrain control at 6000 you have a shift point problem. :D
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Lol. I understand. 10k? Lol
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Just drove home. At WOT from 1st to 2nd the car shifted at 4900. Car starts to fall flat at about 3400 RPM during that period. When nailing it, cruising at 45 MPH, the car downshifts firmly but pulls weak, from about 3500 RPM up. Most diagnostics i could get just from the drive home due to traffic.
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Your panties are going to fall off when you get that sorted out!
If it's falling off at 3400, a very large portion of your powerband is lagging along doing nothing.
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just did another WOT, and the car shifted this time at 4457. This is the most fun experiment. :icon_eyes:
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but it def falls off at 3400, and this time with it shifting earlier(not sure why...maybe because i was in overdrive?), i got hit in the chest with pure power from the next gear. this car def hauls arse, but there's a lot left in it!! I can feel it.
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can you guys point in the direction of the exact valve spring set i need for my current setup? No cam wiping!! Lol. Thanks
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I believe the 980's are what everybody runs on stock cams...
http://www.jegs.com/i/Comp+Cams/249/980-12/10002/-1 (http://www.jegs.com/i/Comp+Cams/249/980-12/10002/-1)
Full throttle offers them for $43.99 and offers price matching if you want to support a Buick vendor.
I tried to find the PAC equivalent but for some reason they're website won't load for me.
huh huh
"load"
huh huh
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Hahaha. Thanks Earl. Im so amped about this. I've been reading and reading and I KNOW this has to be the issue.
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If they are original springs they are definitely an issue.
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Hahaha. Thanks Earl. Im so amped about this. I've been reading and reading and I KNOW this has to be the issue.
...or:
weak ignition system ( bad plugs , bad wires , bad coil
tuning issue (too rich too lean)
exhaust restricted (plugged catalytic or muffler baffles loose)
or fuel supply issue
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all of the above have been addressed. Might be a little rich in 1st, but def not 2nd and 3rd. Timing chain just got replaced(original) and I've covered everything else myself. Valve springs have to be it. :atbeer:
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well maybe not HAVE TO, but im def hoping so. Otherwise im still gonna be on the hunt!! :D
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They are at least one of your problems. If you hop in a time machine and test drive your car at the dealership, the valve springs are weak.
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I wish I could Earl. I would. Probably stay back there too and live the next 20 something odd years driving a Buick I got fresh from the dealership. and the problem Im experiencing is what the car would've driven like back then? it's amazing they were as successful as they were with weaker valve springs. very mean cars :powersix:
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They're a little weaker now just from age, but yes, they were borderline when new.
A stock intake valve is 1.7" minus the stem sealing off the intake. That means you have roughly 2.18 sq" of valve face with 12.5PSI of stock boost trying to push it open. That will negate over 27#s of seat pressure... Turn the boost up to 17 and you're now pushing an extra 37#s against the spring. Just by increasing the boost it's the same as losing 20# of spring preload
When you think about it like that it's pretty easy to see how 55#s of seat pressure can be a really crappy valvetrain setup.
Keep in mind back then the "fast" cars like 5.7 cameros, Vettes and 5.0 mustangs were running high 14's/low15's. It wasn't that hard to destroy them in a so-so state of tune.
Hotrodding those cars required real money for not much where we could hang a throttle return spring on the wastegate rod, squish the FPR in a vise, add some race fuel and be in the 12's.
I guess it also helped that GM would warranty a few headgaskets and crate engines were available!!
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That makes a LOT of sense actually. Its amazing that I've had my car for approximately 8 years or so, and I've learned the most within the last 6 months.
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Renewing this thread because I'm finally getting around to purchasing some valve springs. Any "special" things to look out for when I have the guy install these springs? I read somewhere that a couple of them where a B-word to get to. Thanks
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I've done a gazzilion sets. Make sure the springs, locks and retainers are clean and dry. Two people is easiest. One to compress the springs...the other to drop the locks in. Drop the bottom lock in first...let the spring come up a little to "seat" it...compress the spring again...then drop the top lock in. Use a pen magnet with the locks. I give 'em a love tap with a rubber mallet to make sure they're locked in. The rear two on the passenger side can be a whore.
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Lol. Thats what i read before about those two. Thanks
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Might have to make a tool for those
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Thats no good. Im so sick of this. I dont get why shit just cant be straight forward and easy(like an injector swap). Lol. Im having other issues, but not sure if i should start a new thread or not.
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those overhead valve spring compressors with the wheel on top will clear #6 and it only takes one person to do the job.
Just make sure the piston is at TDC while you have the springs off. IF a spring happens to drop down below flush DO NOT turn the crank to push it back up. use a hose to suck the valve back up into the head (much like that time Cartman had to suck the sea people he bought through a hose).
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I've always just hooked an air hose to the cylinder I was doing and kept the valve in place with air pressure
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Ah, air tools. That sounds like a disaster. The guy who's doing the work(i plan to help if i can) sold Charles his GN. He did all the work on it, but I'm not sure he went through the "proper" fundamentals throughout Charles car. I mean, his GN is stout, but its mismatched IMO. Anywho, I dont think he ever changed out the valve springs. He put the GN1 heads on there, so i dont think he ever had to do it(change the actual springs). Im sure he'll figure it out though. The guy who did my timing chain is who I'd prefer, but a part of me feels like he don't want my business. Oh well
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not a tool, just a fitting that screws into the spark plug hole that you connect to an air hose. Simple as it gets.
the GN heads (assuming we are talking about aluminum heads) probably had new springs on them. On the other hand, they will slow a near stock GN down unless one runs more boost, compression, and/or timing
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the GN heads (assuming we are talking about aluminum heads) probably had new springs on them. On the other hand, they will slow a near stock GN down unless one runs more boost, compression, and/or timing
ok tid bit of info.. Even why BUYING new heads (alum or steel) Check the damm springs !!! I have found a lot of mis matched stuff over the years. So don't "ASSUME" :chin:
Oh if ya do this yourself get the spring tool with the round thing on top.. When ya get to the hard ones you can take the top off and use a wrench.. Makes things a little easier.
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not a tool, just a fitting that screws into the spark plug hole that you connect to an air hose. Simple as it gets.
That's the best way to do them.
You can also make more power with lighter springs and titanium retainers. But I don't think anyone here is making that kind of power or pulling high rpms to take advantage of them.
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You can also make more power with lighter springs and titanium retainers. But I don't think anyone here is making that kind of power or pulling high rpms to take advantage of them.
The most cost effective way to get rid of sprung weight is to go beehives. The difference in mass between steel and Ti on those is marginal.
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the GN heads (assuming we are talking about aluminum heads) probably had new springs on them. On the other hand, they will slow a near stock GN down unless one runs more boost, compression, and/or timing
ok tid bit of info.. Even why BUYING new heads (alum or steel) Check the damm springs !!! I have found a lot of mis matched stuff over the years. So don't "ASSUME" :chin:
Oh if ya do this yourself get the spring tool with the round thing on top.. When ya get to the hard ones you can take the top off and use a wrench.. Makes things a little easier.
seems like I used a crow's foot wrench once on the hard ones
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I use a double shot of whiskey on the hard ones.
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You can also make more power with lighter springs and titanium retainers. But I don't think anyone here is making that kind of power or pulling high rpms to take advantage of them.
The most cost effective way to get rid of sprung weight is to go beehives. The difference in mass between steel and Ti on those is marginal.
That's why I run beehives on my engine.
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I have been told that a double shot or so of whisky will fix most leg problems
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I have been told that a double shot or so of whisky will fix most leg problems
Well, the longer two anyways.....
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yep, they open much easier