IHADAV8.com - Turbo Buick Tech, and Nonsense
Tech Area => General Buick Tech => Topic started by: Joel Russo on November 13 2013, 10:08:25 AM
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If you were to change valve springs on a stock motor with stock heads and cam.... would you use the Comp 980 or the Comp 981 springs?
980's are rated at 92lbs at 1.700 and the 981's are rated at 105lbs at 1.700"
When you change the springs, and eliminate the stock spring cup, do you need to use shims?
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To do it right. You need to measure the height on each and every valve and measure each spring and shim from there.
To just shotgun them on the car, I'd do a search and find a pattern for what other people did and got away with.
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99% sure the combo is 980s without the cups.
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99% sure the combo is 980s without the cups.
yes
stronger springs do no good whatsoever on a street car with a stock cam other than to accelerate lobe wear
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To do it right. You need to measure the height on each and every valve and measure each spring and shim from there.
To just shotgun them on the car, I'd do a search and find a pattern for what other people did and got away with.
Listen to this guy! If you want to do it right, this is the proper method.
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If the engine's bone stock and you're not gonna be beating on it then 980's without the cups are fine.
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Thanks guys.
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I recently did the 980 springs on my engine that had original springs with cups. One of the best and cheapest mods I have done to car.
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I recently did the 980 springs on my engine that had original springs with cups. One of the best and cheapest mods I have done to car.
Assuming you have stock heads, where did you see improvement with the new springs?
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The engine will quit falling on it's face before the shift points.
The downside is the valve sealing surfaces will still be all black and scorched from years of not sealing.
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I am pretty sure one of my valve seats/valves is fried from years of abuse. Which is contributing to low compression in one cylinder... but, damn do fresh springs help a lot!
I am still pushing 25-30psi on the backside of those valves and it is holding over 10 years later.
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It's amazing just how much you can get away with on these engines.
They defiantly aren't the delicate little snowflakes some make them out to be.
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The engine will quit falling on it's face before the shift points.
The downside is the valve sealing surfaces will still be all black and scorched from years of not sealing.
Well said, my car wouldn't even rev to 5 grand. After the springs it runs much stronger all the way to the 5 grand shifts now.
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I recently did the 980 springs on my engine that had original springs with cups. One of the best and cheapest mods I have done to car.
Assuming you have stock heads, where did you see improvement with the new springs?
The engine will rev out cleaner and quicker.
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Looks like there's no real downside to upgrading the springs.... On the "to do" list for the winter.
Thanks guys!
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You really need to consult with your machinist as to what his recommendation is for valve spring pressure. Boost pressure, cam selection and RPM's are a big factor in determining what you need.
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that is good advice-particularly if one is using an aftermarket cam. I would suspect a lot of machinists may not be familiar with these engines and turbo cars in general so I would tend to start with what the cam manufacturer suggests.
In this case, we know what we are dealing with so the comp 980's, or the equivalent, is the tried and true spring that will allow the engine to rev to 5300, or a bit more, without undue wear on the lobes and they should provide a bit longer life.
It is seldom mentioned, but Brad just did above, boost in the intake will try to hold the valve open when it should be closing and if one figures the psi on the back of the valve, this can really make an old set of springs struggle which is the reason we see engines go flat on power in the lower 4000 rpm bands so often