LT1/4 valve spring questions
Thread Starter
Safety Car
Joined: Sep 2002
Posts: 4,030
Likes: 6
From: Maryland
LT1/4 valve spring questions
What are the spring forces at max lift in the LT1 w/stock springs and cam?
Same for LT4?
What kind of spring is best for a cam like I am installing: 214/224 @050 dur, 566/563 lift, 112 deg LSA ? Do any of you have a cam like this, and if so, what spring do you use?
Any help is greatly appreciated!
Andy
Same for LT4?
What kind of spring is best for a cam like I am installing: 214/224 @050 dur, 566/563 lift, 112 deg LSA ? Do any of you have a cam like this, and if so, what spring do you use?
Any help is greatly appreciated!
Andy
Race Director
Joined: Apr 2000
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From: Texas
Re: LT1/4 valve spring questions (sothpaw2)
The specs on the LT4 spring are 101# closed and ~250# open @ 1.78" install height.
Neither spring will work with the lift you have. The LT4 spring is the better of the two, but is only good to .525
I'm running custom springs from Combination Motorsports. 115# closed, 315# open, 1.78 install height. They're good to .590
You can reach CM at 702-798-8504 They have a website at http://www.cmotorsports.com/
Neither spring will work with the lift you have. The LT4 spring is the better of the two, but is only good to .525
I'm running custom springs from Combination Motorsports. 115# closed, 315# open, 1.78 install height. They're good to .590
You can reach CM at 702-798-8504 They have a website at http://www.cmotorsports.com/
Thread Starter
Safety Car
Joined: Sep 2002
Posts: 4,030
Likes: 6
From: Maryland
Re: LT1/4 valve spring questions (96GS#007)
What is your cam?
I think what I have here are comp cam 941 springs, 447lb/in, 360 lb open at 1.75 installed height. What bothers me is that my cam has 566 lift and the spring is recommended for 500 max. However, it would appear that it shouldn't bind. And if installed at 1.80", not 1.75, I can't see why 550 would be a problem.
I think what I have here are comp cam 941 springs, 447lb/in, 360 lb open at 1.75 installed height. What bothers me is that my cam has 566 lift and the spring is recommended for 500 max. However, it would appear that it shouldn't bind. And if installed at 1.80", not 1.75, I can't see why 550 would be a problem.
Race Director
Joined: Apr 2000
Posts: 15,344
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From: Texas
Re: LT1/4 valve spring questions (sothpaw2)
I have the HOT Cam.
With regard to the Comp 941 springs being good to .550, your initial post references a cam with lift of .56x
Two other things to consider...The ID of the 941 spring may be (and I beleive is) too small for the spring to seat on the stock LT1/4 spring locator. This means you need to switch to a flat valve spring seat or an L98 seat.
The CompCams recommendation of .500 max lift may be a result of the spring damper vs the valve spring coils.
With regard to the Comp 941 springs being good to .550, your initial post references a cam with lift of .56x
Two other things to consider...The ID of the 941 spring may be (and I beleive is) too small for the spring to seat on the stock LT1/4 spring locator. This means you need to switch to a flat valve spring seat or an L98 seat.
The CompCams recommendation of .500 max lift may be a result of the spring damper vs the valve spring coils.
Thread Starter
Safety Car
Joined: Sep 2002
Posts: 4,030
Likes: 6
From: Maryland
Re: LT1/4 valve spring questions (96GS#007)
I am working with ported/polished heads, and the heads guy should have done what's necessary to get the spring seated correctly.
Can you explain more about spring damper vs valve coil springs?
--It is .566 lift, I was just being lazy when I said 550. This 941 spring would seem to have enough to handle over 600 if seated just right, I don't get why they say 500 max.
Can you explain more about spring damper vs valve coil springs?
--It is .566 lift, I was just being lazy when I said 550. This 941 spring would seem to have enough to handle over 600 if seated just right, I don't get why they say 500 max.
Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,009
From: Texas
Re: LT1/4 valve spring questions (sothpaw2)
I am working with ported/polished heads, and the heads guy should have done what's necessary to get the spring seated correctly.
Can you explain more about spring damper vs valve coil springs?
--It is .566 lift, I was just being lazy when I said 550. This 941 spring would seem to have enough to handle over 600 if seated just right, I don't get why they say 500 max.
Can you explain more about spring damper vs valve coil springs?
--It is .566 lift, I was just being lazy when I said 550. This 941 spring would seem to have enough to handle over 600 if seated just right, I don't get why they say 500 max.
Port and polish doesn't mean he has or will machined the heads to accept larger valve springs. I would double check.
A manufacturer typically won't understate the capability of a product. While the spring may support more than .500, I'd talk with a CompCams rep before exceeding that. Actually, if the heads are being machined, the best and easiest thing to do would be to get a different p/n spring matched to your specs. Considering the cost of cylinder head work, the extra $100 or so for different springs is a drop in the bucket.
The damper is inside the valve spring. Typically they are made of wound flat (in cross section vs oval or circular for a valve spring) metal. Their purpose is to dampen valve spring harmonics. The clearance between the damper "coils" is typically the same or less than the valve spring coils, hence the reason the .500 lift limit may be predicated on the damper vs the spring itself. There can also be issues with the damper contacting the valve guide boss.
Le Mans Master
Joined: Aug 1999
Posts: 7,339
Likes: 137
From: WilkesBarre PA
Re: LT1/4 valve spring questions (96GS#007)
I'm running custom springs from Combination Motorsports. 115# closed, 315# open, 1.78 install height. They're good to .590
Thanks. :cheers:
Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,009
From: Texas
Re: LT1/4 valve spring questions (RichS)
I'm running custom springs from Combination Motorsports. 115# closed, 315# open, 1.78 install height. They're good to .590
Jim I forgot when we spoke about these springs if they were a drop in replacements or if the spring pad needed to be cut larger.
Thanks. :cheers:
Jim I forgot when we spoke about these springs if they were a drop in replacements or if the spring pad needed to be cut larger.
Thanks. :cheers:
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Thread Starter
Safety Car
Joined: Sep 2002
Posts: 4,030
Likes: 6
From: Maryland
Re: LT1/4 valve spring questions (96GS#007)
GS,
Do you run 7/16" studs & roller rockers with that, or did you keep your 3/8" size? Did you replace the studs with new ones (I'm not sure if your heads are ported) at all?
--I was told to go to 7/16", maybe because of this spring (a little stiffer than yours) and cam (a little more lift than yours but less duration). That was a considerable expense since I already have 3/8" RR's in the LT1.
Do you run 7/16" studs & roller rockers with that, or did you keep your 3/8" size? Did you replace the studs with new ones (I'm not sure if your heads are ported) at all?
--I was told to go to 7/16", maybe because of this spring (a little stiffer than yours) and cam (a little more lift than yours but less duration). That was a considerable expense since I already have 3/8" RR's in the LT1.
Race Director
Joined: Apr 2000
Posts: 15,344
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From: Texas
Re: LT1/4 valve spring questions (sothpaw2)
GS,
Do you run 7/16" studs & roller rockers with that, or did you keep your 3/8" size? Did you replace the studs with new ones (I'm not sure if your heads are ported) at all?
--I was told to go to 7/16", maybe because of this spring (a little stiffer than yours) and cam (a little more lift than yours but less duration). That was a considerable expense since I already have 3/8" RR's in the LT1.
Do you run 7/16" studs & roller rockers with that, or did you keep your 3/8" size? Did you replace the studs with new ones (I'm not sure if your heads are ported) at all?
--I was told to go to 7/16", maybe because of this spring (a little stiffer than yours) and cam (a little more lift than yours but less duration). That was a considerable expense since I already have 3/8" RR's in the LT1.
I had to swap to 3/8" studs because the OEM LT4 studs are 10mm shouldered (you can't set the lash on the OEM roller rockers, you torque them to 18 lb/ft and go). FWIW, the engine has been spun to 6800rpm on numerous occasions without valve float or other issues. My hp peak occurs just shy of 6500rpm.
How you intend to use the car will determine if 7/16" are overkill. IMO if you plan on lots of racing and running the h*ll out of it in general, given your setup the 7/16" studs aren't a bad idea. If it's primarily a cruiser with some occasional aggressive driving, 3/8" should be fine.
Drifting
Joined: Jun 2001
Posts: 1,997
Likes: 1
From: Lake Ozark MO
Re: LT1/4 valve spring questions (sothpaw2)
Listen to Jim on this one. He's done his homework and has worked through some high RPM difficulties with good success.
I will be following his recommendations when I perform my near future upgrades.
I will be following his recommendations when I perform my near future upgrades.
