LT1 cam & rocker question
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if you are talking about stock LT1 springs, they need to be replaced with a new spring that has the specs to support the new cam. The cam card will note min seat & open spring pressures needed.
would also recommend changing valve stem seals also. FelPro Viton ones
would also recommend changing valve stem seals also. FelPro Viton ones
The stock springs when brand new are not great for a stock cam. To even consider reusing them at 20 years old with an aftermarket cam is way way way out of line.
A stock cam shows gains with better springs.
A stock cam shows gains with better springs.
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Joined: Jan 2013
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From: Las Vegas
FYI this is the stock LT1 spring data: 10206040 - Valve Spring This single valve spring is use on LT1 Production Corvettes. Technical Notes: Single spring with 1.30" O.D. and 1.26" solid height. The pressure at installed height is 85# @ 1.78" with 373# the average rate of pounds per inch. Use with retainer P/N 10168424.
So u take the 1.78" installed height subtract the 1.26" solid height and have 0.52" travel but most cam companies say u still need 0.060" safety margin which leaves only 0.46" max cam lift for that stock spring.
U can look at all the cam companies for the LT1 and max u will find on 2 or 3 cams that have 0.460" lift or less. I do like the GM RAM350 cam (used in the HT383 also) cam #14097395 Hydraulic Roller which should slide right in. Make 350hp and 400ft-lbs in the lower compression RAM350. For '96 and later u need to change to longer pin and drill bigger center hole.
Let us know what u choose Formula.
So u take the 1.78" installed height subtract the 1.26" solid height and have 0.52" travel but most cam companies say u still need 0.060" safety margin which leaves only 0.46" max cam lift for that stock spring.
U can look at all the cam companies for the LT1 and max u will find on 2 or 3 cams that have 0.460" lift or less. I do like the GM RAM350 cam (used in the HT383 also) cam #14097395 Hydraulic Roller which should slide right in. Make 350hp and 400ft-lbs in the lower compression RAM350. For '96 and later u need to change to longer pin and drill bigger center hole.
Let us know what u choose Formula.
Thread Starter
Staging Lane
Joined: Jun 2014
Posts: 82
Likes: 1
From: Detroit, Mi
Ok so new question. You all got me wondering.... My car smoked and a oil smell at high speed. about 50mph+ .. so I figured valve cover gasket, which is new. So I tightened them, they were a little loose than expected. No noticeable smoke, but still smell a little oil. I looked lastnight and No oil wet around valve cover or behind intake but I seen it was wet at the lower rear of the head & oil pan. I thought valve stem seal maybe. But my spark plug was not oily. It was dry.
The intake is known to leak at the rear sometimes, presumably due to the heat cycling caused by the EGR.
On the springs, what the new LT1 spring specs are doesn't matter one bit on a 20 year old car.
On the springs, what the new LT1 spring specs are doesn't matter one bit on a 20 year old car.
Thread Starter
Staging Lane
Joined: Jun 2014
Posts: 82
Likes: 1
From: Detroit, Mi
It's not that. I redid the intake gasket and heat wrapped the egr pipe when I put headers on. It's dry back there.
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Joined: Jan 2013
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From: Las Vegas
On the springs, what the new LT1 spring specs are doesn't matter one bit on a 20 year old car.
Ah so it is age that expires vlv springs not heat, use and a abuse. U are a wealth of knowledge. U must be a metallurgical expert. So what is the expiration date of vlv springs in any car or how 'bout sitting on sales shelf? Do we need date codes before purchasing? Springs are not engineered to last over what period of time? No margin engineered into them? When do when we need to change all our vlv springs?
Ah so it is age that expires vlv springs not heat, use and a abuse. U are a wealth of knowledge. U must be a metallurgical expert. So what is the expiration date of vlv springs in any car or how 'bout sitting on sales shelf? Do we need date codes before purchasing? Springs are not engineered to last over what period of time? No margin engineered into them? When do when we need to change all our vlv springs?
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On the springs, what the new LT1 spring specs are doesn't matter one bit on a 20 year old car.
Ah so it is age that expires vlv springs not heat, use and a abuse. U are a wealth of knowledge. U must be a metallurgical expert. So what is the expiration date of vlv springs in any car or how 'bout sitting on sales shelf? Do we need date codes before purchasing? Springs are not engineered to last over what period of time? No margin engineered into them? When do when we need to change all our vlv springs?
Ah so it is age that expires vlv springs not heat, use and a abuse. U are a wealth of knowledge. U must be a metallurgical expert. So what is the expiration date of vlv springs in any car or how 'bout sitting on sales shelf? Do we need date codes before purchasing? Springs are not engineered to last over what period of time? No margin engineered into them? When do when we need to change all our vlv springs?
But, since we can't prove any of that with solid links, stock OE springs are great!
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Joined: Jan 2013
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From: Las Vegas
High spring pressure with fast ramp rates accelerate spring fatigue (and cam wear). Thats why u should only use enough sping that u need and those stock springs are as wimpy as any, combine that with the wimpy stock cam.
Any overhaul manual will prescribe test the spring before replacing at overhaul. But i guess "overhaul" is a dirty word to hp addicts. BTW the GM RAM350 cam (used in the HT383 also) cam #14097395 Hydraulic Roller has typical long slow ramp of a GM cam and will be fine with a stock LT1 spring.
Any overhaul manual will prescribe test the spring before replacing at overhaul. But i guess "overhaul" is a dirty word to hp addicts. BTW the GM RAM350 cam (used in the HT383 also) cam #14097395 Hydraulic Roller has typical long slow ramp of a GM cam and will be fine with a stock LT1 spring.
As has been covered repeatedly the stock LT1 springs are not really good enough for a stock cam, that cam is pretty stockish other than the more attractive LSA, with the LT1 intake liking rpm I would fully expect that cam to want LT4 springs rather than LT1 springs when used on an LT1.
I believe the b-bodies got the same springs as the other LT1s and with a 191/195 .418/.435ish cam it sees benefit from a spring upgrade.
If someone wants a VERY near stock rebuild I would consider that cam but not with LT1 springs, LT4 yes.
I believe the b-bodies got the same springs as the other LT1s and with a 191/195 .418/.435ish cam it sees benefit from a spring upgrade.
If someone wants a VERY near stock rebuild I would consider that cam but not with LT1 springs, LT4 yes.
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Joined: Jan 2013
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From: Las Vegas
U are assuming too much. First the springs are bad because of age/to old. Then they are not up to the task for a short cam with long sloping ramps. So i look up the RAM350 vlv spring #10212811 and its specs are less than the LT1 spring.
"Part # 10212811
Spring Type: Single spring. Outside diameter: 1.25". Pressure @ installed height: 80# @ 1.70". Solid height: 1.20". Average Rate (lbs@in): 256... CT350/350, 350HO engines"
10206040 - Valve Spring
This single valve spring is use on LT1 Production Corvettes.
Technical Notes: Single spring with 1.30" O.D. and 1.26" solid height. The pressure at installed height is 85# @ 1.78" with 373# the average rate of pounds per inch.
So by a simple comparison the LT1 is much more spring than that RAM350 cam needs. Yet it makes 350hp and 400ft-lbs in a low compression engine with very similar heads and intake.
FWIW that RAM350 cam #14097395 is only 200 bucks and slides right in on a Ver 1 opti car - no vlv springs, lifters, p-rods needed or even drive pin changed. Result is somewhere in the 350hp/400ft-lb range for very little money.
Just an economical option - take it or leave it. But a new enthusiast on the learning curve with a somewhat high mileage car - why not????
"Part # 10212811
Spring Type: Single spring. Outside diameter: 1.25". Pressure @ installed height: 80# @ 1.70". Solid height: 1.20". Average Rate (lbs@in): 256... CT350/350, 350HO engines"
10206040 - Valve Spring
This single valve spring is use on LT1 Production Corvettes.
Technical Notes: Single spring with 1.30" O.D. and 1.26" solid height. The pressure at installed height is 85# @ 1.78" with 373# the average rate of pounds per inch.
So by a simple comparison the LT1 is much more spring than that RAM350 cam needs. Yet it makes 350hp and 400ft-lbs in a low compression engine with very similar heads and intake.
FWIW that RAM350 cam #14097395 is only 200 bucks and slides right in on a Ver 1 opti car - no vlv springs, lifters, p-rods needed or even drive pin changed. Result is somewhere in the 350hp/400ft-lb range for very little money.
Just an economical option - take it or leave it. But a new enthusiast on the learning curve with a somewhat high mileage car - why not????
U are assuming too much. First the springs are bad because of age/to old. Then they are not up to the task for a short cam with long sloping ramps. So i look up the RAM350 vlv spring #10212811 and its specs are less than the LT1 spring.
"Part # 10212811
Spring Type: Single spring. Outside diameter: 1.25". Pressure @ installed height: 80# @ 1.70". Solid height: 1.20". Average Rate (lbs@in): 256... CT350/350, 350HO engines"
10206040 - Valve Spring
This single valve spring is use on LT1 Production Corvettes.
Technical Notes: Single spring with 1.30" O.D. and 1.26" solid height. The pressure at installed height is 85# @ 1.78" with 373# the average rate of pounds per inch.
So by a simple comparison the LT1 is much more spring than that RAM350 cam needs. Yet it makes 350hp and 400ft-lbs in a low compression engine with very similar heads and intake.
FWIW that RAM350 cam #14097395 is only 200 bucks and slides right in on a Ver 1 opti car - no vlv springs, lifters, p-rods needed or even drive pin changed. Result is somewhere in the 350hp/400ft-lb range for very little money.
Just an economical option - take it or leave it. But a new enthusiast on the learning curve with a somewhat high mileage car - why not????
"Part # 10212811
Spring Type: Single spring. Outside diameter: 1.25". Pressure @ installed height: 80# @ 1.70". Solid height: 1.20". Average Rate (lbs@in): 256... CT350/350, 350HO engines"
10206040 - Valve Spring
This single valve spring is use on LT1 Production Corvettes.
Technical Notes: Single spring with 1.30" O.D. and 1.26" solid height. The pressure at installed height is 85# @ 1.78" with 373# the average rate of pounds per inch.
So by a simple comparison the LT1 is much more spring than that RAM350 cam needs. Yet it makes 350hp and 400ft-lbs in a low compression engine with very similar heads and intake.
FWIW that RAM350 cam #14097395 is only 200 bucks and slides right in on a Ver 1 opti car - no vlv springs, lifters, p-rods needed or even drive pin changed. Result is somewhere in the 350hp/400ft-lb range for very little money.
Just an economical option - take it or leave it. But a new enthusiast on the learning curve with a somewhat high mileage car - why not????
And again LT1 intakes mean an LT1 needs more rpm with a given cam, more rpm means more spring needed.
Also GM has a tendency to use valve float as the rpm limiter on crate engines, to keep warrantied engines at lower safer rpm levels.
They also have a tendency to use cheap parts they have in the parts bin, like the LT1 TB on the Ramjet 502.
Bet those springs are just what is on production Vortec heads and just slapped together as "good enough".
So your logic is very deeply flawed.
Go ahead and say I am assuming too much, but my assumptions are based on experience and knowledge, not flipping through a catalog.
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From: Las Vegas
Maybe I am assuming too much but you don't have a clue how engines are rated the 350/400 rating on a CRATE engine is not comparable to production car. Crate engines are rated without intake tract or exhaust system, tested the same way an LT1 will make just as much.
Im just posting what GM lists lists in their catalog as hp - no i dont do corrections of hp ratings. If u do then lets hear it or shut up if u cant.
Bet those springs are just what is on production Vortec heads and just slapped together as "good enough".
The stock Vortec head does use 10212811 vlv springs. So what. As ive said many times u should only use enough spring to get the job done. BTW the RAM350 uses those springs with that RAM350 cam #14097395 using 1.6 roller rockers. That gives that cam 0.460"/0.481" lift while the stock Z28 cam has only 0.450"/0.460" lift.
So your logic is very deeply flawed.
Well im not using hardly any logic at all - just simple comparisons. If u expect a dyno result for proof of every part then u are on the wrong forum as dont know anyone on this forum that owns one. And dyno testing of every part becomes very expensive let alone exhausting. So i use what others have proven and published rather than what someone else told me they heard. Or assume a vlv springs are bad just due to age even though the car/engine runs fine and still runs hard.
Im just posting what GM lists lists in their catalog as hp - no i dont do corrections of hp ratings. If u do then lets hear it or shut up if u cant.
Bet those springs are just what is on production Vortec heads and just slapped together as "good enough".
The stock Vortec head does use 10212811 vlv springs. So what. As ive said many times u should only use enough spring to get the job done. BTW the RAM350 uses those springs with that RAM350 cam #14097395 using 1.6 roller rockers. That gives that cam 0.460"/0.481" lift while the stock Z28 cam has only 0.450"/0.460" lift.
So your logic is very deeply flawed.
Well im not using hardly any logic at all - just simple comparisons. If u expect a dyno result for proof of every part then u are on the wrong forum as dont know anyone on this forum that owns one. And dyno testing of every part becomes very expensive let alone exhausting. So i use what others have proven and published rather than what someone else told me they heard. Or assume a vlv springs are bad just due to age even though the car/engine runs fine and still runs hard.
TECH Addict
Joined: Dec 2010
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From: Maricopa, AZ
An installed spring is under tension all the time.
You both agree that the stock LT1 springs wont work. Different reasons sure, but same result.
There does seem to be a bit of over springing it going on though. GM finds the peak hp of the cam in a certain engine (Stock LT1 @5000 rpms) then gives it just enough spring to go 1000 rpms or so higher then sets the rev limit below that (Stock LT1 5800 rpms). Shouldn't we do the same? Yes I know ramp rates, valve train weight, and rpms all come into play here.
You both agree that the stock LT1 springs wont work. Different reasons sure, but same result.
There does seem to be a bit of over springing it going on though. GM finds the peak hp of the cam in a certain engine (Stock LT1 @5000 rpms) then gives it just enough spring to go 1000 rpms or so higher then sets the rev limit below that (Stock LT1 5800 rpms). Shouldn't we do the same? Yes I know ramp rates, valve train weight, and rpms all come into play here.
Last edited by hrcslam; Jul 10, 2014 at 03:27 AM.
