2V spring upgrade - final word?
02-02-2010, 07:59 PM
#1
Rennlist Member
Thread Starter
2V spring upgrade - final word?
Is there a final word on this? Years ago I used Ford springs, NLA. I had to cut the seats, use weird spacers - not the best plan.
02-03-2010, 10:58 AM
#3
Rennlist Member
Thread Starter
It seems so from a PM I got.
02-03-2010, 11:28 AM
#4
Rennlist Member
what is wrong with stock springs? are you going to tach this thing out to 7000rpm or use stock red-lines? The stock stuff works well in racing environments. I think scot had some purple colored springs on his 2v that seemed to work However when we pulled the motor the 4th time for the last change, one of the springs was broken. we replaced it with stock stuff
02-03-2010, 11:34 AM
#5
Administrator - "Tyson"
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Mark, Brendon is trying to close the valves with 20-30psi of manifold pressure trying to keep them open.
There are also those who feel part of the GT cam wear issue has a lot to do with valve float at the upper RPM's which means the springs are too weak.
There are also those who feel part of the GT cam wear issue has a lot to do with valve float at the upper RPM's which means the springs are too weak.
02-03-2010, 01:28 PM
#6
Rennlist Member
Thread Starter
Now,
what is wrong with stock springs? are you going to tach this thing out to 7000rpm or use stock red-lines? The stock stuff works well in racing environments. I think scot had some purple colored springs on his 2v that seemed to work However when we pulled the motor the 4th time for the last change, one of the springs was broken. we replaced it with stock stuff
They need to be replaced whenever you rebuild an engine.
BUT - the new Porsche springs are insanely priced. Way too much for what they are. Springs are pretty much springs, and we can delve into the import or domestic market for our parts for simple things like this - paying attention of course to:
1) Coil Bind
2) Total free length
3) Lb pressure at valve open
4) Lb Pressure at valve closed
5) Stock installed height.
If you don't believe me - ask how much time Greg Grey spent trying to figure out springs. Springs are springs as I mentioned -but getting the RIGHT spring to work in our heads is very important.
The 2V heads that I have are an 82 usa set, and an 80 euro set. I will be making a 4.5L stock motor just to keep around for Leeroy, and a 5L 2V race motor. The 2V race motor will see over 7000rpm - so those springs will need to be better than stock. The 4.5L stocker will need to be new, so new springs, even if they are only near stock in strength, will need to be new.
Its the definition of insanity to continue to do the same thing over and over again expecting a different result. Springs are wear items, just like valve seats, valves, valve seals, rings, bearings, shocks, brake rotors, brake pads, engine seals, spark plugs, lifters.
When a domestic engine is rebuilt, MOST of the engine is replaced except for maybe the crank and rods. Because we believe Porsche is the end all be all, many of us reuse parts that are simply not meant to be reused.
I simply spend too much money, and too much time for me to practice the idiocy of reusing parts that could fail from age in a new motor
Trending Topics
02-03-2010, 02:48 PM
#8
Rennlist Member
Thread Starter
I have... Twice. The first time I lucked out, and bought a set of high compression 4.5L euro pistons - that may have been the deal of the century back in 2003 or so. They cam with rings and pins!
But this last 4.5L I rebuilt, I had to scrounge around for a good deal on rings - and did - so the bottom end is done. Now I will work on the heads, and have a nice fresh 4.5L just in case I need one.
But this last 4.5L I rebuilt, I had to scrounge around for a good deal on rings - and did - so the bottom end is done. Now I will work on the heads, and have a nice fresh 4.5L just in case I need one.
02-03-2010, 03:30 PM
#9
Rennlist Member
Maybe thats why my power has been so high on the stock stuff, the valve springs are weak and I have more duration and lift at high rpm. 
I dont think age has anything to do with it, how many revolutions the engine has been put through would be a concern. so far, there is no indication that the valve springs are weak based on dyno curve shapes. It would be really interesting to see a known valve spring issue'd engine, and its dyno, before and after.
why would you be worried about 30psi on the valve back? it would help the valve open, on the intake stroke, and under closing, there would be no net force on it as both sides of the valve would have 30psi on it. what am i missing here?
mk
I dont think age has anything to do with it, how many revolutions the engine has been put through would be a concern. so far, there is no indication that the valve springs are weak based on dyno curve shapes. It would be really interesting to see a known valve spring issue'd engine, and its dyno, before and after.
why would you be worried about 30psi on the valve back? it would help the valve open, on the intake stroke, and under closing, there would be no net force on it as both sides of the valve would have 30psi on it. what am i missing here?
mk
Yes. The 2V head may eventually see that as well (the 30psi from T's SC till be going into the S4 motor with the shimmed 944S2 springs) Possibly from another SC unit or from a Turbo
Now,
mark - The "stock stuff" as you suggest is *30 years old! - and is no longer in top form. The springs lose their properties over time (DECADES!) So therefore, they need to be replaced whenever you rebuild an engine.
They need to be replaced whenever you rebuild an engine.
BUT - the new Porsche springs are insanely priced. Way too much for what they are. Springs are pretty much springs, and we can delve into the import or domestic market for our parts for simple things like this - paying attention of course to:
1) Coil Bind
2) Total free length
3) Lb pressure at valve open
4) Lb Pressure at valve closed
5) Stock installed height.
If you don't believe me - ask how much time Greg Grey spent trying to figure out springs. Springs are springs as I mentioned -but getting the RIGHT spring to work in our heads is very important.
The 2V heads that I have are an 82 usa set, and an 80 euro set. I will be making a 4.5L stock motor just to keep around for Leeroy, and a 5L 2V race motor. The 2V race motor will see over 7000rpm - so those springs will need to be better than stock. The 4.5L stocker will need to be new, so new springs, even if they are only near stock in strength, will need to be new.
Its the definition of insanity to continue to do the same thing over and over again expecting a different result. Springs are wear items, just like valve seats, valves, valve seals, rings, bearings, shocks, brake rotors, brake pads, engine seals, spark plugs, lifters.
When a domestic engine is rebuilt, MOST of the engine is replaced except for maybe the crank and rods. Because we believe Porsche is the end all be all, many of us reuse parts that are simply not meant to be reused.
I simply spend too much money, and too much time for me to practice the idiocy of reusing parts that could fail from age in a new motor
Now,
mark - The "stock stuff" as you suggest is *30 years old! - and is no longer in top form. The springs lose their properties over time (DECADES!) So therefore, they need to be replaced whenever you rebuild an engine.
They need to be replaced whenever you rebuild an engine.
BUT - the new Porsche springs are insanely priced. Way too much for what they are. Springs are pretty much springs, and we can delve into the import or domestic market for our parts for simple things like this - paying attention of course to:
1) Coil Bind
2) Total free length
3) Lb pressure at valve open
4) Lb Pressure at valve closed
5) Stock installed height.
If you don't believe me - ask how much time Greg Grey spent trying to figure out springs. Springs are springs as I mentioned -but getting the RIGHT spring to work in our heads is very important.
The 2V heads that I have are an 82 usa set, and an 80 euro set. I will be making a 4.5L stock motor just to keep around for Leeroy, and a 5L 2V race motor. The 2V race motor will see over 7000rpm - so those springs will need to be better than stock. The 4.5L stocker will need to be new, so new springs, even if they are only near stock in strength, will need to be new.
Its the definition of insanity to continue to do the same thing over and over again expecting a different result. Springs are wear items, just like valve seats, valves, valve seals, rings, bearings, shocks, brake rotors, brake pads, engine seals, spark plugs, lifters.
When a domestic engine is rebuilt, MOST of the engine is replaced except for maybe the crank and rods. Because we believe Porsche is the end all be all, many of us reuse parts that are simply not meant to be reused.
I simply spend too much money, and too much time for me to practice the idiocy of reusing parts that could fail from age in a new motor
02-03-2010, 03:42 PM
#10
Rennlist Member
as I mentioned (or asked to Brendan), there would be no manifold pressure trying to keep them open while they are closing, (due to pressure equalibrium), but when they are closed, you would have 30psi trying to make them all leak if they were not being called on to open. that seems like a valid concern.
Think about it, on the intake stroke, 30psi helps the valve open and as far as the valve is concern, soon there is no net pressure force on the valve surface. it starts to close, and then you have a seal. the piston comes up and compresses the volume with 200psi, but there is still 30psi acting on the back side of the valve. combustion occures, 1000 psi still keeping the valve closed, and on the exhaust stroke, you might have a chance of a leak due do to the 30psi acting on the back of the valve. is 30psi on the back of the valve worth getting stronger springs? I dont know. thats an interesting situation. I guess all the blower guys know the answer to it.
Think about it, on the intake stroke, 30psi helps the valve open and as far as the valve is concern, soon there is no net pressure force on the valve surface. it starts to close, and then you have a seal. the piston comes up and compresses the volume with 200psi, but there is still 30psi acting on the back side of the valve. combustion occures, 1000 psi still keeping the valve closed, and on the exhaust stroke, you might have a chance of a leak due do to the 30psi acting on the back of the valve. is 30psi on the back of the valve worth getting stronger springs? I dont know. thats an interesting situation. I guess all the blower guys know the answer to it.
02-03-2010, 03:48 PM
#11
Administrator - "Tyson"
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Mark,
Do a search in the 951 forum for valve float.
Do a search in the 951 forum for valve float.
02-03-2010, 04:00 PM
#12
Rennlist Member
didnt find much there. maybe didnt look hard enough. valve float is mainly an RPM and spring/cam thing. again, what pressure is acting on intake valve after it has finished its cylinder fill. the pressure will be equal on each side of the valve at that point, so closing it is only a factor of the cam, spring and engine speed. So, it cant be an issue anytime other than under the exhaust stroke, but even then, there is still a positive pressure in the cylinder. How much, who knows. . So, I dont think that turbo/supercharged engines have a factor valve float due to boost. maybe leaks under the exhast stroke, and before the intake stroke, but no where else. what do you think?
. So, I dont think that turbo/supercharged engines have a factor valve float due to boost. maybe leaks under the exhast stroke, and before the intake stroke, but no where else. what do you think?
02-03-2010, 04:33 PM
#14
Administrator - "Tyson"
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Did you search the 356 forum by mistake? 
I found no less than two pages in the 951 forum alone with chatter on this topic.
This should clear things up, if this isn't good enough....send an e-mail to Lindsey Racing
I found no less than two pages in the 951 forum alone with chatter on this topic.
Hi Ian,
Considering the turbo you are running and the boost/power levels, you may not see the full advantages of some of the items you are considering.
1a- The valve springs should be looked at as a maintenance item first then as a performance mod second. If your valve springs are worn out, then it's time to replace them. With the appropriate valve springs you don't have to worry about valve float at higher boost. When chosong a performance spring, you also need to worry about coil bind, which is related to the valve lift based on the cam. So if you need valve springs, upgrading to performance springs makes sense.
1b- Cams move your powerband around. Some are lumpy at idle, many do not address some of the inherited characteristics of the 951 (spoolup, back pressure,...). The more aggressive the cam is, the less streetable it will be. A cam that makes a ton of power up top, may not be the best cam for street driving. So cam selection can be a bit tricky. It's easy to see the performance gains on a dyno chart, but street manners are something you must experience to decide on what you can live with. If there are any emissions to deal with, it makes the selection even harder. So when deciding on a cam, focus your search on what is more important to you, street, track,... There is no one size fits all! In addition to the cams you expressed interest in, JME offers a good selection as well.
2. Aftermarket rods are not going to hurt drivability. There are many rods to chose from, Pauter, Carrillo, Wossner to name a few.... Most are in the same weight class till you jump to TI, which is extreme for a 951. The LWF will make some difference, however it's not a problem, you'll get used to it in no time.
3- A big valve head is nice to have. But with the turbo you have and the boost level/power you are running, you will not see the full benefits. A nicely modified head, where flow and velocity are both addressed will increase the Volumetric efficiency of your engine. Of course you will need a cam to compliment the head. At the power level you are dealing with, a good valve job (good seat work) and minor porting using a stock head might be more beneficial hp/$ wise.
A few more items that will help you make a educated decision and save you lots of headache and heartache.
- Talking to someone who actually used a product is a big plus.
- Investigate before you pay. There are plenty of questionable parts offered (talk about a head/cam that self destruct, or a engine that comes apart in a short period after initial run, or a replacement engine that sits at the builder's shop for a long time while the customer is waiting...). Make sure a 2 week turnaround does not turn into a year plus!!!
- When changing heads/cams make sure your your engine management can handle the new changes.
- Look at it as a system vs. a component.
Good luck.
Considering the turbo you are running and the boost/power levels, you may not see the full advantages of some of the items you are considering.
1a- The valve springs should be looked at as a maintenance item first then as a performance mod second. If your valve springs are worn out, then it's time to replace them. With the appropriate valve springs you don't have to worry about valve float at higher boost. When chosong a performance spring, you also need to worry about coil bind, which is related to the valve lift based on the cam. So if you need valve springs, upgrading to performance springs makes sense.
1b- Cams move your powerband around. Some are lumpy at idle, many do not address some of the inherited characteristics of the 951 (spoolup, back pressure,...). The more aggressive the cam is, the less streetable it will be. A cam that makes a ton of power up top, may not be the best cam for street driving. So cam selection can be a bit tricky. It's easy to see the performance gains on a dyno chart, but street manners are something you must experience to decide on what you can live with. If there are any emissions to deal with, it makes the selection even harder. So when deciding on a cam, focus your search on what is more important to you, street, track,... There is no one size fits all! In addition to the cams you expressed interest in, JME offers a good selection as well.
2. Aftermarket rods are not going to hurt drivability. There are many rods to chose from, Pauter, Carrillo, Wossner to name a few.... Most are in the same weight class till you jump to TI, which is extreme for a 951. The LWF will make some difference, however it's not a problem, you'll get used to it in no time.
3- A big valve head is nice to have. But with the turbo you have and the boost level/power you are running, you will not see the full benefits. A nicely modified head, where flow and velocity are both addressed will increase the Volumetric efficiency of your engine. Of course you will need a cam to compliment the head. At the power level you are dealing with, a good valve job (good seat work) and minor porting using a stock head might be more beneficial hp/$ wise.
A few more items that will help you make a educated decision and save you lots of headache and heartache.
- Talking to someone who actually used a product is a big plus.
- Investigate before you pay. There are plenty of questionable parts offered (talk about a head/cam that self destruct, or a engine that comes apart in a short period after initial run, or a replacement engine that sits at the builder's shop for a long time while the customer is waiting...). Make sure a 2 week turnaround does not turn into a year plus!!!
- When changing heads/cams make sure your your engine management can handle the new changes.
- Look at it as a system vs. a component.
Good luck.
