Dyno GURUS- performance analysis questions/comments please!!
Thread Starter
Drifting
Joined: Jan 2000
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From: Phoenix Arizona
Originally Posted by zwede
Yes, but the open load at 1.2" is a useless spec. With an installed height of 1.900", 1.2" is 0.700 lift. So sure they have 399 lbs, but only if you have a 0.700" lift cam. With your 0.555 lift it will be 339 lbs which is a great open pressure for a hydraulic you intend to take to 6000 rpm.
I have learned quite a bit in the last few days....
I just ordered the 925 springs.... My plan is this- check existing height with the 924's since I didn't install them, see where they were at and then set up the 925's......
I have a much better understanding with ALL of this based on this posting.... thanks for the input!
Bob
Instructor
Joined: Mar 2004
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From: La porte Texas
Hey Bob , Zwede is on the right track ( as usual ) I have an old LS6 solid cam w/ seat press. 115# . It pulls hard to 5600. If you can get a height mike and get that installed height to spec. My little 305 race motor has 360# on the seat .(sorry different deal)
Thread Starter
Drifting
Joined: Jan 2000
Posts: 1,612
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From: Phoenix Arizona
Originally Posted by Super Stock
Hey Bob , Zwede is on the right track ( as usual ) I have an old LS6 solid cam w/ seat press. 115# . It pulls hard to 5600. If you can get a height mike and get that installed height to spec. My little 305 race motor has 360# on the seat .(sorry different deal)
Bob
Thread Starter
Drifting
Joined: Jan 2000
Posts: 1,612
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From: Phoenix Arizona
I removed one spring from the motor on the exhaust side with the air compressor hooked up and measured the CURRENT valve spring installed height- It is 1.870" or so.
Is there a significant difference here between running a height of 1.900" and the current 1.870" for my new 925 springs?
Any comments?
Thanks to all for the help over the last week!
Bob
Is there a significant difference here between running a height of 1.900" and the current 1.870" for my new 925 springs?
Any comments?
Thanks to all for the help over the last week!
Bob
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Let me get this straight. You now bought 925 spring and they are supposed to be installed at 1.900 Your present spring on the motor that your removing are installed at 1.870. Is it ok for me to install my new springs at 1.870 vs 1.900
IMO - Your increasing the the #'s significantly. Look at the CC spring chart for a simular spring closed and open pressure. Then look at how it reacts to a .050 change and then figure yours out at @60% of that.
How many shims do your Edelbrock heads have and how thick are they? Maybe you can mix and match or even buy one to get you to the required 1.900
IMO - Your increasing the the #'s significantly. Look at the CC spring chart for a simular spring closed and open pressure. Then look at how it reacts to a .050 change and then figure yours out at @60% of that.
How many shims do your Edelbrock heads have and how thick are they? Maybe you can mix and match or even buy one to get you to the required 1.900
Thread Starter
Drifting
Joined: Jan 2000
Posts: 1,612
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From: Phoenix Arizona
Originally Posted by gkull
Let me get this straight. You now bought 925 spring and they are supposed to be installed at 1.900 Your present spring on the motor that your removing are installed at 1.870. Is it ok for me to install my new springs at 1.870 vs 1.900
IMO - Your increasing the the #'s significantly. Look at the CC spring chart for a simular spring closed and open pressure. Then look at how it reacts to a .050 change and then figure yours out at @60% of that.
How many shims do your Edelbrock heads have and how thick are they? Maybe you can mix and match or even buy one to get you to the required 1.900
IMO - Your increasing the the #'s significantly. Look at the CC spring chart for a simular spring closed and open pressure. Then look at how it reacts to a .050 change and then figure yours out at @60% of that.
How many shims do your Edelbrock heads have and how thick are they? Maybe you can mix and match or even buy one to get you to the required 1.900
Yes- the present spring- exhaust side is 1.870. Intake- 1.83! I have '73 049 stock heads- (I only took one cylinder apart thus far).
No shims on these valves- there is an exhaust "rotator" replacement on the exhaust side.
Zwede recommended that I go with a +.050 lock from comp. That will bring the heights up to 1.92 ex/1.88 in (valve height) and then add in a .015" shim for the exhaust to drop closer to the intake.
What do you think of this lock idea?
At this point it seems to be the best alternative to pulling the heads off......
I did learn quite a bit about pulling the springs out with the air holding the valves in- so I am not disappointed in today's progress!
Thanks!
Bob
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Joined: Apr 1999
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From: Reno Nevada
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I'm not familiar with what a rotator replacement is. Back in the 70's the heavy rotators and spring caps were one of the first things you threw away.
I have always bought the correct for the spring chromemoly retainers. I have also had correct spring heights through the use of offset locks and offset retainers.
I would install an intake and exhaust with your existing retainer/lock setup to verify the height. If your measurements are correct and +.050 locks make it 1.920 exhaust and 1.880 intake without shims. I would call it good.
You have to remember that exhaust valves are often much lighter than intakes because of the smaller size. So unless your running some kind of split duration and lift cam with a big difference in values you can get away with less pressure on the exhaust side. If you feel the need for a .015 or .020 shim on the E, go for it.
I have always bought the correct for the spring chromemoly retainers. I have also had correct spring heights through the use of offset locks and offset retainers.
I would install an intake and exhaust with your existing retainer/lock setup to verify the height. If your measurements are correct and +.050 locks make it 1.920 exhaust and 1.880 intake without shims. I would call it good.
You have to remember that exhaust valves are often much lighter than intakes because of the smaller size. So unless your running some kind of split duration and lift cam with a big difference in values you can get away with less pressure on the exhaust side. If you feel the need for a .015 or .020 shim on the E, go for it.