Notices
C3 Tech/Performance V8 Technical Info, Internal Engine, External Engine, Basic Tech and Maintenance for the C3 Corvette

ValveSpring Upgrade

 
Old 01-22-2019, 08:47 PM
  #1  
[email protected]
Junior Member
Thread Starter
 
Member Since: Oct 2018
Location: miami fl
Posts: 6
Thanks: 0
Thanked 0 Times in 0 Posts
Default ValveSpring Upgrade

hello, i have a 1975 corvette l48 auto, it has RPM performance intake, longtube headers with 2 1/2 exhust and x pipe, edelbrock 600 CFM carb, the car has a cam, i do not know the specs on it , it use to work fine and everything, i had to change the lifters because a couple failed so i change them all and istalled comp cams pushrods and 1.6 roller rockers, it has dual springs, the problem is when i floor it the tras shift around 6k to 6500 and at that rpm the engien is flooding the valves, i need a valvespring upgrade but dont know the specs of the cam, any idea whats prings i can use?
keydelj@yahoo.com is offline  
Old 01-23-2019, 01:09 AM
  #2  
Vetteman Jack
Moderator
Support Corvetteforum!
 
Vetteman Jack's Avatar
 
Member Since: Mar 2001
Location: Missouri. Currently own 2014 Stingray Coupe.
Posts: 266,254
Thanked 3,812 Times in 3,337 Posts
MO Events Coordinator
St. Jude Co-Organizer
St. Jude Donor '03-'04-'05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15-'16-'17-'18-'19
NCM Sinkhole Donor
CI 5, 8 & 11 Veteran

Default

Moved to C3 Tech/Performance Section.
Vetteman Jack is offline  
Old 01-23-2019, 01:24 AM
  #3  
sstonebreaker
CF Senior Member
 
sstonebreaker's Avatar
 
Member Since: Mar 2006
Location: Willow Park TX
Posts: 1,239
Thanked 76 Times in 60 Posts
Default

Hydraulic or solid lifters? RPM at idle? What's the idle quality - OEM-like, a little cammy, or really choppy like a race car?
Use these to degree the cam and get its lift:
edit: cam checker tool
Degree wheel

Last edited by sstonebreaker; 01-23-2019 at 01:33 AM.
sstonebreaker is online now  
Old 01-23-2019, 10:06 AM
  #4  
HeadsU.P.
CF Senior Member
 
HeadsU.P.'s Avatar
 
Member Since: Aug 2017
Location: Cool Northern Michigan
Posts: 1,921
Thanked 326 Times in 311 Posts
Default

Ever think that running dual springs was the cause of the lifter failure to begin with? Dual springs puts tons of pressure on the lifters and cam lobes. Are you using oil w/ Zinc? Why do you need to turn more than 6500 RPMs?

If you feel that your engine is slacking at the upper RPM range, perhaps its the small 600CFM carb issue. Or an IGN system that can't keep up.
Leave the springs alone. For street use, dual spring is plenty.

If you want a lower shifting point change out the transmission vacuum modulator to an adjustable unit. Then you can tweak it where you really want it.

Last edited by HeadsU.P.; 01-23-2019 at 10:08 AM.
HeadsU.P. is offline  
Old 01-23-2019, 10:32 AM
  #5  
gkull
CF Senior Member
 
gkull's Avatar
 
Member Since: Apr 1999
Location: Reno Nevada
Posts: 19,094
Thanked 330 Times in 299 Posts
Default

Usually I don't even post to questions like this because of so many errors.

first of all it takes planning to exceed 6000 rpm safely. The word is valve FLOAT and it is very distructive. What exactly happened to your past lifters? Do you know if the cam lobes are still good? Higher seat pressure might keep you out of valve float, but do you know if your ignition is sparkling correctly over 6000 rpm.

l 48 were not built with good internal parts and maybe it would be smarter to invest in a good digital sequential rev limiter and set it to a 6000 or less red line

h flat setups are not made to exceed 6000 rpm not even most h roller cams.
gkull is offline  
Old 01-23-2019, 11:37 AM
  #6  
Jebbysan
CF Senior Member
 
Jebbysan's Avatar
 
Member Since: Mar 2012
Location: New Braunfels Texas
Posts: 2,886
Thanked 311 Times in 280 Posts
Default

You do not need to rev past 6k if you have stock heads....period.
That said.....you need to take a photo of your valvetrain setup.....I cant give you any more insight than that until I know what you have now.

Jebby
Jebbysan is offline  
Old 01-23-2019, 12:25 PM
  #7  
cuisinartvette
CF Senior Member
 
Member Since: Oct 2004
Location: Valencia Ca.
Posts: 67,534
Thanked 1,072 Times in 985 Posts
St. Jude Donor '05
Default

If you want to run it up past 6k a lot get a solid lifter cam. Kits are about $200, get the right springs, start over youll be much happier.
cuisinartvette is offline  
Old 01-23-2019, 12:52 PM
  #8  
pauldana
CF Senior Member
Support Corvetteforum!
 
pauldana's Avatar
 
Member Since: May 2003
Location: LA county ca
Posts: 9,664
Thanked 259 Times in 208 Posts
Default

you did not say you replaced the heads... stock heads will not work with 1.6 RR without binding... Compcams make a 1.52 RR for this purpose..

And if you have stock heads, they dont do 6000rpm... lol:-) they will chock out..

Last edited by pauldana; 01-23-2019 at 12:53 PM.
pauldana is online now  
Old 01-31-2019, 07:00 PM
  #9  
[email protected]
Junior Member
Thread Starter
 
Member Since: Oct 2018
Location: miami fl
Posts: 6
Thanks: 0
Thanked 0 Times in 0 Posts
Default

i have stock 882 heads, i have 1.6 roller tip scorpion rocket arms, i have Lucas High Zinc oil, engine use to run fine and shift great now i cant go WOT cause i have to let go cause the engine starts to run like crap amd exhust sounds changes like if engine wasn’t working properly
keydelj@yahoo.com is offline  
Old 01-31-2019, 07:09 PM
  #10  
derekderek
CF Senior Member
 
Member Since: Jul 2015
Location: Westville NJ
Posts: 4,255
Thanked 539 Times in 506 Posts
Default

Start with a compression test. Pull the valve covers and check all your push rods and valve action.
derekderek is online now  
Old 01-31-2019, 07:55 PM
  #11  
HeadsU.P.
CF Senior Member
 
HeadsU.P.'s Avatar
 
Member Since: Aug 2017
Location: Cool Northern Michigan
Posts: 1,921
Thanked 326 Times in 311 Posts
Default

Valve Float as some call it, is a warning sign. Take heed. The valvetrain is trying to tell you, you have crap boat anchor heads, small valves, large chambers, poor flow, miss-matched 1.6 rockers and the valvesprings will self destruct soon because the retainers might be striking the valveguides. Pushrods could be rubbing the heads slots. I am surprised you can get 6500 out of it.
I think you have other issues too that only show up at higher revs. Fuel or IGN.

Last edited by HeadsU.P.; 01-31-2019 at 07:56 PM.
HeadsU.P. is offline  
Old 01-31-2019, 08:46 PM
  #12  
pauldana
CF Senior Member
Support Corvetteforum!
 
pauldana's Avatar
 
Member Since: May 2003
Location: LA county ca
Posts: 9,664
Thanked 259 Times in 208 Posts
Default

Originally Posted by pauldana View Post
you did not say you replaced the heads... stock heads will not work with 1.6 RR without binding... Compcams make a 1.52 RR for this purpose..

And if you have stock heads, they dont do 6000rpm... lol:-) they will chock out..
Originally Posted by HeadsU.P. View Post
Valve Float as some call it, is a warning sign. Take heed. The valvetrain is trying to tell you, you have crap boat anchor heads, small valves, large chambers, poor flow, miss-matched 1.6 rockers and the valvesprings will self destruct soon because the retainers might be striking the valveguides. Pushrods could be rubbing the heads slots. I am surprised you can get 6500 out of it.
I think you have other issues too that only show up at higher revs. Fuel or IGN.
yea... what I said but a little more ..... forceful?? :-) And I do agree with most of what you state..
pauldana is online now  
Old 02-01-2019, 11:43 AM
  #13  
68post
CF Senior Member
 
Member Since: Nov 2012
Location: Indianapolis IN
Posts: 397
Thanked 9 Times in 9 Posts
Default

If,and when, you pull the heads you need to inspect the cam and lifters very closely. You may have introduced more wear when you installed the 1.6 rockers because of pushrod bind. If you find lifters that are no longer convex on their bottoms then the cam lobes have the same wear. Look closer at the lobes that had already worn their lifters, or better yet - plan on a new cam, lifters, and heads instead.
68post is offline  
 


Thread Tools
Search this Thread
Quick Reply: ValveSpring Upgrade


Sponsored Ads
Vendor Directory

Contact Us - About Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: