Increasing P/V Clearance - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 06-15-2013, 08:27 AM
S10 Racer's Avatar
http://www.warsprints.com
 

Last journal entry: W.A.R. (Wingless Auto Racing) Sprint Car Racing
Last photo:
Join Date: Nov 2007
Location: At The Dirt Tracks
Age: 55
Posts: 1,863
Wiki Edits: 0

Thanks: 3
Thanked 57 Times in 52 Posts
Increasing P/V Clearance

I need to increase the P/V clearance on our motor for the Sprint car. I'm really looking for ways to do this without changing pistons since they are new. The pistons are JE (SRP) domes and I have talked with them about cutting the valve reliefs deeper and they said that .030 is about the maximum I can go safely which still is not enough. The problem is the exhaust valve clearance, the intake is fine. We dropped a valve during a race and during disaasembly, I notice that every exhaust valve had been "kissing" the top of the pistons. The heads are being repaired now with all new exhaust valves. I also will be buying a new set of rods since it appears there are some that are slightly bent and making the piston crooked in the bore. This could also affect the P/V clearance but I still would like more clearance. My question is what would be the best way to increase the clearance? I am not wanting to change rocker ratios, currently I have 1.5 exhaust and 1.6 intake. I'm running this cam but would consider changing it if that would help.
Isky Racing 201ASCS11 ASCS 360 Solid Roller Cam, Sprint, 4500-8300 RPM

Thanks

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 06-15-2013, 11:01 AM
Member
 
Join Date: Apr 2004
Location: Cassville,MO
Posts: 800
Wiki Edits: 0

Thanks: 21
Thanked 41 Times in 37 Posts
What is your clearence currently? You need to know if you have a clearence problem or a valve lofting problem.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 06-15-2013, 11:18 AM
Member
 
Last photo:
Join Date: Oct 2004
Location: New Jersey Shore
Posts: 156
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Is there a chance you could use a thicker head gasket?
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 06-15-2013, 03:13 PM
How fast is fast enough?
 
Last photo:
Join Date: Jun 2005
Location: St. Louis, MO
Age: 29
Posts: 8,682
Wiki Edits: 0

Thanks: 17
Thanked 282 Times in 262 Posts
Lots of ways to do it, how much are you looking for?
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 06-15-2013, 03:25 PM
S10 Racer's Avatar
http://www.warsprints.com
 

Last journal entry: W.A.R. (Wingless Auto Racing) Sprint Car Racing
Last photo:
Join Date: Nov 2007
Location: At The Dirt Tracks
Age: 55
Posts: 1,863
Wiki Edits: 0

Thanks: 3
Thanked 57 Times in 52 Posts
Quote:
Originally Posted by ap72 View Post
Lots of ways to do it, how much are you looking for?
Well, I need to check how much I have once I get the heads back but because the exhaust valves were hitting the pistons at high RPM, I am guessing around .070 or so because the indentations in the pistons range from .000 to about .020
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 06-15-2013, 03:47 PM
How fast is fast enough?
 
Last photo:
Join Date: Jun 2005
Location: St. Louis, MO
Age: 29
Posts: 8,682
Wiki Edits: 0

Thanks: 17
Thanked 282 Times in 262 Posts
.070" is a lot more than I was guessing. Maybe the easiest way would be reducing your rocker ratio on the exhaust or changing the lobe on the cam.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 06-15-2013, 06:45 PM
Silver Surfer's Avatar
More machine than man
 

Last journal entry: bwaahhaahahaaahhaa
Last photo:
Join Date: Jul 2005
Location: Kansas City, MO
Age: 36
Posts: 791
Wiki Edits: 0

Thanks: 83
Thanked 57 Times in 47 Posts
You can also advance/retard the cam change the valve events in relation to the piston.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 06-15-2013, 10:06 PM
vinniekq2's Avatar
Registered User
 
Join Date: Jun 2012
Location: BC,Canada
Age: 56
Posts: 7,413
Wiki Edits: 0

Thanks: 292
Thanked 707 Times in 682 Posts
retard the cam,machine the 30 thou,sink the valves
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 06-16-2013, 06:22 AM
1Gary's Avatar
Registered User
 

Last journal entry: 383 dyno sym
Last photo:
Join Date: Oct 2010
Location: Roch,NY
Age: 66
Posts: 1,515
Wiki Edits: 0

Thanks: 201
Thanked 153 Times in 139 Posts
You know what S10racer.I am after reading your posts kind of disappointed in you that you didn't measure this out during the build.Really I thought you have a handle on things.

Something doesn't feel right to me on this thing.Call it a gut feeling or what.Don't know.Are you sure about the measurements you taking??. Are you sure that your not having valve float with the wrong springs or one that are either weak or installed at the wrong height or springs that are not rated for either the cam you have or RPM range.

I'm saying I guess,go back and triple check you measurements before you start changing anything.
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 06-16-2013, 06:33 AM
CNC BLOCKS NE's Avatar
CNC Blocks Northeast
 
Last photo:
Join Date: Sep 2006
Location: NORTHEAST
Age: 54
Posts: 1,427
Wiki Edits: 0

Thanks: 1
Thanked 15 Times in 15 Posts
Quote:
Originally Posted by vinniekq2 View Post
retard the cam,machine the 30 thou,sink the valves
Retarding the cam will make P/V clearance on the exhaust worse. Advancing will help but will hurt clearance on the intake.

Most exhaust valves stick out of the head. On my circle track engines I will drop the exhaust valve .015 to .030 more then the intake which will help in over lap.
Reply With Quote Quick reply to this message
The Following User Says Thank You to CNC BLOCKS NE For This Useful Post:
vinniekq2 (06-16-2013)
  #11 (permalink)  
Old 06-16-2013, 07:17 AM
vinniekq2's Avatar
Registered User
 
Join Date: Jun 2012
Location: BC,Canada
Age: 56
Posts: 7,413
Wiki Edits: 0

Thanks: 292
Thanked 707 Times in 682 Posts
Thanks cnc,had a brain fart.I had intake issues on a 454 and put the cam in 2 late
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 06-16-2013, 11:15 AM
S10 Racer's Avatar
http://www.warsprints.com
 

Last journal entry: W.A.R. (Wingless Auto Racing) Sprint Car Racing
Last photo:
Join Date: Nov 2007
Location: At The Dirt Tracks
Age: 55
Posts: 1,863
Wiki Edits: 0

Thanks: 3
Thanked 57 Times in 52 Posts
Quote:
Originally Posted by 1Gary View Post
You know what S10racer.I am after reading your posts kind of disappointed in you that you didn't measure this out during the build.Really I thought you have a handle on things.

Something doesn't feel right to me on this thing.Call it a gut feeling or what.Don't know.Are you sure about the measurements you taking??. Are you sure that your not having valve float with the wrong springs or one that are either weak or installed at the wrong height or springs that are not rated for either the cam you have or RPM range.

I'm saying I guess,go back and triple check you measurements before you start changing anything.
I did measure it and if memeory serves me correct the exhaust was at .060 but after I tore it down, I noticed that there are some pistons sitting in the bore crooked by .040 (front to back) so that will affect my clearance as well. It looks like there is more than one thing going on that is causing this issue. I am in the process now of looking to see if there are some rods that are bent, they are Lunati I-Beams. It's very possible that there is some valve float because of the springs. I am having the machine shop check that out as well. It just does'nt make sense to me if it was valve float it would only affect the exhausts. I know the exhaust is more critical than the intakes because the piston is "chasing" the exhaust valve during the exhaust stroke. The valve assembly should be stable, using T&D shaft rockers and 3/8" Comp Chrome Moly push rods.
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 06-17-2013, 04:18 AM
1Gary's Avatar
Registered User
 

Last journal entry: 383 dyno sym
Last photo:
Join Date: Oct 2010
Location: Roch,NY
Age: 66
Posts: 1,515
Wiki Edits: 0

Thanks: 201
Thanked 153 Times in 139 Posts
I'll go with bent valves,but bent rods too is alittle over the top for valves just kissing the pistons tops.Are you very sure this cam is installed right????. Ya know long durations on the exhaust side cam profile...
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Increasing HP 66 ChevyHotRodder Hotrodding Basics 3 03-18-2011 01:57 PM
Increasing of engine bay Nightrider Body - Exterior 26 02-27-2007 06:07 PM
Increasing Performance nrh General Rodding Tech 8 08-29-2003 02:33 PM
Increasing Compression meschnebly Engine 14 08-13-2003 05:56 AM
any ideas on increasing hood clearance? swoodard23 Engine 9 01-14-2003 06:03 PM


All times are GMT -6. The time now is 12:51 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.