No compression after cam swap - 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 04-15-2012, 05:26 PM
Joe428's Avatar
Registered User
 
Last photo:
Join Date: Jun 2011
Location: Tennessee
Posts: 34
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
No compression after cam swap

For starters sorry for the long post. I recently swapped my cam in my 383. I set the timing chain on the cam and crank at the stock position (circle to circle). I lined them at 12 and 12 and dropped the distributor in the #1. I cranked the motor and was having some trouble getting it to start. I made several attempts but couldn't get it to turn over, so I gave it a break and tried again the next morning. I tried to start it up several times and it made attempts but still no fire all of a sudden on a certain crank something didn't sound right so I thought I'd recheck my timing. I removed the #1 spark plug to get to TDC but there was no compression on my thumb. I adjust the valves with Frisco's quick adjustment so I feel confident in that sense. It sounds like the starter is the only thing moving ( I want to stress that this occurred out of the blue and did not happen initially or for a while at that.) Idk what happened but now we have no compression. Any help would be greatly appreciated.

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 04-15-2012, 05:45 PM
68NovaSS's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Working with chromed bolts
Last journal entry: New to me T-Bucket
Last photo:
Join Date: Sep 2002
Location: Nine Mile Falls, Washington
Posts: 5,218
Wiki Edits: 9

Thanks: 101
Thanked 130 Times in 121 Posts
Your terms are a little confusing, at least to me. By crank you mean have the motor rotate with the starter? Then by turn over you mean the same or actually start and run? And saying "on a certain crank" you mean rotation with the starter?

Do you have compression in any cylinders? Did you turn it over and witness the rockers working? Have you looked at the top end to see if your rockers have come loose or you have dropped a valve? Maybe a spring keeper came out? Could a valve have hit a piston and broken? It sounds like now the starter isn't engaging the flywheel or flexplate. Have you had someone look at the starter to see if it's kicking the gear out into the flywheel? I think it's obviously something in the valve train timing chain. What is "Friscos quick adjustment"?
__________________
Boost adds dignity to what would otherwise be a vulgar brawl...

Midnight Sun Street Rod Association
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 04-15-2012, 06:41 PM
Joe428's Avatar
Registered User
 
Last photo:
Join Date: Jun 2011
Location: Tennessee
Posts: 34
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by 68NovaSS
Your terms are a little confusing, at least to me. By crank you mean have the motor rotate with the starter? Then by turn over you mean the same or actually start and run? And saying "on a certain crank" you mean rotation with the starter?

Do you have compression in any cylinders? Did you turn it over and witness the rockers working? Have you looked at the top end to see if your rockers have come loose or you have dropped a valve? Maybe a spring keeper came out? Could a valve have hit a piston and broken? It sounds like now the starter isn't engaging the flywheel or flexplate. Have you had someone look at the starter to see if it's kicking the gear out into the flywheel? I think it's obviously something in the valve train timing chain. What is "Friscos quick adjustment"?
[QUOTE=68NovaSS]Your terms are a little confusing, at least to me. By crank you mean have the motor rotate with the starter? Then by turn over you mean the same or actually start and run? And saying "on a certain crank" you mean rotation with the starter?

Yes to all. Sorry for my rambling there

I have not checked the rockers. The motor is rotating with the starter engaging the flywheel. I did not encounter a collision with the top of a piston this motor ran well with the previous cam but it was a bit too much for a daily driver so I went a little milder (to a Lunati 60103 from a Crane 1064)
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 04-15-2012, 07:08 PM
Joe428's Avatar
Registered User
 
Last photo:
Join Date: Jun 2011
Location: Tennessee
Posts: 34
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Found the problem. Pulled the rocker cover and I had a bunch of loose rocker arms even some with the pushrod out of its seat. I have no idea how they became loose when I followed Frisco's guide and even triple checked the lash and set my set screws( roller tips). Any reasons why my rockers loosened?
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 04-15-2012, 07:15 PM
Registered User
 
Last photo:
Join Date: Jul 2011
Location: Wentzville,MO
Posts: 185
Wiki Edits: 0

Thanks: 0
Thanked 2 Times in 2 Posts
Use the intake closing exhaust opening method.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 04-15-2012, 08:42 PM
Registered User
 
Join Date: Nov 2011
Location: pennsylvania
Posts: 104
Wiki Edits: 0

Thanks: 0
Thanked 2 Times in 2 Posts
no compression

on sbc shouldnt dot on cam gear be at 6 oclock and dot on crank gear be at 12 oclock?
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 04-15-2012, 09:00 PM
psbaker75's Avatar
Registered User
 
Join Date: Mar 2011
Location: riverside, ca
Posts: 60
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
@alkey I was just thinking the same thing. I'm trying to visualize what swapping 12/12 instead of 6/12 would do, swap intake and exhaust events, or relate all timing events to bdc instead of tdc? Either way, I can't imagine getting it to run at all that way.

Last edited by psbaker75; 04-15-2012 at 09:05 PM.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 04-15-2012, 09:43 PM
Joe428's Avatar
Registered User
 
Last photo:
Join Date: Jun 2011
Location: Tennessee
Posts: 34
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
That's just to get them lined up correctly. You need to turn the crank one more revolution to get TDC on #1. If not you'll be stuck on #6
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 04-16-2012, 09:57 AM
1971BB427's Avatar
Registered User
 

Last journal entry: Latest changes
Last photo:
Join Date: Dec 2010
Location: Portland
Posts: 1,481
Wiki Edits: 0

Thanks: 12
Thanked 224 Times in 195 Posts
Quote:
Originally Posted by alkey
on sbc shouldnt dot on cam gear be at 6 oclock and dot on crank gear be at 12 oclock?
Absolutely correct! If the timing set is installed at 12 and 12, not 6 and 12, then that's what's causing the valve adjustment issues, and a lot more problems if it's not fixed!
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 04-17-2012, 12:07 AM
theg's Avatar
Registered User
 
Last photo:
Join Date: Nov 2010
Location: australia
Posts: 62
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Cam timing wrong

Quote:
Originally Posted by alkey
on sbc shouldnt dot on cam gear be at 6 oclock and dot on crank gear be at 12 oclock?
Agree . Sounds like this is the problem .
Also if the pushrods were sitting in the lip of the lifters when the adjustment was made could cause the loose rockers problem.
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 04-17-2012, 05:41 AM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
Quote:
Originally Posted by alkey
on sbc shouldnt dot on cam gear be at 6 oclock and dot on crank gear be at 12 oclock?
I'm thinking he first aligned them at 6 and 12, then rotated the crank one revolution (dots now at 12 and 12) to bring #1 up on compression stroke to set the distributor in.
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 04-17-2012, 09:59 AM
T-bucket23's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Engine basic condition - how to check Last photo:
Join Date: Aug 2005
Location: Massachusetts
Age: 57
Posts: 5,111
Wiki Edits: 26

Thanks: 7
Thanked 106 Times in 91 Posts
either 6 and 12 or 12 and 12 will work. The only consideration is the distributor install. At 12 and 12 you are on compression on # 1, on 6 and 12 you are on compression on #6.

It is a 2 to 1 ratio so 6 and 12 will become 12 and 12 with one rotation of the crank.
The reasoning for using 6 and 12 is it is much easier to align as the dots are closer together
__________________
Artificial Intelligence is no match for Natural Stupidity



Chet
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 04-17-2012, 10:01 AM
T-bucket23's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Engine basic condition - how to check Last photo:
Join Date: Aug 2005
Location: Massachusetts
Age: 57
Posts: 5,111
Wiki Edits: 26

Thanks: 7
Thanked 106 Times in 91 Posts
Quote:
Originally Posted by Joe428
Found the problem. Pulled the rocker cover and I had a bunch of loose rocker arms even some with the pushrod out of its seat. I have no idea how they became loose when I followed Frisco's guide and even triple checked the lash and set my set screws( roller tips). Any reasons why my rockers loosened?
You did something wrong. Read over the instructions again.
__________________
Artificial Intelligence is no match for Natural Stupidity



Chet
Reply With Quote Quick reply to this message
  #14 (permalink)  
Old 04-17-2012, 10:07 AM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 6,713
Wiki Edits: 0

Thanks: 3
Thanked 406 Times in 351 Posts
Quote:
Originally Posted by alkey
on sbc shouldnt dot on cam gear be at 6 oclock and dot on crank gear be at 12 oclock?
No it shouldn't. Most instructions show starting with the marks facing each other. That would be the crank gear with the pip mark up at the 12 O'clock position and the cam gear having the pip mark at the 6 O'clock position. The marks are facing each other, therefore, it's easy to see that the tooth alignment is correct (or not). This position times number 6 on firing and number 1 on overlap stating the intake stroke.

Rotating one complete crank rotation returns the crank gear's pip mark to the 12 O' clock position and the cam gear to the 12 O'clock position. This has number 1 at the TDC firing position. There's nothing wrong with initially assembling in this position other than it's more difficult to get a visual between the pip marks that insures they are in alignment. So the typical is to put the timing set on with the pip marks facing each other then rotate the crank 360 degrees or one complete revolution which is 1/2 a revolution of the cam gear resulting in the pip marks of both gears facing in the 12 O'clock position and number 1 at TDC firing. The opposite position of crank at 12 and cam at 6 has number 1 at TDC on overlap ready to start the intake cycle where the exhaust is closing and the intake opening. This would be the model for any other cylinder that is one crank revolution from TDC on the firing stroke.

Why Chevy chose this positioning makes no more sense to me than the old Ford Y Block having 12 timing chain pins between the pip marks when they are horizontal to the engine or timing the old International from cylinder #3 instead of #1. The need to be different boggles my simple mind, I like the KISS method.

Bogie
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
Vortec Head Swap....Too much compression?? zildjian4life218 Engine 18 01-04-2010 04:40 PM
compression and cam help schottout Engine 2 09-20-2009 04:17 PM
Cam Swap, No Compression, Help?! Houman SS '70 Engine 6 05-16-2005 04:42 AM
cam/compression? SBC4ME Engine 5 01-26-2005 09:23 PM
cam/compression? SBC4ME Engine 1 01-24-2005 09:35 PM


All times are GMT -6. The time now is 09:36 PM.


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.