This confused the hell out of me, a little help please. - 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 05-17-2004, 02:51 PM
Bad Rat 414's Avatar
www.bigblock67chevelle.com
 
Last photo:
Join Date: Oct 2003
Location: www.bigblock67chevelle.com
Age: 53
Posts: 170
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
This confused the hell out of me, a little help please.

My engine is a big block chevy and the cam is a Comp Cam 286H. With the vacuum advance disconnected the timeing is set at 12*. When I connect it it goes to 15* with manifold vacuum at the carb. on the vacuum advance unit. When I advance the throttle the timeing mark doesn't stop moving to around 56*.

I just did a vacuum check on the engine. I've got less than 5" of vacuum, which the guage says "late valve timing or leak at intake maifold".

I pulled the timing cover and check it out. The marks line up at 6:00 on the cam and 12:00 on the crank. BUT the distributor is 180* off. I've never seen an engine run with the distributor 180* out. It's time to start banging my head against the wall. Has anyone else ever heard of that. I didn't think it was possible.

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 05-17-2004, 03:03 PM
Grumpy
 
Last photo:
Join Date: Dec 2002
Location: D.C.
Posts: 1,447
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts


Please remember that the cam only rotates once per 2 times of the crank.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 05-17-2004, 03:07 PM
poncho62's Avatar
Out of the Loop Moderator
 
Last wiki edit: Streetbeasts links
Last journal entry: at car show
Last photo:
Join Date: Oct 2003
Location: Hanover, Ontario, Canada
Age: 62
Posts: 16,857
Wiki Edits: 5

Thanks: 20
Thanked 247 Times in 201 Posts
How does it run at those settings?

87442 is right about the timing marks on the cam. Turn the crank 1 revolution and everything will line up fine...........
__________________
Ontario Rodders

Budget RVs
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 05-17-2004, 03:31 PM
Bad Rat 414's Avatar
www.bigblock67chevelle.com
 
Last photo:
Join Date: Oct 2003
Location: www.bigblock67chevelle.com
Age: 53
Posts: 170
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
That's true, but remember what I said. The cam gear mark is at 6:00 and the crank is at 12:00. That is the correct position, but the rotor button is 180* off (pointing towards the firewall).
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 05-17-2004, 04:02 PM
Member
 
Last photo:
Join Date: Sep 2003
Location: Omaha, NE
Posts: 162
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
At actual top-dead center, both the crank and cam dots will point to 12:00. Your distributor and cam alignment are fine.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 05-17-2004, 04:04 PM
Bad Rat 414's Avatar
www.bigblock67chevelle.com
 
Last photo:
Join Date: Oct 2003
Location: www.bigblock67chevelle.com
Age: 53
Posts: 170
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Sorry that's not true.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 05-17-2004, 05:04 PM
Registered User
 
Last wiki edit: Mopar tapered axle rear brake conversion
Last journal entry: What I'm doing now...
Last photo:
Join Date: Jan 2002
Posts: 4,267
Wiki Edits: 49

Thanks: 0
Thanked 4 Times in 4 Posts
Quote:
Originally posted by orangef4
At actual top-dead center, both the crank and cam dots will point to 12:00. Your distributor and cam alignment are fine.
This is incorrect for a Chevy. The cam timing mark should be at 6 o'clock and the crank timing mark should be at 12 o'clock. If you're distributor rotor is pointing towards the firewall when you're at top dead center on the compression stroke on #1 cylinder then you need to pull the distributor out and rotate the rotor 180* and reinstall it.

Centerline
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 05-17-2004, 05:20 PM
Bad Rat 414's Avatar
www.bigblock67chevelle.com
 
Last photo:
Join Date: Oct 2003
Location: www.bigblock67chevelle.com
Age: 53
Posts: 170
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I totaly agree, but how did it run like this?????
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 05-17-2004, 05:29 PM
Registered User
 
Last wiki edit: Mopar tapered axle rear brake conversion
Last journal entry: What I'm doing now...
Last photo:
Join Date: Jan 2002
Posts: 4,267
Wiki Edits: 49

Thanks: 0
Thanked 4 Times in 4 Posts
If you have the plug wires set 180 out as well it will run but not all that well.

Centerline
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 05-17-2004, 05:41 PM
Bad Rat 414's Avatar
www.bigblock67chevelle.com
 
Last photo:
Join Date: Oct 2003
Location: www.bigblock67chevelle.com
Age: 53
Posts: 170
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I didn't!!!!
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 05-17-2004, 05:56 PM
Grumpy
 
Last photo:
Join Date: Dec 2002
Location: D.C.
Posts: 1,447
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally posted by Centerline
This is incorrect for a Chevy. The cam timing mark should be at 6 o'clock and the crank timing mark should be at 12 o'clock. If you're distributor rotor is pointing towards the firewall when you're at top dead center on the compression stroke on #1 cylinder then you need to pull the distributor out and rotate the rotor 180* and reinstall it.

Centerline

Nooo...

The crank is really at TDC twice(4 stroke) per cam rotation. The distributor is fine.

If the distributor were 180 deg than the plugs would be firing on the exhaust stroke, this would make it impossible for the engine to run.

Last edited by 87442lover; 05-17-2004 at 06:02 PM.
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 05-17-2004, 07:07 PM
Jmark's Avatar
Hotrodders.com Moderator
 
Last photo:
Join Date: Sep 2003
Location: phoenix
Age: 61
Posts: 4,786
Wiki Edits: 0

Thanks: 0
Thanked 3 Times in 3 Posts
Quote:
Originally posted by Bad Rat 414
That's true, but remember what I said. The cam gear mark is at 6:00 and the crank is at 12:00. That is the correct position, but the rotor button is 180* off (pointing towards the firewall).
Ok, here goes the story as told my hundreds of first time chevy engine builders across the country.

"I don't know why it won't run!!!! Piece of Junk!!! I set the cam gear at 6 and the crank gear at 12. I oil primed the engine, dropped in the dist with the rotor pointing just like it was on the old cap. Dropped on the cap, old wires still there, tried to start it and it blew flames out the carb and almost blew both mufflers off!!! Piece of junk!!! So now I pull number 1 plug and crank it until number 1 pushes my finger out of the spark plug hole and then line up the timing marks on the balancer and pointer and then pull the cap. Hey!! Its pointing to the firewall, not to number 1 like its supposed to!!! Piece of junk jumped timing!!!" or "My gears are stamped wrong!"....or.... "My dist gear spun!".....

So now you decide to pull the dist and set the rotor to point to number one and give it one more chance before you have it towed to the shop to have it fixed. Guess what??? Its starts and runs fine now. Why did it do this you ask??? Well, you're just so happy its running that you blow it off, throw on the hood and go for a spin.


When you install the gears as per the book, with the dots facing each other, the engine is set up at TOP DEAD EXHAUST on #1. You then need to rotate the engine one turn before installing the dist. You ask "Why is it like this?"....... I don't know! But its true. Thats how they made it. Is it stupid? YES it is, but i'm not in a position to change it.

If you like, pull out number 1 plug and rotate the engine until you are on compression, line up your timing marks, then pull the timing cover off and look at the gears. Cam will be at 12 and crank will be at 12, engine is set to install the dist IF you are using the normal cap configuration, IE: number one towards the front of the cap.

Mark
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 05-17-2004, 07:40 PM
Bad Rat 414's Avatar
www.bigblock67chevelle.com
 
Last photo:
Join Date: Oct 2003
Location: www.bigblock67chevelle.com
Age: 53
Posts: 170
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Mark, I belive your right. I turned the engine untill the rotor pointed at #1 that's when I pulled the cover to see the gears at 12:00 and 12:00.

I've got a realy bad feeling about my symptoms, I've got low vacuum and blow-by. I'm thinking maybe somehow I've got some rings in upside down or somehow wrong? I think I'm going to be sick.
Reply With Quote Quick reply to this message
  #14 (permalink)  
Old 05-17-2004, 07:49 PM
Jmark's Avatar
Hotrodders.com Moderator
 
Last photo:
Join Date: Sep 2003
Location: phoenix
Age: 61
Posts: 4,786
Wiki Edits: 0

Thanks: 0
Thanked 3 Times in 3 Posts
Well, with that cam, you're lucky to have 5 inches of vacuum, at low idle anyway. It should perk up once you get some timing in it.

My sons 400 has the 286 Comp roller and his vacuum sucks too.

Try NOT using the vac advance and set it like this:
Hook up an adjustable timing light and wind it up to 2700 and set the timing to 36 degrees and go for a spin. (56 is WAY too much total timing!)

If the weights are working in the dist, you should end up with around 20 degrees mechanical plus base timing at 14/16 degrees. That cam will need LOTS of inital timing to even idle at all. We ended up setting my sons at 20 base timing and another 14 with the mechanical and NO vacuum advance at all. Seems to be good.

Mark
Reply With Quote Quick reply to this message
  #15 (permalink)  
Old 05-18-2004, 05:57 AM
Hotrodders.com Moderator
 

Last journal entry: PICTURE TEST
Last photo:
Join Date: Jan 2004
Location: york pa
Age: 52
Posts: 2,795
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
dist

I didn't see in your post what kind of distributor your running. If it's a HEI and has never been re-worked the chances are good that it has way to much mechanical advance. With that cam i would not use the vacuume advance at all. Try to get it set at 18 deg intial with 36-38 total. as a base point.

Can you give us some more info... Do you know the static compression or the cylinder psi???? auto or stick, rear gears,


The dots on the chain have many people messed up!!!! It really does not matter iF you assemble the motor with the dots at 6:00/12:00 Or 12:00/12:00 . The cam rotates at 1/2 speed of the crank, so no matter how you align the marks when you rotate the motor 360 degrees they are at the oppisite from where you started. What matters is where the motor is set when you install the distributor. I tell all my customers to remove the valve cover rotate the motor untill you see the # 1 intake open then close continue untill the balancer is at tdc and install the distributor at # 1. When doing this they have never called back with a distributor out 180 deg..... It's a little more work but for the less skilled it works every time.

keith
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



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