Trouble with TDC - 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 02-17-2006, 08:48 AM
joe350s10's Avatar
Bigger is better
 
Last photo:
Join Date: Jan 2006
Location: North Carolina
Age: 36
Posts: 131
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Trouble with TDC

I recently pulled the dist. out of mt truck to do a few repairs.

Now I am ready to drop the dist. back in and fire the truck up again...but now I can't seem to get it on TDC.

I have tried going by the mark on the harmoinc balancer...no dice

I think the mark on the balancer may be off.

I had a helper place their finger over the hole for the plug on #1 and spun the crank by hand. When they felt compression, it was no where near the mark on the balancer.

Now I have no helper and still haven't determined true TDC and really need to today.

So, is there another easy one man way to determine true top dead center on a small block chevy?

The engine is out of a 71 camaro.

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 02-17-2006, 09:11 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
tdc

Pull the valve cover off of the drivers side. rotate the engine watching the intake valve open and then close. continue rotating untill the balancer is at the tdc mark... if you think you have the wrong timing tab or the balancer spun. Do the same thing but you will need a dial indicator in the plug hole... rotate untill the piston is at tdc...

Another way ( more accurate) is to us a piston stop. Remove all the spark plugs, rotate the engine by hand untill it contacts the stop, put a mark on the balancer. Rotate the engine by hand in the opposite direction untill it contacts the stop. Mark the balancer. Exactly half way between the 2 marks is your ture TDC. Then rotate the engine watching the intake valve open then close, continue untill you reach your new TDC mark..


Keith
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 02-17-2006, 09:22 AM
joe350s10's Avatar
Bigger is better
 
Last photo:
Join Date: Jan 2006
Location: North Carolina
Age: 36
Posts: 131
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
One problem...

I don't have a piston stop and getting the valve covers off and on again is a real chore.

but, I'll try pulling the covers and see what I can do. Beggars can't be choosers...

thanks for the reply. it is always appreciated.
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 02-17-2006, 09:27 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
tdc

Well you will have to go out and buy a piston stop then....

You may be able to take the breather out and look through it at the intake rocker...If you have a hole in the front of the valve cover on that side...

Keith
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 02-17-2006, 09:29 AM
nettio's Avatar
Member
 
Join Date: Oct 2003
Location: Reno Nevada
Age: 83
Posts: 41
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Tdc

Old school method:

Tear a 3" by 3" piece of plastic bag. Stuff it with a plug of toilet tissue. Push it ito the number one plug hole. Turn the engine clockwise by hand until you hear a "poof" (you will hear it) You are now close enough to drop in the distributor with the rotor pointing to the number one hole. The drive tang on the distrib usually lines up with the rotor position. Use long flat blade screwdriver to line up oil pump drive wo distrib will drop in. Double check plug wire firing order.

Be patient.

Nettio
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 02-17-2006, 09:39 AM
Member
 

Last journal entry: frame build
Last photo:
Join Date: Apr 2005
Location: sioux falls, sd
Age: 68
Posts: 601
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Pull the Number one plug. Turn the motor by hand till you start to get compresssion. With just a little manual dexterity you can put one finger in the hole and turn the engine with a ratchet with the other hand. OK, when compression starts, stop and drop a foot long piece of wooden dowel (1/4" preffered) in the plug hole. Turn the motor on up till the dowel stops coming out of the hole. This will get you close enough to TDC to spear the distributor. At this point, your timing marks should be fairly close to TDC and timing can be set. If not, you have another problem that's needs to be addressed. Stock Chebbie balancers have been known to slip, throwing the timing marks off. The only real fix is to replace it.
If you have trouble turning the engine, loosen the rest of the plugs to relieve cylinder pressure
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 02-17-2006, 10:38 AM
Member
 
Join Date: Dec 2005
Location: Yerington, Nevada
Posts: 103
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
NOTE: DON'T EVER USE A POSITIVE STOP WITH THE VALVES STILL ACTUATING.

If you use a positive stop, pull the pushrods for the cylinder so the valves won't have any chance to hit the stop.

61bone gives good advice. One hand on ratchet/socket, the other index finger on the plug hole.

On engines after 1986, the side timing marks will no longer match up, as the new marks were moved to behind the water pump in the 12:00 position. This was done because these engines had so many brackets on them, the side scale just wasn't visible. So, new marks at noon, timing light down from the top, behind the water pump.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 02-17-2006, 01:28 PM
SecGenLvr's Avatar
Registered User
 
Last photo:
Join Date: Jan 2006
Location: tucson
Age: 28
Posts: 80
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
An easy way docvette told me to do, was use a slurpie straw in the cyl one spark plug hole and watch for the straw to move up and down, when it starts to move and it moves the oposite direction, you know you just passed TDC...
Then use whiteout to mark your balancer...
Are you sure you aren't on TDC or were you forgetting about comp and exhaust strokes I did that about a month ago...
Good luck...
John
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 02-17-2006, 05:35 PM
Member
 
Join Date: Oct 2004
Location: Los Angeles
Posts: 173
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
I think you are forgetting that when you turn the engine over you will get air pushing out of the spark plug hole twice for each firing cycle. Once for when the plug fires and again when the burned gases are pushed out the exhaust valve. The reason your TDC was so far off is probably because you checked it on the exhaust stroke. You needed to turn the engine until you got pressure at the spark plug hole a second time.
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 02-17-2006, 09:33 PM
techinspector1's Avatar
Senior Curmudgeon
 
Last wiki edit: DynoSim combinations Last photo:
Join Date: Oct 2005
Location: Hemet, California, USA
Age: 72
Posts: 12,809
Wiki Edits: 326

Thanks: 747
Thanked 961 Times in 810 Posts
with the exhaust valve open, you won't get any compression at the plug hole.
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 02-18-2006, 04:31 AM
docvette's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Rebuild an alternator Last photo:
Join Date: Mar 2004
Location: Lafayette, california
Age: 62
Posts: 7,362
Wiki Edits: 12

Thanks: 0
Thanked 6 Times in 3 Posts
Doc here,

Number 1 cylinder, TDC, compression, Timing marks aligned, Both intake valves closed , no pressure on the lifters (not too much slack either..) If you can't co~ordinate these, you have timing chain/gear or balancer issues..

Drop the dizzy in, and watch the rotor, It will advance clockwise a bit, this is because the gear teeth are diagonal cut, It will go about a tower in a half in some cases..Note the amount of change and then withdraw the dizzy.

Line the oil pump shaft up to that location with a large screw driver, and reset the dizzy, for number one plug tower, allowing for advancing as the gears seat..

The easy way to do this is make magic marker lines on the base of the dizzy, for exact #1 plug tower, and the difference of rotor movement as it seats..due to the cut of the gears..(I.E...#1 and the amount of distance BACK required to make it sit on #1 plug tower when bottomed out..)

#1 plug tower in the stock location for SBC's is 5 to 7 O'clock, (depends on year, and obstructions) 7 is usually good.

Direction of rotation is clockwise.

The F.O. is 1 8 4 3 6 5 7 2..

Put on your hold down just tight enough to hold it but enough to forcibly move it by hand, and start it up..set your static and total timing..

Static 10 to 12 is a good starting point advance defeated and vacuum line plugged.

Total around 34 to 36 is usual on a stocker with advance hooked back up..

Tighten down the hold down, set your idle for 650 Manual trans, 950 Automatic, and drive it .. hammer it on the freeway, If it pings or runs hotter than usual, retard it a few degrees..If it dogs, advance it..Try also lugging it up a steep hill highest gear as slow as it will pull, If it pings check the timing again.

That's it.

Doc
__________________
Aftermarket Solutions
Electronic & Electrical
Innovations
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 02-18-2006, 11:22 AM
joe350s10's Avatar
Bigger is better
 
Last photo:
Join Date: Jan 2006
Location: North Carolina
Age: 36
Posts: 131
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Ok problem solved....and it only took most of the day.

The problem wasn't the timing at all...although I thought it was.

what was happening :

no matter how many times I aligned the dizzy with #1, it just wasn't firing clean. It ran like at out of balance washing machine...like it was either 180 degrees out or at least a tooth off.

So I spent most of the day checking and rechecking the timing marks, actual TDC, etc.

Then I called in some reinforcements...namely my buddy anthony. He helped me rebuild that engine and i figured a fresh brain and set of eyes may do some good.

It did. We dropped the dizzy in at TDC once again and still wouldn't run right.

checked for fire on #1. Checked cap, rotary button, coil, etc.
All good.

Pulled the rotary button of and BINGO!

One of the leads from the pickup coil to the module was off but still just barely making contact. It would fire off the module, but it was doing so extremely erratically. I put a new end on the offending wire and reconnected it.

Ran like a top. fired right up and was exactly where I wanted it.

So, after over 8 hours of rewiring, pulling the valve covers off and checking TDC, replacing the plugs and wires,etc, etc, etc it all boiled down to one measly connection.

But now all is well and the truck runs GREAT.

Thanks again for all the help guys.
I guess assuming that the dist. wasn't the problem anymore was my downfall.

Note to self: always check the simple connections first.
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 02-18-2006, 11:35 AM
Member
 
Join Date: Dec 2005
Location: Yerington, Nevada
Posts: 103
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Look at it this way, you learned to troubleshoot it, and you had a great time with your friend helping.

How's the curving and vac advance working? Should be good.
Reply With Quote Quick reply to this message
  #14 (permalink)  
Old 02-18-2006, 12:52 PM
xntrik's Avatar
Save a horse, Ride a Cowboy.
 
Last photo:
Join Date: Jul 2005
Location: Arkansas
Posts: 5,131
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Thanks for reporting back to us. You'd be suprised how many people don't.
x
Reply With Quote Quick reply to this message
  #15 (permalink)  
Old 02-18-2006, 07:56 PM
joe350s10's Avatar
Bigger is better
 
Last photo:
Join Date: Jan 2006
Location: North Carolina
Age: 36
Posts: 131
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Oh, the truck has never ran so good. The new weights are perfect and the vac advance works like a new one.

I'm always happy when I learn how to diagnose a new problem, but yesterday really pushed my patience to the edge.

But, problem solved and a new symptom is stored in the old memory banks for the next time.

It just kills me that I can fix someone else's vehicle the first time every time but always seem to have problems with my own.

Hopefully my misadventure will help the next guy who has this problem.

I think I may tinker with the timing next week. I have a vette to race at the local drag strip soon. Should be a pretty even match...hell, I helped set it up.

Thanks again for the help guys.
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
Kids and trouble Kevin45 Hotrodders' Lounge 15 02-20-2006 04:27 PM
True TDC / using a piston stop driveability Engine 6 01-07-2006 12:44 AM
TDC and timing chain adrock430 Engine 4 03-04-2005 02:45 PM
TDC or 180 degrees off? jerseyjeff Engine 2 11-05-2003 08:29 PM
c4 transmission trouble Steve W Transmission - Rearend 2 11-04-2001 07:04 PM


All times are GMT -6. The time now is 02:17 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.