The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1973 - 1987 Chevrolet & GMC Squarebody Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 09-16-2010, 12:20 PM   #1
billetproofcustoms
Registered User
 
billetproofcustoms's Avatar
 
Join Date: Aug 2010
Location: lubbock texas
Posts: 96
TDC and timing chain question

OK, confused still about TDC and timing chain relation, my 350 is on a stand right now almost finished with the build, the motor #1 cylinder is at tdc on the compression stroke, dot on the crank cam gear is at 12 o'clock, my question is this, I have been told that in the #1 cylinder TDC compression stroke position, the cam gear dot is actually at 12 o'clock also, otherwise you are 180 degrees out, the next revolution of the crank lines the dots up (cam 6 and crank 12 o'clock) which is TDC for #6 cylinder. (companion cylinder), as it sits right now at #1 TDC compression stroke, where should the dots on my timing chain be? I got this info from the "real fixes real fast" youtube channel, it is video #5 (engine rebuild video) at the end of that video in case any of you need to reference it in order to HELP me out...LOL...please help..
billetproofcustoms is offline   Reply With Quote
Old 09-16-2010, 12:32 PM   #2
Restrorob
The One And Only !!!
 
Restrorob's Avatar
 
Join Date: Jan 2007
Location: Hole in the woods Florida
Posts: 4,567
Re: TDC and timing chain question

Leave the crank at TDC #1 cylinder (dot at 12:00) and rotate the camshaft gear so the dot lines up with the crankshaft gear dot at 6:00 position......
__________________
93 Jeep XJ
88 Buick La Sabra
Toys;
88 TA-GTA in the works....
97 GMC Ext. Cab
502 Crate 5 Spd......Sucks Gas But Haulz Azz !


The primary function of an Engineer is to make it difficult for the Fabricator and impossible for the Mechanic.


"Why go out preserved when you can go out beat up, worn out, sliding in sideways screaming, Holy Sh!t What A Ride" !!!

Last edited by Restrorob; 09-16-2010 at 12:34 PM.
Restrorob is offline   Reply With Quote
Old 09-16-2010, 08:13 PM   #3
LONGHAIR
just can't cover up my redneck
 
Join Date: May 2004
Location: Columbus OH
Posts: 11,414
Re: TDC and timing chain question

You are combining things and making yourself crazy.
For get the distributor for a second.
When the crank do is up (12:00) the #1 piston is at TDC. Now, the cam dot determines whether it is on the compression stroke or the exhaust stroke. The cam and crank can never be "180 degrees out" from each other. They are connected by the timing chain and the crank rotates twice for every single rotation of the cam. Every single rotation of the crank moves the cam half way. One time the dots are together, the next time the cam's dot is up at 12:00
The "variable" factor is in the distributor. You are correct in your statement about the cam dot in relation to the rotor. When the cam dot is up at 12:00, the rotor should be pointed toward the #1 terminal of the cap.

The "180 degrees out" comes from someone just turning the crank around to the TDC mark on the harmonic balancer and "assuming" that it is at the correct stroke.
__________________
You can review the site's rules here.



Quote:
Originally Posted by Longhorn Man View Post
As for reading directions...
The directions are nothing but another man's opinion.
Learn from the mistakes of others, you won't live long enough to make them all yourself...

Bad planning on your part does not necessarily constitute an instant emergency on my part....

The great thing about being a pessimist is that you are either pleasantly surprised or right.
LONGHAIR is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not 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

Forum Jump


All times are GMT -4. The time now is 10:03 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com