Cadillac Owners Forum banner

1 - 14 of 14 Posts

·
Registered
2002 DHS
Joined
·
168 Posts
Discussion Starter #1
Hi, I hate to ask this as im sure there are plenty of threads about it already!! If so a link would help alot!! I can't find any that explain it well enough! But I have the photos and know all about the timing marks, also understand that the cams have to be aligned not by the sprocket but by the pin. My question is not so much about the timing marks only all line up again after 7 rotations but say its all apart and i have cylinder 1 at tdc does that always put the crank sprocket at 12 and how do i know if thats the firing stroke or does it matter since it has a positioning sensor? So once i have Cylinder 1 a tdc then i put the intermediate sprocket at 6 o'clock then do the cams. Does this sound correct? I guess my question is if cylinder 1 is up the crank will always be at 12 and that's that right?
 

·
Registered
2001 eldorado,2008 DTS,2005 XLR, '96 eldo,'95 eldo,' 89 eldo,'78 eldo,'11CTS-V
Joined
·
1,850 Posts
P
Put the engine at #1 tdc. I use crude method that works by inserting a welding rod in #1 plug hole and cranking the engine to TDC. It's pretty accurate.
That said, setup your cams and chains for marks per the shop manual. Forget the marks on the intermediate gear. The crank sensor takes care of the ignition.
 

·
Registered
Joined
·
4,170 Posts
You would start with the #1 cylinder at TDC, crankshaft sprocket timing mark at 12:00, intermediate sprocket timing mark at 6:00 so the both timing marks match. Then you are left with the cam timing marks which all need to be 90 degrees from the surface of the head. Some Northstars have special exhaust cam sprocket at bank 1 due to CMP. Those use timing marks that are away from RE designation.



Cylinder #1 being at TDC will not always mean the timing marks are at the default set position. That only happens in every some revolutions. Don't remember if it was 7, 14, 17, whatever it was.
 

·
Registered
2002 DHS
Joined
·
168 Posts
Discussion Starter #4
So if i have cylinder #1 at tdc and all other timing marks correct im good right!!
 

·
Registered
2001 eldorado,2008 DTS,2005 XLR, '96 eldo,'95 eldo,' 89 eldo,'78 eldo,'11CTS-V
Joined
·
1,850 Posts
Yes.
That said, what good are the timing marks on the crank and intermediate sprockets?
You set valve timing by placing the cam sprockets 90° from the camcover surface.
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
70,391 Posts
Probably has to do with the dissimilar number of teeth on the crank and intermediate sprockets. The timing procedure in the GM service manual specifically discusses the crank and intermediate sprocket timing mark alignment - necessary.

There is also a procedure for collapsing and pinning the timing chain tensioner pistons.

Might as well do it by the book and possibly save great heartache later ..............

It takes 2 full revolutions to get the cam and crank sprockets back to #1 TDC firing stroke. Each cylinder fires 90 degrees apart, so it takes 2 full revolutions to fire all 8 cylinders. It takes 14 or 17 full revolutions to get it all plus the chains back to assembly points.
 

Attachments

·
Registered
2002 DHS
Joined
·
168 Posts
Discussion Starter #7
Does that mean cylinder #1 will be at tdc twice and if so how do i know which one is the firing stroke?
 

·
Registered
2001 eldorado,2008 DTS,2005 XLR, '96 eldo,'95 eldo,' 89 eldo,'78 eldo,'11CTS-V
Joined
·
1,850 Posts
Y
Yes, there Is a TDC each revolution; the ICM will fire a spark at each one, however one's a 'waste spark'; fires on the end of the exhaust stroke.
The cam setting determines which TDC is compression or exhaust.
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
70,391 Posts
His 2002 does not have a waste spark system - that ended in 1999. Our engines have 8 coils, individually triggered by the crankshaft reluctor wheel acting on the CKPs and the right bank exhaust cam button acting on the CMP.

That right bank exhaust cam button is what sends the "firing stroke TDC" signal to the PCM: Remember - cams turn at 1/2 engine speed, so each cylinder has only one firing stroke every two engine revolutions, and the CMP sends one TDC pulse for Cylinder 1 every two revolutions. That TDC pulse is only for initial ignition "mechanical" setting; advance is controlled by the PCM, CKPs, engine speed, load, power demand, many other conditions. Ignition advance in these engines is incredibly dynamic - MUCH faster and more accurate than any points distributor with flyweights and vacuum advance.

The OTTO internal combustion cycle:

Intake - V - piston goes down = vacuum, fuel charge enters cylinder

Compression - ^ - piston goes up, squashes fuel charge (end of one full revolution)

Power - V - ignition, piston forced down, power stroke

Exhaust - ^ - piston goes up, dead exhaust pushed out (end of second full revolution).

So ................ for a V-8 it takes two full engine revolutions to fire all 8 cylinders: One power stroke every 90 degrees.
 

·
Registered
2001 eldorado,2008 DTS,2005 XLR, '96 eldo,'95 eldo,' 89 eldo,'78 eldo,'11CTS-V
Joined
·
1,850 Posts
I
I missed the fact that he had the newer version engine.
I regret the error...
 

·
Registered
Joined
·
1 Posts
2006 Cadillac dts 4.6L northstar I have bottom crank lined up 12:00 and 06:00 all 4 upper cam sprockets are at 90', Cylinder #1 TDC. One question, are all four locking cam pins on the bottom of the cam sprockets.
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
70,391 Posts
Because of the valve and timing changes in the later "DTS" engines you will need the current timing diagrams. Lots of things changed after 2005, the end of the Deville.

Either in the GM/Helm (www.helminc.com) DVD (if published) or in a subscription to the online GM service manuals in www.alldatadiy.com.

Welcome to CF !!! Please update your profile so that your login banner looks like those of other members. It sure helps to know at a glance what car we're working on.
 

·
Registered
1998 Deville Concours
Joined
·
64 Posts
Yes.
That said, what good are the timing marks on the crank and intermediate sprockets?
You set valve timing by placing the cam sprockets 90° from the camcover surface.
Having just done this operation, I would say that the primary/intermediate timing marks were very useful. They allow you to be 100% sure that you have kept the engine exactly on TDC when you’re working on the two long cam chains, fitting them to the sprockets. With the timing marks perfectly lined up you can be sure that the 90 degree measurement actually corresponds to the correct piston position. Without this, it would be very easy to be one or more teeth off.

I believe it is 7 crankshaft revolutions for the index marks to line up, but that would now correspond to cylinder 4 firing. Another 7 will get you back to cylinder 1 firing. But the cams will stay at the 1:2 relationship. It’s only the index marks that ‘move around’. This is because they have designed in a ‘double reduction’ ratio system. It uses the square root of 2 for both reductions, but of course it has to round to the nearest tooth count. So one actual ratio is slightly under and one actual ratio is slightly over, but it makes 2 to 1 when combined.

As both #1 & #4 pistons are at TDC when doing this cam timing, the only thing that differentiates which one is being fired is the CMP or CaMshaft Position sensor. As previously stated, it is reading the pin on the right bank exhaust sprocket, and it only passes by that sensor once per firing cycle, thus ensuring that the correct cylinder actually receives spark near the end of the compression stroke.
(2000+ needs this. 1999- have them but can operate without it because of the waste spark system.)
And the computer can use that info to know which cylinder is acting up and set appropriate DTC’s.

Hope this info helps....

Bjc789
 

·
Registered
2006 Cadillac STS-4 1SG V8 PREM PERF V8
Joined
·
11 Posts
Probably has to do with the dissimilar number of teeth on the crank and intermediate sprockets. The timing procedure in the GM service manual specifically discusses the crank and intermediate sprocket timing mark alignment - necessary.

There is also a procedure for collapsing and pinning the timing chain tensioner pistons.

Might as well do it by the book and possibly save great heartache later ..............

It takes 2 full revolutions to get the cam and crank sprockets back to #1 TDC firing stroke. Each cylinder fires 90 degrees apart, so it takes 2 full revolutions to fire all 8 cylinders. It takes 14 or 17 full revolutions to get it all plus the chains back to assembly points.
Simply put there is a lot of questions a perfectionist / over thinker can come up with to skew ones perception of correct timing
Look at these photos and it will allow you to set the crank / int. Sprocket correct which is numeral uno regardless
This wrong =all off
This correct = a possibility of it set lol
This info is correct for 04-11 rwd North Star it does include a vvt setup that appears different than transverse setups
585050
3E8DBDF2-E1FD-4A04-8EE5-F26D6BF84DD6.png
3E8DBDF2-E1FD-4A04-8EE5-F26D6BF84DD6.png
 
1 - 14 of 14 Posts
Top