ILLINTENT

iTrader: (4)

OK, so let me start off by saying that I have searched this forum, youtube, LS howto and also bought an LS1 performance book from HP publishing, and nobody seems to address stock timing gear marks on a 2005 LQ9, or which cycle the #1 piston needs to be when putting at TDC prior to installing the cam gears.

Heres what I'm working with:

stock 2005 LQ9 shortblock
Stock timing gears
7.400 Texas speed pushrods
Stock rocker arms
New Stock GM headgaskets
New LS2 chain
Brian Tooley custom grind cam for a stock LQ9 shortblock .607/ .585 lift
PRC 243 CNC ported heads with 2 inch intake valves

Here's the problem:

Every thread I read says "just line up the dots on the timing gears and you're good." My LQ9 stock timing gears do not have "dots" like I have seen in all the other LS engine cam threads, or any of the other old school engines I've built. It has a dot on the crank gear, and a "U" shaped mark cast into the cam gear.

Assuming that the "u" shaped mark was the "dot" I brought the number one piston to TDC on the compression stroke, then lined up the "u" on the cam gear with the "dot" on the crank gear, just like I would on any other motor. I put clay on the pistons to check PTV clearance, torqued down the head, and turned the motor over. Much to my dismay, the intake valve hit the piston, when the piston was still 1/8" away from TDC.

I found a couple threads that were not consistent with the other cam install threads on here, saying that when timing a cam, the #1 piston needs to be brought to TDC on the exhaust stroke so I tried that. This leaves both the "U" and the "dot" on the two gears both in the 12 O'clock position when the #1 cylinder is at TDC on the compression stroke. (obviously)

When checking the PTV clearance in this position, I have .250" PTV clearance on the Intake valve, and even more than that on the exhaust valve, which seems like a lot to me. What am I doing wrong? I would assume that more people would mention in threads on here that LS motors need to have the cam installed with #1 on the exhaust stroke if that were the case...

Thanks
Matt

01ssreda4

iTrader: (96)

I think you are over thinking this. First, tdc has to do with the crank. Nothing else matters. Exhaust stroke or compression stroke is determined by the valves events, nothing else. For every one turn of the crank, the cam turns 1/2. Imagine the dots, cam 6 crank 12 is tdc intake (intake is getting ready to suck in fresh air). Spin one revolution and you have 12 and 12, that's tdc exhaust, spin one revolution and you're back to where you started. There's only two ways you can situate this and they are both THE SAME.

gMAG

iTrader: (1)

Matt, Your last paragraph is correct.
When both timing marks are aligned (facing each other), #6 should be at TDC. This does not change the firing order.
Therefore, for LS1/LS6, the sequence is 6-5-4-3-1-8-7-2.
...Some info from "Joseph", an engine builder and LS1 Gooroo...

Re: "when torqueing the rockers"

Glenn, I'm glad you found my info helpful, not many people know the valve events for all 8 cylinders and when they happen. You would naturally assume with the dots aligned it would be the firing position of cylinder #1, when its actually the start of the intake stroke as far as the piston/intake valve is concerned. With the dots aligned cylinder #6 is the one to set preload/lash/ or for installing rockers. Each 90* (720* / 8cyl = 90*) on the crankshaft gear is another cylinder firing, while each 45* (360* / 8cyl = 45*) on the camshaft gear is another cylinder firing. Having the timing cover off helps to watch the sequence. Here's a copy/paste of a manuscript I'm working on that may help also:

LSX Firing Order 1, 8, 7, 2, 6, 5, 4, 3
TDC Cyl. #1) Camshaft dot at 12:00 / Crankshaft dot at 12:00
TDC Cyl. #8) Camshaft dot at 1:30 / Crankshaft dot at 3:00
TDC Cyl. #7) Camshaft dot at 3:00 / Crankshaft dot at 6:00
TDC Cyl. #2) Camshaft dot at 4:30 / Crankshaft dot at 9:00
TDC Cyl. #6) Camshaft dot at 6:00 / Crankshaft dot at 12:00<<DOTS/MARKS ALIGNED
TDC Cyl. #5) Camshaft dot at 7:30 / Crankshaft dot at 3:00
TDC Cyl. #4) Camshaft dot at 9:00 / Crankshaft dot at 6:00
TDC Cyl. #3) Camshaft dot at 10:30 / Crankshaft dot at 9:00

If you have that and the timing cover off you don't even half to measure how far you turned the engine over, just line up the dots to the correct orientation and install. Thanks,Joseph

ILLINTENT

iTrader: (4)

I find it odd that information is not more common on this site, nor was it in the LS1 performance book that I bought.

There are so many knowledgeable people here, but for some reason 95% of the cam install threads I read said to: "just put #1 at TDC and line up the dots" which apparently, is totally incorrect.

gMAG

iTrader: (1)

So true!
Joseph has produced his own publication, and I'm sure the info is there.
The same happened to me. Imagine my confusion when none of the cam lobes lined up at what traditionally was the "right" location (TDC #1)!
More than a few ever-aggressive "what the F's" passed my lips. How could Comp Cams possibly have messed this up?
Makes me wonder if anyone is actually able to run their motors with the mistake...and also, how many people set their pushrod lengths the same way.
No doubt, you too will be answering the same question for someone else, down the line.

ILLINTENT

iTrader: (4)

Well, to make matters more interesting, I spoke with Aaron at Texas Speed, and he is offering contradicting information- that the dots DO in fact get lined up (cam gear dot @ 6 O'clock, crank gear dot @ 12 O'clock)

When I had both Dots @ the 12 O'clock position with #1 piston at TDC, the valves cleared the pistons, but by TOO MUCH. The PTV clearance was over .250" on the intake, and even more on the Exhaust. This seemed like way too much PTV clearance for a flat top piston and a .600 lift cam with healthy duration. Aaron at TS agreed with this, and also said that the dots need to be lined up with the #1 piston at TDC...

I also found something else that may shed some light on the situation- With the exhaust cam lobe in the closed position, (put pressure down on the pushrod on the lifter with my hand and rotated the crank 60 degrees past when pushrod stopped going any lower) I tightened down the rocker arm bolt and THE VALVE OPENED about .080". This is obviously way wrong, but I can't figure out why it is doing it.

Stock casting 243 PRC heads
Stock rocker arms that came on the 6.0L
Stock length pushrods for this engine 7.400
LS7 lifters that are the exact same height as the 6.0L lifters
Stock rocker arm stands off the 317 6.0L heads

Do 243 heads use a different style rocker arm stand rail that is taller or something? Could these heads be meant for a different length pushrod or something?? I am at a total loss on this one... but the valves being open when they shouldn't be would definitely account for the PTV interference with the timing dots lined up.

gMAG

iTrader: (1)

[QUOTE=ILLINTENT;18089377]Well, to make matters more interesting, I spoke with Aaron at Texas Speed, and he is offering contradicting information- that the dots DO in fact get lined up (cam gear dot @ 6 O'clock, crank gear dot @ 12 O'clock)

gMAG^^^this is true, not contradictory.

When I had both Dots @ the 12 O'clock position with #1 piston at TDC, the valves cleared the pistons, but by TOO MUCH. The PTV clearance was over .250" on the intake, and even more on the Exhaust. This seemed like way too much PTV clearance for a flat top piston and a .600 lift cam with healthy duration. Aaron at TS agreed with this, and also said that the dots need to be lined up with the #1 piston at TDC...

gMAG^^^I respectfully disagree, and went out to my removed engine, and verified this.
Dot to dot=#6 @ TDC.=perfect alignment of the valve events, in the correct sequence.



I also found something else that may shed some light on the situation- With the exhaust cam lobe in the closed position, (put pressure down on the pushrod on the lifter with my hand and rotated the crank 60 degrees past when pushrod stopped going any lower) I tightened down the rocker arm bolt and THE VALVE OPENED about .080". This is obviously way wrong, but I can't figure out why it is doing it.

gMAG...Have you measured your pushrods, then measured for the correct, desired pushrod length?

QUOTE]

01ssreda4

iTrader: (96)

Cam at 6 and crank at 12 and then them both at 12 is the SAME THING. How are you getting different readings?

ILLINTENT

iTrader: (4)

They are not the same thing. The cam lobes are in a totally different position that way, 180 degrees difference. The cam only turns once for every two revolutions of the crank.

ILLINTENT

iTrader: (4)

[QUOTE=gMAG;18090101]Pushrods are 7.400 long, identical to the stock pushrods that came out of this engine.

I'm thinking that the valve is opening because I modified the lifters to be solid for the purposes of checking PTV clearance and rocker arm geometry. .080" is close to how much the hydraulic piston on the lifter should compress when the rocker arm is bolted down.

joecar

Yes, but the same two cylinders will have their pistons simultaneously at TDC.

Do you have a cam for a different (non-LSx) engine...?

joecar

Get another cam sprocket (with a dot on it) and compare it to yours.

gMAG

iTrader: (1)

With your "dots" lined up, if the #6 intake had been closing, and then both valves are closed at "dot" to "dot", and #6 piston is at TDC, you are in the correct spot.
What amount of clearance should there be?

ILLINTENT

iTrader: (4)

I believe I figured out the problem.

I compared the Cam gear off of my 05 LQ9 to my 03 LQ9. The 2003 gear had a standard "dot" marking on it, and it in fact was in the exact same location as the "u" marking on the 2005 cam gear, so that ruled out any weirdness on the marks.

I spoke to the folks over at Cam Motion, and they were very helpfull, basically told me what everyone else said, "just line up the dots."

The reason why the valves where hitting the pistons when the dots were lined up is because I did not adjust the pushrod length for the solid checking lifers that I put in. Because they were just stock hydraulic lifters that were made solid, when using the standard 7.400" pushrod that I was going to run, it would actually open the valve a little bit even when the lifter was on the back or "closed" part of the cam lobe.

I used my adjustable pushrod length checker, and adjusted the length of it until there was just a little bit more than zero lash preload, which opened the valve about .005" or so when the rocker arm was tightened. I figured this would be good to give me a solid worst case scenario PTV clearance number. Once I did that, I rotated the engine over, and took the head off to measure the clay. If anybody wants a number for reference, the length of the setup push rod ended up being 7.320" long.

I ended up with .130 clearance on the exhaust and .120 on the intake, which is about what I expected with this cam on a flat top piston. The motor is all buttoned up now. Thanks for the help.