: Resetting Timing after Head Gasket job.



mshamba
11-14-09, 10:11 PM
Just finished my Headgasket job on 98 deville. Motor out from the top, cradle dropped after the fact, timesert inserts and almost 5 weeks. Here's the problem: The car started fine but made awful noise. I thought it might be low oil pressure but the dash (DIC) was clear. I put it in reverse and backed it out of my shop, put it in drive and started to pull away and it died. Happened twice. I'm thinking the timing is off a tooth because this has happened before to me on a pushrod engine. I marked the chain to cam sprocket locations before removing and I put them back on the same way. The cam drive pins were at 90 deg to the top but the marks on the idler and main gears did not line up. When I rotated the crank until the marks on the idler and main gear lined up, the cam drive pins were at 90 deg. at the bottom. Since the FSM just says they have to be a 90 degrees and doesn't say top or bottom (although it shows top) I left it. I didn't rotate it around multiple times as I have since noticed in other threads. My questions are: Can the timing be fixed without removing the front cover? Does it matter if the cam drive pins are up or down at TDC? If I have to remove the front cover, do I have to pull the engine again?
Thanks

bigtone
11-15-09, 08:23 AM
Read the post titled "Head gasket help" a few posts down. I posted how I set the timing on mine in the car. The pins do need to be 90 degrees up from the head. But, as you said your engine made some noises, I'm afraid some damage may have been done if the timing was actually off. You need to time it at tdc # 1 cylinder for everything to be aligned.

eyekandyboats.inc
11-15-09, 10:11 AM
actually i beleive the northstar engine is non interference engine. thus meaning it has full clearence. so even if the vavles are fully open at TDC they wont hit.

tateos
11-15-09, 10:43 AM
Timing marks need to perfect..or else

tateos
11-15-09, 10:49 AM
actually i beleive the northstar engine is non interference engine. thus meaning it has full clearence. so even if the vavles are fully open at TDC they wont hit.

Nope - definitely interference design. I hope all that noise wasn't valves hitting pistons - if so, you're going to be dropping that cradle again, or pulling the heads, at least, to replace all valves that are bent. There will normally be some valve noise upon initial startup after a HG project, until you get full oil pressure to the heads - mine clicked for maybe 4-5 minutes.

eyekandyboats.inc
11-15-09, 11:13 AM
Oh Okay thanks tatoes.
i thought i read it some where but i must have been mistaken!

zonie77
11-15-09, 01:12 PM
They don't put a lot of oil to the top end so if the lifters drain from sitting they take quite a while to fill.

mshamba
11-15-09, 09:31 PM
Thanks for the help. I has probably run only 3 min. total. I cranked it up again today-It didn't want to start- and drove it back into the shop. I'll look at it tomorrow after work. Bigtone, I read your post before I wrote mine and I understand what you did but I had to put sealant on my timing cover gasket because the one that came in my set was wrong so I don't know if I can do a good re-seal job. Tateos, If the timing is close enough for the engine to start wouldn't it be close enough not to cause valve damage. There has to be some tolerances built into the engine.
Roland

zonie77
11-15-09, 11:29 PM
If the timing is close enough for the engine to start wouldn't it be close enough not to cause valve damage. There has to be some tolerances built into the engine.
Roland


That's a question that only a few Caddy technicians/engineers would know the answer to. There is some tolerance, but how much? one tooth is probably not going to cause broken parts, is it 2 or 3 or 4 that will?

Submariner409
11-16-09, 08:52 AM
As far as valve timing, chains, gears, sprockets, lifters, and pistons there is NO (nada, none, zilch) "tolerance" for errors.

Count the number of teeth in a Northstar cam gear sprocket. Divide that into 360 (degrees). That will give you the valve timing error, in degrees, for a one-tooth mistake. Don't forget that the cams rotate at half engine speed, so crankshaft rotation error is double the cam error.......

Anywhere near an 8-10-12 degree error at TDC could very well cost you both valves on the affected cam, a piston, and who knows what other damage.

If, in fact, the crank and intermediate gears are off even one tooth, you have big, expensive problems. Big problems. Yes, the Northstar is an interference design, hence the valve fly cuts in the piston crowns.

tateos
11-16-09, 12:28 PM
As far as valve timing, chains, gears, sprockets, lifters, and pistons there is NO (nada, none, zilch) "tolerance" for errors.

Count the number of teeth in a Northstar cam gear sprocket. Divide that into 360 (degrees). That will give you the valve timing error, in degrees, for a one-tooth mistake. Don't forget that the cams rotate at half engine speed, so crankshaft rotation error is double the cam error.......

Anywhere near an 8-10-12 degree error at TDC could very well cost you both valves on the affected cam, a piston, and who knows what other damage.

If, in fact, the crank and intermediate gears are off even one tooth, you have big, expensive problems. Big problems. Yes, the Northstar is an interference design, hence the valve fly cuts in the piston crowns.

Couldn't have said it better myself.

OK - I was not going to go into detail, but here's why I say it is an interference design:

When I reassembled my engine, I placed the head on the block with one or maybe both of the cams not at 12 o'clock, with everything else where it should be. I could not rotate the cam gears to get them in the proper place - valves hitting pistons prevented that. So, I had to lift the head off the block with shims - I forget what I used - paint stirrers or something like that - to get enough clearance to rotate the cam into the proper position.

Those valve stems are pretty small - I think they would bend pretty easily, but at least maybe that means they wouldn't punch any holes in the pistons.

mshamba
11-16-09, 12:39 PM
You guys are not very encouraging. I'm going to labor under the assumption that I did not damage the valves. I did rotate the crank several times after assembly to attache the engine to the tranny and I felt no unusual resistance. I'll do a compression check before I pull the covers and see if I can tell which bank is questionable. If I do have a timing issue I should be able to see it in the compression numbers right?
Roland

tateos
11-16-09, 04:09 PM
You guys are not very encouraging. I'm going to labor under the assumption that I did not damage the valves. I did rotate the crank several times after assembly to attache the engine to the tranny and I felt no unusual resistance. I'll do a compression check before I pull the covers and see if I can tell which bank is questionable. If I do have a timing issue I should be able to see it in the compression numbers right?
Roland

That's what Bigtone said - and probably he's right - but, personally, the only way I could be confident that the timing is correct is to visually verify that the crankshaft, idler, and camshaft gears are all in their proper location.

bigtone
11-16-09, 05:39 PM
What I would do is put the engine exactly at tdc # 1 cylinder. Look at the pins on the cam gears. They need to be exactly 90 degrees perpendicular to the head flange. What I did when I did mine to make life easier was stop the engine at tdc #1 before I disassembled it, tie wrapped the chains to the cam gears, and lock the crank and the cams. That way, I knew upon reassembly the timing had to be right. Now, I installed the front chain and gear with no problem, but the rear would not line up. I knew the crank or the cams did not turn, so it had to be the chain on the upper gear inside the engine had slipped a few teeth. I tried to keep them tight, but when removing and installing the heads, it must have got loose enough to slip. I slipped the chain 4 teeth and the cam gear lined up. No problems yet in over 13k miles.

mshamba
11-19-09, 12:11 PM
I think I found the problem. All four cam sprockets were loose. I think I must have snugged them up and them checked everything rotated the engine until the dots lined up and saw the cam drive pin at the bottom (see earlier post) and forgot to torque them. I'll know for sure when I get the valve covers back on. My stupid gaskets have stretched and won't stick in the groove. Any suggestions? What will shrink new Fel-pro gaskets? I may try putting the old ones back in.

tateos
11-19-09, 01:14 PM
I say, just get new ones, while you have it apart - not that expensive

mshamba
11-20-09, 07:16 AM
Got it all back together again and as of this morning it's running fine. Took it to work-not over 45-but it's running fine. Smells like burnt oil though. So I have a Timesert tool used once and a rear bearing installation tool used once for sale. I'm not doing this again if I can help it. Even after the timserts, two head bolts didn't feel right on the last tightening pass and two main bolts also felt questionable. If this motor goes again I'll get a rebuilt or refurbished one from Northstar Performance with the studs. This forum has been a great help. Thanks to all
Roland