I threw in a new tensioner from the LNF when I built my block. However just over a few hundred miles later I started to notice some chatter of the chain at higher rpms. I was looking for a boost leak otherwise I would have not heard it due to the 3 inch exhaust at WOT (hahn). So anyway I went to investigate after babying the car for a few hundred miles and found some issues that both scared me and relieved me.

Found my timing chain guide bolt broke clean off. The bolt is a 9.8 grade metric stock. I found the same thread pitch and size at an auto parts store with a 10.9 grade. Both used a 10 mm socket. So I upgraded.

They are 1/3 stronger according to this site. Metric Bolt Properties, Grades, and Strength
The beating that this bolt takes is very considerable since the chain is "riding" along the guide as it rounds up and over the guide on the way to the cams. Add problems with old tensioner designs (my lsj tensioner slapped) and it can beat the guide to death. Causing fatigue, and sheering it off in the block.

I had to drill a small hole in the stock bolt and use a set of bolt extractors to get the part that broke off in the block. The guide rattled around in there and wore a small groove into the machined surface so I cleaned it up a bit with a chisel and file so that there were no high spots. Before you start yelling it needs machined it was only a small amount that would have had an uneven surface, just took it down to smooth. Kind of like taking the gnarled edge off a copper pipe so to speak.

So install your new 10.9 bolts to 89 inch lbs and use red locktite after reinserting the guide. Time the engine, reinstall the tensioner after you have reset it, and run the car in flood mode (gas and clutch to the floor) to set the revised tensioner. There are better writeups for this part, just follow them to the T. Here is where I bought my tensioner for 31 bucks.
(cobaltss is causing two links, I only see one in the editor)

I have seen many videos of the ecotec family of motors with noise and many choose to ignore it but there is always a reason to crack the cover and investigate. Dont ignore noises, LNF, LSJ, whatever...

 

Damn. I've got one heck of a a rattle that started out of the blue on Friday, not to hijack a great bit of advice but did it sound like what I recorded? https://www.cobaltss.net/forums/prob...n-here-296355/

All of those bolts under the front cover are too small IMHO, the timing chain guide bolts with the bulbous heads look like an easy shear and I wish they had designed them a little smarter.

If I have my cover off this summer I will definitely upgrade to the 10.9 grade.

 

Out of curiosity, what valve springs did you install when you built the engine?

 

answered you in your post.

yes, 82# zzp titanium retainers

 

My engine's got them in it and I can't go over 2k RPM until the car is over ~150-160* coolant temp or else I get a bunch of valvetrain noise. The others I've talked to with the ZZP 82 pounders on the LNF have the exact same thing that happens. I try to keep the car under 2k RPM until it warms up a bit, and then once the engine is warm it's business as usual with no noise.

I flashed a tune that happened to still have the cat warmup enabled once and it was downright scary when I did the cold start. During cat warmup it's common for the car to immediately jump up to around 2,300-2,500 RPM. There was chain noise, intake cam correlation code, misfire on every cylinder... it was really bad. I swore I almost jumped timing. Never again.

 

run 10w30, I live in the south so its a better viscosity for warmer climates. In the winter I run 5w30. Viscosity changes pressure on the system. My Oil pressure is over 40 on cold start but drops to 30 at idle when warmed up on 5w. The oil doesn't flow as well to the tensioner when cold... obviously. So the higher psi oil is actually telling us the oil is having a harder time traveling around in the engine.

My recommendation is run an oil pressure gauge. I run matching innovate gauges. Get the better bolts cause that cold slap will eventually shear the stupid bolts. Try different oil viscosity.

Here is a reference from another site about viscosity.

According to Sometimes, but usually not. The crux of the issue is this: the bigger the difference between the cold oil viscosity and the hot oil viscosity, the more the volume of viscosity modifiers and the less the volume of base stock. If you are good about following the manufacturer’s recommended oil change interval then stick with the 5W30 if that is the preferred oil for your vehicle, even if 10W30 is acceptable in warmer climates. Older cars may specify 10W30 only. This is because they need a little more viscosity when cold to keep a protective film on the cylinder walls. There have been instances where the larger amount of viscosity modifiers that are present in 5W30 have broken down due to excessive heat and have left carbon deposits on the valves, but this is extremely rare. The proper fix would be to reduce the excessive heat, but the workaround was to use an oil with less viscosity modifiers.

 

what did you torque that bolt....... ive built numerous lnfs and cnt say ive EVER had one break or seen one break unless its been over torqued at one point or another. not saying its not possible just curious.

 

Hmm, I've got the 82# with steel retainers on my LE5 and have had the winter from hell. From -40*C with windchill one week to near zero the next and then back to -30 after that. Nothing until last week, cold starts at -40 don't sound pretty but I can't say it was terrifying. My oil pressure is just under 40 at idle when warm with amsoil 5w30. These engines don't settle down until fully warm, I'd pull my front cover to take a look but the ATI balancer is pressed on and it isn't so simple to anymore.

 

89 inch lbs, i built my block from the ground up and was very **** about everything, used an inch lbs tq wrench. Gave me something to add to my mods list, LOL, and helps me sleep at night knowing all the issues I and others have had.

I want an ATI but not sure if its worth it. Especially since its pressed on!? I thought it was bolt on and you just need the modified cover.

 

Naw, it's definitely press on. Yeah, you need the modified cover, but it's not as easy to get the timing cover off after you go ATI due to the press on thing. Despite being press on, it's a pretty legit and respected balancer though.

 

I am hitting 7500 occasionally now with just NB deletes and valve springs. I know the balancer is the last thing I need to go 8K but not sure if necessary yet. If its pressed on how is it removed? You press it on on a bench would you have to pull the motor to get to the timing components?

 

Its worth it if you have $$$ to burn. If not, don't loose sleep over it ESPECIALLY if turblowed. Only thing I refused to do myself, spent $5k for a forged ZZP gen2 block they no longer make because they suck **** and didn't want to (f)suck it up even moar. Mechanic had a tool, or thought he did anyways but didn't and ended up hammering it nice and slow along the extended keyway that came machined into the crank.

**** I should have bought another crotch rocket instead, 11 flat all day long and the front end wouldn't be made of cardboard. /rant

 

I haven't had to pull it yet (thankfully), so I can't answer that, sorry.

 

yikes, did your gen2 block take a crap?

 

It has bolt holes so you can mount a harmonic balancer removal device through the m14 crank bold and pull it off that way. The one most commonly available up here has all the wrong sizes but I'm sure it would be an easy mod. Probably goes on easier than it pulls off lol.

 

Well, if it is I'm gonna burn the balt to the ground and go 100 crank horsepower hyundai. Only so much one man can take but no I think the block is fine, only 5000 miles.

 

I would think you could take it to a machine shop and take off a thousandths and slide it on like stock. My stock balancer is a very snug fit and the engine seems very stable and happy at 7500.
The goal of my car is to be a beast and a good daily driver. If I mod it to the point of crap doesnt bolt or unbolt it starts to become a pain in the butt. I am slowly getting my kinks worked out of my build but I have two cars/trucks so the cobalt sits when something needs fixed. Making a lot of power in these cars takes a lot of attention and detail to all aspects of the engine. Its not like a v8 or near as reliable in my opinion.

 

The whole point of the ATI damper is the interference fit, if you machine the crank snout to slide it on you've spent $400 (plus machining costs) on something that the $60 stocker is doing already.

 

good to hear on both accounts, I have had days where I wanted to give up on the balt but I just get a wrench out and move forward. Glad to hear the gen2 block is holding up. Are you running 600 hp?

 

ATI - Crankshaft Dampers 101



Once these vibrations get to the front of the motor, something there needs to counteract that motion. That is where the damper comes into play. The damper’s job is to absorb and counteract as much of the twist as it possibly can. If you have the right damper on your motor, almost all of the twist can be eliminated. However with the wrong damper virtually all of the twist can remain. A dampers job is to rebound, the recoil of a spring. In this case the spring is your crankshaft twisting and when it tries to rebound past that natural state we discussed earlier, that is when the damper needs to stop it.

Don't mess with the fit as it counteracts the twist!

 

i guess that makes sense. I think I am just going to retain the stock balancer and get cams that make power up to 7500 and call it a day.

 

good read, kind of knew that stuff but I like the part about the rope.

 

I just snapped a bolt last weekend... Glad I found this as I was just looking into a stronger alternative. Was considering modifying all of the guides and drilling the bolt holes up one size. Do you happen to know the exact thread and under head length?

 

Am I running 600whp?

*slaps yous*

I'm the grand champion of $$$ spent for the least result. I'm running barely 300, and patiently waiting for nearly 8 months now on Euthansia to deliver my MP-90 kit. As a SC fanboi, its all about power under the curve. My goal is 325ish wickedly fun whp that hits like a ton of bricks off idle at around 15lbs of boost running through my nearly new 3.63 4t45e ZZP 2750TC automatic tranny. It was 147whp bone stock, beaten by a toyota matrix for **** sakes. No more!

Got one dyno in town, nobody here cares about that ****. classic cars and carburetors are king. I'm in this for fun, first and last hot rod for me.

If I had to do it over again, stage 3 turbo and would have left the motor bone stock.

 

I bought a box of 6 of them if you want one, I only replaced the bolt on the guide. If you were to do the entire system you would need to take all of them out and check each one at a store bolt display board with the holes, as they are different lengths/sizes. I feel this completely unnecessary as most of the bolts are adequate. The upgrade for the main guide that takes the brunt of the stress is GRADE 10.9 M6-1.0 30mm Dorman (6 dollars for 6 at O'Reilley's)