timing chain NIGHTMARE?!?!?

[CMV]

I want to first off thank Q45 guru for the responce of my last post. I am an old school GM/ FORD engine guru. Now the first thing i said when i got the lower cover off was " you gotta be kidding me?" " how did this engine ever last more than 1 minute of running ?" next was " typical Japanese trying to overengineer or should i say *out overengineer * the gremans. ok ok ... chain guides looked all good, metal backed ect... so that had been done. I have never seen such a clamity as this timing chain setup. < still baffeles me that it works.>Q45 guru was right it had jumped time. 1 tooth so it still ran < like crap but it ran sorta>. right side tensioner had stuck i think?

My question is or .. i turned the crank backwards real slowly and the left side jumped about 3 teeth.. blah blah ect ect...

I put everything back like it was supposed to be tensioners felt weak, but anyways . I got the chains back right ect. turned the crank again by hand and all seemed ok. before i was to put this mess back together i had to turn it over OOPS. no fuel spark ect... just crank the moter with the starter. it made about 2 turns and what happened????? CLICKITY CLACK, JUMMPY JUMP @#$$#%^^%&^&^&*&* jumping teeth goes the chains. yes the upper guides above the cams were on.

Are the chain guides so weak and the chains so streached that its causing this. Shouldnt ya be able to rotate backwards without chains jumping???.. Any input here would be appreacited. 215k mi is it worth buing new chains/ tensioners/ect.. or total rebuild. <sigh> i'll probally scrap it if rebuild it just isnt worth all that $$ then a month later everything else goes one by one. / cas / injectors/ ingnition packs/ cpu/ blah blah.. i like the car but dam its a $$$ pit.

Some info about how these chains should behave and feel would be helpful as this is my first < japanese engine >.

signed < might save it might not >

[maxnix]

Chain tensioners.

[ScottJackson]

Something's very screwed. If you cranked the starter and it jumped a bunch, you've got valve issues. The tensioner springs aren't THAT stiff and it's normal for it to rattle a bit right after you get it back together. However, the chains should NOT jump in that time. Do all the chain gears look good or are the teeth sharp on the points? If they're sharp, they're worn. A good meter of how stretched a chain is is to look at the timing gear teeth. If they've got the full width flat spot on the ends of the teeth, they're great. By the time the teeth are pointed sharp, a chain/gear replacement is long overdue.

Yes, the timing chain setup looks complicated compared to a typical single cam engine, but it's not that funky. The Ford SOHC 427 in the '60s had a timing belt that was over 6 feet long!

[CMV]

ok well the cam gears and crank gears look good. too good acctually.. they must have been replaced at some point.. and i guess i wasnt trying to imply that the setup looked complicated.. i am a robotics engineer, put myself through school working as a mechanic at a chevy dealorship.. i guess i was frustrated and trying to imply that the setup is really cheezy ::; for lack of better terms.. god i hate this car.

i want to thank those who have given input to my cause.

[Q45tech]

So cheezy, that with revised guides [and original chains] it can last 314,000 miles and still function at ~~~7300 rpm [momentarily] without failure.

[Q451990]

Yeah... something is definitely wrong. Are you sure the guides are updated? It's the slack-side guides that would be all plastic if they aren't - the tensions side guides were all the same.

Heath

[ScottJackson]

Opposite, tension side guides (straight ones) were the plastic. Slack side (curved) were all the same.

[Q451990]

Scott, I believe you're right. I have never understood why the guides with the tensioners, that push on the chain - are called the slack side guides. I always mess that up...

Heath

[ScottJackson]

I used to think the same way. It's easy to think of it the other way when you consider that the crankshaft is pulling TENSION on the straight part of the chain and the tensioners are on the other part taking up the SLACK.

[Q451990]

That would explain it! Maybe this will actually stick in my head this time...

Heath

[CMV]

yeah ok.. anyways.. the guides are the new style .. all have long riged steel back, none are broken, none are really worn much either, so all that is good. I'm thinking very streached chains and weks tensioners. No matter what the setup it shouldnt jump time while running and shouldnt jump when cranking backwards by hand<provided the tensioners are pumped up and tight. I think I'm gonna do 1 of 2 things. new chains and tensioners, or scrap the car and use the rear end in my Triumph TR8 it needs an independant rear suspension anyways. not to mention the disc brakes. if i scrap the car then there will be lots of good parts for someone.