Timing Chain Jumped?
 

Just got done reapiring my port engine. 454/420HP. I bought the boat last season and since I bought it, the port engine ran crappy. Was really hard to start. It would crank over, fire for a secong then immeditaly stall. Didnt have much power, kinda sluggish and the exhaust just dint sound healthy compared to the other engine I just had the heads done, all new valves, etc. New distributor, cap rotor, plugs, wires, cam, lifters. Now the chain has jumped, and it wont even start. It cranks over like no compression, like when the plugs are out. Im guessing this thing had a loose chain from the get go. It ran the smoothest idle at about 30 degrees on the crank right before it jumped. DO you think this was my problem all along??

Re: Timing Chain Jumped?
 

Being that the chain jumped, the valves are out of time with the pistons. There is a good chance the valves are now bent.

Re: Timing Chain Jumped?
 

I thought chevy motors were ok if the chain jumps a tooth? If my valves got ruined after a 1200 dollar valve job, Im gonna light a match to this boat for sure

Re: Timing Chain Jumped?
 

what makes you think the chain jumped ?????????


very rare on bb chev mtr, possible dist off after all you did just have it out ??????

Re: Timing Chain Jumped?
 

It was running poorly, sluggish, no power, made it out the harbor, chopped the throttles a bit then it just died wouldnt restart. Returned on one engine. At the dock, tried to start it, cranks fine but sounds just like it has no compression, like cranking without the plugs in, spins fast.

Re: Timing Chain Jumped?
 

Depends on the motor. Clearances can get tight. Is the motor stock?

Re: Timing Chain Jumped?
 

Its a stock 420HP 454 with stock GM pistons. I think the compression ratio is 8.8:1

Re: Timing Chain Jumped?
 

no pops or backfires when cranking ??????

Re: Timing Chain Jumped?
 

nope. Just cranks over. I know the chain didnt break cuz the rockers still move when I rotated it by hand.

Re: Timing Chain Jumped?
 

You should be able to tell if the chain jumped pretty easily with the valve covers off. Bring #1 to TDC and see what the timing mark shows.

Re: Timing Chain Jumped?
 

And yes, you can bend the valves if the chain jumps. Chances are you would have heard them banging though. For the engine not to start, and act like you say, its jumped a lot more than one tooth.

Re: Timing Chain Jumped?
 

Sounds like low compression to me, maybe valve lash is not right, valves are being held open when should be shut.

Re: Timing Chain Jumped?
 

I tend to side with jmherbert, valves to tight, dist off its just very rare for a bb chevy mtr to jump time

Re: Timing Chain Jumped?
 

I agree, but it was cranking normally and would start. Then died, then cranks like no compression. I adjusted the valves as follows

when exaust valve begines to open adjust intake, when intake opens and begins to close, adjust exhaust valve. I went zero lash plus 1/2 turn. Is that correct?

Re: Timing Chain Jumped?
 

no that is not correct

here you go

Re: Timing Chain Jumped?
 

Did you soak the lifters in oil?Are you sure the outside ring on the damper didn't spin?

Re: Timing Chain Jumped?
 

Just about correct.
1st part is correct - exhaust valve just starts to open...adjust intake.
2nd part should say = intake valve just about closed or just closed, adjust exhaust valve.

This way, you know 100% lifter is on base circle.

Goodt's way is fine also, makes it faster but harder to remember.

BTW: super easy to turn over motor is from loss of compression or no/little timing lead. Either valves open at wrong time, bent and staying open, or a sealing issue from the pistons or headgaskets, or as simple as spark plugs not being in tight enough.

Start with simple things first.

Make sure correct seat plugs are in and tight.

Then ignition timing - a very retarded ignition timing makes engine a lot easier to turn over with starter and can creat some real drivability issues.

Check compression next.

Check valve timing after.

Re: Timing Chain Jumped?
 

By any chance, is this motor a counter rotating engine ?

Re: Timing Chain Jumped?
 

ive never seen the timing jump and ive seen some shot out timing gears.

Re: Timing Chain Jumped?
 

Valve lash is to tight and when pumped up and hot, the vales are staying open!I would reajust your valves using a good engine book and follow it step by step,take your time and no short cuts! Why though with all the parts youve added does just this motor run bad?It sounded as if you had twins and im sure you did the valves and heads to both motors at the same time!Did you adjust the valves the same way on bothe motors?Pull the valve covers and the plugs and make sure everything lines up on tdc(#1 rockers,timing mark on pulley,look inside #1 with flash light and make sure the piston is up)tdc on #1 can fool you,@ tdc and 180 off almost look the same! Good luck!

Re: Timing Chain Jumped?
 

I have to agree with JJ like I said before very unlikely you jumped timing chain........

go back and readjust valves if you do it as I posted the merc book procedure its pretty much fool proof just take your time

Re: Timing Chain Jumped?
 

We need more diagnostic work.

You:
removed intake manifold
removed cyl heads
Had the heads done
replaced the camshaft / lifters

So, you had a lot apart. Wires where removed, ignition removed, etc/etc/etc

Basically - a lot has been removed and replaced.

Let's do compression test first, electrical, ignition, and then carb.

Impossible for a good guess at this point.

Re: Timing Chain Jumped?
 

SB,

I agree with you but first need to get the valves right as of now we do know it was done incorrectly, then we can move on to the std routine :drink:

Re: Timing Chain Jumped?
 

Edited: I caught it - don't respond to mwhat I just typed here.

Doh.

Re: Timing Chain Jumped?
 

Results are in. Pulled Timing cover and marks (dots) were off a bit. Removed valve covers, put a straight edge across valves, intake valves no good. Pulled head on left bank, all intake valves were hit by pistons. Pistons have marks from valves. Exhaust valves ok. :mad: :mad:

Those valves had a short life, about 30 minutes. :rolleyes:

Next question, would it be ok to just put new intake valves in, and run it for another month or two?? The pistons have marks on them from the valves, but not too bad. A full rebuild on the motor would be great, but that would mean that the only chance I got at being on the water in 2006 was for 15 minutes :(

Timing chain had about 1/4 inch of slop on one side, and 1/2-5/8 inch on the other side. When I realigned the cam gear and crank gear, I lined the dots as follows; cam dot at 6 oclock, crank at 12 oclock. When I rotated engine the crank gear was at 12 oclock, cam gear at about 1230 position.

I learned a valuble lesson here. Never take shortcuts, especially when it involves a 50 dollar timing chain, and everything was apart already, and now i had to take it all apart again!!!!

Re: Timing Chain Jumped?
 

I have had the valves just lightly hit the pistons due to a brain fart during assembly. Bent every intake valve and broke half the intake rockers. Slight half circles on the pistons. I fixed the brain fart, replaced the valves and all was good. Ran the boat for a 60 hrs and the next owner ran it for 150 or so. Never had any issue with the pistons. Just make sure its not deep enough that it creates a hot spot.

Re: Timing Chain Jumped?
 

Just don't let this guy GOODT (Joe Heller) work on your boat. He is a dirtbag and still owes me $1,000.00 :mad:

Re: Timing Chain Jumped?
 

If the ignition died the engine would turn over much faster than if the ignition was operating.
Do you have spark???