Timing Chain Issue

[Goliat6288]

1 rotation of the crankshaft (bottom sprocket) moves the idler sprocket (large center sprocket) 1/2 rotation. 1/2 rotation of the idler sprocket (large center sprocket) moves BOTH camshaft sprockets (top left and right sprockets) 1/2 rotation.

The pistons are at TDC twice during a full cycle, once on the compression stroke and once on the exhaust stroke.

awesome. thank you very much

 

[El Huapo]

Hi Goliat6288: The entire engine assembly would need to rotated all at once, with all the gears and chains moving with it. If you roll it w/o some of the pieces it is recoverable but a PITA. From your description on the drawing post, I think 180 degrees out is likely---happily, an easy issue to fix---rotate.

The only V8's I've torn down were not OHC's so I am not the expert, but one of the first steps in an engine mechanical analysis is to find true TDC. It's where you want your motor to be before any timing parts are removed for sure. Now be sure the spark plugs are out to make it easier to rotate too. I have also used a pair of ty-raps-one pushed into the other to make a "T" to stick in the #1 hole so I can watch it rise with the piston.
I see on an quickee search that a few YouTube video's claim to show how to change the timing chains on that engine. I use YouTube video's a lot but never just one, I view several to get as clear a picture in my mind as I can. The drawing you posted is excellent BTW, a good thing to have.
Now engines do "Jump Time" with stretched chains, but they usually run so horribly that you wouldn't try to drive them. But with 2 cams, maybe just one jumped a notch so it could just be running rough, I dunno.
One more critical test for engine mechanicals is the Compression Check. Done with the spark plugs all out, throttle wide open (on newer cars that may mean propping open the intake however you can---let all the air in possible to get a good reading. I've heard from a few good mechanics over the years that the first two things they do when they get an engine in that's running poorly is the timing check and the compression test. If those two don't check out, no amount of ignition or fuel parts or adjustments will save the day. Some also swear by a "Leak-down Test" too, but that's probably unnecessary here.
One last thing: You say you're changing the Timing Chains---are you also changing the gears? Worn chains could mean worn gears too. Inspect them closely if you're leaving them. Worn gears get a "Hooked" shape to them and a new chain will wear extra fast and not really be properly tight on a warn gear. Bravo on tackling a tough job, perseverance counts.

 

[Goliat6288]

Hi Goliat6288: The entire engine assembly would need to rotated all at once, with all the gears and chains moving with it. If you roll it w/o some of the pieces it is recoverable but a PITA. From your description on the drawing post, I think 180 degrees out is likely---happily, an easy issue to fix---rotate.

The only V8's I've torn down were not OHC's so I am not the expert, but one of the first steps in an engine mechanical analysis is to find true TDC. It's where you want your motor to be before any timing parts are removed for sure. Now be sure the spark plugs are out to make it easier to rotate too. I have also used a pair of ty-raps-one pushed into the other to make a "T" to stick in the #1 hole so I can watch it rise with the piston.
I see on an quickee search that a few YouTube video's claim to show how to change the timing chains on that engine. I use YouTube video's a lot but never just one, I view several to get as clear a picture in my mind as I can. The drawing you posted is excellent BTW, a good thing to have.
Now engines do "Jump Time" with stretched chains, but they usually run so horribly that you wouldn't try to drive them. But with 2 cams, maybe just one jumped a notch so it could just be running rough, I dunno.
One more critical test for engine mechanicals is the Compression Check. Done with the spark plugs all out, throttle wide open (on newer cars that may mean propping open the intake however you can---let all the air in possible to get a good reading. I've heard from a few good mechanics over the years that the first two things they do when they get an engine in that's running poorly is the timing check and the compression test. If those two don't check out, no amount of ignition or fuel parts or adjustments will save the day. Some also swear by a "Leak-down Test" too, but that's probably unnecessary here.
One last thing: You say you're changing the Timing Chains---are you also changing the gears? Worn chains could mean worn gears too. Inspect them closely if you're leaving them. Worn gears get a "Hooked" shape to them and a new chain will wear extra fast and not really be properly tight on a warn gear. Bravo on tackling a tough job, perseverance counts.

thanks for that info. i didnt even think of removing the spark plugs thought i did plan on replacing them. ive also watched quite a bit of videos on the timing job. but mostly following martinbuilt youtube videos. i was never able to turn it on the engine because battery was dead as well and the previous owner didnt try it either due to being told not to turn it on because he could damage the engine.

as far as the compression test, i didnt even think of doing it which ill look into doing it. after the timing job.

and yes i order everything. the cloyes kit which brings tensioners, chains and sporckets.

 

[EdGs]

if i needed to rotate the crankshaft would removing the tensioners (picture in previous post shown as #2) make it easier to rotate?

In a normal, working engine with good compression, it is difficult to rotate the engine at certain points (in the proper direction), because of said compression.

If you have a broken valve, that could bind things up (and cause ALOT of damage).

 

[Goliat6288]

is the proper direction clockwise or counter clockwise?

ive only found one person say the correct direction for these engines is counterclock wise.

 

[EdGs]

is the proper direction clockwise or counter clockwise?

ive only found one person say the correct direction for these engines is counterclock wise.

I believe clockwise looking at the front of the engine.

 

[EdGs]

In your pictures of the crankshaft and idler sprocket, is that after you opened it up, or was ot already open?

The reason I ask is that the pin is still in place on the crankshaft chain tensioner. You can see the pull ring in the photo.

 

[Goliat6288]

In your pictures of the crankshaft and idler sprocket, is that after you opened it up, or was ot already open?

The reason I ask is that the pin is still in place on the crankshaft chain tensioner. You can see the pull ring in the photo.

i put the pin there.

 

[El Huapo]

is the proper direction clockwise or counter clockwise?

ive only found one person say the correct direction for these engines is counterclock wise.

I think the best way is to look at the fan---if it's a mechanical one. I guess it's off the engine, but you can probably still tell.
Another way is to have someone watch and just bump the starter---in your case that may be harder to do than to say if you don't have a good battery or jumper cables.
The last way I can figure is the most work: rotate the engine by hand (plugs out, right?) and watch the intake valves/rockers if you know the firing order and see the sequence. There's only 2 possibilities so it'll just take a little muscle work.
If I may add here, working on an engine w/o a lot of experience take patience---you can do it if you just persevere, and once it's done you can take real pride in the accomplishment. Best of luck to ya.

 

[demonram]

thanks for that info. i didnt even think of removing the spark plugs thought i did plan on replacing them. ive also watched quite a bit of videos on the timing job. but mostly following martinbuilt youtube videos. i was never able to turn it on the engine because battery was dead as well and the previous owner didnt try it either due to being told not to turn it on because he could damage the engine.

as far as the compression test, i didnt even think of doing it which ill look into doing it. after the timing job.

and yes i order everything. the cloyes kit which brings tensioners, chains and sporckets.

So the mechanic shop told the previous owner not to try to crank it because it could damage the engine, is that right? I agree with taking the spark plugs out and try turning it by hand. If you still run into a situation where it won't turn more, there is most likely something more internally. You might want to check with the shop who had it to see if they know of any other problem with the engine before proceeding any farther.

 

[EdGs]

So the mechanic shop told the previous owner not to try to crank it because it could damage the engine, is that right? I agree with taking the spark plugs out and try turning it by hand. If you still run into a situation where it won't turn more, there is most likely something more internally. You might want to check with the shop who had it to see if they know of any other problem with the engine before proceeding any farther.

^^^^ this.

Hopefully, they can give you some background on it. And at least by removing the plugs you will know if there is a physical binding going on.

I hope you get it sorted out as economically as possible.

 

[Goliat6288]

I did get it sorted out somewhat. I turned the crankshaft sprocket (with the plugs off) on full turn and got the other sprocket marks line up. I also ended up changing the plugs.

thanks for idea of calling or going to the mechanic. I’ll see if they’ll tell me anything.

how can you check for binding with the spark plugs off

 

[EdGs]

If it is binding you would most likely feel it. If it turned easy with the plugs out, so far so good.

Next, I would check compression on each cylinder. If each cylinder has good compression, another big plus.

 

[Goliat6288]

i did get all the timing chain stuff done just need to torque everything down and close it up. i bought the compression test tool so i can do it before closing it all up.

any one know what numbers i should get on a compression test?

im guessing i dont need coolant, need to connect the radiator or need to attach the fan for a compression test? i know i do need engine oil.

dont want to close everything up and use up coolant then have to take it all apart and drain it to fix it something if it goes bad.

 

[LoneWolf3574]

All cylinders should be within 10% of each other and compression should be around 150psi if I remember correctly. Someone will correct me if I am wrong on the pressures, but the cylinders should definitely be within 10%.

 

[Goliat6288]

ok so i did the compression test today. not sure if i did it right

had the throttle body wide open with the butt end of a rubber mallet while turning the key.
i let the engine turnover between 6-8 times.
also not sure if having alternator, idler pulley, serpentine belt and compressor off makes a difference.

here is what i got



had to do the drivers side a second time because i decided to round up the first time around.

i did the same thing on the passenger but they all fell on or over 110. one of those 120 might be a 115 or 125

 

[Goliat6288]

Any one know what would cause compression to be low on two cylinders?

assuming 120 is normal for this engine and altitude ( read somewhere that comes into play with compression results, not sure if it’s true)

 

[LoneWolf3574]

Low compression could be a valve(s) not seating fully due to carbon buildup, a broken/damaged spring, or a bent valve. Ring blow-by could be another possibility but is far less likely, you would see rapid bleed down of cylinder pressure instead of low to no pressure. I am sure I am forgetting something here, but as I always say, someone will come along and correct me or add on.

EDIT - BTW, cylinder #3 may not be passing on compression, but #5 looks like it is as well as it is more than 10% lower than the other 6.

 

[Goliat6288]

I’ve also read that maybe head gasket in between those two low cylinders.

any way to know which one it is?

would taking the heads off help me eliminate some of those?

 

[Goliat6288]

hey guys
so i ended up speaking to a mechanic. he said i was better off putting it back together and seeing how the engine runs. something about the difference in compression is significant enough to tear it apart further yet, also because everything was new and pretty much dry so to let it run and get everything lubricated.

went to turn it on and.......... no start. cranks but doesnt start. found a couple of videos that suggested canceling out fuel before testing spark. there is no fuel in the fuel rail, pressed in the little nipple thing on the passenger side fuel rail and no fuel came out. a buddy suggested spraying ether or starting fluid to see if it turned on. did that and it did for about 3 seconds then shut off. im guessing this points at the fuel pump.

went to look at where fuel tank was and found something else that caught my eye. there is a rubber hose on the rear axle that isnt connected anywhere and i cant figure out where its supposed to connect. can anyone help me