just another snapped timing belt

[ricktb]

I snapped a timing belt, heard what sounded like a crunch. I pulled the valve cover and about 10 of the rocker arms were popped off the ball joints, and 3 were completely loose and laying down in the oil wells. So clearly the valves must have smacked the top of the pistons. Is there a way to check if the valves are bent without removing the head? from the top they look stright but its tough to tell. Could the rocker arms be designed to pop off to prevent valve damage in this event? Can I still do a compression test somehow?

When the belt snapped I was barely boosting maybe 5 psi in second gear, going about 55km/h so less than 4500 rpms but I'm sure the engine got a few more revolutions in there before it stalled.

The reason I dont want to pull the head is because the exhaust mani bolts are seized on there and i've stripped one a little already trying to remove it.

Also how hard is it to remove the intake manifold? is there bolts tucked way under neath? Thanks for the input.

Possibly looking at a head rebuild or whole engine depend on damage. Anyone know any good shops in Alberta, Canada?

 

[Calan]

You could do a leak-down test (not a compression test), but the head needs to come off regardless, if you popped 10 rocker arms. The odds are very good that you bent valves and damaged (or destroyed) some valve seals, and you probably have some piston kiss marks to clean up at the very least.

You can pull the head without removing the EM. You may as well take this opportunity to fix the stripped EM bolt holes once the head is off, and clean up any other issues that need attention. The intake bolts aren't difficult to get to with the right tools and a little patience. Pick up some 10 and 12mm gear wrenches, and work from the driver's side.

Do it right, and do it once.

 

[primo513]

There will definitely be bent valves. And hopefully there isnt any bottom end damage but there most likely will be if all the rocker arms were all over the head. I knew a guy who thought he had the motor in time and tried to start the car and bent almost all the valves just trying to crank and he had rocker arms laying all over from what he told me. when he took the head off he had broken the valves off the stem. if you cant get the exhaust mani off, I recommend just taking the head off with the exhaust mani still on. It will need to come off. The intake mani has bolts instead of studs and nuts, they are lined up similar to the exhaust mani studs though. Taking the intake mani off first will lighten the load when you pull the head.

To add to what calan said: Do it right, or do it twice!

 

[gieri002]

You definitely have bent valves. You could reinstall the rockers and do a compression test but I'd save yourself the time and remove the head. Also, you don't need to pull your exhaust manifold to remove your head. This would be a good time to fix the stripped exhaust mani bolts as well.

 

[BogusSVO]

The quick way to check, pull the cams and do a leak down test.

From what you are saying, you have bent valves, and a very good chance at cracked guides.

So a whole head rebuild or swap is in order.

 

[bluehaze420a]

If 10 rockers poped off its not worth a compression test in my eyes. I would pull the head off. You can unbolt everything you can then try to heat up the seized bolts with a small torch.

 

[silvreclips]

4500 rpms ... yea you deffinately caused some damage. Dont even bother with a leak down or compression test.

 

[Calan]

You could reinstall the rockers and do a compression test...

If 10 rockers poped off its not worth a compression test in my eyes.

4500 rpms ... yea you deffinately caused some damage. Dont even bother with a leak down or compression test.

If there is any suspected engine damage at all, it's never a good idea to continue spinning the motor to do a compression test; especially if there is a possibility of bent valves. All that can come from cranking over a damaged motor is more damage.

http://www.dsmtuners.com/forums/articles-engine-fuel/338152-compression-leak-down-testing.html

In these situations, a leak-down test is the proper way of diagnosing things. In the OP's case however, even that probably isn't worth the time. Might as well just pull the head and get to work.

 

[ricktb]

Thanks for the useful advice, i didnt even think to leave the exhaust mani on, ill just bypass all testing and tear into it, will try to post pics when im done.

 

[Calan]

...i didnt even think to leave the exhaust mani on

Well since you mentioned it, you can leave the IM bolted up to the head also if you really want to. Just pull the fuel rail, disconnect the TB, vac lines, brackets, etc.

Personally, I go ahead and pull the IM since I don't have a lot of stuff in the way and I am familiar with it. I can usually have the IM off in 10-15 minutes. YMMV.

 

[ed1380]

The valves are bent. Time to pull the head.

I'd take the manifolds off and get some new studs for the exhaust side

 

[bluehaze420a]

The valves are bent. Time to pull the head.

I'd take the manifolds off and get some new studs for the exhaust side

Wouldnt it be easier to pull the head and work on the seized studs on a bench to get the manifold off?

 

[Calan]

Wouldnt it be easier to pull the head and work on the seized studs on a bench to get the manifold off?

Depends on which studs (nuts) are seized, and how badly. It's sometimes easier to break them free while the head is clamped firmly in place....like to an engine block.

From the sound of it, you're probably going to be needing some helicoil repair work done no matter which route you take. Let the studs all soak in some PB blaster for a while, and don't work too fast and try to force everything.

 

[bluehaze420a]

Very true on that. I have always had a hard time getting the right angle with an easy out on a bolt in the engine bay. I usually go to the machine shop and let them hassle with it.

 

[ricktb]

Im almost there I think im going to leave both mani's on and lug the whole assembly out in one piece I cant get under the IM to reach the lower bolts. I think its going to work, the head is loose its just catching on the drivers side I think I have to remove the timing belt cover engine mount and possibly the PS pump and alternator, and pulleys trying to do the minimun work here.. will carry on tomrrow. thanks again for the tips.

 

[2gtalonfwd]

What timing belt were you using?

 

[primo513]

Im pretty sure the only bracket that should stop the head from coming off should be the PS mount on the block. That was the only thing stopping mine when I pulled the head the first time since I left the exhaust mani on

 

[comsoldier20]

I ended up changing my timing belt with a bad auto tension or. this resulted in the timing belt jumping the first time I was cranking the car. The car never started but the engine sounded fine and didn't make any crunching noises. I pulled the head and all of my intake valves were bent just enough to cause no compression. I would bet money that you have bent valves. I HIGHLY recommend you get both timing belt tools in order to do the timing belt properly.

 

[primo513]

Just need some clamps and some rags, the tool makes it nice but not necessary

http://www.dsmtuners.com/forums/art...l-installing-timing-timing-belt-6bolt-2g.html

 

[ricktb]

finally got the head off, there was an electrical harness on the rear driver side catching, and one manifold to turbo bolt still threaded partically, and the two intake manifold support bolts attached. Once I removed these the head came off without much trouble. Did not need to remove the power steering pump or belt, same with alternator, and did not need to remove the engine mount. left all that stuff alone. And I also left both the intake manifold and the exhaust manifold attached, this will make removal of these much easier as one of you suggested.

I know all the valves are done because they all hit the pistons. The pistons are damaged too bad enough I think I'm looking at a full rebuild at this point. Or do you think I can just do the head and leave the pistons as is? The question left is can anyone diagnose any other problems I may have had due to color such as rich or lean mixtures or detonation or does this look pretty typical of a normal engine? There was some small metals flakes in a couple of the cylinders and all the exhaust valves are white. I havn't looked too deeply into this yet just snapped a couple quick photos and I'll get more into it later on. Can I do a full rebuild without removing the bottom end? crank, rods, pistons etc? I'll probably tackle the bottom myself and have the head sent out for a performance build. What you think?

Here are the photos..

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[BogusSVO]

The good news is, none of the valve heads busted off and caused major damage. From the valves I see it looks like they are the factory installed 6T.

(For those that find this at later times, this is a reason I say use 6T valves or a stainless steel valves)

For the pistons, you can roll them to TDC and buff off the sharp damaged edges.

You will also want to make sure the rings did not get pinched when the valves hit the pistons.

For the head, I will say the exhaust side guides are cracked and need replaced, the intake side may need them too.

Now depending on the machine shop you select to rebuild the head, they may want to sell you some replacement valves that they say are OE" spec replacement. I will suggest you avoid these on turbo head, most stock replacement valves are of a 2 piece design. Find a set of 6t valves, or install a stainless steel valves.

 

[ricktb]

im glad to hear i can possibly buff out the pistons and use them, the bottom end isn't something I want to get into just yet. Does anyone have a solid reason I shouldn't do this? I will clean them off and take a closer look for cracks in the piston tops as my brother suggested. Did you mean check the pistons rings? Good call And I hear the guides/valve seats are something that may need replacement is this possible to do with common tools in my shop (spare bedroom is my shop for now) heh. I saw some great HD vids on rebuilding a 4g63 head on youtube and it really looks like something I can tackle myself. I figure I can get all new valves, guides, seals, springs, revised lifters, maybe I can reuse the rocker arms with a good clean. they look in really great shape.


4g63 Engine Tech - YouTube

 

[Outdorsman]

Regardless if you can perform the rebuild at home or not, you must get the head resurfaced. It will need to go to a machine shop.

Idk but wouldn't purchasing a replacement head be cheaper? Unless you want a performance rebuild.

 

[ricktb]

not sure about the availability of a 4g63 head in my area so far ive come up empty on a whole new engine. I checked the deck surface with a metal ruler and a feeler guage it seems pretty flat maybe enough for a quick scrape with razor, then oil sand with some fine grit emery cloth and a new gasket? I did this for a exhaust header one time and got close to a mirror finish. Bogus I just found your tech on valve guide replacement, some useful info there thx. In the end I'll probably end up taking it to a machine shop

 

[Outdorsman]

not sure about the availability of a 4g63 head in my area so far ive come up empty on a whole new engine. I checked the deck surface with a metal ruler and a feeler guage it seems pretty flat maybe enough for a quick scrape with razor, then oil sand with some fine grit emery cloth and a new gasket? I did this for a exhaust header one time and got close to a mirror finish. Bogus I just found your tech on valve guide replacement, some useful info there thx. In the end I'll probably end up taking it to a machine shop

I'm pretty sure Bogus advises against sanding your head, it will not end well, he wrote an entire article dedicated to not belt sanding or sanding your head. A resurface only ran me 60 bucks total from a reputable shop. I don't see why you would want to risk it. Honestly just buy a new head, Miller import parts can ship you one for a reasonable price. If not, let the machine shop do a rebuild.

Do it right or do it twice.