legacycentral bbs

I"ve been getting ready for my engine swap and I went to replace the broken timing belt cover on the Booostjunkie engine and found that the driverside cam sprocket got smacked and is bent. It's snagging the timing belt. I'm looking for any suggestions that might save me from replacing the cam sprocket entirely. I was thinking about filing it back so it doesn't snag the belt but that would throw off the rotational mass. Would it be ok or is that a definite no, no?

Here's some pics. They turned out bad, I discovered that my new camera doesn't take close ups very well.







Any suggestions?

Couldn't you just take the one off your busted engine?

Time and resources are limited so he's trying not do have to do that...

I can't tell from the pictures -- is the entire sprocket bent, or is it just near that one part where it looks chewed up?

It actually doesn't look nearly as bad as what I had been imagining. What do things look/feel like when you turn the motor by hand?

Maybe your camera has a "close-up" mode where it allows itself to adjust focus for very short range. It looks like in the fuzzy pictures the camera was trying to focus on the tarp.

vrg3 wrote:Time and resources are limited so he's trying not do have to do that...

Ya, I'd rather not have to do that if I can avoid it.

I can't tell from the pictures -- is the entire sprocket bent, or is it just near that one part where it looks chewed up?

The ring (or lip) around the outside that would keep the belt from sliding off is kinda loose and bent all the way around. Or lopsided might be a better discription.

It actually doesn't look nearly as bad as what I had been imagining. What do things look/feel like when you turn the motor by hand?

Ya, it's hard to see in the pics and I'm not sure what you were imagining but it's like rolled over and smooshed. The lip is kinda loose and lopsided too, like I said.

It's spins pretty good but with there being no oil and no real compression, it's hard to tell if everything's kosher or not. I would imagine it's probably ok internally. It's just hard to tell.

Maybe your camera has a "close-up" mode where it allows itself to adjust focus for very short range. It looks like in the fuzzy pictures the camera was trying to focus on the tarp.

Maybe, I'll have to check that. You'd think it would be able to take better close ups.

Hmm... Is the aft lip also tweaked the same way?

Hehe, I went back to answer one of your other questions that I forgot to answer and you already posted! Damn you and your lightening fast fingers!

By aft do you mean the rear lip? The side towards the engine? If so then I'm not sure. I didn't actually check. I can check tomorrow though.

Hehe. My fingers have a mind of their own.

Yes, that's what I meant by aft... I'm thinking that the state of the rear lip can help us figure out whether the sprocket just got chewed up or actually deformed.

I'm not that familar with the whole cambelt setup... Do people feel that the lip on the sprocket is critical to the task of keeping the belt on?

OK, I'll check the rear lip today and let you know.

Does anyone have any feed back about either filing the bad section of the front lip out, so that it doesn't interfere with the belt or removing it entirely? The only thing I worry about is the rotational mass changing either across the board or making it lighter in just the area I file. Would that make it "lopsided"? So that it would rotate weird and cause damage or is it really not that big of a deal?

I do not feel that the lip on the cam sprocket is crucial to keeping the belt on it. If the belt needed to be held on by that lip, then there is something else wrong anyway.

EA82's don't have any lips of any sort on any timing belt sprockets.

I do understand Matt's concern though about upsetting the balance of the sprocket by filing that dent off (i.e. removing weight). I don't know if it will matter that much, but I could see that happening.

I don't think the weight difference would be too bad as the diameter is fairly low, but that's just a guess. Is the cam bent, though? I can send you a cam sprocket for the price of shipping - I'll never get around to rebuilding the N/A engine like I want. I assume the cam sprockets are the same for turbo and N/A.

Steve

Camshafts rotate at one-half crankshaft speed, right?

Correct, so rpm wouldn't be that high.

Steve

3250 at max.

I could've sworn I posted this last night but check to see if there's a macro button on your camera, most times theres a picture of a flower on it.

Honestly I cant see the lip doing much, but then I don't know why it's there in the first place. The right sprockets on DOHC heads dont have a lip on them, but the left do. The right sprockets are sort of the inverse of the left sprocket, which is the same shape as ours. Then again they're made of plastic also so who knows.

Personally I'd replace the sprocket. I know you're pressed for time but it's either replace it now or replace it later. It'd be much easier to do it now than later. What you should do is break the sprocket bolt on your engine while it's still in the car. If there's enough slack you may be able to remove the bolt and the sprocket without having to ttake off the other covers/belts. Even then it's only a few more minutes, 30 at the max.

He'll have to remove the belt to put a sprocket back on anyway as the tensioner will try to take up the slack.

Matt - PM me if you're interested in the cam sprocket.

Steve

I know, but what I meant was he wouldn't have to remove two timing belts, just one.

some of the machines I have at work have the same style of press-on side rings on the belt sprockets. Any time one has become damaged, it inevitably screws up later by throwing the ring off, usually fraying or breaking the belt.

replace it regardless of how much work it is.

The lips are pressed on?

Yeah, my concern would be the filed edge catching the belt.

Steve

Here's a couple better pics thanks to Hardy's advice about the macro function (flower and all )




That first one gives a pretty good idea of how bad it is.

Steve- That's a really nice offer. If they're the same then I might just take you up on that.

Hardy- I'd like to avoid having to pull the belt and cam sprocket off my blown motor because it'll be easier to not have to swap it all back on when I go to put it back in after the rebuild.

The motor with the bad sprocket is sitting in a tire on the garage floor. A buddy is supposed to give me his hoist for a while so I'm going to get it up on my engine stand. Then it won't be so bad to work on. From the damage to the sprocket it looks like it got smacked pretty damn hard so I should probably just replace it. I really hope everything in the valve train as well as the cam seals and stuff are all ok and didn't take a big jolt. I might just end up having to pull it all apart to make sure.

Vikash- I totally forgot to inspect the rear portion of the gear while I was there today. It was bitter cold and it slipped my mind. I did get the new steering wheel on though and it looks tight!

I'd really swap that sprocket out myself. Try turning it to see if the cam feels right, too. It may not be a perfect test, but could give you a fair idea if there's further damage. I'd bet on the valvetrain being OK just the same.

Steve

Definately replace that. It looks like to me that whatever damaged the sprocket also damaged the timing cover. Is the front damaged aswell? Could you tell what hit it?

Ya, you could see on the Boostjunkie Leggy where the frame smacked the engine. The timing belt cover is broke, that's what I was replacing when I found the damage.

I think I'll probably end up tearing down the front and replacing the sprocket.

Steve- I did turn the crank and it seems ok, it's just that the motor hasn't really had in oil in it for over a year so the compression is real low. It makes it hard to tell if there is any unwanted interference.

Hmm, okay, it looks a little more like I imagined now . Seeing the rear lip will help clarify things further.

It seems to me that if one were going to replace the sprocket it might make sense to replace the entire head, since that way you'll know the camshaft and its bearings are good.

vrg3 wrote:Hmm, okay, it looks a little more like I imagined now . Seeing the rear lip will help clarify things further.

Next time I get to go over and do some work I'll be sure to check it.

It seems to me that if one were going to replace the sprocket it might make sense to replace the entire head, since that way you'll know the camshaft and its bearings are good.

Man, I don't know. *sigh* That's an extreme amount of additional work. If I have to do that I may as well just go about rebuilding my original engine. It's in better shape anyways. I don't really want to have to go through all this just to get the BJ (boostjunkie) engine in working order. I wanted to just drop it in to use while I rebuilt my original engine that has almost half the miles. The other thing is that once I do rebuild the original engine and want to swap it back in, I can't be having to pull all my parts back off the BJ engine. That's going to be a bitch and cause my car to be off the road again at that point, which isn't really feesable for me because it's my daily.

Man, this whole thing's getting me bummed.

Yeah. This sucks.

Is swapping the head an extreme amount of work compared to just changing the sprocket? After you remove the belt and sprocket, don't you just have to undo the head bolts and pop the head off? I know that either way it's not a walk in the park; I'm just asking about comparing the two tasks.

I have a spare head but I can't get to it until I go back to DC.

What the worst thing that could happen if you just filed down the chewed-up portion of the sprocket? The belt eventually pops loose and the engine stops running? Maybe you could have some advance warning if that was gonna happen if you kept the timing cover off so you could inspect the belt and sprocket periodically.

I don't think the weight imbalance is really an issue. The sprocket turns relatively slowly and we don't care that much about the long-term condition of the camshaft bearings there anyway.

I just thought of something. The engine has turned numerous rotations with the pulley in that state. Why would the belt be frayed only at that one spot? Or is it frayed in multiple spots at regular intervals?

Non-turbo and turbo cam sprockets are the same. The left sprocket is different from the right one.

If you did file the lip down but were worried the belt would come off, maybe after the car was running you could take it to a skilled welder to have a little bit of a lip put back on.