HELP ME! Troubles with a 1992 Z34

[MACE]

I have a 1992 Lumina Z34 with a 3.4L dual twin cam V6.
I was recently attempting a road trip with a few buddies, and while climbing a hill & passing another vehicle the RPM hit about 6 grand & the car quit.
I had assumed that maybe I had snapped the timing belt, & my mechanic seems to agree although we haven't stripped it apart yet.
I guess my question is, if you break the timing belt in this motor, is it ruined?
I've heard that they are a "0 tolerance" motor & my valves are likely all bent.
If this is the case, would it be cheaper to hunt down another 3.4 and do an engine swap? Also, will the newer style 3.4 motors (Monte Carlo, Impala etc) bolt down?

Any help would be appreciated.

Thanks in advance.

[HayesPerformance]

If you use the a 96-97 engine you will need the exhaust manifolds too.

Did you check What is damaged?

[MACE]

No we haven't bothered digging into it just yet. These motors are so labor intense that we didn't strip it apart. However, they did a compression test on it. The 1st 2 cylinders have no compression and the 3rd has a little bit.
Doesn't sound promising, so that's why I figured I'd inquire about my options for an engine swap.
Is the 96-97 motor a dual twin cam as well?
Would you need a new computer as well?

[HayesPerformance]

Yes, the 96-97 3.4 DOHC is still a Dual overhead cam engine.

Just to make things very simple for you just swap in a 91-95 3.4 DOHC

If it is a 94-95, just leave the cam sensor unpluged.

[MACE]

I was just talking to a local junkyard that suggested that I just put in a 3100 V6 motor as they don't have a 3.4L available.
Any thoughts?

[55trucker]

Have you actually verified that the timing belt has indeed decided to take a vacation?..If the shop mechanic is attempting to do a compression test and the valves are not doing what they are supposed to do...then some of the cylinders valves will be open and there will be no or little compression. Pull off the plastic access cover on the forward head to see if the belt is still intact. The engine is designed to be non-interference, but if the belt did let go at 6g's the clearance between the pistons at top center and valves when at full lift is extremely small (something in the neighborhood of .010 to .015) and contact can happen. Not fun stuff.

[pocket-rocket]

Have you actually verified that the timing belt has indeed decided to take a vacation?..If the shop mechanic is attempting to do a compression test and the valves are not doing what they are supposed to do...then some of the cylinders valves will be open and there will be no or little compression. Pull off the plastic access cover on the forward head to see if the belt is still intact. The engine is designed to be non-interference, but if the belt did let go at 6g's the clearance between the pistons at top center and valves when at full lift is extremely small (something in the neighborhood of .010 to .015) and contact can happen. Not fun stuff.

I completely agree. Take the timing belt cover off and have someone crank it. Where are you located? Maybe someone on the board lives close to you and would help you with it. I know the last time I did a head swap on my car, I pulled in the drive around 1pm on Friday and Saturday morning afternoon I was firing it back up and driving around with the ported and polished heads on, so to the right person it's not really that hard.

[MACE]

I live in Prince Edward Island 7 since I've owned the car I've only ever seen maybe 2 others still alive in this province. I haven't pulled the timing cover off just yet, but like I said, one can only assume that when you're hauling 5 large adult males on a road trip to a concert passing a vehicle revving 6 Grand, chances are something likely snapped.
Cylinder 1 showed 0 compression, #2 about 40% & #3 0. The local scrap yard has a 3100 series motor with low mileage to put into it, so I may have to take that route since everyone I've met seems to hate working on the 3.4L Twin Dual cam motor. I hate to put a motor in that doesn't match, but it's just too $$$ to maintain. Time to sell her I guess.

[55trucker]

Replacing the DOHC with the pushrod engine is not quite as simple as out with one & in with the other....you'll have to consider the rear exhaust manifold to head pipe, they are not quite in the same location (close but not quite), the pushrod engine uses a pair of upper strut rods, the DOHC uses just one, the pushrod engines in the W body *roll* (that's why there are 2 upper strut rods), the DOHC does not.. the engine mounts are different, ...then there's the wiring, you'll need the 3100 ECM (with chip) as it is not the same one that is used with the DOHC engine, and any harness discrepancies that will have to be worked out. Now, I'm not attempting to put you off....just want you to be aware that it's not a simple case of..*out with one & in with the other* Don't write of the DOHC too soon......do the diagnosis first.....as pocket rocket said, you'll need 2 individuals to check the belt...pull the DIS fuse from the electrical center near the passenger side shock tower (it's a red 10 amp fuse in the #7 position) so the coils are not live and crank the engine....note if the belt is moving with the crank, if the belt has not snapped, but is still intact.. but is not moving.. then more than likely some of the belts teeth have sheared off and that spot is right under the crank pulley.

[MACE]

Pocket-rocket & 55 Trucker:
Thank you very much for the info. I appreciate it very much. It's heartbreaking that the 'ol girl has quit on me since the body is still in exceptional condition for the year of the car.
Is there any other GM motors that will fit this car better than/ easier than a 3100 series IF I do have to do a motor swap?

In the interim I'll certainly get the boys at the shop to pull the timing cover at the very least to have a peek.

[55trucker]

[QUOTE...note if the belt is moving with the crank, if the belt has not snapped, but is still intact.. but is not moving.. then more than likely some of the belts teeth have sheared off and that spot is right under the crank pulley.[/QUOTE]

Correction...what I should have said is...the belt teeth have sheared off and that spot is right under the *intermediate shaft* drive gear.... 3100 or 3400 engine swaps are not uncommon...3400 is more desirable than the 3100, I've not done one in a W body....have done so with a Fiero.....again, the engine will go into the car and mate to the 4T60e trans...you just have to take the time to make the necessary changes to pull it all together.

[MACE]

I'll have to mention this to the guys at the auto salvage that said they had a 3100 to go into it. I've never met them or delt with them before, but I've heard they are more about "move 'em in & get 'em out" type of operation, so they may not be aware that the mounts etc won't match up.

Does any one know if the "LA1 3400" motor that was in the 200-2005 Chevrolet Impala would fit? I'm sure there must be a few of the newer style Impala's kicking around in the salvage yard.

[walterdude]

I'd make SURE that the engine is toast before I'd talk about a swap! These engines are SWEET!! I've got pushrod and DOHC and like the DOHC MUCH better,,, that could be just me... You can check on the belt yourself real easy... As said pull the little cover on the front head,, 2 bolts I believe and the belt is visible. If you can see (if you can't see, it's broken) the belt go ahead and pull the fuse that was mentioned and crank it, see if the belt moves. If not, then teeth are missing..
You don't mention if there was any noise when it stopped. If you slammed valves at 6,000 RPM I'd think you'd HEAR that!! As you were going uphill AND fully loaded, the engine likely slowed down real quick,, possibly avoiding contact... The only time I've heard of contact issues is with HIGH revs, redline is at 7,000, just maybe you got lucky... I'd sure rather do a belt than swap a whole engine!! Besides, as I said I like the DOHC better!! When you work on them awhile they aren't that hard to work on, no worse than anything else, really...
Good luck,,,
Tom....
Just make SURE it's shot before swapping engines....

[pocket-rocket]

I agree with Walter. I've driven a Monte with a 3100, and I wouldn't trade either of my DOHC for them (no offense pushrod guys). If you are really hellbent on installing a pushrod engine, go test drive a car with the kind you are thinking of putting in to make sure that is indeed what you want. One way you could check the belt by yourself is mark it with a paint pen, then crank it to see if the paint mark moves. I've had mine sheer the teeth off the way 55trucker mentions, so I know for a fact that the belt doesn't just have to snap, making a line instead of a loop. If it were valves, if you wanted to just get a set of new heads instead of messing with replacing valves, talk to Ben (sappyse107). I know he has quite a few sets of heads laying around, and he might let a set of stock DOHC heads go at a decent price. These engines aren't as complex as shops make them sound. They are based off of an old pushrod design, they don't have variable valve timing, variable intakes or VTEC. Truth be told, they aren't any more complex then a 3100 as far as technology goes. They are simple engines as far as any DOHC engine goes, shops just don't want to deal with them because they are not what they are used to seeing/working on.

[walterdude]

Check in the "Bargain" section of the WOT site.. Ben actually does have heads listed.. Think some were ready to go,,, CHEAP also!!!
Tom...