Taranis

A friend of mine decide to sell her fully loaded 94 Grand Prix to me for $3,000 - a steal since the engine had only 78K on it. She is transferring to Europe and couldn't keep the car. The body and interior were in perfect shape, and she had all the maintenance paperwork on the car. Everything was done that should've been for the mileage it had.

I figured this would be an awesome buy. I could use the GP for my daily driver and make my RX my "project" - new wheels, LSD upgrade, new paint, window tint, etc....

So, I took the Grand Prix for a test drive up to 110 mph and was really impressed with how it drove and handled for such a big car... plenty of power (DOHC V-6) and comfort to match (I'm 6'6" - and size DOES matter.) Anyway, we decided that I'd give her the $3,000.00 and we'd transfer the title AFTER she was done using the car.

Well, on the day she was to drop the car off with me, she was driving down the road when it just quit.... cold dead right there in the road.

She called me on my cell in a panic wondering what could be wrong.

Now, I'm not as mechanically inclined as some folks on here, but I know there are three essential things that make a car go - Fuel, Air and Spark.

At first I thought it was the alternator, but after she had it towed to my place, I found that wasn't the problem. It was turning over, but wasn't catching, like it wasn't getting fuel - so I assumed it was a fuel pump and scheduled it to go in the shop for a replacement. AAA is a good thing. I had it towed and didn't cost me a cent. Keep in mind that at this point, I still hadn't transferred the title to my name.

A few days go by and I hear nothing from my mechanic. Finally, they call me and give me the worst news - the timing belt broke.

For any of you that know anything about "boingers"... that's a BAD thing. To make a long story short, a Duel-Overhead Cam engine has 4 valves per cylinder.. which makes 24 valves on a V-6 - and she bent every single one of them. After a compression check and a few other things looked into, it's going to cost HER (since I backed WAY off on buying the car) about $3,500 for an engine rebuild. All for one stupid serpentine belt that some dumb-sh*t forgot to replace at 60K.

I love my 7.

Node

iTrader: (1)

muwahaha stupid timing belts
we dont need no stinkin timing belts. We're geometrically timed :-D

No7Yet

Uh, hate to say this, but you were probably responsible for bending those valves, in turning the engine over. Good thing she doesn't know that

Anyway, not all boingers will eat valves when the timing belt breaks. I have a few friends who just run 'em till they break, and worry about it then. Those types of engines are called "non-interference" engines. Basically, instead of using a "dish" faced piston, the compression "pocket" (hell, what's that area called? not up on my boinger terminology) is made up of little detents which correspond to the valve locations. Pretty nifty, if not conducive to great intake swirl patterns.

Oh, and the timing belt isn't on the "front" of the engine (a serpentine belt). The timing belt is actually under the front cover of the engine, and on most FWD cars requires an engine pull to replace. Not cheap. And she's probably getting ripped, since IMO the chances of destroying a bottom end with a bunch of puny valves is small. At worst, she'd have to replace the entire head. Tell her to take it somewhere else and get a second opinion. (also keep in mind that proper valve seating is necessary for a cylinder to build compression. bent valves = leaked compression = "you need a new engine" )

Brandon

Node

iTrader: (1)

bah, we still don't need no stinkin timing belts

1.3 litres
2 rotors
3 moving parts
Ya ain't got a rotor, Ya ain't got a motor

Taranis

You might be right. Honestly, I don't know.

I can tell you that she cranked the engine after it died plenty of times before I got my hands on it. I only tried it twice.

I did ask my mechanic about what you suggest - I thought of it too. He told me (with 30+ years experience under his belt) that cranking a car with a broken timing belt will not ruin the valves because there isn't enough load on the engine. Is he right? Hard to say, but he's kept my 7 on the road without so much as a hiccup.

You ARE right on the second point. the timing belt isn't on the front - it's on the passenger side. This is one of those that doesn't require that the engine be pulled to be replaced.

Originally, they thought the heads would have to be rebuilt or replaced, but after tearing down more of the engine, they discovered more damage to the pistons and cylinder walls. I don't remember the specifics, since after the initial diagnosis I completely lost interest in buying the car. However, I seriously doubt turning the engine over would cause that much damage, because upon cranking it, there would be less load on it that even when the motor was at idle, much less under driving conditions. But again, I have to admit I'm a bit naive when it comes to 1980's + piston engines.

They did mention this one was an interference engine. Hell, I thought pistions were pistons and that was that...

No7Yet

Yeah, well,

bah, we still don't need no stinkin timing belts

1.3 litres
2 pistons
5 moving parts
Ya got more than 2 strokes, Ya got more motor than ya need



Brandon

Node

iTrader: (1)

wtf kinda coked out 2 stroke is that?
2 stroke hayabusa ;-)
personally I would lov ea suzuki quadzilla.
500cc 2 stroke. probly fastest quad there is (yes faster than banshees)
does 1/4 mile faster than most cars, and top speed of 80mph and thats stock. :-D

No7Yet

Granted, I'm sure this guy knows engines, but...

Valve and piston travel are fixed for an engine's given geometry, within tolerances. With the exception of VTEC engines, valves and pistons will always travel the same distance in a given direction during one complete cycle (not rotation, necessarily). That is, engine load has nothing to do with how far "into" the cylinder a valve will travel, nor how far "up" a cylinder will travel - it's all fixed by cam lobe lift and duration and piston stroke, respectively.

Now, emprically, an idling engine may do less damage after a timing belt break, simply because they'll rotate fewer times (or even not one complete time) before stopping. But, if you rotate a cam indepently of the crank (with the crank at TDC) in an interference engine, the valve(s) will contact the piston(s), without exception (try it ).

As for the serpentine belt terminology, yeah, I know, but when people throw around the s word, they're usually referring to drive/accessory belts I'm sure the timing belt for that engine could be serpentine.

Anyway, that's my core dump on boingers for now. I haven't seen the engine, so I can't possibly second-guess this guy. I was just trying to throw my $0.02 into the mix

Brandon
98 Camry V6 - 3.0L four-cam 24V V6
89 RX-7 TII - 1.3 no-cam 0V roundy-rounder

No7Yet

Heh. I didn't even think about how rediculously large a 1.3L 2-stroke would be Oh well, just trying to point out that the number of moving parts in an engine isn't an "advanced-ness" metric.

Hell, AFAIK turbine engines only have ONE moving part (the turbine )

Brandon

Taranis

Very true. I agree 100%. Thanks for pointing that out


Ummm... no thanks!

Thanks for the input. Even when the guy has 30 years experience and whatever else, it's always a good thing to keep 'em on their toes - yet another reason I come to the forum.

Blue Goose

Might I add that cranking the motor over with no timing belt will only cause the valves that are open to interfere, as the cam won't open the other valves if it doesn't turn. So if damage was on all 6 cylinders, it was not your fault...and the timing belt is not serpentine, as it powers only one component, and uses only one side of the belt. Definitely take it for a second opinion though, and if all is good, go yank a set of heads from a junkyard...you coulod probably have the car for $1000 now, plus $200 for the heads at a u-pull-it and a $20 timing belt? Time to get your fingernails greasy!

Felix Wankel

Where do you get 5 moving parts?

I thought Grand Prixs ran timing chains, not belts. Unless it has that horrid 3.4L DOHC engine.

hurddawg

Those are called valve reliefs. Also all Mazda piston engines, that I'm aware of, are non-interference.

<edit>
You can have dished pistons with valve reliefs...my 626 (F2/F2T engines)is that way.

No7Yet

1 crankshaft
2 pistons
+ 2 piston rods
---------------------
5 moving parts in a two-stroke engine. Node already called me on the rediculousness of having a 1.3 litre 2-stroke tho :p

tesla042

I'm SURE you can get a used engine for MUCH less than 3500$.. There's your little project--putting that engine in!