According to this site, an engine should never be rotated backwards. Why?

It does not hurt the motor, I have rotated it backwards by hand a few times to adjust timing and ect.

I guess for belt timing engines it might have the belt skip teeth or something, But that's the only problem I can see happening. Timing chains or gears I cant see that happening

The only thing that will do is break the crankshaft bolt loose,and if that happens your lucky to catch it.It surely would have come loose at some time and ruined your crankshaft.Though this is highly unlikely.

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#1112
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I don't agree for the simple reason that when you use a degree wheel to find TDC on engine You rotate crank in both directions using a stop bolted to block (heads off)or special tool screwed into spark plug hole (heads on). ==== alf

on most engines, its not a real problem, but in some rare cases, an engine with a timing belt, the belt may walk off the pullies if spun backwards, but even then it takes quite a few rotations. I see no harm other then that.

3) As mentioned before, the new engine assembly should NEVER, at any time, or for any reason, be rotated (even a small amount) opposite of its intended direction. This mistake can easily be made while trying to hook up your torque converter in the car, or I've seen mechanics with a wrench on the crankbolt working the engine back and forth to align the spline on stick-shift application installations.

Sounds like bull to me. In small acft you check cylinder compression by finding TDC on each cylinder, pumping in 80 psi, and seeing how much is maintained. You need to rock the prop, thus crank, back and forth to find TDC, so it's impossible to not turn it back and forth. I could see potential problems with a twin overhead cam engine tat is belt driven, especially a V8 OHC engine. I doubt I will turn it backerds, but I would any pushrod motor.

Well, speaking from experience......it sounds like a bunch of bunk to me. Obviously over the years I have worked on a great deal of engines of different designs and configurations. Unless, there is some possiblity that timing component such as a spring might get caught in something, I can think of NO reason not to turn the engine backwards. I've turned hundreds backwards. I would say and warn that the older the engine the less apt I'd be to rotate it backwards due to wear in a particular direction.

However, what happens when the engine backfires and spins backwards? I've had this happen countless times and never seen it cause any problems.

Is there anyone that can explain this? Perhaps some of the newer engines are more sensitive to this.

As for the 2.8.......spin it backwards all you like.

Phil

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GTDude
OVER 25 years GM experience

PURE BS
chevy motors are converted to run backwards and are used in boats, all the time, cams and water pumps, are changed, but stock motors can be had in both right or left hand rotations all most all, twin eng boats, have one of each, so prop tork cancels out!!

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When working on marine engines it is not advisable to rotate the engine oppisite to the way it runs,reason being that the rubber impeller in the raw water pump may be damaged. This is especially true if the impeller is old as they tend to take a set in one direction and the vanes may crack or even break off if forced to flip over the other direction.With that exception i have to agree with everyone else,it wont hurt a thing. My $.02

Not this again!! I actually worked with a couple of VERY old Fairbanks Marine engines that were in tugs that had no reverse garing. Direct drive. When the pilothouse called for astern, you would stop the engine completely-shift a large lever that slid the camshafts. It had a dual direction starter. When you restarted th engine, it would be running in the opposite direction it was running before-IF it started. We hit the pier a lot.

[This message has been edited by maryjane (edited 12-23-2002).]

quote Originally posted by maryjane: Not this again!! I actually worked with a couple of VERY old Fairbanks Marine engines that were in tugs that had no reverse garing. Direct drive. When the pilothouse called for astern, you would stop the engine completely-shift a large lever that slid the camshafts. It had a dual direction starter. When you restarted th engine, it would be running in the opposite direction it was running before-IF it started. We hit the pier a lot. [This message has been edited by maryjane (edited 12-23-2002).]

LOL,LOL,LOL,LOL,LOL,LOL,LOL,LOL I am laughing so hard I can barely see to type!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
I can only image the explitives coming from the wheelhouse and the engine room while this evolution was being performed. I spent the last 25 years around marine operations and never got to see anything like that.

I understand the liberity ships did it this way.

Some timing belt equiped engines will unload the timing belt adjuster and you'll jump the belt crashing the valves.

It's not a problem with any GM engines I know of.

There are all sorts of things you should NOT do on very specific model vehicles. Certain cars WILL grenade the transmissions if held for any length of time over 1500rpms in park, Volvo... things like that. I know one engine that you can lose the cam timing tensioner changing the water pump which is outside the cover... but the tensioner pushes against the case, BMW. Things like DO NOT turn the crank by the crank bolt... only real engine I know this applies to is GM. Their weak bolt will snap off in the crank.

quote Originally posted by Scott-Wa: Things like DO NOT turn the crank by the crank bolt... only real engine I know this applies to is GM. Their weak bolt will snap off in the crank.

Weak? I had to torque that sucker to 110 ft/lbs, plus another 90* on my Q4.

What way can we use to rotate the engine if we need to? Unless you're talking about a bolt other than the balancer pulley to crankshaft bolt..

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Theres a flexplate/flywheel tool, that turns the engine over.

I agree with 99% of the posts, only engines with timing belts cant be turned backwards because the timing belt will come loose or jump a tooth.

The only time i might not want to turn the crankshaft bolt is when the engine is hydrolocked or has been sitting for 10 years. But ive heard people use 5ft breakerbars and got an engine unstuck without breaking the bolt.

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There's absolutely nothing wrong with turning an engine "the wrong way" a little bit to set timing, etc. If you keep rolling it over the wrong way, then the oil pump is going to de-prime the system, since it's pumping into the oil pan when turned backwards. Is this bad? Not really. It's just a few more seconds that the top end has to do without oil when the engine is started.

A reverse rotation kit obviously includes a reverse rotation oil pump.

quote Originally posted by fierospeeder: Theres a flexplate/flywheel tool, that turns the engine over. I agree with 99% of the posts, only engines with timing belts cant be turned backwards because the timing belt will come loose or jump a tooth. The only time i might not want to turn the crankshaft bolt is when the engine is hydrolocked or has been sitting for 10 years. But ive heard people use 5ft breakerbars and got an engine unstuck without breaking the bolt.

Sorry, Small block chevy v-8... gotta be the weakest crank pulley to crank bolt on the market. Not all GM's... just the most popular one ever produced :-0

The only thing I ever heard for not rotating an engine backwards (in the days before timing belts) was that a minor rollback was ok. During an engine build-up, when assembling the crank, bearings, and rods, some people would rotate the engine either way with a speed wrench or breaker bar, to check for resistance. Resistance would tell them they had tightened something too much. Sometimes they hadn't tightened enough.

Because of the tabs on the bearings being on the end toward which the rotation occurs, the bearings would sometimes try to ride out when the engine was rotated in reverse. You could feel the resistance increase when this happened. Occasionally, it would score the crank.

Not rotating the crank backwards was an admonition which usually came from the folks who had to build engines the way I did in the 50's and 60's. Simple hand tools; no torque wrenchs or plastigage. Just experience and the teachings handed down from the elders who repaired their tractors and vehicles under the shade tree, or in the shed on the side of the barn.