engine concerns

At the last autox I had a motor event

Just after my first run started, the engine started rattling like crazy. When I came in, the engine wouldn't idle. The engine was slow to turn over but with the help of a jump box I was able to get it retstarted but it sounded like it was missing. I pushed it on the trailer.

With the help of Speedturn we've tried a few things.

I've replaced the spark plugs. The cap and rotor appear to be okay.
The battery was low on charge. It checked okay and since has been recharged.
I've turned the motor over with a 3/8" drive ratchet and it seems okay.
3 wooshes on each rotor. Same needle position on the gauge.
Restarted the motor to check the timing. It appears to hold steady on the mark at around 2k. Couldn't go to 3k because it was rattling like crazy.
Crawled underneath the car and you can hear the motor rattle at idle.
Pulled the inspection plate and checked the aluminum flywheel bolts. All appeared to be okay.

The rattling sounds like it's coming from the rear of the engine.

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Originally posted by Chas.
rattling

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Does it have power? When you rev it does it take forever to rev up? You could of dumped the rear rotor. What your saying seems a lot like the problems I encountered. Even though you said you heard 3 woshes. But saying that the rattling stopped when the apex seal shot out of the exhaust. So maybe I am way off here.

Brent

__________________

84 GSL

I think you're going to have to tear it down and see.

__________________
Erik Ugly doesn't matter as long as it passes tech.

Standing beside the car, the engine sounds almost normal at idle. Blip the throttle a bit and the engine rattles as the rpm drops.

How else to describe the rattle. It's not a tinny sound like sheetmetal. It's much deeper. Maybe clunking is the better word.

All tests were done with the car in neutral. I guess I could try running it while pushing the clutch in.

Power was reduced. I initially thought it was broken apex seal. Power could have been reduced though because of the increased drag on the motor and it wouldn't rev.

If you have a mirror you can try to spy through the leading plug hole to see if you have apex seals. A better way is to pull the exhaust and go through there. Through the exhaust you can actually push on the seal to make sure it springs. Sometimes a seal will break and leave enough there so that a quick glance will show you the remaining piece in place, but if it still springs it's likely in one piece.

I suppose I should've started with this... A deep clunking sound is a bad sign. You're likely looking at a motor that lost an apex seal and lodged it in the rotor face and the sound you hear is the seal hitting the housing as it goes by. At the same time, you say it idles well. That's not what you get with a missing apex seal. If you lose 1 seal you lose compression on 2 combustion chambers...that's like losing 2 cyls on a V6, very rough idle. You also say you lost power. That's typical for a lost apex seal. On the otherhand, if you spun a brg you'd be getting a noise that sounds more like what you described and a reasonable idle, but power loss would not be as significant. The loss of power would be dependant on the failure. Sometimes a brg will release after it spins and be undetectable. Normally it will begin to float, not connected to the rotor or e-shaft with relatively low power loss in a low output motor. At the same time, the alignment tab shears and is pushed out to the stationary gear. A few passes between the gear set will cause enough damage to lock up a motor all by itself.

Losing the input shaft brg in the trans is also noisy and can be misleading unless it is stopped with the engine running, ie in gear and stationary. Simply depressing the clutch may not stop it entirely as the angle the disk should maintain between the flywheel and plate is no longer up to par. It will often cause clutch slippage for similar reasons.

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At the same time, you say it idles well. That's not what you get with a missing apex seal.

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__________________
Erik Ugly doesn't matter as long as it passes tech.

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Out of curiosity, what happens when your stationary gear breaks?

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Well if it's a race engine, your engine builder rubs his hands in glee.

__________________
John Powell

The Man's Prayer:
"I'm a man, but I can change ... if I have to ... I guess."

My car (story and photos) http://www.cardomain.com/memberpage/716903

quote:

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if it's a race engine, your engine builder rubs his hands in glee.

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Yeah, but you shouldn't be able to hear that over the racket (I think) the engine would make.

It's better to be a smartass than a dumbass, huh?

__________________
Erik Ugly doesn't matter as long as it passes tech.

Last edited by flyboy_es on 16.11.2007, 05:07.

quote:

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Originally posted by 83RX796

quote:

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Out of curiosity, what happens when your stationary gear breaks?

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Well if it's a race engine, your engine builder rubs his hands in glee.

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I would be thinking something bearing or gear related.

Time to come apart...

__________________
Shallow Pockets Racing Team - "That blowed up real good"

Life is too short for smooth idles.

quote:

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Originally posted by SPRT
I would be thinking something bearing or gear related.

Time to come apart...

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__________________
John Powell

The Man's Prayer:
"I'm a man, but I can change ... if I have to ... I guess."

My car (story and photos) http://www.cardomain.com/memberpage/716903

Last edited by 83RX796 on 16.11.2007, 21:19.

+ 1

On my stock car it was knocking its brains out. Thought it was the motor but turned out to be the clutch. Only knocked in gear.

Brent

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84 GSL

Is your flywheel lose?

I dont know...Blew the motor soon after that. ITs all got to come apart the winter

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84 GSL