Bigport, Weird engine sound

carina4age
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Bigport, Weird engine sound

Postby carina4age » Thu Jun 17, 2021 2:35 am

Hey, its me again...

So my bigport has had this weird sound as long i can remember, but today it was different so it made me worried. It happens usually in morning when i go to work. Much worse in winter. This morning was quite warm, something like 12°C.

I start the car up, let it run few minutes and then i go. Every time when i press gas it sounds little bit like diesel. No tick or knock kind of sound. Very hard to describe. It sounds like normal valvetrain, but ten times louder. Sound goes away when idling or cruising. Its only there when i give it some gas.

After a while of driving, when engine is close to the operating temperature , sound goes away.

totta crolla
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Re: Bigport, Weird engine sound

Postby totta crolla » Thu Jun 17, 2021 4:06 am

Could be spark knock.
If the ignition timing is correct the problem may be with a failed engine sensor.
Spark knock can cause engine failure so it may be best to have it diagnosed professionally.

carina4age
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Re: Bigport, Weird engine sound

Postby carina4age » Thu Jun 17, 2021 6:21 am

I managed to get the sound on the video. Its the strange whirring or what ever. Here is link to video https://youtu.be/KVZKWZby_qk

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jondee86
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Re: Bigport, Weird engine sound

Postby jondee86 » Fri Jun 18, 2021 10:49 pm

If you watch the first three minutes or so of the linked video, you will hear the "grunt" for want
of a better word, produced by a typical 4-cylinder engine when the throttle is blipped. It is a
kind of deep throaty sound and is very obvious on engines with open ITB's or carbs. It is mostly
heard when the throttle is opened at low rpm's... under load the engine will make this kind of
sound until the revs build up and then it is replaced by other sounds.

https://www.youtube.com/watch?v=fj_-AE3tZRw

The noise comes from the ITB's/carbs and although it may sound a bit like exhaust noise, it is
produced by pressure waves in the intakes. On a single throttle engine the sound is muffled,
but can still be heard if you run the engine without the intake ducting and resonators.

So just checking if this is the sound you are hearing as I don't hear anything unusual in your video.

Cheers... jondee86
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persists in trying to adapt the world to himself. Therefore, all progress
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oldeskewltoy
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Re: Bigport, Weird engine sound

Postby oldeskewltoy » Sat Jun 19, 2021 7:51 pm

jondee86 wrote: as I don't hear anything unusual in your video.

Cheers... jondee86



nor did I.....


SOME bigports do develop a vacuum leak at the TVIS butterfly shaft bushings, additionally, a few of these cars also tend to have a slight knocking sound also related to the worn TVIS assembly
OST Cyl head porting, - viewtopic.php?f=22&t=300

Building a great engine takes knowing the end... before you begin :ugeek:

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totta crolla
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Re: Bigport, Weird engine sound

Postby totta crolla » Sun Jun 20, 2021 12:43 pm

My TVIS plate makes a definite knocking sound. So l changed the opening rpm :lol:

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jondee86
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Re: Bigport, Weird engine sound

Postby jondee86 » Sun Jun 20, 2021 3:09 pm

The "sound" is reported as being temperature dependent and also that it suddenly
became more noticeable. This tends to point towards some operating condition of
the engine having changed.

Without being able to offer any scientific reason, when I have been fiddling with
engines I have found that changes in fueling and timing sometimes do affect the
induction sound of the engine. This is most apparent when blipping the throttle
from under the hood with the air filter and intake ducting removed.

So probably a good idea to check the cam and ignition timing. Also check that the
exhaust manifold gasket has not developed a leak.

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

carina4age
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Re: Bigport, Weird engine sound

Postby carina4age » Wed Jun 23, 2021 1:31 am

Hey,

last few days the sound has been "normal". It happens when i press throttle slightly, its like valve train sound coming out of intake. Maybe im just listening my engine little bit too closely :D Im still waiting to get my toda cam gears, but when i get them im going to check and adjust my cam timing and then ignition timing. They should arrive soon.

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oldeskewltoy
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Re: Bigport, Weird engine sound

Postby oldeskewltoy » Fri Jun 25, 2021 2:02 pm

carina4age wrote:Hey,

last few days the sound has been "normal". It happens when i press throttle slightly, its like valve train sound coming out of intake. Maybe im just listening my engine little bit too closely :D Im still waiting to get my toda cam gears, but when i get them im going to check and adjust my cam timing and then ignition timing. They should arrive soon.



check your cam clearances too

Image


and if the cams are not OEM - ask, I have quite a few cam cards for different cams that show their clearances.
OST Cyl head porting, - viewtopic.php?f=22&t=300

Building a great engine takes knowing the end... before you begin :ugeek:

Enjoy Life... its the only one you get!