Squeak sound - air leak? (video)

G

Guy 600N

Well-Known Forum User
After replacing the exhaust manifold, exhaust and refurbing the carbs, i've now been gifted with a squeaking noise coming from the engine bay... I have a feeling it's an air leak but any advice would be greatly appreciated.

Also, the engine is revving rather slowly when idling, sounds like it's running off one cylinder too... ideas?

video:
[YOUTUBE]EouWb0KZ2Z4[/YOUTUBE]


thanks in advance!
Guy
 
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Sounds like more than one cyl is not firing, pull plugs to check what ones are good.
Sound quite ill, you could also check compression as well.
 
What Andrew said. I'd also check you've got the plug leads on in the right order, there's fuel to all 3 carbs and they're reasonably in sync.
If there is an air leak, it's a big one, probably at the seal between carb and manifold; you can test it by gently pushing the carbs in and levering them up and down to see if that changes things.
 
Sounds like a dry cam?

Yep check plug leads for firing order too.

You need to check for an air-tight seal with the manifolds too - a common problem.
 
Guy

Im using a Samsung tablet so cant directly run your video, could you let me know where on you tube it is so i can listen
 
aside from anything
Carbs look bolted up to tight, those helical washers (Thackeray washers) shouldnt be completely compressed.
 
SKiddell said:
aside from anything
Carbs look bolted up to tight, those helical washers (Thackeray washers) shouldnt be completely compressed.
Click to expand...

Slightly on a tangent but AFAIK in Japan they don't use the soft mount washers to mount carbs and use the traditional bakelite (ceramic) type gaskets only. So what do they know that we don't? :confused:...
 
I read that you only *need* the soft mounts on 4 cyl engines because of the vibration frequency frothing up the fuel in the float chamber, but 6 cylinder with their better harmonic balance don't need it.

I didn't feel the need to test it out though :)
 
The soft mount have the advantage of having an O ring so they seal better but as mentioned they require the thackery washer to be compressed correctly. The engine in question doesnt seem to have these soft mounts Guy what are you using in between carb and manifold (question asked to try and diagnose possible air leak)

Was the engine running ok before ??

Already mentioned (by Rob)
Air leak aside I would check ignition timing (leads in right order), cam timing.
What else have you dismantled (Ocams Razor)
 
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Looking at the video, it seems it has the MISAB plates fitted (the aluminium plate with o-ring soft mounts you mention Steve. They, along with the Thackary washers look very compressed though, certainly compared to how I have them on my car. Maybe over tightened, leading to sealing issues?
 
Thanks so much for the advice guys. Didn't get back from work until late last night so didn't manage to look into it further - will do today / over the weekend!

Don't think i need a new distributor then? I replaced the leads....definitely put them back in the same order but it wasn't working very well before so maybe they've never been in the right order...?
 
Squeak/screech sound - as I said earlier check that the cam is getting oil.

You wouldn't drive it with the leads wrong but it might run (badly).
 
Taking is to a garage today... Hopefully they can solve the problem. I'm a bit anxious that the cam isn't getting enough Oil, Rob. How would I check that?
 
Guy 600N said:
Taking is to a garage today... Hopefully they can solve the problem. I'm a bit anxious that the cam isn't getting enough Oil, Rob. How would I check that?
Click to expand...

Ask your garage man to take the rocker cover off and check. Opening the oil filler when the engine is running will give a rough check but you need to see if oil is being squirted by the spray-bar all along the length of the camshaft.

I'm speaking from experience here because I've heard that screech.

It's worth checking tappet clearance at the same time.
 
I'd suggest learning to do it yourself - all you need do is take the cam cover off, unplug the spark leads and crank the engine over - you should see all the lobes of the cam getting covered in oil within a few seconds.
 
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