Dave,
There can be a number of reasons for a nocking noise in an engine, rod
bearings, a loose wrist pin in a piston, oil pump, wide valve lash, bent
distributor shaft. Main bearings don't normally cause a nocking noise unless
they are so worn that there is no oil preasure (and in that case it's not the
mains knocking, it's the rods!). I suppose that you could change bearings in
the engine with the engine in the car. I've done it many times in bigger
American cars and trucks, but I'm not sure I'd want to try it laying on my
back, under a Spit.
One thing you could do to try and isolate the noise is get a 'mechanic's
stethescope'. You can buy one for not too much ($15-$20 US) at most discount
parts stores. Use it to find where in the engine the noise is coming from
(high, low, front, back, etc.). A cheaper way to go is just use a long
screwdriver or metal rod, just be very carefull how close you get to moving
parts. When placed up by your ear and then touched to the engine the
screwdriver will transmit the sound and help isolate it.
Good luck!
Thanks,
Paul Mostrom
'77 Spitfire 1500
'80 Ford F-100 (Triumph Support Vehicle)
'Black holes, where God divided by zero......'
-----Original Message-----
From: Dave Chu [mailto:dave@ece.concordia.ca]
Sent: Tuesday, August 31, 1999 3:52 PM
To: Tom Shirley
Cc: Spitfire List
Subject: Re: 1500 dual SU and Knocking noise
In message <00c001bef3e4$02788b20$94ac2ad1@tomshirley>you write:
>
>> The only draw back is, it now does not
>> have as good pick up as before (even with the now AN needle). I guess is
>> because with the .009" jets it is not sucking in loads of fuel like it was
>> doing with the .01" jet. With the car running better and
>> less noisy I now notice a knocking noise from the engine. It is there
>> when the car first starts up and sometime I can hear it while
>accelerating.
>
>Sounds like you've got the mixture too lean. Better check your plugs. If
>they're white or light gray looking, your mixture is too lean and in a worst
>case scenario, you'll burn a piston, probably #2 or #3.
>
I don't think the problem is the mixture. I've check it with my
Colourtune (finally got to use it) and set it a little rich. To
make sure I also pulled the plugs after a drive and found them to
be gray/brown.
However, I did recall awhile back there was a discussion about bearings
making knocking noise when worn. But I don't remember if it was the main
or rod bearings. On the other hand it can be just me looking for more
things to do on the car now that I have the electrical (BTW, thanks for
the wiring diagram) and carb. fixed up.
Dave |\ | | |
Dave Chu \/ \/ | /| | |
Dept. of Elec. & Comp. Eng. |/ | | |
Concordia University Voice:(514)848-3115 Fax:(514)848-2802
1455 de Maisonneuve W. H961 Email:dave@ece.concordia.ca
Montreal, Quebec, Canada H3G 1M8 http://www.ece.concordia.ca/~dave/addr.html
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