10 replies to this topic

[The-Wizard]

Clubman with 1293 and 1.5 rockers
1970

When giving throttle i get an high pitch rattle noise from the engine, that i even can feel in my feet trou the thottle pedal.
the noise is not there when i give no throttle.
but if i slowly increase power, the noise comes, but when the carburettor starts making a higher sucktion noise it seems the noise is damped a bit.

I used my camera to record the sound when driving.
the other rattle sound at the end of the movie is the remote bushing thats missing.
http://s168.photobuc...nt=MVI_1115.flv


i've just bought this car, and i dont know all details regarding the engine, but i'll list up what i know:

1293ccm
performance cam
bigger valves, and what looks like high lift rockers.
hs2 carb(!!)
original iron exhaust/inlet manifold.

I know the setup with hs2 and standard exhaust isnt ideal, but i dont think that is was causing the sound. and since i just bought the car i dont want to do alot of work on the car if i the problem is very big. then i dont want the car, and can return it.

anyone got an opinion to what it could be?

sorry about my bad english..

[Cooperman]

It could be 'pinking' which is caused by too much ignition advance. If it is, and you continue to drive it, you may break some piston rings (expensive to repair). Check the ignition timing before driving much further.

[bmcecosse]

Can't tell - but if pinking, retard the ignition and/or use top grade fuel. A single HS2 carb is just ridiculous!

[Sleepy Stu]

Yep get yourself a HIF44 and then get yourself to a rolling road, on a trailor if needs be, to get it all tuned and running sweet!

[The-Wizard]

how many degrees should the timing be? when i checked it, it was WAY beyond 20degrees, now i have taken it down to 11-13 degrees btdc. its an 41030 distributor(25D?)

[Rosslin Racing]

how many degrees should the timing be? when i checked it, it was WAY beyond 20degrees, now i have taken it down to 11-13 degrees btdc. its an 41030 distributor(25D?)

you will find that awnser in your Haynes. other wise I will look later.

I once had an MGB which had a rattle under throttle it turned out to be a brass manifold nut in the inlet which the garage has put or left behind. That took me ages to pin it down.

[The-Wizard]

how many degrees should the timing be? when i checked it, it was WAY beyond 20degrees, now i have taken it down to 11-13 degrees btdc. its an 41030 distributor(25D?)

you will find that awnser in your Haynes. other wise I will look later.

I looked in the Haynes manual(maybe not good enough) but i couldnt find the combination of 41030 and 1275 engine. but i can look again, and probably take it down more, i guess its not a problem for the cause of troubleshooting.

[guesstimator]

What is the compressione ratio?

check the timing at different speeds and to be safe stay on the retarded side of things untill you can get it correctly set up.....but only once you have changed the carb. single hs2 is killing any performance from the other higher spec components.
Check the timing at 2000 rpm keep it below 20 degs, maybe 17-18(always vacuum disconnected)and then rev up to say 4000 and theen 5000 and check full advance and when the advance is all in. maximum advance aroud 28-30 degs. Combined with high octane fuel this should give safe running unitll set up time
(assuming a reasonable compression ratio no higher than 10:1)

[The-Wizard]

What is the compressione ratio?

check the timing at different speeds and to be safe stay on the retarded side of things untill you can get it correctly set up.....but only once you have changed the carb. single hs2 is killing any performance from the other higher spec components.
Check the timing at 2000 rpm keep it below 20 degs, maybe 17-18(always vacuum disconnected)and then rev up to say 4000 and theen 5000 and check full advance and when the advance is all in. maximum advance aroud 28-30 degs. Combined with high octane fuel this should give safe running unitll set up time
(assuming a reasonable compression ratio no higher than 10:1)

Compression is 11.5-12Bar(165-175psi)
I'm going to change the carb and the exhaust. but if the sound is caused by an bearing in the engine or other big "out of car" engine repair. i'm not keeping the car. then ill return it. and get my money back.
if theres an "simple" explanation to the sound, i'll have it repaired and get an refund for my cost of parts and time.

[Cooperman]

Set the timing statically at between 5 deg and 6 deg BTDC if you don't have a strobe. That will then run at acceptable timing without the risk of 'pinking'. However, as 'bmcecosse' says, a 1.25" carb is way too small for a big engine. A single 1.25 is barely adequate for a standard 998.
If it's s throttle-open noise, then it is most likely to be pinking.
A big-end will rattle 'off-load' and a main bearing will 'rumble' rather than rattle. You'll tell the difference yourself.

[bmcecosse]

So - if you have retarded the ignition - and the 'rattle' has gone, all is well. Otherwise - assume it's something more serious and get your money back! If you can.
But you should realise that 90 % of the value of an older Mini is in the condition of the bodyshell etc - the engine/gearbox unit is easily and cheaply exchanged - so do consider ALL the car before rushing back for a refund.

Edited by bmcecosse, 14 August 2009 - 03:44 PM.