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The 100 Forum

BN1 engine vibration

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San Jose, CA, USA   USA
In reply to # 206917 by BobAH100 Agree with everything except scuttle shake, which emerged only with the heavier sixes (as did frame cracks around the engine mounts, which you really don’t see on the Fours, as even these engines are far lighter than the Healey six)....

My BN2 has pretty much the same scuttle shake my BJ8 does (but the BN2 has the original 48-spoke wheels which are probably not particularly well-balanced). My 1965 Mustang convertible also has the same shaking at about 55-60MPH. Some of it, I believe, is due to the lesser structural rigidity of topless cars in general.

Bob

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cpcooper Craig Cooper
Chico, CA, USA   USA
Looks about like mine. I can see some movement at the air cleaners. I’d try to ID and tighten up what’s buzzing.

Trevor Parker Avatar
Trevor Parker Silver Member Trevor Parker W
Sidney, BC, Canada   CAN
1954 Austin-Healey 100 "Healey Beep Beep"
1955 Austin-Healey 100
Hi Dave I had a similar problem and it turned out to be an unbalanced clutch I'm not sure if you mentioned that you had the clutch balanced. Cheers Trevor yes I live pretty close to you I've had might be in one for 40 years you like to come and have a look at your most welcome.

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PAN Avatar
PAN Alwyn Keepence
Ipswich, Queensland, Australia   AUS
G’day Dave,
I notice that there are suggestions about the mounting of the exhaust system, but I don’t see any reference to the section of flexible pipe in front of the muffler. I have done away with the flex because of failures but a rigid pipe can send vibrations through the car. If the flex is deleted then the rubber mount at the front of the muffler should also be deleted as even this is too rigid. Not wanting to have the system without support between the manifold and the mount near the rear spring ‘eye’ I fitted a flexible strap mount at the front of the muffler.
But, as has been pointed out the 100 engine does vibrate, and by modern standards (or even compared to six cylinder Healeys) the vibration is intrusive and to some, uncomfortable.
I have never thought of the original fan belt as a source of vibration but when I changed to a more flexible toothed belt the engine felt more willing and “ free-er”. No need to change the pulleys for this type of belt.
Cheers,
Alwyn

BobAH100 Bob Markovich
Patterson, NY, USA   USA
You can replace the stock flex portion of the exhaust with modern woven stainless as used on fwd Honda’s. Much more robust, yet allows the flex needed to help reduce vibration and prevent the exh system from being unduly stressed.

BobAH100 Bob Markovich
Patterson, NY, USA   USA
Looks perfectly normal to me. Indeed, your engine mounts may be stiffer than normal, which accounts for the vibration.

As I’ve said, addressing crank vibration with (easy) the thinner drive belt and pulleys and (pricier) front vibration damper and light flywheel is all about longevity, rather than annoyance. Looking at the video, my guess is stiff motor mounts transferring engine vibration into the frame, perhaps combined with exhaust system vibration. Aside from replacing the stock exh flex portion with Honda style woven stainless steel, I’d simply live with it.

A final thought: could your drive shaft be out of balance? Again, easily rectified.

petnatcar Avatar
petnatcar Silver Member Peter Carbone
Watertown, NY, USA   USA
Dave,
I had a steel fan blade part company with the rest of the group one day at 4,500 rpm/s and was surprised at
the amount of noticeable engine vibration I experienced immediately.
To the point where the vibration scared the crap out of me so I took the car right home.

I replaced the steel fan with a much lighter plastic asymmetrical fan
which is more efficient and quieter and soaks up less horsepower.

So check the fan.


Attachments:
DSCN2219.JPG    56.8 KB
DSCN2219.JPG

PAN Avatar
PAN Alwyn Keepence
Ipswich, Queensland, Australia   AUS
G’day Peter,
The 100 does not have the made up steel fan found on the six cylinder cars. On a 100 the fan is cast aluminium and looks more like a propeller.
Cheers,
Alwyn

cpcooper Craig Cooper
Chico, CA, USA   USA
And a handsome brute it is.


Attachments:
fan (2).jpg    72.7 KB
fan (2).jpg

davewood Dave Wood
Saanich, BC, Canada   CAN
Hi Everyone,

I loosened the exhaust manifold/pipe from the beginning of the muffler where it is attached via a pretty hard rubber mount and the vibration lessened somewhat. Trevor (member) just lives close by so he showed me his BN2 which had a Honda flexible pipe between the exhaust manifold/pipe and the pipe entering the muffler. There was noticeable movement on the engine side (i.e. gentle rocking) but none of it was transferred to the muffler. So I'm going to try that.

As far as the annoying buzz, a lot of it went away when I discovered the grill was loose to the point where I could lift the bottom out a mm or two - temporary fix for that was some cardboard shoved between the grill and the body shell. That made a big difference.

Trevor connected with me after seeing my postings on this site and I can't tell you all how helpful and encouraging you all have been. Trevor really knows his stuff and he's been generous in sharing his knowledge with me.

I'll keep you posted as to the vibration and how the flexible pipe works.

Cheers and merry Christmas to everyone. Dave

PAN Avatar
PAN Alwyn Keepence
Ipswich, Queensland, Australia   AUS
G’day again Dave,
Have you checked the link that adjusts the fan belt tension? I got so fed up with replacing the link that I got a neoprene link that Denis Welch supplies.
Cheers,
Alwyn



Edited 1 time(s). Last edit at 2018-12-11 02:11 AM by PAN.

davewood Dave Wood
Saanich, BC, Canada   CAN
Hi Alwyn,

No but I'll do so. Thanks for the tip.

Cheers, Dave

zblu Ian R
Perth, WA, Australia   AUS
Does your exhaust have the flex section still installed?

davewood Dave Wood
Saanich, BC, Canada   CAN
Hi - there is something that looks like a flex pipe but it isn't very flexible - not like the Honda flex pipe Trevor showed me.

Cheers, Dave


Attachments:
flex pipe on exhaust01.jpg    24.5 KB
flex pipe on exhaust01.jpg

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