Engine/bodywork vibration

[gouldsborough7]

Hi Guys
Noticed that this section was lacking in new enquiries, and vibration is beginning to bother me with my Hunter. So here goes.........

My Hunter was factory-built in 1998 based on a 2 litre Sierra with DOHC and electronic ignition (no distributor). A while ago, the engine was suffering from a flat-spot at 1500-2000rpm, which I cured by fitting an adjustable fuel-pressure regulator set at 40psi - a good mod at fairly low cost (£40 all in). However, I am still left with engine/bodywork vibration at low revs, particularly when pulling up a slight gradient e.g. my driveway.

I suppose with thin aluminium side-panels each held on by 4 tiny allen screws, and bonnet (same metal) in 2 halves held in place by 2 simple locks, it is not altogether surprising that it all vibrates. However, on the move the engine is sweet-as-a-nut, and the vibration is neglible.

The engine does not visibly move on its mountings, and the exhaust system is well strapped in place. I don't think there is anything wrong with the way the engine runs. So, is there an area that I can beef-up to resolve this vibration problem? Your thoughts would be appreciated.

Cheers
Mike

[Mike]

Re: Engine/bodywork vibration

Mike
I plan to fit very thin neoprene rubber strips in all my body joints on assembly. Available for Woolies, very cheap, and should remove the sond of metal on metal vibration.

[h_m_cumming]

Re: Engine/bodywork vibration

When I built my Roadster I bonded all the body panels with a rubber compound as well as bolting and it's been as quiet as can be. Should be fun if I have to take any apart 'though.

[chris_cussen]

Re: Engine/bodywork vibration

I have something like this http://www.cbsonline.co.uk/product/10_x_5mm_Rubber_U_Channel_For_2mm_Panels_TRMU2 along the front and rear edges of the bonnet, and use these IVA compliant bonnet catches http://www.cbsonline.co.uk/product/Rubber_Bonnet_Catch_BNLCH that pull everything down nice and tight. No rattles. Wouldn't recommend bonding it though:- Sooner or later you will have to remove the panels.

[gouldsborough7]

Re: Engine/bodywork vibration

Thanks guys
With a fully built car, I think there will be problems with rubber compounds etc. I am not sure about the appearance of the IVA compliant bonnet catches, but will investigate them though.

Re the bonnet halves: I could attach sound-deadening fabric to the underside of the bonnet - can anybody recommend a suitable version? Obviously I don't want to have a fabric coming unglued and dropping down on top of the engine.

Re the side-panels: I was thinking along the lines of beefing them up in some way. Of course I cannot fit sound deadening material because of the vent slots. Maybe I could stiffen the panels with metal strips, or perhaps fit some bars across the top of the engine attached to both panels? Any thoughts?


Cheers
Mike

[gouldsborough7]

Re: Engine/bodywork vibration

Can anyone recommend a source/type of under-bonnet insulation material?
I've checked out eBay, and there are all types of bewildering versions. I have in mind to go for a self-adhesive heavy duty fire-retardant sponge, with perhaps a tin-foil finish. What do you think?

Cheers
Mike

[chris_cussen]

Re: Engine/bodywork vibration

Hi Mike,
I tried some self adhesive stuff under the bonnet on my last kit car (Spartan Treka)and the heat from the engine made it fall off. Didn't help that in doing so it draped itself around the air filter and made the engine stop.
Chris

[gouldsborough7]

Re: Engine/bodywork vibration

Oh dear!
Don't want to follow your example.
Cheers
Mike

[djj_engineer]

Re: Engine/bodywork vibration

Perhaps your engine is too firmly held by the mountings.
The panels must be vibrated by the engine, so how does the vibration get transmitted form the engine to the panels?

[greyV8pete]

Re: Engine/bodywork vibration

Just a long shot Mike. Does the engine have a standard flywheel or by chance has it been fitted with a lightened one? The latter will need a faster tickover and will tend to vibrate more at low revs as there is less mass to dampen out the energy pulses as the cylinders fire. Has the engine always vibrated? Peter.