Hawk RV8 mount position?

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rhattersley
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Location: Devon

Hawk RV8 mount position?

Post by rhattersley »

Hi all,

For a Hawk 289 with a Rover V8, should the engine mount rubbers be bolted to the front face of the chassis brackets or the rear face? Or doesn't it really matter?

Thanks
Richard
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peterc
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Re: Hawk RV8 mount position?

Post by peterc »

Hi Richard,
Having just checked I can confirm that my engine mounts bolt onto the front of the chassis plates.
I assumed that this was the natural location when lowering the engine and gear box into the car as the assembly moves the last few cms into position.
I fitted mine in 1999 and don’t remember any issues with the gearbox mount aligning with its bolt holes.
Peter C
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rhattersley
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Re: Hawk RV8 mount position?

Post by rhattersley »

Thanks for checking Peter.

I'm glad I asked as my best guess in advance was the rear!
allan horsfall
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Re: Hawk RV8 mount position?

Post by allan horsfall »

Mounting it in front gives you the clearance you need for Gerry's exhaust manifold. Its pretty tight at that point.
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rhattersley
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Re: Hawk RV8 mount position?

Post by rhattersley »

After some long delays for parts I was finally able to drop the engine and LT77 gearbox into place on Sunday. As Peter mentioned, bolting in front of the chassis plates seems to give the correct alignment for the gearbox mounts.

I'm curious what others have used for the gearbox mounting rubbers though. I've got a pair of CRC454A (e.g. https://rimmerbros.com/Item--i-CRC454A) but the threads are too long for the vertical holes in the gearbox, so I've added a couple of packers as shown below.
lt77-mounts.png
This puts the bottom of the output flange about 19 mm above the chassis.
output-flange.png
Alternatively I could trim the end off the thread on the rubbers, which would lower the output flange by a few mm.

Does it matter either way? Am I using completely the wrong rubbers?! :?
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cobraboy
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Re: Hawk RV8 mount position?

Post by cobraboy »

The height of the gearbox flange will affect the angle the face of the flange is to the vertical. In order to avoid driveline vibration in a prop shaft it is accepted that the flanges of the gearbox and diff are to be the same angle from the vertical to within 1 degree.
In order to achieve this the gearbox tail, and diff nose may need shimming up / down to get to the required spec.
I fitted an LT77 into a P6 auto and the flanges were 5 degrees out, there was vibration, after shimming both box and diff the vibration went.
There are other clearance issues to consider though when raising or lowering. Headers, bellhousing to firewall, etc etc.
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peterc
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Re: Hawk RV8 mount position?

Post by peterc »

I can’t get in far enough to take other dimensions as I can’t get the car over the pit right now. I can say my g/box rubbers are approx 35 high and bolted in without any spacers.
I just assumed that as Gerry had made the chassis to suit the SD1 box with a Rover engine so the mounting would be in the correct place. I just bolted the rubbers to the gearbox and dropped it in. Never occurred to me that I would need to adjust anything.
Peter C
PS I have found an invoice with 0454 Mounting so looks like you are correct.
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