Bonnet hinge shims

[ChrisC]

Hi Guys.

I have a series 1 FHC.

Not sure if I have an issue or whether I am fundamentally doing something wrong...

I have just fitted a new set of engine frames (from Etype fabs) and started the bonnet fitting last night. It goes to the paint shop on Friday for final body finishing then paint (exciting times)

Right now to get the bonnet-sill gap even from front to rear - I am needing to insert nearly 1cm of shims on top of the hinge to lift the bonnet up at the front. This seems a lot to me.

I would imagine that once the frames are fully loaded with the engine, suspension and bonnet etc that they would flex slightly upwards and therefore lift the bonnet a little but I dont know by how much.

I am also aware that I can tilt the bonnet frame up slightly using shims between the bonnet frame and the picture frame but my old frame used no shims at all - hence my dilemma on how to do the fitting.

Can you guys take a quick look at your bonnet and give me a feel for the amount of shims you have in place ON TOP of the hinge?

Or perhaps shimming the bonnet with a totally empty shell is simply the wrong way to do things.... any advice would be appreciated.

Cheers

[christopher storey]

Mine has 5 shims on the top of the hinge on each side, I think of the 128 thou thickness, because the total looks to be over 0.5 inches . You do not say whether you have a new bonnet or wings, or new sills. If any of these items have been replaced , then all of these really need to be matched either by altering the bottom line of the wings, or leading the horizontal face and/or front face of the sills, or both . Although in theory putting engine and suspension in can alter the match, in practice on my recent rebuild with the bonnet/sills being fettled before assembly, the fit was just as good after reassembly. Frankly, (provided they are thoroughly familiar with E types) I should leave it to the professionals if you can

[kingzetts]

My '62 OTS has a pretty substantial set of shims in the top of the hinges - I'd guess from memory about 1cm or so. It has new ETF frames, picture frame and bonnet support all fitted last year by CMC, who then fitted the original bonnet and returned the shell to me (sans engine, suspension etc) for me to refit the mechanicals.

I'm pretty sure CMC would have said something if there was any danger of the bonnet alignment changing when the mechanicals were fitted, and I'm not expeocting that to be a problem.

The frames are very stiff as is the main front bulkhead assembly of the tub, and as the weight of the engine is taken by the frames very near the suspension pickup points, which in turn are near the picture frame axis, there will be little or no bending moment created in the frame by those items. The weight of the bonnet when closed is shared between the front attachment points and the locating pins/latches on the firewall, so it is not wholly taken by the front attachments.

I'd say if you can get the bonnet to fit well with shims without needing to use very long hinge bolts, you're good to go.

[ChrisC]

Thanks guys,

I am fitting a new bonnet onto new sills, but I only recently decided to replace the frames just-in-case. so the same bonnet fitted the sills on the old frames but with less shims.

Perhaps I was just being overly cautious about adding more (that and I didnt have any spare...) I will order up a few more and relax a bit or let the body shop do the adjustment before they paint it....

Thanks all

[christopher storey]

[quote="kingzetts"]The weight of the bonnet when closed is shared between the front attachment points and the locating pins/latches on the firewall, so it is not wholly taken by the front attachments.
[quote]

Although it probably does not matter much, I do not agree with this. Only the most minimal amount of weight is taken by the locator pins ( which is why you need to push the bonnet down to engage the locks ) . The centre of gravity of the bonnet is amazingly far forward, at about the front of the front wheel arch, and the rest of the rearward weight component is taken by the horizontal force exerted by the assister springs. In practice the only time this matters is when you come to lift a bonnet

[kingzetts]

You're right, Christopher. I'd forgotten the springs - my mind was dwelling too much on the time the bonnet trapped my fingers between the trailing edge and the scuttle - ouch! New springs fitted since but not yet refitted the bonnet so I have not had the joy of having to push the bonnet down.

I still don't think much will change when the engine goes in.