Series 1 bonnet fitting

[keith.brown]

Hi All,
I am almost at the end of fitting a 'new' bonnet to my 65 FHC.
(The 'new' bonnet is made up of some new pannels, some NOS, and some original but repaired.)
So I'm not sure if I have a problem, or just run into a feature of the bonnet, and that is, when the balance springs are fitted the fit against the bulkhead changes. Fitting the springs moves the bonnet forward about 5mm.
Is this to be expected, and if this is not right, any ideas as to what I need to do to remedy it?
Thank you for any thoughts.
Keith

(I previously had a series 2 bonnet fitted, and don't remember seeing this)

[DWW]

Not 100% sure what the problem is yet, are you using shims on the bonnet fixings?

[bitsobrits]

While the balance spring assemblies will no doubt exert force (forward, likely) on the bonnet assembly when closed (this is when the springs are at maximum tension) the bonnet shouldn't move at all unless something is loose or flexing at the hinges or pivot bolts. So something is not right here.

Are you sure it's not the latch guide pins pushing or pulling the bonnet? The bonnet latches should be adjusted so the guide pins are near dead center when closing, and also so it takes just a small amount of force against the firewall top seal to close/latch the bonnet.

[mgcjag]

Also see all similar topics below....Steve

[gtjoey]

Keith, its a 65 that has a series 2 correct?
If so did you know the original owner?
Im asking for a reason....
GTJOEY1314

[keith.brown]

Can I answer these responses individually?
Cant see how, so I will answer all of them here...

I am using shims, I have adjusted with shims to give a good fit against the bulkhead. BUT, that is without the balance springs attached. Attaching them moves the bonnet forward about 5mm.(It did move forward more than this but I didn't have all the fixings done up tight)

I detect no movement in the hinge or hinge bolt.
However I do not have the bonnet latches fitted, as at present the bonnet is a fraction long.
(This is where I am really, I want to trim for length, but not knowing if I should trim for length with springs attached, or removed... I don't want to end up with a gap 5mm more than expected, when I fit the springs. Or a bonnet which is too long if I close it without the springs... especially when it is painted.)

Is it possible to quantify how much the bonnet should move closer to the bulkhead by locking the latches?

(I'm not seeing any links to similar posts)

I know all the previous owners by name at least,(its a UK car), I can see GTJOEY1314 is a member, but cant see his question.
(I don't think it was unusual to fit the later bonnet to older cars as all the older ones went rusty, and why not have one that looks like the newer model !?)

Anybody interested in an original unused ex-factory series 2 bonnet?

[bitsobrits]

I am using shims, I have adjusted with shims to give a good fit against the bulkhead. BUT, that is without the balance springs attached. Attaching them moves the bonnet forward about 5mm.

Something is not right here. When I recently adjusted my bonnet, without latches or springs, it didn't change at all once those items were put in place. The forward pivot bolts on the bonnet should preclude any fore/aft bonnet movement. Have someone push the bonnet closed while you observe the hinge area for flex or movement.

Is it possible to quantify how much the bonnet should move closer to the bulkhead by locking the latches?

Locking the latches should have no impact on bonnet fit. As per my previous post, you should adjust the latches so the pins are centered in their receptacles, i.e. no non axial force on the latch. The only force on the latches should be vertical, caused by the rotation of the 'comma' shaped latching piece under he bonnet pulling the bonnet down against the pressure of the seal at the top edge of the firewall.

[Paul bow]

Hi I had exactly the same problem, my bonnet was an excellent fit, without the balancing springs, all painted and ready for final assembly I couldn’t believe it when the bonnet gaps increased by 5mm, no more movement backwards on the hinges I ended up fabricating a pair out of angle iron and the original pin locator, tbh it was hard to tell from original, I got the extra 5mm by offsetting the locator pin.. I’d like to claim this as my own but infact Monoque metalworks make such an item, I just copied it.. hope that helps

[abowie]

As above, the bonnet is located securely at the front by the brackets and the 2 bolts that hold them into the trapeze. The bonnet can rotate about this point, but should not be able to move fore and aft.

When you say that you have fitted the "springs", I assume that what you mean is that you have attached the whole balance link rather than just installing the springs on the link.

The only thing that springs (LOL) to mind is that when you fit the balance links they are in some way "too long", and they are pushing the front of the bonnet forwards and deforming the area of the bonnet where the hinges are fitted.

From memory this area is a flat section with a tapped plate behind it to accept the hinge bolts. It might be worth checking to see if there is any movement in this area when you close the bonnet with the links attached, or whether there is some reinforcement missing on the inside where the plate is.

Probably also worth ensuring there aren't any cracks in the trapeze.

[keith.brown]

Some really helpful information in here thank you all.
(I have already played the hinge modification game to get more adjustment, I just chopped it with a hacksaw, and got it TIG welded up, picture attached)

[keith.brown]

... Worth saying I made a small jig to keep everything good and square when welding, and it gave an extra 7mm adjustment for length only. (extra height adjustment was not required.

[bitsobrits]

Your modified pivots won't have an impact on the movement you are seeing. Something is flexing, broken, or loose.

Do you have the nylon pivot bushings in place with new 'top hat' pivot bearings?

[keith.brown]

Steve, I think I do, do you mean as seen in the last picture I put up?
When fitted, they are quite tight, ie no play.
Regards,
Keith

[Paul bow]

Keith that’s exactly correct, by altering the pivot you will be able to close that gap, the only problem you may have is the inside frame of the lower valance may touch slightly on the bonnet support frame right at the front. Hard to describe it on here but it’ll be straightforward if it does and how to fix it..

[rubyfloriley]

Hi
Having read all the info on series 1 bonnet moving away from the bulhead when fitting the spring balances 5mm causing a larger than needed gap at the bulkhead. I cant really see how this happens if the hinge bolts are tight no amount of flexing would cause a 5mm increase. im just about to fit my series1 bonnet so questions,

Is it not the case that the bonnet has to be moved forward in order to get the balance spring fixings to line up with captive nuts on the undertray, if so would it not be easier to adjust the hole positions on the balance spring arms.

Assuming remedial action will be needed has anyone come up with an alternative hinge as per the shortened and welded version as pictured on here.

Any more info greatly received to help understand how it happens and the best remadial action.

[Geoff Allam]

Installing the balance mechanisms does cause the gap to increase. I found this out on my own car and in the ensuing discussion on the JL forum was assured by some very competent restorers that this is the case. I was also cautioned not to do the final fit without the weight of the power train or equivalent asthatcan also affect it. I have not reached that stage yet. The choices are to shim the bonnet farther back or add metal to the edge of the bonnet depending on how the fit in other critical areas is.

[rubyfloriley]

Thanks Geoff,
I dont think you can shim back shimming will only increase the gap. What has been done on here is take 5mm out of the width of the hinges, so i asked the question had anyone produced a reduced width hinge.
I will let you know how my fitting goes.

On my series 2 when fitting the bonnet i loaded the engine frames with sandbags to simulate the weight of the engine.

[Chrisx]

Hi Rubyfloriley,

i am at the stage fitting the bonnet to the sills and the Firewall. You mentioned that you placed in some load to simulate the weight oft the engine and transmission and i am am also thinking of doing it. Did you notice any influence to the fitment by the weight?

On the other hand i am thinking that if there is an influence by the weight it must be correctable by changing the shims on the pivot. I do not think that the weight will change position between the sill and firewall.

What was your experience? Any feedback is welcome.

BR
Chris

[bitsobrits]

If you have new engine frames (i.e. no internal corrosion) you shouldn't see an appreciable change in bonnet position with engine in or out. Note that some noted E type restorers do final body fitment and panel gaps when the body/chassis is bare. That should tell you all you need to know.

FWIW, I did a bonnet re-alignment when I had my engine out for front frame replacement, and the bonnet alignment didn't perceptibly change when the engine gearbox was re-installed. Took the better part of a day to get it right as there is a certain amount of tail chasing involved.

[eddiecross]

Apologies if not relevant. Hinge panel was flexing under the pressure from the bonnet springs so I added a reinforcing bracket on both sides in 18 gauge.






Regards
Eddie