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Installing a rear firewall


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I’m looking to fit a rear firewall to OGB (a TR2) as recommended by many.

 

I know this topic has been dealt with or referred to a number of times and there are lots of encouraging comments and some photos of the how the bottom of the firewall is riveted to the floor but I can’t find any photos of how to fix the top.

 

I’m OK with the general principle, aluminium angle to the floor and inside faces of the wheel arches to which the firewall is then riveted but I’m struggling with the detail of how to attach the top of it to the front of the rear deck and seal it.

 

The rear cockpit liner (tank board) is fitted by pushing the top edge into bent strips under the rear deck. This locates the top edge of the liner under the front edge of the rear deck and then a couple of screws into the floor hold it in place. It would be really easy to just pop rivet the firewall to the front edge of the rear deck but it looks as if it gets tricky where the rear deck curves forward at the sides but also the nicely trimmed cockpit liner would have to be mucked about with and it would need self tappers on the top to hold it in place

 

The photo below shows the space to be filled showing the tabs under the rear deck that the cockpit liner locates in (acknowledgements to Revington TR for the photo and who also describe fixing the top edge as being “the tricky bit”!)

 

On the basis of a picture is worth a thousand words, does anyone have any photos of a firewall fixed and sealed to the rear deck and which also allows the cockpit liner to be fitted? Also any recommendations for sealant.

 

Thanks

 

Phil

post-12767-0-37015300-1457430048_thumb.jpg

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Thanks John

 

At one level, any sealant does a job, but upside down, trying to get, or be got, out (heaven forbid) I think a fuel resistant seal is the order of the day.

 

One would hope that there wasn't any fire present, in which case we are, potentially, in the deep, deep poo!

 

Phil

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  • 4 weeks later...

one further query if i may

 

i am told the fuel tank on an early 3a comes out (as it will be on friday) via the passenger compartment rather than boot

 

if a firewall is fitted by rivetting, is the tank then effectively a workshop job to get out

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Firstly well done for recognising the importance of a fuel tank bulkhead seal between yourselves and the fuel.

 

Never fitted a sidescreen car with a firewall only TR4 but looking at your photo could it be possible that the top edge could be bent underneath the rear fibreboard clips and then bent up and secured (pop riveted) to the bottom of the channel which goes around the cockpit ? Any firewall fitment is sealed either with a non tumescent sealer which as explained under fire conditions swells and helps prevent leaks, or as I've always done using a windscreen sealer which is non setting underneath the firewall.

 

The bottom line is it's obviously possible because of the number of sidescreen cars competing in motorsport (banned if no firescreen in place) and somebody with one completed will no doubt advise shortly. However sometimes priorities demand compromises and if securing the firewall means a front edge of cockpit fitment with an small unobtrusive alloy seal over the edge of the rear fibre board screwed to the cockpit front edge then my choice would be for this, (is that area viewable under the hood sticks and hood ? The over the wheel arch area is the most difficult part on any of the TRs and requires a little fiddling and sealing but it can be done, the equivalent of fitting the gearbox back onto the engine with it in the engine bay.

 

I don't know if a cockpit removal is the ONLY way for the fuel tank to come out on an early 3a, from my days of owning one (30+ years ago) I can't remember, butin my view if it won't come out through the boot then removal of the firewall for fuel tank removal and the added safety the firewall gives again is a worthwhile compromise.

 

Mick Richards

Edited by Motorsport Mickey
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John,

 

Thanks for correcting me, yes intumescent, my other spelling means something else entirely ! Never a barny with you John, as if !

 

Mick Richards

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Do I have to rivet (to me this seems to be just more rust opportunity!) Can I not just seal in place with something like CT1 ?

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Up to you as long as it seals and stays in place.

 

Mick Richards

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  • 4 years later...

Phil, as a matter of curiosity, and to add to the history of prior history of OGB 800 ownership, I can tell you that it had a rear firewall installed when Stuart Jenkins owned it.

As it happened, I kept it, though I didn't really appreciate its purpose, initially. I covered it in red vinyl to match the rest of the cockpit. Subsequently, during the (mostly unnecessary) Revington restoration, it was evidently removed and not refitted, quite surprising, really, when you consider it was being set up as a far more competitive motor.

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David

Curious indeed. By rear firewall, do you mean a barrier to prevent petrol from a ruptured petrol tank getting into the cockpit? How was it fitted?

When coming to fit the firewall, which I now have, there were absolutely no signs of a firewall at the rear of the cockpit having been previously fitted. There were no signs of any holes in the floor, inside wheel arches or rear scuttle panel, nor any signs of the gap above the wheel arches having been sealed in any way that would have provides an effective barrier to fuel. In particular it would have been almost impossible to remove all traces of the seal between the inner wheelarches and the top deck and there are no signs of any holes having been filled either from inside the car or from underneath

I have no doubts that that part of the car is original as the original red paint is evident in a number of places. (See photo)

I will leave Neil and the previous owner to comment on whether a restoration was in order and whether the cost thereof was money well spent!

 

Phil

DSC_1647 Rear infill NS 2 V2.jpg

DSC_1654 Rear firewall 2 V2.jpg

DSC_0035 NS front quarter V2.jpg

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1 hour ago, PhilipB said:

David

Curious indeed. By rear firewall, do you mean a barrier to prevent petrol from a ruptured petrol tank getting into the cockpit? How was it fitted?

When coming to fit the firewall, which I now have, there were absolutely no signs of a firewall at the rear of the cockpit having been previously fitted. There were no signs of any holes in the floor, inside wheel arches or rear scuttle panel, nor any signs of the gap above the wheel arches having been sealed in any way that would have provides an effective barrier to fuel. In particular it would have been almost impossible to remove all traces of the seal between the inner wheelarches and the top deck and there are no signs of any holes having been filled either from inside the car or from underneath

I have no doubts that that part of the car is original as the original red paint is evident in a number of places. (See photo)

I will leave Neil and the previous owner to comment on whether a restoration was in order and whether the cost thereof was money well spent!

 

Phil

DSC_1647 Rear infill NS 2 V2.jpg

DSC_1654 Rear firewall 2 V2.jpg

DSC_0035 NS front quarter V2.jpg

Great to see the photos, thank you so much. Actually, the "new" firewall reminds me of the old one, but the shape of the old one was curved, with no sharp angle.

There is an explanation. As I have already said, it is clear that the car benefitted from enhancement, and it is a much better car as a result. The previous oener spent a fortune so that is hardly a surprise. No contention whatsoever, and good for you!

One is still left wondering as to whether it needed a total restoration. Ehatever the case may be, the fact is that OGB 800 was transformed into an effective, reliable, rally car and the 4A engine it already had was expertly tuned indeed.

Who knows? One day, we might swop cars for a spin, wouldn't that be something?

Bearing in mind, of course, that neither KST 277 nor OGB 800 have much in common wirh their respective original specification, as driven by Billy Jack jnr and Heather Fleming. Gone the skinny crossplies, the 4J steel wheels, the original lump and box, not to mention bhp.

As for the original firewall, it was fitted in typical Stuart Jenkins style. It was made of aluminium and shaped to fit and replace the rear panel between cockpit and tank. I upholstered it to make the cockpit look nicer, or so I believed.

It had flanges which were squeeze fitted into the body work. No rivets, no welds. In the event of a fuel spill, of course, fuel would have seeped past. In the event of a fire, it would have, in my opinion, afforded some protection. But certainly, it is surprising that it was scrapped, when it could have been welded, as it was such a perfect fit.

OGB 800 had already had substantial work done you know. A 4A box, clutch plate, A type overdrive, and a 4 or 4A engine, all synch gearbox. The head was perfect, no cracks. I know, I decoked it when it didn't even need it. No matching numbers, as far as I recall. I did have the original chassis plate, but a new one was fitted to the scuttle. Just like KST 277, also delivered to Scotland, Inverness, not Glasgow, and also built in 1955, just a few months later. I like these coincidences very much.

It didn't have the front disc conversion at the time. When the overdrive broke down, I sent it to the main experts at the time. Second time, for free.

So, there's a little more history for you. If you send me a PM with your address, I shall gladly part with the only surviving photo of OGB 800 in my possession, taken when I went to the Lake District. I shall endeavour to get in touch with my old friend John Lehane who probably still has the 1970s ones that came with the car.

As I said, I seriously doubt it was fitted a third chassis. My informed guess is that the front member was replaced or straightened and perhaps it was waxoyled.

The driver side front member might possibly have been affected by my second accident, but consider this: it could hardly have been a serious hit, since I drove all the way from Ireland back to Oxford on my own steam, no rattles, no vibration, no juddering, no weaving, in the steering. See what I mean? And boy, was that Californian chassis, sourced by Glen Hewitt of Protek Engineering nice or what! I should have given young Glen the job to refit it, but it went to someone working around Exeter, or Cornwall, my geography is very poor, a guy who owned one of the TR3 green rally cars. But that is another story, Phil.

Edited by DavidBee
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1 hour ago, RoyM said:

great idea fitting a fire wall, very strange not having one on a car, most manufactures put the boot floor between you and the tank and all you are doing is buying a little time to escape before it all goes up, such a good idea i think i will make one for mine, though it will will have to be removable to get at the tank. thanks for the idea.

Would it work to have self tappers?

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1 hour ago, RoyM said:

great idea fitting a fire wall, very strange not having one on a car, most manufactures put the boot floor between you and the tank and all you are doing is buying a little time to escape before it all goes up, such a good idea i think i will make one for mine, though it will will have to be removable to get at the tank. thanks for the idea.

Roy

My priority was effective sealing of the firewall. Without that, you may as well just leave the rear cockpit panel in place.

If you look at the photos of the one I fitted, there is aluminium angle glued and pop riveted to the floor and inner wheel arches. There is also aluminium angle glued and riveted to the forward facing edge of the rear apron. The final sheet of aluminium was then screwed (with self tappers) to the aluminium angle and sealed with a non setting sealant thus enabling me to get to the fuel tank relatively easily.

The challenge is how to stop fuel from entering the cockpit through the gap between the inner wheel arch, the underneath of the rear apron and the inside of the rear wing should the car go on its side or invert. The way usually recommended is to fibreglass some form of barrier in that space but there are never any clear instructions as to how that is to be achieved. That space is difficult to get to and I wasn't confident that the seal would be 100% effective.

My solution was to close off the access holes to the rear wing fastenings with aluminium sheet, again sealed and screwed to allow access if required. The tricky bit for me was the triangular pieces above the wheel arches which had to follow the curve of the rear apron round the corner and also allow the roll bar to be refitted. Much bashing of aluminium required.

The firewall itself is not structural so small self tappers and pop rivets are sufficient to hold stuff in place allowing the sealants and glue to do their job

The final challenge was refitting the rear cockpit panel. This normally fits underneath the rear apron edge jammed into strips welded underneath that edge. This is clearly shown in the pnoto I attached to my first post, at the top. I solved this by gluing velcro to the firewall and panel which was trimmed at the top to fit.

Phil

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Well, Phil, you set a good example to follow! I shall keep this technique in mind. I wonder how Stuart does it.

Safety First, to cite the MG slogan.

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I did this firewall installation a couple of years ago using the technique of ally angle iron pop riveted to the rear floor and inner wings and slipping the top edge of the firewall into the clips for the hard board at the top.


From memory:

The first thing to do is to make a template with stiff cardboard, then you begin to realise where  the difficult bits are. The bottom and sides are fairly easy (mine is a post 61000). The challenge is at the top, especially above the wings which require much patience and beer. Getting the sheet to follow the curve over the fuel tank takes a bit of time if too, like me, you lack bodywork skills. The original hardboard panel piece can help here to get it right.

Stick some felt on the inside of the firewall to reduce drumming. Finally seal the edges with non hardening mastic, which can fill the gaps you have inevitably left at the top.

On putting the original hardboard panel back I think I lost about a cm of the cockpit space.

I cannot say it is totally fire and fuel proof but I am certain that it gives the occupants a bit more time to get out in event of an incident. 

The disappointing bit is that if you need to get the fuel tank out later on then - as it only comes towards the front - you will have to seal it again !

Finally, I found the pre-cut panel supplied was way too big and had to use the template to recut it. It would have been considerably cheaper to have just bought a piece of ally sheet and started from scratch.

james

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