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Longer chrome bolts for dash support / H frame


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I've given up after two or three days wrestling with the H-frame dash support in my GT6 Mk1 - the four bolts simply will not reach the captive nuts in the chassis. I'm using standard 5/16 x 1" as supplied by most suppliers but they're just not long enough, certainly not by the time I add the spring washer and the flat washer. I've trimmed the gearbox tunnel edges severely - so much so that I think the rubber seal will no longer work, in case the lip was holding the frame off the bodywork - but the standard bolts will not bite, despite the captive nuts being cleaned out and rethreaded. I've tried mild steel bolts at 1 & 1/4 inch and they work perfectly, but don't look as good as chrome. 

Anyone have any idea where I can source chrome headed bolts in 5/16 by 1 & 1/4?

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6 hours ago, Colin Lindsay said:

I've given up after two or three days wrestling with the H-frame dash support in my GT6 Mk1 - the four bolts simply will not reach the captive nuts in the chassis. I'm using standard 5/16 x 1" as supplied by most suppliers but they're just not long enough, certainly not by the time I add the spring washer and the flat washer. I've trimmed the gearbox tunnel edges severely - so much so that I think the rubber seal will no longer work, in case the lip was holding the frame off the bodywork - but the standard bolts will not bite, despite the captive nuts being cleaned out and rethreaded. I've tried mild steel bolts at 1 & 1/4 inch and they work perfectly, but don't look as good as chrome. 

Anyone have any idea where I can source chrome headed bolts in 5/16 by 1 & 1/4?

How about these Colin? They have other sizes as well.https://www.ebay.co.uk/itm/UNF-BUTTON-HEAD-SCREWS-ALLEN-KEY-SOCKET-BOLTS-10-1-4-5-16-3-8-A2-STAINLESS-STEEL/360966344358?var=630311766081&hash=item540b454ea6:m:m3eccWMmu1ARdOk-s2XvLOQ

Tony.

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Yes - I had looked at similar, Tony, but the only ones I could find were in the USA. Those would do at a pinch and would look less workmanlike than ordinary mild steel bolts.

The price frightened me until I realised it was for a pack of 50... but I'm seriously considering ordering four right now. I think I'll try inch and a half first, then shorten them as required.

The only other option I had considered was some kind of cap for the mild steel, maybe black plastic push-on caps, to hide the look of them.

Richard - I've done that, using an inch and half bolt with a nut on it to shorten the length, but still the rearmost chrome bolt will not bite. I think the top threads are badly worn and it's only the lower 50% or so that's actually gripping. Another alternative is to use an insert but I'll try longer bolts first.

 

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You need to be carefully as the threaded holes are blind and over long bolts may take the threads out if over tightened.

If you can't get chrome headed bolts then use the standard headed type and paint the heads black and they will blend in with the black carpet.

Dave 

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3 hours ago, dave.vitesse said:

You need to be carefully as the threaded holes are blind and over long bolts may take the threads out if over tightened.

If you can't get chrome headed bolts then use the standard headed type and paint the heads black and they will blend in with the black carpet.

Dave 

 

1 hour ago, Spitfire6 said:

Hi,

 How about a threaded rod or whatever its called, screwed all the way in and then cut with enough showing so that you can add a washer, spring washer &  screw on a Chrome Acorn/Nipple/Scania nut?

Cheers,

Iain.

Tw excellent ideas there; I had just considered helicoiling it to see if that makes any difference with the original bolts; painting the nuts black is something that had never occurred to me but the idea of a threaded rod makes a lot of sense, especially as I can use dome nuts or some other nice looking blind nut. All I need now is about six inches of threaded 5/16 rod... in fact I don't even need that as I can behead four 5/16 bolts and use the threads. Off to the garage I go...

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5 hours ago, dave.vitesse said:

You need to be carefully as the threaded holes are blind and over long bolts may take the threads out if over tightened.

If you can't get chrome headed bolts then use the standard headed type and paint the heads black and they will blend in with the black carpet.

Dave 

My threads were stripped, so I drilled through into the chassis rail and tapped with a metric thread ( can't remember what size) and used threaded bar with chromed dome nuts..  seems to make the H support more supportive.

 

Danny

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Colin 

The way I do it is to use a std 1 1/4  bolt on the back holes and tighten up (with washers if necessary) then fit the chrome bolts in the front holes and tighten.  Take out the std ones and replace with the chrome 

This way the carpet gets squashed and thats all that's needed 

Aidan 

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Funnily enough I never noticed for years that I had three chrome and one unchromed, and two of the chrome ones were loose in the frame. The frame appears to have been drilled out for some reason and the bolt heads were too small. I made up a rectangular plate for each side with two holes for the bolts, then inserted it under the h-frame cover before regluing it again, and this will enable standard chrome bolts to tighten the frame once again. It's very thin, no thicker than washers, but may have raised the unit just high enough so that the old worn threads at the top no longer gripped. I'm going to try threaded rod with dome nuts - four purchased from the Net yesterday but for £1.65 if they don't work it's no big loss. The next step will be helicoils and if that fails, I'll replace the captive nuts in the chassis with new items welded into place and try those. I'll get there - it won't defeat me!

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Just an update to thank the team for all the excellent suggestions; I went with threaded 5/16 rod and stainless dome nuts. I was able to cut the rod to length, insert it into the chassis nuts then slide the carpet and h-frame down over the top before adding washers and nuts. It looks better than it has in years, even if I never really noticed until recently that the bolts didn't actually grip the frame due to wear, and only one was holding it in place. A little thread-lock on the ends will keep it secure for the next few years. Just one more little job complete thanks to the forum.

DSCF6732.jpg.7cd64e55b774c3b495b5aab7ae8a3335.jpg

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