Bonnet Bolts

[The Hatter]

My bonnet bolts are in a sad state and need replacing before getting the car to BBWF...

An M8 bolt seems to have the same thread but only goes in a few turns before jamming. I have the same thing going on with my 350i, does everyone else have this? It doesn't seem a very secure way to hold the bonnet on! I've seen the threads about wiring the bolts in and that seems logical, but I'd have though that originally the bolt would go in further and there would be some sort of stop to wind the bolts up to.

Are the original bolts some sort of special tapered thing, or should a standard M8 bolt go in and then come up against some sort of stop to stop it un-doing?

[adam quantrill]

Wow! I've seen better exhaust bolts!

If M8 doesn't work try the imperial equivalent - a 1/2" spanner will fit the head. I always know them as 1/2" bolts but I'm sure there's a "proper" measurement.

[benebob]

Where did you get that bolt, the titanic? Sorry no help here but I think your right about it not being a standard M8

[dixiebabes]

adam quantrill said:

Wow! I've seen better exhaust bolts!

If M8 doesn't work try the imperial equivalent - a 1/2" spanner will fit the head. I always know them as 1/2" bolts but I'm sure there's a "proper" measurement.

Thats the way i do it as well Adam


Dix

[Mr Tank]

Adam is correct its an imperial bolt!

Andy

[dixiebabes]

Take it down to any good hardware store and they will match it up i just have for my manifold bolts and by the way they look an awful similar thread they were 9/16 UNC.

Dix

[Wedg1e]

dixiebabes said:

Take it down to any good hardware store and they will match it up i just have for my manifold bolts and by the way they look an awful similar thread they were 9/16 UNC.

Dix

9/16?! I thought the manifold bolts were 3/8" UNC when I did mine (bought a tap specially).

[dixiebabes]

Wedg1e said:

9/16?! I thought the manifold bolts were 3/8" UNC when I did mine (bought a tap specially).

The heads of the bolts are 9/16 and its definately a UNC thread and like you say its 3/8 Whitworth. All this old money confuses me. Got 16 allen cap heads out of the stores tonight for the manifolds for F all like yeah .

Dix

[Wedg1e]

dixiebabes said:

The heads of the bolts are 9/16 and its definately a UNC thread and like you say its 3/8 Whitworth. All this old money confuses me. Got 16 allen cap heads out of the stores tonight for the manifolds for F all like yeah .

Dix

Ah right, so 3/8" UNC thread and 9/16" spanner... gotcha

[dixiebabes]

Yup your right though Ian its just the way i get through all the old money stuff.

I speak out loud when i talk to myself.

Dix

[dixiebabes]

Mr Tank said:

Adam is correct its an imperial bolt!

Andy

I found out that most of the cars bolts are imperial and of course i have just bought last week a lovely expensive bacho socket set in 80% metric Jeez

Dix

[combine]

Aren't all wedge fixings unc ?

[The Hatter]

I tried an Imperial bolt and it seemed to jam even quicker... The pitch of an M8 is spot on (when you compare the two by holding up to the light. On my cars it seems that everything Jag or Rover is imperial but alot of the rest on the car is metric fine.

There's probably less corrosion on the titanic! Moral is... don't leave your TVR in a field for 15 years! I'll be bringing some examples of what I've had to deal with to BBWF.

[adam quantrill]

Best way to compare threads I have found is to place the bolts head to tail and fit them together like a jigsaw. Or if you have the nut to go with, put that on the other bolt.

I assume the old ones go into the holes just find and don't jam?

I must say I thought they were for 1/2" spannrs on these ones, not 9/16 but I stand corrected.

My original ones are still nice an shinney - testament to 20 years dry storage...

Edited by adam quantrill on Wednesday 29th June 23:44

[leorest]

If you look at the picture you can see a hole in the head of the bolt to allow it to be wired. They do work loose over time. Not too much of a problem on the bonnet but the light pod pivots are the same and these definitely are worth wire locking. The new bolt won't have the cross hole in the head but is easy enough to do yourself.
In my experience most bolts on the Wedge are UNC ...or at least they were to start with.

[Oz2]

I have a great shop/warehouse, old school, all they sell is nuts bolts and bearings of all shapes and sizes, guages and measurments.......as I replace mine I'm putting in stainless steel.

[TVRleigh_BBWR]

combine said:

Aren't all wedge fixings unc ?

Some are unf plus a few are metric

If your 100% in a M8 then the nut may have rusted a little also, hence a new bolt sticking but the old rusted one don't as maybe slightly smaller.

you may want to run a tap though the hole to re-make the thread, also as said if your going to replace the bolts you may as well put stainless ones in. or stainless cap head bolts, these will also be easier to drill.

[cerberatony]

just fitted M8 bolts in mine, like yours mine started to tighten so i used a spare bolt with anti sieze on it then wind it in and out to help clear the thread as i dont have a tap. now all sorted

[taz turbo]

Both '82 wedges Iv'e had were M8 bolts mounting the bonnet, as are the gas strut mounting inserts. IMO most if not all the TVR parts are metric, all the imperial bits relate to the non TVR items, diff, RV8, seatbelts....

Chris.

[dixiebabes]

You ahve opened a can of worms here Martin.

Dix