Jump to content

Engine mount


Recommended Posts

They were very popular some years ago and fine if you pre drill a guide hole for the screw to fit into. Make sure the guide hole is wide enough to accommodate the center part of the screw so that the threaded part can cut into the mounting material. 

The downsideof using ST screws is that unless the guide hole is not central to the engine mounting hole then there is a real risk of breaking the engine mount lug.

Provide you get the ST screws central to the engine mounting holes then they will perfectly fine and in my experience have never come loose .

Personally I now drill and tap a thread in a mount or use cap screws and bolts but that's just my choice. 

 

Link to comment
Share on other sites

I've found that even M4 threaded holes in a plastic engine mount will strip after a few tightenings. Self tappers have a much coarser thread which suits softer materials better.

If you use machine screws then you would be advised to use a nut, the problem is that the underside of most plastic engine mounts are tapered which doesn't allow it to be tightened properly without first creating a flat.

Link to comment
Share on other sites

Depending on the mount, I think self tappers are fine, especially into the glass filled nylon mounts with the wedge shaped arms. The only proviso is that I try not to remove said screws once they are in. If I need to adjust anything significantly, I'd rather spend a few quid on a new mount than risk redrilling etc. 

 

Always machine screws and tee nuts or nylocs for fixing the mount to the firewall however! 

 

 

Link to comment
Share on other sites

IMO it's the fit in the engine mounting lugs that is important (3mm for an OS 46LA?), a ST is not necessarily going to be the correct diameter plus the surface of the ST in contact with the lugs is going to be less than a machine screw (if it's a fully threaded one).

Link to comment
Share on other sites

I hadn't thought about it in that way Ron. Interesting. Maybe tapping a thread into the nylon mount would work, otherwise on some mounts, fitting a nut isn't very straightforward, at least to me, as the underside of the mount arms isn't flat. Perhaps I'm being dense. 

 

 

Link to comment
Share on other sites

2 hours ago, Matt Carlton said:

I hadn't thought about it in that way Ron. Interesting. Maybe tapping a thread into the nylon mount would work, otherwise on some mounts, fitting a nut isn't very straightforward, at least to me, as the underside of the mount arms isn't flat. Perhaps I'm being dense. 

 

 

Make it flat.

Link to comment
Share on other sites

@Matt Carltonyou can always put the machine screw in from the bottom of the mount with the nylocs washered against the engine lugs. If you can’t get at the heads then use slotted heads and solder a wire between 2 of the bolts.

 

@Nigel Rthread contact is relevant, a bolt that is too small will allow movement which will cause elongation of the lug holes.

Link to comment
Share on other sites

loads of Irvine 53's (I miss them ?) over 10+ years, all ST using 3.5m OD with a pilot hole and a washer under the head = never had one work loose or move.

When I have used cap heads with nuts on a tapered underside, I have just used a drum sanding disc to create a flat and radius to prevent a stress point. ( as JS1 mentioned)

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...