11 replies to this topic

[jeroendewil]

Hello,

 

a couple weeks ago i bought a 1275gt with a cooper s (thin flange ) engine in it. The car was used for slalom in the 80's and had been standing still verry long so was opened for inspection. When removing the rods i discovered this : 

 

 

 

 

Does onyone have an idea what it is for? is this crank cross drilled?  It is an AEG480 casting.

 

thanks!!

[MIGLIACARS]

do u want to sell the engine

[jeroendewil]

no sorry it's not for sale 

[cian]

Yep its cross drilled, they plug the factory drilling

[jeroendewil]

is there a better way to plug these? 

[cian]

Not sure, i just got an med crank and they plugged it in the same way

[carbon]

Jeroen - the brass plug with the small hole through it is fitted to the cross-drilled cranks, and the idea to help reduce the amount of oil going to the big-ends at high crank rpm (centrifugal effect).

 

There should be another one or two drillings for all of the big-ends without the plug, these are typically at about 120 degrees to the plugged drilling.

 

Would suggest leaving all in place as is. If you are going to take out then make sure you replace with identical type brass plug with small 'bleed' hole as you don't want these working loose...

[jeroendewil]

Thanks for the answers! so this is original then? 

 

The problem is that it seems that they have come loose they made a big scratch in the crank bearings.

[carbon]

Taking a closer look at the pictures I can now see the problem with your old plugs moving...

 

Just to check, do your old plugs have a small (about 1.5mm) drilling going all the way through them?

 

You will need to drift these old plugs out (should be easy) and get some new brass plugs. Would also be worth checking the o/d of the old plugs, and make sure the new ones are slightly larger outside diameter and give a much more more permanent fit.

[Artful Dodger]

remove these, tap the hole out and fit a grubscrew in there with a bit of locktite in there for good measure!   simples

[jeroendewil]

thanks for the answer! is it possible to tap thread ? Tha crank is hardened so this may be difficult

[dklawson]

Do not tap the crank.  Threads are stress concentrators.  

 

Press fit the plugs or... as daft as it sounds, degrease the plugs and crossdrillings and put the plugs back in with a bit of Loctite-680 on them.  Loctite-680 (green) is used to assemble things like bearings to shafts.  It is permanent, hard, and very tough.  It will fill the gaps between your existing plugs and crossdrillings without introducing any stress concentration.  If you cannot find Loctite-680, check with your local bearing distributor and ask them what similar products they have.  This is NOT the same type of Loctite as -242 (blue) or -222 (purple) used on screws.  It is however, a bit similar to Loctite-271 (red) which is very hard and also considered permanent.