Paul Woods
24-09-2006, 19:04
I wasnt even aware of this one myself up until last week when tony (fourveesix) told me about it,so many thanks to him for this priceless info.
During a recent V6 engine head rebuild i noticed the exhaust cams gears that interlock with the inlet cam gear are split into two sections,id never noticed this before or never paid enough attention one of the two!
So on further inspection i noticed one half of the exhaust cam gear could be moved and was in fact spring loaded! So i dropped our tone a quick pm to ask if he knew wtf this spring loaded gear was for.And by jove he knew! (hes a good lad y'know!) Apparently this spring loaded half of the exhaust cam gear is a backlash device,or anti backlash device i should say,it makes sure that both edges of the inlet cam gear are in constant mesh with the exhaust cam gear and its there just to reduce the noise of the gears coming into mesh,simple as that....
However! if someone takes the cams out of the heads the backlash gear springs back and out of tension...and to the unknowledgable you would easily rebuild the cams without even knowing there was anything wrong.
Ive no pics at the moment cos my camera is crap at detail,perhaps lodge or someone with exhaust cams at hand could help me here! On one side of the exhaust cam gear you will notice three holes,one of these holes lines up with a threaded hole in the other half of the exhaust cam gear.When you twist the backlash gear into tension you can stick an m6 bolt through this hole and lock the gear under tension.Then when you refit the exhaust cam you take the bolt out and thats the gear fitted and under tension.If you dont do this it will flap about and it will be noisier than normal.
(lodge i think this was half the battle getting your old engine to quieten down in the early days,well that and shims out of tolerance but it certainly didnt help mate!)
So i thought the rest of you v6 builders best know about these backlash gears that must be tensioned during refit.The easiest way is to lock them in place before removal to make it easier.
If nobody else can supply some detailed pics of what im bangin on about i will try to get some uploaded shortly.
Sincere thanks to fourveesix for shedding light on what this does :thumbsup: learning as we go fellas.
During a recent V6 engine head rebuild i noticed the exhaust cams gears that interlock with the inlet cam gear are split into two sections,id never noticed this before or never paid enough attention one of the two!
So on further inspection i noticed one half of the exhaust cam gear could be moved and was in fact spring loaded! So i dropped our tone a quick pm to ask if he knew wtf this spring loaded gear was for.And by jove he knew! (hes a good lad y'know!) Apparently this spring loaded half of the exhaust cam gear is a backlash device,or anti backlash device i should say,it makes sure that both edges of the inlet cam gear are in constant mesh with the exhaust cam gear and its there just to reduce the noise of the gears coming into mesh,simple as that....
However! if someone takes the cams out of the heads the backlash gear springs back and out of tension...and to the unknowledgable you would easily rebuild the cams without even knowing there was anything wrong.
Ive no pics at the moment cos my camera is crap at detail,perhaps lodge or someone with exhaust cams at hand could help me here! On one side of the exhaust cam gear you will notice three holes,one of these holes lines up with a threaded hole in the other half of the exhaust cam gear.When you twist the backlash gear into tension you can stick an m6 bolt through this hole and lock the gear under tension.Then when you refit the exhaust cam you take the bolt out and thats the gear fitted and under tension.If you dont do this it will flap about and it will be noisier than normal.
(lodge i think this was half the battle getting your old engine to quieten down in the early days,well that and shims out of tolerance but it certainly didnt help mate!)
So i thought the rest of you v6 builders best know about these backlash gears that must be tensioned during refit.The easiest way is to lock them in place before removal to make it easier.
If nobody else can supply some detailed pics of what im bangin on about i will try to get some uploaded shortly.
Sincere thanks to fourveesix for shedding light on what this does :thumbsup: learning as we go fellas.