Cam Belt change

[J.D.]

I would like to ask your advice on this method of fitting a new cam belt that a friend of mine showed me on hatchback – Fiat Punto 🤔

 

i. Remove spark plugs to allow engine to be turned over easier with a spanner on the crank pulley nut.

ii. Then once all the covers removed around the cam belt, he then cut the cam belt vertically with a Stanley knife all the way round by turning the engine by hand, so that it is in 2 halves but still in place.

iii. Once this is done, he cuts horizontally through the outer half of the old cam belt and removes, exposing one side of the cam wheels etc.

iv. Then he slides the new belt into position up to the old half of cam belt.

v. Then cuts horizontally through the remaining old belt and removes.

vi. Finally slides the new belt fully home.

vii. He then checks the cam belt tensioner and adjusts if needed.

 

He does mark up everything first with paint in case the old belt breaks while he is cutting it. He says it often easier this way than trying to lock everything in place to prevent movement of the pulley’s and engine. It seems to work okay, but can you see any potential problems doing it this way 🤔

 

 

J.D

[oilyhands]

You can get the new belt on without removing the bottom pulley, when you do the bottom sprocket is inclined in some cases to fall off the end of the crank which is great fun, the chances are the old belt may be slightly stretched which may mean the new belt simply wont go on.. otherwise it can hurt. reckon once the bottom pulley is undone I could fit one the conventional way faster...

 

Oily

[J.D.]

May be my post was not very clear, but the bottom pulley or any others are undone. This way just prevents any change in the timing marks and you don't have to lock the cams or anything.

 

J.D

[J.D.]

May be my post was not very clear, but the bottom pulley or any others are NOT undone. This way just prevents any change in the timing marks and you don't have to lock the cams or anything.

 

 

J.D

[Sheds Moderator]

I follow your reasoning and I've heard of this trick. Oily makes the point that if the old belt has stretched then the tensioner will stop you getting the new one on. Having fitted a Rover cambelt following a head replacement I can tell you they are a VERY tight fit even with the tensioner off. I'd do it the conventional way.

[clive powell]

Reminds me of splitting timing chains at the top of a cam pully, using a split link to join new chain to old then just slowly turn it over letting the new chain be pulled into place. 3 people 1 turning 1 feeding 1 keeping the cams tight. 1 hour for V12 Jags bit less for V8 Merks.

Cost off taking the front covers/heads off? £££££££lots of them

[elise_s1]

I think a really clever mod could be to grind off the bottom ali shield (the one integrated with the oil pump cover) and make a removable steel one (firmly bolted at the bottom) to allow an easy change without undoing the pulley bolt. A similar shield could also end a bit closer to the V-belt pulley, giving better protection in case this belt jumps toward the cambelt.

[oilyhands]

I've made exactly that mod before to help accomodate a crank trigger ring on the back of the pulley, it can save some time with the belt but it's still quite tricky to change.

 

Ideally the pulley part of the bottom pulley should be detachable from the cambelt sprocket part, that would make life easier.

 

Oily

[Bare]

Interesting techinque.. but unlike A chain onna Jag.. not of any significant advatage.. the Factory method of replacing a Cam belt is V straightforward.. and it's often 'Clever' to replace the Waterpump at the same time. .. rendering the Shadetree method simply inapprpriate. Besides Cam belts on any reasonable motor are at a minimum 60,000 Mile intervals... rather a long time on yr average 7 :-)

[stevefoster]

Caterham recommend 24000 miles or 5 yrs on the VX XE belt in the manual. The engine was rev limited to 7500 in the ECU Caterham supplied if that is at all relevant.

I did my VX at 5 yrs ~14000 miles.

 

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