Cam Change Woes

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Tig9619

Tig9619

Active Member
Posts
642
Location
Royal Forest of Dean
Evening all,
Put a new crane cam in my 3.9 yesterday. all went well, replaced chain and sprockets while i was there. Put it all together, timings marks perfect.
Started it and it fired and ran for a while but then stopped and wont go at all anymore. Have checked everything twice as in dizzy been in and out and swapped 180 and back again at TDC with no.1 valves closed but to no avail. everything is set up right as far as I can see.
If the cam was out, (which it cant be because i checked more than twice before putting the cover back on) surely the valves would hit the pistons?
Did wonder if it was lack of oil in the lifters as these were new aswell so towed it up the road and it would run but struggled to keep it going as in foot to the floor and only 1000rpm. Oil pressure is good now so not that!
I can normally work thing out but this has me baffled and dont want to take it apart again!
Any ideas from v8 gurus?
Cheers
 
bedding in the cam requires the rev raiesed to 3,000 rpm for 5 min! you could have a air locked follower did you use genuine followers? did you preload the followers? all you can try is some easy start once going rev up for 5 min or else you will have an accelerated cam wear do ot unbedded followers
 
well you didn't say that so would gues you have either the timing out either too advanced or retarded
 
well i am not a novice by any means and have done many timing belts/chains and rebuilt engines and am definate the timing dots were together. not like a belt where you put it on after the sprockets you can get it wrong, sprockets were aligned with the chain on the bench then put on the engine still lined up, rotated several times with dots still perfect.
 
The guy that did my cam swapped the coolant and fuel temp sensor plugs. Thing was impossible to start when hot. Swapped the plugs and its run beautifully since.
 
checked all timing again the other night and it is still spot on. checked it against my other v8 and its the same so theres no reason why it wont go. big spark and lots of fuel it should really.
I am going to take the rocker covers off and turn it over to check if all the rockers are moving properly, could have some empty lifters perhaps. my other engine haad been stood for a long time and the lifters had drained down so i pushed a load of oil through from the prssure switch hole and it went straight away. i might try that actually just incase.
 
well tried the oil trick up through the pump but no luck definately not the lifters. swapped the dizzy for another one out of a runner, air flow meter, ecu, cap, arm, plugs and leads, basically all of my spares, nothing. It will attempt to fire as soon as i push the button but thats it, it then just spins over. Getting loads of fuel cos i can smell it and the plugs are wet.
I dont get it, everything is as it was.
I'm stumped!
 
Cover your bases
1)if you have played with oil pump be sure when you crank oil light goes out-if not then the easy way of priming it is petrolium jelly in either a grease gun or metal cake icing tool. remove oil pressure relief valve blank,spring and plunger. squirt in-must get pump hole and not relief hole, quick filck of starter and another squirt-do this 3 times and then refit pressure relief.
2)compression test it-will tell you if your getting valves opening and closing.
3)after the above=timing next step

I think your issue is oil pressure and while getting some valve lift, not enough
 
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Ok got it running after playing with some more oil, and altering the dizzy. It will run but only rev fairly freely if the timing is somewhere around 30-35 btdc. this is slightly excessive! if i set it back to 6 btdc it will still run but will blowback through the afm and rev very poorly. it is now at about 14 and is no way driveable. as for idling it is non existant it has to be at about 1.5-2k rpm to stay running.
 
sounds like valve timing is incorrect also check ignition leads are fitted correctly-possibly correct sequence but bumped to far on if that makes sense i.e you run out of adjustment

Can't remember how the pulley fits to cam, but if it is original then the new cam out or new pulley marked incorrect. Finally was a vernier pulley recommended with kit?

With out being there-can be difficult to suggest
 
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well this is what i am thinking as the only different thing is the cam. i replaced the sprockets and chain, lifters and rockers all with standard parts. the only thing i can think of is fitting a vernier pulley and dialing in the cam. however i dont want to spend any more money on this engine as it is only to do a few races this season. then i should have rebuilt the bmw engine so that will go back in. i had no hassle with that engine at all!
The cam is a crane powermax, i think its about 280 and suitable for all rover v8 engines (not p38) and buick 215 engines. i would have thought it would be a straight fit. there is no mention on the paperwork that you need anything different to fit it or make your engine run. Its getting quite annoying! I did wonder if the cam was a bit "hot" for a standard 3.9 but having read articles about 3.5's with similar cams it should be fine.
Another thought is that maybe the cam is meant for mechanical lifters and adjustable rockers/pushrods? but surely it would be timed the same whether mechanical or hydraulic.
 
fancy a phone call?
Has to be simple
to any 01 0r 02 number pm me
 
So if you check the valve timing with plastic degree gauge on crank you will know valve opening and closing and overlap. Which you can compare to the cam specs.

Also without teaching you to suck eggs-if your valve timing is incorrect your ignition timing will never work correctly.
Secondly If your leads are incorrect or you have them on in incorrect point distributor will not have correct adjustment.
 
i suspect cam timing due to everything else being correct. i will investigate further with a protractor and see what i come up with. wont be today though but i will keep you posted. if it is out it may be possible to just jump a tooth on the chain and re-mark the sprocket for future reference but it probably wont be that simple!
cheers for your help mate
 
Tig9619 said:
i suspect cam timing due to everything else being correct. i will investigate further with a protractor and see what i come up with. wont be today though but i will keep you posted. if it is out it may be possible to just jump a tooth on the chain and re-mark the sprocket for future reference but it probably wont be that simple!
cheers for your help mate
Click to expand...

no probs out of interest what box are you running with 300hp-auto ?
 
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