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bad/rough idle after installing cams

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i recently finished installing a set of bc 264 cams and now having some idle issues. it sits around 850rpms at idle, but the motor seems to vibrate very bad and the boost vaccum seems to fluctuate sporadically between 6-7.5, which it didn't do prior to installing the cams. at times, it also feels like the engine is bogging down and about to die. during my test drive, when the car is in motion, it pulls strong and feels fine, but when slowing down or coming to a stop, the car died a couple times. any suggestions on what could be wrong??? thanks for any help!!
 
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It sounds like your timming chain/crank pully's are one tooth out. Did you mark your timming chain and pullys before you took the stock cams out?
 

subzero

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have you a power fc ?? or after market ecu ??

i was messing with my fc today and moving fiddling with the rev options and ended up with a dreadful idle, fluctuating badly. might be your problem .

but if there agressive cams , there supposed to be like that aren't they at idle.
 
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StarletRick

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with 264s you should probably aim the idle closer to 1000 rpm.

850 is cutting it a bit close.
 
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Timing off a tooth and it should be very lazy. Happened to me as well, took me three times to get it right, trick is to start from the exhaust side and ensure the chain is taught and line that up good and then count the dowels and then the intake markings and then install the bitch of a tensioner and release it ensuring that everything is fine. Then you should be able to time the engine properly after that. Of course all of this while no. 1 is a TDC.
 
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It sounds like your timming chain/crank pully's are one tooth out. Did you mark your timming chain and pullys before you took the stock cams out?
is it possible for the timeing chain to be off if i never removed the cam sprockets? when i did the install, i aligned the sprockets to TDC and the timing mark at 0 degrees (2nd notch). i then released the tensioner and pulled the cams, leaving the sprockets in place. after i replaced the cams, i checked the chain, sprockets, and timing mark with everything lining up. is there a way to verify that the chain is off a tooth without having to pull the cover back off? i think that was the biggest pain...15 bolts!!!
 
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You need to ensure that no.1 piston is at TDC (top dead center). Remove the coil pack, and no.1 spark plug, get something long like a screwdriver and rest it in and manually rotate the engine via the crank pulley and ensuring the piston is at TDC. Once that is set then work from there.
 
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with 264s you should probably aim the idle closer to 1000 rpm.

850 is cutting it a bit close.
with the new cams in, it does feel like 850 is a bit too low... is raising the idle to 1000 rpm the norm for 264 cams? the reason i ask is because i don't want to adjust the idle higher, just to cover up the symptoms to another problem.
 
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It's fairly normal yes.

Longer duration cams will hold the valves open longer. You begin to get some overlap and at lower revs this allows some loss of compression as you're way off the point where that little overlap works in your favour. Thus you need to up the tick over a bit to get it smooth. When you're on full chat that overlap works to 'venturi' the gas out of the combustion chamber quicker which helps increase power.

If you've not got an after market ECU or any way of mapping yours then they wont benefit you, probably worse if anything.
 
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Did you replace the rockers/shims/spacers too?
Good question and also, if not did you mark the cam caps so that you know which one goes where? Cam caps are specific if I can remember as clearances are minutely different.
 
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Matt_S

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Yeh the cam caps are also in effect the bearings, so you need to make sure you put them back on where they came off - theyre line honed specifically on each head.
 
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Matt_S

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THese things shouldnt affect the idle by the way - I was just asking, as if you didnt you could have long term issues :wack: Same with the caps :wack:
 
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It's fairly normal yes.

Longer duration cams will hold the valves open longer. You begin to get some overlap and at lower revs this allows some loss of compression as you're way off the point where that little overlap works in your favour. Thus you need to up the tick over a bit to get it smooth. When you're on full chat that overlap works to 'venturi' the gas out of the combustion chamber quicker which helps increase power.

If you've not got an after market ECU or any way of mapping yours then they wont benefit you, probably worse if anything.
I'm still running the stock ECU, i've been looking into getting a nistune sometime in the next few months or so..
 
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Good question and also, if not did you mark the cam caps so that you know which one goes where? Cam caps are specific if I can remember as clearances are minutely different.
i didn't replace any of the rockers or shims, the only thing i changed out were the cams. I'm 100% sure that all the cam caps were put back on in the correct order, as i had everything labeled.

i'm gonna try to raise the idle as suggested. if it's still giving me problems, i'll further look into the timing/chain.

Tons of thanks for all the support!
 
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Matt_S

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Mate you should have really replaced the rockers at least! These would have worn to the old std cams.
As for idle, try using the IAC to up the revs a little.
 
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Mate you should have really replaced the rockers at least! These would have worn to the old std cams.
As for idle, try using the IAC to up the revs a little.
Thanks for the tip! I guess it's time to start sourcing a set of new rocker arms!
 

DeanS15

My car is so clean you could eat off it.
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i'm running tomei 256 poncams with 11.5mm lift and tomei valve springs, i didnt replace the rocker arms and havent any wear on the new cam lobes through not doing so. you really do need setting up to get the benefit of them, once sorted if mines anything to go by then when cold the idle will be smooth - approx 1100rpm - but when warm you can hear a bit of miss. this shouldnt affect performance in a negative way but as has already been said you will notice the benefits of cams, but mostly when you are travelling at high speeds. before my car would run out of puff higher up the rev range but the other night (on a private road;)) i was pulling 145mph in sixth, with what seemed like no effort at all and plenty left in reserve and it felt completely different to how it did before. this is on a 2871r. just made me want to take it somewhere and find out how fast it actually is capable of:D

i highly recommend these cams to release more power up top as they dont really have any negative affects other than the poor idle, which most people think is cool anyway for some reason....
 
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Matt_S

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TBH dean, the poncams are so mild I doubt youd get any idle problems - not to the extent this guy is anyway.
 
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