cammed and missfiring

[e30power7931]

Hi everyone im new to the forum but a few weeks ago myself and a master tech rebuilt a head and put a 272 cam in. The car is missfiring in the lower rpms and really not making the same power it was stock....last sat we installed and adjustable cam gear and advanced the timing 3 teeth...and its still missfiring and not makin power....it has a vacuum leak in the brake booster where the master cylinder meets the booster and we are fixing that tomorrow and even my master tech is stumped at whats going on.....any ideas whould be greatly appreciated :stupid: THANKS!!!

[VacMan]

Sounds like you already found the problem. Vacuum leaks = bad.

[itsbrokeagain]

big cam = low vacuum at idle = injector on-time goes up. Might need a chip too?

[e30power7931]

thanks guys. yeah i got a chip just put it in a few hours ago....but the booster has always been like that and have had a rough idle lol. for example i have never been able to beat my friends e30 while we both had drop in filter and exhaust and it was from a 50 roll...but thats the only spot we can think of for a vacuum leak......we have checked all the others and have found nothing.....im prayin..lol keep our fingers crossed

[winfred]

depending on the cam it'll can get pretty lumpy at idle and i have herd not much good about regrind cams if that is what you have, lotsa stories about them being ground wrong and never running correct
here is what my 2.8 stroker sounds like with a BAS 280* 110 degree separation and 10.6/10.6mm lift
cold start

http://www.youtube.com/watch?v=Ba91_ZVH7Cc

and hot

http://www.youtube.com/watch?v=_VglqzwX4pw

[e30power7931]

yeah its a reground....fixed the break booster/master cylinder vacuum leak....runnin a ittle better... i dont know if im just being ignorant and expect a 272 to make a good difference or what....but my master tech says its acting like it has a HUGE vacuum leak.....for example...when you pull the line out of the brake booster that runs to the throttle body the car "should shut off almost immediatly"but nothing is happenin lol. we have checked all the vacuum lines such as the breather hose from he valve cover and the ones on the throttle body....were pretty stumped....

[dashboardmonkey]

Use a propane torch to check for vacuum leaks. Propane ONLY!!

Open the valve on the torch, do NOT light torch.

Start engine.

Probe around vacuum hoses, gaskets and anywhere else it can leak and if your idle rises you have found a leak.

Hope this helps you find any leaks, if in fact it is a vacuum leak.

Andy

[e30power7931]

thanks! ill give it a try as soon as i can

[SpecM]

you prob wouln't get that much more power only that cam

GL with the vac leak, remember to check the EVAP vac line under the TB

[Dyno4mance]

I would question the cam timing....Why did you/or your mechanic advance the cam timing by 3 teeth? what was the logic behind that move?
I would also question the head rebuild
Are the valves seating?
Are they bent now?
Is the head gasket leaking coolant into the cylinder?
Has the timing belt jumped teeth?
Has the lash on the followers been set correctly?....Is there any clearance at all?
have the injector seals and isolators been checked for correct sealing?
It always concerns me when people use the term MASTER before technician
My 2c

[SpecM]

I would question the cam timing....Why did you/or your mechanic advance the cam timing by 3 teeth? what was the logic behind that move?

...

It always concerns me when people use the term MASTER before technician

really

[napabavarian]

Where did you get the regrind?

[digger]

advancing timing 3 teeth is a massive change i would put it back before troubleshooting any further

[e30power7931]

i got an ireland engineering 272. we had it runnin for 2 weeks without the adjustable cam gear. after installing that it made the car run much better. And yes dyno4mance all of those have been checked.....and my master tech is a good friend of mine and has been a master for over 20 years. he started on e21s and has had every training course you could get.

[e30power7931]

and i dunno if it was teeth per say but it was three little notches on the cam gear....it has little things that look like this.............................................. ...............................................
...R | A
|||||||||| but kinda circular lol