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-   -   engine start up help needed (http://forums.pelicanparts.com/porsche-911-technical-forum/486221-engine-start-up-help-needed.html)

freezing14 07-19-2009 12:55 PM

engine start up help needed
 
hi there, engine is a 914-6 ( real one) it starts fine, now all the cylinder run a bit rich , may be too rich ( before i had 2 lean because of sticking float valve ) now they are all the same

the engine is new, all rebuilt top and bottom the whole nine yard

the issue is really weird ( may be a stupid thing )

because i was hesitating to run a new engine at 6000 rpm to do the 30 degree, it timed idle 900 rpm at TDC

with no load on the engine ( free reving)if if push the throttle slowly it run faser and faster unitl it hits about 3500 rpm, then it cough and spits , and once pass that it seems stable , sounds perfect no suspect noise , even if i rev up to 6000 for breif period

i check the temperature of the pipes and they are not what i would expected , ( all in C)( 123456) 120, 60,60,120,60,60, but i measure just after the heater box with a IR meter

the issue is , if i put a load on it ( like letting the clutch go to go forward) it sound like a diesel, like bad knocking , any advice

thanks in advance

Aurel 07-19-2009 02:34 PM

If you are saying that you set the timing to 30 deg at 900 rpms, then this is your problem right there. The timing value at 900 rpms should be 5 degs. Then, the distributor advances it to 30 degs at 5000 rpms. So, if you are starting at 30 degs, you will end up way too high, and what you are hearing is detonation that will destroy your pistons if you run the engine like that.

It is worse for the engine to run with the advance set so high, than to rev it to 5,000 rpms to set the full advance to the correct value. No need to go to 6,000 rpms, the distributor reaches the maximum before that.

ossiblue 07-19-2009 04:13 PM

I read the post to mean you timed the car at TDC, during idle. If so, you are a bit advanced still as, I believe, the 78 is vacuum retarded at idle by 5 degrees. Still, that means a bit too much advance, and I agree with Aurelein that the sound you hear is detonation--an absolute engine killer. Even if I'm incorrect about the SC timing at idle, your detonation problem needs to be taken care of and in most cases it is a result of an over advanced timing setting.

freezing14 07-20-2009 06:33 PM

engine knocking
 
i did timed the engine 0 degrees at TDC at idle , i double check tonight that i did not time at the 35 degree mark, or some other stupid mistake

as soon as i heard the knocking it let the load go and the knocking stopped , again if it rev freely it sounds fine

a racer friend of mine from the PCA in toronto came over , says the engine sounds perfect when free reving but almost fell down when he heard the knocking , we came to the conclusion that i used the wrong distributor( 0231 121 006) but the weird thing is that the shaft had been machined 0.5 mm down but only on the top parts , it was on a 2.2T i wonder why

both the original dizzy and that one are only centifugal advance no vacuum at all

would there be a compatibility issue with the 914-6 engine ( all stock)


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