dagah2x

Need a little help guys. I recently replaced a camshaft in a 502mpi. We set the motor to TDC and took the gears off and they were dot to dot like they should be. Put the same cam back (the first one broke the dist gear off) and put back together the same way. Boat ran like crap and the egts got hot even at idle when I set it to 8 degrees BTDC. AFter screwing around for a while I realized the more I advanced it the better it ran. I ended up with base timing of 30 degrees and it will advance to over 50. Now I know this cant be the real timing or the boat wouldnt run but thats what the balancer says. Any ideas where were off? Im 99% the gears are not off a tooth but thats the only thing I can think of that would make the balancer read high? Any sugggestions???

1BIGJIM

iTrader: (1)

Check your timing mark to make sure TDC is TDC. Your Harmonic Balancer might have slipped. Happened to me years ago.

awsomethunder

leave the boat on the trailer,buy 2 30 packs and you can ride with me.someone help this poor guy out,don't want to hear him complain all weekend

SB

iTrader: (1)

Did you use the jumper wire to lock the distributor timing when setting base timing ? If not, you are trying to set it off computer induced timing and where very retarded when at the supposed 8, now seeing 50 you are probably closer.

Anyway - use the jumper wire technique and bring rpm to specified amount. I forget this rpm off hand - someone needs to chime in on this.

mjb

DITTO- To set the timing on an MPI motor you need to use a scan tool to put the engine in service mode or use the jumper wire. Otherwise your timing readings will not make any sense. Do a search here. There are several good posts that go into detail on how to do this.

dagah2x

I did use the jumper plug and its set to 30 degrees base timing with the plug in. I set it at around 2000rpms with the jumper in, Suppose to be 8 but ran like crap. When I take the jumper out then it advances up to 50+. Somethings wierd.

dagah2x

OK I just checked and TDC when my balancer is on TDC # 1 is on TDC so everything there looks OK. The rotor is sitting quite a ways past the #1 wire when im on TDC mainly because I have the distributoe advanced so far, If I set it to 8 degrees it would sit correctly. So why does it not run good at 8 degrees but it does run good at 30 degrees? Any ideas??

mjb

possibly your distributor was installed 180* off or you were set on TDC evacuation...not TDC compression. That might explain why you have to rotate the distributor to extremes just to get it to run.

Wobble

generally speaking, at #1 tdc compression stroke on a chevy v8, rotor should be pointed at #1 cylinder. Both valves should be closed and you should be able to move the rockers side to side.

dagah2x

Its definately set right. When im at TDC the rotor points to #1 and it is on compression stroke. My new though is after speaking with a few EFI pros the motor is in full rich mode for some reason and thats why it runs like crap. It would make sense because the plugs look black. When I turn the timing up it compensates for way too much fuel and brings my egts down and runs better. Kind of a band aid for the real problem. Its going on a scanner today to check all the sensers. Any other ideas would be great....