248 cam swap problems

[DanThaMan]

So I tried to do the dual 248 cam swap today. I thought I did everything correctly; set cyl. 1 at TDC, mark the dizzy, put the cam in and rotate the sprocket 3 teeth ccw. then I put it all back together, torqued to specs etc. Then I turned it over by hand to check and everything was gravy. So I go to start it and the motor just shakes and kinda fires a little bit, so I pull the dizzy and retard one tooth, nothin, so then I advance it a tooth, still nothin. I don't know what to do now, any ideas?
thank you! I want to get this b**** done tomorrow

[LoserCard]

Sounds like you messed up the timing (mechanically). Possibly by 1 tooth on the idler sprocket. Also take into consideration the 248 cam swap will make your idle kind of rough sounding, like a muscle car. =)

Here is the perfect solution for timing:

1. Set timing to TDC (second notch from the left) with the #1 piston at TDC.
2. Look at the idler sprocket mark for the crank chain. Count to the right how many visible chain links there are including the one on the mark. There should be 5 with one halfway down chain guide.
3. Check the idler sprocket mark for the cam chain. Count counter clockwise (right) up the chain and include the link on the mark. It should be 1(Idler sprocket mark), 2, 3, 4, 5, 6, 7, 8(exhaust cam mark), 9, 10, 11, 12, 13, 14, 15(normal cam mark), 16, 17, 18(dual exhaust setup cam mark). Note that the normal cam would have been at the 15th chain link, but since you retard the chain links it would be at the 18th chain link.

Here is a STOCK picture for your reference.


Oh and I forgot to mention, you distributor should be somewhere near the middle/right for stock timing, if it is in one of the the extremes then your idler sprocket is off.

[DanThaMan]

thanks man, thats some good info! I noticed before I took anything apart, the marks on the stock cam sprockets lined up on the inner chain plates (between the outer chain plates) I thought this was strange, and the chain doesn't have a colored plate like most of em...

[moso]

@ DanThaMan
really sorry to threadjack but i have been looking for this answer for some time now.

@ loosercard
i have had a timing issue ever sence i rebulit my motor. the dizzy twisted all the way to the right. I have checked my timing chain and it seems to be correct but what you say is the intermediary gear is off a tooth, i agree. the question i have is which way do i need to jump a tooth on the intermediary gear to get it back in line? please shoot me a pm.

[DanThaMan]

lol nevermind, I redid my cam twice today..problem ended up being a crossed plug wire....

[SX APPEAL]

Its 4 teeth CCW btw... front lobes should point directly away from each other, like this: