thePH03NIX

hey i don't know a whole lot about timing. got a car from somebody and the timing is wayyy off. i was just wondering what a general base timing should be.

the engine is a 306 with aluminum heads, x303 cam, and 10.5 compression

Venomantidote95

10* base works well in every case its conservative can be from 8-16* base though!

.boB

The first question is, why are you sure the timing is way off?

Venomantidote95

Where the hell did you get 10.5 C/R from that head? hope theres trueflats or a small dome piston under them! Sorry off topic! We just put a GT-40 crate engine in my brothers car and it specs out to 9.5!

thePH03NIX

well it runs really hot...and i forget how else it runs lol, i haven't been around the car for a couple weeks since it's not at my house (i don't have a garage at my place) my friend just told me that the way it was running meant the timing was way off.

i'm not 100% sure that it's even 10.5 c/r because that's just what the guy i got the car from said, annnnd he didn't build it either so it's really just a guess.

on a side note, the car does run it's *** off even how ****ty it feels, i raced my friend whose car was about even with my old one, and this one just takes off like a rocket. there's a misfire though and i don't know why, this weekend i'm going to try a compression test on all the cylinders, set the timing so it's all good, and tune the carb...we'll see how it goes from there

.boB

OK, tell your friend to stop there, and actually put a timing light on it. Check base timing, mechanical advance, and vacuum advance. Once you know exactly what it's doing, you'll know - exactly - what needs to change. If anything.

thePH03NIX

okay, regarding the vacuum advance, i have an msd 6al box and the msd coil also.. so i'm guessing that that has a lot to do with the fact that it doesn't want to idle at all when we hook up the vacuum to the carb??

oh, and we got a timing light and set it to 14* but it still misfires, and last night it even shot a spark plug out of the head! i put some octane booster in it just in case 93 isn't enough for the 14* and it seems a little bit better, but i can't ever get rid of the misfire... this weekend i'm going to check the compression on each of the cylinders.. maybe i have a dead cylinder

.boB

14* is fine. Timing is not the issue. You've eliminated that as a problem, now start looking elsewhere. be sure and check the basics - firing order, loose plug wire, bad cap, etc. Even an exprianced mechanic sometimes makes a bone head mistake.

Don't add Octane boosters. Some of them will quickly foul the plugs and give you a misfire. Of course, if you've used them before, that very well could be the issue. Try a new set of Autolite copper core plugs and see what happens.

I'v never seen a spark plug shoot out of a head. I'v heard of it, but (fortunatly) never seen it. Sounds liek you'll need to pull the head to repair the plug hole. I can't imagine what kind of forces you'de need to do that for a healthy head and plug.

thePH03NIX

okay, i've checked the firing order, that's right, pushed on all the plug wires on all the plugs and on the cap to make sure those are good, have a new cap too, but i couldn't change the rotor since the one i bought was different from the one that was on there, it looked like i could have cleaned it up a little bit but i didn't bother with it.

and the octane booster i used was STP, only used it twice, the last time i used it, it seemed like it helped with a misfire so idk... i'll try the autolites next, not sure what heat range though? i guess i'll get them for stock range?


with the spark plug, maybe it was a detonation that caused it?? every once in a while the car would make a loud *POP* sound from the engine, i've never heard a detonation or spark knock so my guess is that was it. and could i maybe helicoil the spark plug in the hole and fix it that way?

thePH03NIX

alright i took the easy (and more expensive) way out, and just took it to a shop, they said all the cylinders were hitting, one was stronger than the rest, and the most likely cause of my misfire is the jets in the carb, i'm guessing it's lean down low and maybe a little bit lean up top, because when the 4 barrels open up there's less of a misfire