So i have a 352 freshly rebuilt from the bottom up. Everything is stock. Except the distributor. Got rid of points and have some drop in ready to run one. Anyways I set the timing at 10 degrees btdc runs at 1200to 1500 idling and backfires ALOT. I've tried 1, 1.5 2, 2.5 turns out with the air mix screws and nothing works. I've also turned the dist. A bit turning it counter clock wise til it idles at 900 to 800 but then it back fires through the carb. When I accelerate its constant back fire. Is this a float problem or still timing. Thank you

 

Check your firing order.

 

Also check that your damper/harmonic balancer ring hasn't shifted due to age

 

Disregard the last as I see you have a fresh build.

 

I didnt buy a new harmonic balancer and I did check the firing order I had 2 and 3 switched around. I'll try firing her up in the morning and see if that did it

 

Don't mess with the carb until you make sure you have the firing order and timing nailed. What cam are you running? Manual or Auto? Those idle numbers sound really high unless you're running a bigger cam, have a vacuum leak, you're in park (with an automatic) or you're still on the fast idle...

-Find TDC on #1. Then back it up so you're at 10* BTDC on the balancer. Then drop in Distributor so rotor is pointing to where the #1 cylinder wire would be. This will get you at ~10 BTDC when you start it.
-Ensure your firing order is correct on the distributor cap with wires to the right cylinders
-Set idle mixture screws at 1.5-2 turns out to start. (if you messed with the curb idle at all i'd recommend getting it back to stock setting so transfer slots = squares)
-Start engine with vac adv plugged. Once warm, using IMS + play with timing to get best vacuum reading at idle. Try not to use the curb idle screw as it will give you hesitation off idle if you have the transfer slots exposed.
-Check mechanical advance timing to make sure it's not too high (~34-36*). Hopefully you have a way to adjust mech advance.
-Hook up vac advance and go for a test drive listening for pinging under all throttle conditions

 

Why?
I just did the top-end of my motor and had the TDC on the front pulley and dropped in a new Dist (electronic/1976) as described above (on #1) and turned the dist a little after drop in before start up and she fired right off.
If I don't install it like you are saying, am I not going to get the advance I need?
Thanks,
JB
P.S. She runs fine but haven't had the chance to road test.

 

My way gets you to 10* BTDC vs your way you are guessing when you "turned the dist a little". Both are fine, one is more precise. I just wanted to outline the entire process as I would do it. On a rebuilt engine with a flat tappet cam and you have to do a break it this helps make sure you're not dancing around with a timing light when you should be doing the break in.

 

He's referring to Bluf100's problem with it not running right and backfiring through the carb.
If yours runs well the way you did it, then it's correct. And you can get advance/retard no matter where the distributor is located. Just how much you can get, or whether it's in the right range is another thing altogether, but you can advance timing from anywhere as long as there is clearance for the distributor body to be twisted.
But I'd say you also got lucky, unless you knew for sure that you had it on TDC of the compression stroke and not the exhaust stroke. Just using the timing marks without verifying TDC on compression is a 50/50 proposition since the timing marks come around twice per cycle. Hence the phrase "getting the distributor 180 degrees out" that you hear so much when an engine won't work after changing things.

To the OP, did you break in your cam? All of this idling and popping and cranking are not good if you did not.
Since you rebuilt the engine (you did it, or someone else did it?) you're probably familiar with the cam break-in procedure? That's where you get the engine started and immediately rev it to at least 2500 rpm and hold it there for at least 20 minutes.
I like to do it for 30 minutes, and I like to vary the rpm between 2500 and 3000, but ask ten cam manufacturers and you get ten variations on that theme. So I choose to err to the high and long side, and have never had an issue.

But if you can't get it to fire and run immediately then you can possibly damage a new flat-tappet cam.
Sorry if you knew all that, but it usually bears repeating for those that don't.

Paul

 

Beat me to it!

Paul

 

Excellent addition to this post/thread.

 

Oh, ok. Thought it was a FE trick I needed to learn.
Thanks,

 

Understood. I just always set to TDC and set the distributor with no problems on the compression stroke and make sure it drops in on the #1 position/cap and also do some distributor cap phasing to make sure if something isn't right.
Just wasn't sure if it was a FE trick.

 

Nah not an FE trick. Can be done on any engine to get initial timing as close to where you want it for start up. Obviously you still need to make sure #1 is on the compression stroke at or approaching TDC. Just the way you describe you drop it in at 0* timing and then twist the distributor to get to some #* BTDC which can be a guess. The way I described will get you to a set # on the first try. there's no right or wrong way just my personal preference. From there you can do all the dialing in and phasing or whatever else you want.

 

Excellent way as well.
Just never heard of it but I like it.
Thanks,
JB