Please help.  My 72 510 has been a headache since I bought it two months ago.  When I first got it, it had a blown headgasket and would barely run. It had been  sitting for a couple months. So I proceed to have the head resurfaced, replaced valve seals&guides, replaced timing set and water pump and all gaskets.  Got the car to run and idle, but it would pop and backfire through the carb when given gas. I thought for sure it was a carb  problem so I got a new one. I put a new weber 38/38 on it with a new filter and regulator. Also added a new pcv valve,plugs, wires, cap, rotor points and condenser. Still with this goddamned backfiring. Idle is good though slightly rough. I can really slowly rev it up and get it past slightly off idle where it back fires. Then it seems to rev freely after that with an intermittent backfire here and there but feels strong. Backfires also if I just stab the pedal. Can't drive it though because it backfires as soon as I put a load on it. Funny, also my 70 pl521 pickup is now doing the same thing after sitting for a month or so. I will try to run some good fuel straight out of a can but I somehow don't think it's bad gas. Any ideas?

Noodles,
This is a simple car!
Is the points and condensor OK if stillusing them.
If dual points ? Use only the main one and unplug the second set of points. Make sure condensor is good or grounded.
IF electric ignition. I think your OK. Did you replace a coil with another type or something while this was down? Hopefully NOT.

YOu time or Cam correctly? Maybe its off a tooth.
Set motor to #1 compression stroke. Cam dowel set right and use the bright links on chain set to the dimple on tha cam sprocket and lower sprocket.?

Did you use cam tower shims if head was milled a big about. If only 5 thou I wouldnt worry about it.

A 38/38 Weber on what size motor? Might be to much if a stock L16. But I think should still be OK.

Ck dist shaft wiggle. See if its enough to open the points(if bearing worn) If you still use points.

adjust timming to like 10deg BTDC with a light, maybe thats all that is needed

Sounds like your motor is timmed correctly.
I have had a dist go bad by the bushing wear. The dist shaft would wiggle enough to open the points itself. It would pop.
I also had a condensor go bad also. Lots of back fireing(blew up a muffler)
I also put aanother dist in from a L18 which had a different mount not knowing you need to use the correct mount. It would idle but give it gas it would cut out. Figured it was to far advanced. But correct mount and timmed it using a light fixed that.

also water under the distributor cap will cause back firing and missing.

also I had a dual point dist go bad. I took it out and it was really rough turning it. I think the weights fell off or the springs cam loose. Maybe pull it out and see if it turns ok. Just pull that 10mm head bolt at the timming plate.

Another thing is you still have your ballast resistor(white ceramic block) in place and no changes to the wiring. Sometimes people pull them out for what ever reason. If not installed the points will fry and coil get HOT.


PS the machinst who machine the head should know if the head was milled alot, should have installed head saver shims under the cam towers. I have 2 .015=.030 milled under my towers. IF not Bitch slap him !!!

this is a long shot but make sure your car is charging and getting the right voltage.

if you have a L16 single point distributor(small cap) 68-69 I went with the Pertronix conversion#1741. Best 70$ ever spent. Throw them points in a Museum! But you did say you have a 72. which is a dual point car. So is this really a single point L20(big cap) dist? Sometime people grap dists from cars and forget the mount then get another mount for the dist to bolt to. The L20s had 2 mounts which could work maybe at idle but if it speeds up.

I think your getting close here keep trying. Maybe put a timming light on there and slowly rev it up. Maybe the timming is boucing around then maybe see it on the crank with the light(timming marks)
also dont bolt the distributor mount own at all then adjust the dist and rev it up and see if loads up.

Noah,
The mount is right under the dist. its has 2 bolts the bolt down to the front cover.
That 8mm bolt under the dist is the dist plate adjustment. You could loosen that and move it around to get more timming adjustment.
Then there is the 10mm bolt that will hold the dist plate to the mount.

What you need to do si time the car to like 10deg BTDC. See where the dist timming plate position is. If it at one end or the other and have no more movement. Then maybe as it revs up its goin out of timming.

also be careful when installing another dist if slightly different. Make sure to insatll as a set unless it exactly the same dist. Over the years some get rebuilt with the dist rotor off 180 degs. So take note the position of the rotor when removing and installing. You can move the spark plug wires 180degs

If need more help send email address and some dig photos

So I put the old cam gear back on today because it had better marks than the new aftermarket one. Now the notch on the gear is closer the left side of the groove on the cam plate. I think maybe I just have barely too much slack and thats my problem. Could i install cam tower shims with the head on the car? maybe i could fix it

Well I see what you're saying but I think electrical and carb are good. Now I've realized that the cam notch is almost competely to the left of the oblong groove on the head plate. Even set on #3 because head is milled so much. I was thinking I could just move the cam and gear one tooth over to make the notch line up to the right of the groove but then i would be going even more advanced on the cam timing. I think its overadvanced as it is having the notch lined up almost to the left set on 3. Or I could move the cam and gear back a tooth but then that would move the notch even furthur to the left of the groove. Sorry if that's confusing. What do you think?

YOu know even if its off abit I dont think it would backfire alot. I seen when not adv enough it wouldnt have power(off one or 2 teeth)

PS while setting up TDC on can ck your dist shaft location I will send a photo tommorrow.