I have a 1973 Mustang that has a freshly rebuilt motor, with rebuilt heads. I put the motor in, and set up the timing. The timing is right, and it turns over smoothly. It has spark to the spark plugs, it has gas. But it won't start! It is blowing flames out the carb. Could it be that someone put a newer Cam from a 302 that has a diff. firing order? Or something like that? I am confused as to what to do.
1973 Mustang WONT RUN Help!!!
- Thread starter SGOODRIC50
- Start date
-
Sponsors (?)
Hmmm, a backfire out the carb or exhaust is 99% timing. other than that its engine damage that you dont have. You probably did this a few times but recheck the timing. also check that the cam is timed right. number 1 piston up on compression stroke (use you finger or a gauge to see when your on the compression stroke )with damper on TDC ( pointer is correct, right )
and dist rotor at cap tower you want #1 to be at or at stock location. If it back fires out the carb your intakes are open and you should move the dist clockwise 1 post and if it backfires out the exhaust move is back 1 post, this only if you cant move the dist enough to get it started or it hits the water neck.
As for a later 5.0 cam installed, yes this can happen. I run a 5.0 cam in my 65 stang 347. You have alot more choices and the pro's say the firing order produces more power. The firing order is 1,3,7,2,6,5,4,8.
You can check for this cam by checking the first 3 cylinders that fire on the compression stroke. This will tell you what cam you have, old style or 5.0 style.
Good luck.
and dist rotor at cap tower you want #1 to be at or at stock location. If it back fires out the carb your intakes are open and you should move the dist clockwise 1 post and if it backfires out the exhaust move is back 1 post, this only if you cant move the dist enough to get it started or it hits the water neck.
As for a later 5.0 cam installed, yes this can happen. I run a 5.0 cam in my 65 stang 347. You have alot more choices and the pro's say the firing order produces more power. The firing order is 1,3,7,2,6,5,4,8.
You can check for this cam by checking the first 3 cylinders that fire on the compression stroke. This will tell you what cam you have, old style or 5.0 style.
Good luck.
Stang_1973
Founding Member
a.vannoy said:
What he said.
BTW, what are the specs on your '73? got any pics? The big body group is growing around here.
I also think the dist. is out 180*
After you've varified the correct timing order.
Mark the dist housing with a felt pen where your #1 spark plug wire connects to the cap. remove cap.
Take #1 spark plug out, bump start or turn it over by hand while your finger is in the #1 spark plug hole (front pass. side) when air has just blown by your finger, and your pointer is pointing at TDC thats TDC.
At that point your rotor should be pointing just at or slightly before the mark you made on the housing.
If it's not, you can remove the dist. and reinstall so it is.
good luck
After you've varified the correct timing order.
Mark the dist housing with a felt pen where your #1 spark plug wire connects to the cap. remove cap.
Take #1 spark plug out, bump start or turn it over by hand while your finger is in the #1 spark plug hole (front pass. side) when air has just blown by your finger, and your pointer is pointing at TDC thats TDC.
At that point your rotor should be pointing just at or slightly before the mark you made on the housing.
If it's not, you can remove the dist. and reinstall so it is.
good luck
Sometimes air will blow past your finger on both the compression stroke and the exhaust stroke, especially on a fresh motor. Have a valve cover off when getting number one to TDC and make sure both valves are closed. If you are 180 off, the exhaust valve should be just closing.
Pakrat
Founding Member
I see where you question the possability of a newer cam from a 302, but did I miss where you say what engine you actually have in your car?
When you say you know it is timed correctly what are you using as a guide, the stock setting? If so the general 6*BTDC is a very enemic setting, espeically if your engine is no longer fully stock. You should really adjust the timing to what YOUR car likes best, not what the manual says, they all are different. (I think my 302 is at something like 16*BTDC FWIW) I'm not even sure how you are verifying it if the car won't start, certainly not with a timing light. If the engine was just rebuilt don't you know what CAM is in it? The CAM should have come with a firing order if different than stock.
What are you running under your distributor cap, Points? Pertronix? What? If points still, having them gapped too open can cause the carb to backfire, at least that was my experience with a set of dual points before I finally converted to a pertronix unit.
When you say you know it is timed correctly what are you using as a guide, the stock setting? If so the general 6*BTDC is a very enemic setting, espeically if your engine is no longer fully stock. You should really adjust the timing to what YOUR car likes best, not what the manual says, they all are different. (I think my 302 is at something like 16*BTDC FWIW) I'm not even sure how you are verifying it if the car won't start, certainly not with a timing light. If the engine was just rebuilt don't you know what CAM is in it? The CAM should have come with a firing order if different than stock.
What are you running under your distributor cap, Points? Pertronix? What? If points still, having them gapped too open can cause the carb to backfire, at least that was my experience with a set of dual points before I finally converted to a pertronix unit.
Similar threads
