This is a first for me and I am scratching my head right now . I am good at figuring out the problems but I m not doing good with this one . I have a Ford 302 with a points distributor , coil , 2 bbl carb . It's on an engine stand . I have the distributor hooked up to an on/off switch with a push ****on for the starter . I have a one wire alt hooked straight up to the battery side of the solenoid . I have a resistor hooked up between the battery and the hot (+) side of the coil . that also is on a on/off switch . Engine has headers and mufflers . The engine came to me as a job NO RUNNING ! Had no carb , exhaust or alt . the balancer was off as well . No plug wire . He had a box full of parts and I picked out what I could use and bought the rest . This is what was replaced with NEW parts ! Points Rotor Condenser distributor cap spark plugs one wire Alt gauges switches all wiring is new oil filter new fuel pump I also had to take the top off the carb because the float got stuck and had the needle valve closed so I got no fuel to the carb . The engine will start up no problem and runs . I have set the points , carb and the distributor I had to set by ear since the timing marks don't line up due due to the wrong balancer being used . It's still a 28 oz balancer ! The engine has been apart before from the signs of different gaskets that are not stock and signs of silicon being used . The engine backfire through the exhaust ONLY and not all the time either ! Backfire through the driver side on the number 5-6-7-8 cylinders . The p***engers side fire OK I think and gets hot on the headers and muffler like normal . NOW the drivers side exhaust is cool and the exhaust g***es are cool coming out the exhaust ! Doesn't matter where the distributor is set , it still back fires out the exhaust and not the carb . I used a stethoscope to listen to each header tube at the heads to see which exhaust valves the backfire is coming from . I hear the backfire in the number 6 & 7 cylinders . I am open to any all all comments or suggestions on this problem ! Jim
You sure you have the plug wires in the correct plugs? You need to get the correct balancer on to make a good timing setup.
I'd suggest checking for mechanical problems as well (besides the previous suggestion) by doing a compression check, and a running vacuum check. Flat cams, bad valve sealing can put a lot of unburned gas in the exhaust. Is it a backfire like a gun going off, or an occasional pop-pop?
I second the mechanical issue vote. Firing order and timing plus if you don't know the history on the engine, check timing chain integrity. I've had one jump due to over stretching from age. Broke 2 rockers and kicked off 2 rockers. Ran ok but popped a bit and no power. Don't you love the frustration Jim? Ed
The intake manifold will be a "cross H" design - designed so that every other cylinder fires off the other "H". ***uming the firing order you are using matches the cam - it could be excessive fuel fom one barrel of the carb (flooding one side of the manifold only) - or maybe a stuck exhaust valve. Take a look at the four plugs fed by one side - versus the four plugs fed by the other side.
I also ran the same post on the main HAMB . I have 2 reply so far . I also saw another post with the same problem . About 90% of the replys said it's an exhaust leak . They tell me that the cold air is being ****ed up into the headers and causing the cold air to mix with the hot air and cause an explosion . It sounds like a shotgun going off ! I did have the engine running with stock manifolds and had no problem at all . It has to be the headers . I will have to try new gaskets and go from there . I have used headers since the late 1960's and this was the first time I ever had a problem like this with headers . Thanks for the help and suggestions so far ! I am still open to all suggestions until I get this thing fixed ! Thanks , Jim
Presuming the firing order is correct on the wires, does the cylinder drop out when you pull the spark plug wire? I'd also check compression on the two suspect cylinders. An idle vacuum reading would also be helpful. If you get no change with the wire pulled on the cylinder, but the other two checks are OK, I'd look for bad exhaust valves / seats / guides in the bad cylinders.
If you have a cooling system hooked up, try this. Warm it up, then at about 2000 RPMs slowley pour about a pint or more of water down the carb. Not enough to stop the motor, but it will clean the backs of the valves. Then do a compression check. You may also need to adjust the valves on that side, it make have sticky valves or lifters.
It is a possibility that someone used a 351W cam which will give the 302 the same firing order as a later 302/5.0 H.O. this is not uncommon, supposedly Ford did this to take stress off the front journals. You might try using a 351W firing order and see what happens.
jeff you beat me to it. also along with ford doing it on some engines i alot of times put a 351w in a 302 . and if someone was to not know it down the road theyd be cornfused unless they knew you could do it .
When I first got it running , it ran just fine . Ran smooth and great with no problems . Since then , the only things I did was change the exhaust to headers , add an alt and hook up the tach and gauges . THAT'S IT ! So I am going with the headers leaking and ****ing cold air in the exhaust causing the backfire , which I know they do leak . That's less than $20 to find out ! The firing order is correct ! I double checked that . I even change the plugs wires just in case . I know the coil wire was leaking since that damn thing bit the hell out of me and using a 40,000 volt coil ! Damn that really hurt ! The old coils were much easier on pain that the new high performance coils we use now . If no one has had the pleasure yet , brace yourself if you are using those big high voltage coils ! It doesn't tickle like the stock coils do . These new coils really hit you hard and there is no tickle at all either ! You will know it when it happens to you ! The jolt goes clean to your chest and neck area ! Then your arm jumps a little for a while along with not holding onto something in your hand for a few minutes too ! Anyway thanks for the help and I will let you known what happens when i get new header gaskets installed . Jim Jim
I pulled the header off last night and could see on the old gaskets where the headers were leaking . I am just going to get new gaskets since the old ones were leaking so badly . I also found 3 bolts that came loose . They bolts will get RED Loc tight when they go back in . I will let everyone know how it turns out next week . Thanks to all ! Jim
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