Misfires and engine dies. Need help please

[DattoDime70]

have a 1970 2dr 510 L-16 , 5 speed dog leg tranny, Weber 2 barrel dcoe 45 9, Cannon manifold, 2 1/2 straight pipe, Matchbox Electric Igniton, 200sx electric coil(Wired right), Stock fuel pump(Had a new one but broke),New dizzy cap and rotor, New fuel line and vent line, New clear house filters(Gets fuel fine), Just did a oil change haha , New starter. I set the ignition timing to 11 btdc yesterday with a timing light installed new ngk r sparkpugs with a 0.41 gap for the dizzy specs, It runs smooth but rough at the same time and still get the misfire and die problems.
Well i been having this probably about a month now it is my daily driver and i am stumped now
This is what happens While im driving on the street everything is fine i hop on the freeway to drive home everyday 20 miles and i get misfires and engine dies and it hiccups and backfires like 5 times a day i try to step on the clutch and press in the gas when it misfires so it wont turn off but it turns off the next quarter mile Ill have to pull over and start it up again and itll sputter but the clear filter on top of my engine would be empty, For the last two weeks it was running Fine but itll just overheat pass the mark on the temp on the freeway and when i get of itll drop down to normal so i decided to retard the timing and got messed up. I havent touched the carb so i was thinking its really dirty jets or flooding alot. Im really iof help, I cant figure it out? Anybody know ill appreciate the help. I really dont want to get rid of her but im getting tired of the problem
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[finn]

[quoteIll have to pull over and start it up again and itll sputter but the clear filter on top of my engine would be empty,http://a6.sphotos.ak.fbcdn.net/hphotos- ... 7821_n.jpg
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have you pulled the fuel line off and turned the motor over to see if your getting enough fuel flow?

[DattoDime70]

It gets the fuel fine. But it dies only on the freeway under a load but on the street its fine , iget home the top filter on the engine is ethier a 1/4 or 1/2 full and the one i got in the bottom is full.

[finn]

your high speed jets could be clogged, limiting your fuel supply. during high rpm, your fuel travels straight through ports in the carb. it could also be your vacuum advance hose. have you checked it for leaks?

[DattoDime70]

I havent checked or tuned anything in the carb, i was thinking it was running to rich, Where should i check leaks? I have the vacuum advance to the manifold but people told me to plug it cause it is retarding my ignition timing.

[finn]

the advance should be from your carb, to my recollection anyway. get a can of carb cleaner and spray small amount in different areas around the carb while the engine is running. if the rpm jump then you found a leak. if it all checks out then dissassemble the carb and clean it. use compressed "clean" air to blow out all passage ways.

[DattoDime70]

Thank you, I might send it to get a rebuild kit and clean haha idk the last time it got a cleaning.
By the way may i ask whats the difference about connecting the vacuum to the manifold or carb?

[finn]

your vacuum lines on your intake manifold are for your PCV, brakes, etc. the small port facing your valve cover on the carb is for your vacuum advance. it will coencide with your throttle response.

[DattoDime70]

Thank you ima try this tommorow if it works, hopefully

[okayfine]

Weber 45 DCOE doesn't have a vacuum nipple, does it?

Does your "street driving" entail any sustained mid/high RPM driving? In other words, does the rpm on the street ever see similar rpm to your freeway driving? Trying to replicate conditions might help narrow things down. If it's a fuel-supply issue then you should be able to see similar troubles by hitting 5K in 3rd or something.

If you can get this to happen again, cut the engine, coast to a safe place, then check the float levels. If dry float bowls, there's your problem.

Your temp problem is probably unrelated, unless you're running lean for an extended period of time, which would raise engine temps.

[finn]

http://www.mgexperience.net/archive/dco ... ly/1041275

there not common but some models had it.

do you use a ignition module? spark advance?

[DattoDime70]

My Carb has no vac port! I haven't touched or tuned the Carb.
I don't have a tach but it only happens on the freeway under a heavy load in 5 th gear. But it seems i get lower rpm on the freeway.

And yes I have a ignition module I have the matchbox dizzy and I got the timing at 11 btdc advanced.

[okayfine]

Check your grounds, especially to the distributor/module.