HELP my 1970 521 truck's exhaust blew like a bomb!

[chasingharm]

Dallas, TX,

 

I am on the road traveling across the country in my truck. Now I am in Dallas where my exhaust blew up. It sounded like a bomb and the exhaust canister under the car disintegrated. The truck was running smooth prior. I just had a new distributor put in and had it timed by a pro mechanic about a month ago. I have had occasional problems with backfiring, but nothing major until this. Unfortunately I do not know a lot about car mechanics. I race bicycles professional (pedal bikes) and thus engines have been out of my league of expertise.

 

Does anyone live in Dallas have advice or know of a mechanic who could help me out? I assume fuel was leaking into my exhaust system and this caused the explosion. I also assume putting a new exhaust on won't fix the issue since the engine is causing it? What can I do with limited engine mechanic knowledge? With my very limited budget I have been ripped off by too many times by mechanics so I don't want to just bring it anywhere.

 

Thanks so much.

 

 

 

 

[datzenmike]

Take a look at the front of the carb and see where the gas level is on the glass front. It should be near the horizontal line when running.

 

Carefully look down the carb when running... do you see any gas dripping?

 

If the fuel level is good and nothing appears to be leaking pull a few spark plugs,. If they are tan or light color then you aren't running rich. If they are dry and sooty then you might be rich.

 

Assuming all the above is fine then a backfire can be caused by a momentary interuption of the ignition system. Unburned gas and air passes into the exhaust system and when the plugs fire it sets this off with explosive results. I would remove the distributor cap and check the points. They should be clean and gapped (0.010" to 0.012" I don't remember off hand so look it up). Be sure the distributor is bolted down securely. Cap and plug wires should be in good shape as well. Check all wires to coil, ballast resistor and distributor for tight connections.

[elmerfudpucker]

Dont worry about the cops, you now will blend in with the rest of them down there!!

[banzai510(hainz)]

I would guess Point adjustment. I little bit more than a matchbox cover. to set the gap.If you dont have a feeler gauge.

If its a dual point you have to set both. Dwell is the term and I never was good at it.

 

Do like Mike said, ck out the distributor.

 

Can you remember what gear you were in.?????????? If 3rd gear it could be the seciond set of points.(just disconnect the wire to the 2nd set. The one with the smaller capacitor.

 

The main point wire is the bigger Capacitor near the valve cover. if it backfires right off idle in nuetral I would make sure the distributor shaft is not loose. meaning is has alot of slop side to side.

 

 

Be honest if you dont have alot of mech exp you should get another car. These things are over 30yrs old and I have to keep on top of them also.

 

 

olddatsuns.com

 

 

pro mechanic = you gave me money but doesnt mean I know what Im doing.

 

A VW Bug shop might be better than those nwer fancy places where you have some more old school techs