Backfiring & popping through exhaust

[Bay Window Steve]

Hey guys. Just recently got my '73 running, and I'm having issues with it backfiring everytime I let off the gas or shift. Also, while it sits and idles, I hear low toned popping noises in the exhaust. The engine starts, runs and idles fine aside from these issues. It is not fuel injected, as the PO switched it to a single carb. Exhaust is a header/collector with a single bugpack muffler. I thought I might have an exhaust leak because it sounds like it when running, but I replaced the gasket between the header and muffler (which was nearly gone) but the issue didn't change. I don't have super deep pockets, so converting back to fuel injection and buying a stock muffler aren't really options for me at this point.

Lastly, is the 1.7l motor typically a loud sounding engine? When its running, it just sounds loud. I know how dumb that sounds, but this is my first dealings with this motor.

Any help is appreciated.
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'73 Transporter - Driver
'69 Deluxe

Member: WTKHABG


Original Air Cooler Member

[Randy in Maine]

Your 73 bus did not come with FI, it came with dual solex carbs from the factory, and looked sort of like this.....

When properly tuned, that 1700 cc engine should sound like a "turbo sewing machine" all the way up to 5600 RPMs when the rev limiter kicks in.

You need to adjust your valves, make sure you have no vacuum leaks, and make sure your timing is correct for the distributor that you are running.

[renobdarb]

Indeed. Make sure your timing's spot on. If you still have off-throttle backfiring, you likely have an exhaust leak.

BTW Randy... got my bus runnig right again. Wasn't the carbs after all... just needed a new fuel pump!
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1978 Campmobile, 2000cc w/hydro lifters, dual Weber 44 IDF carbs (50 idle jets, 115 main jets), SVDA distributor w/Compufire.

[BanDinger]

my bus backfires also when Im off throttle, usually when I let off in third of fourth. I checked my timing and it was off 12 deg.

[DaKine]

I had the same problem last year with my bus...I'm running dual dellortos though. When my bus was idling it would 'pop' and spit like a popcorn popper. I thought it was a exhaust leak too. I replaced everything down to the copper gaskets on the heads. After I did all that and it still was not fixed, I found that old gas had settled in the bottom of my carbs during winter storage and they were full of muck and scale. I rebuilt the carbs and glass beaded them and it ran like a champ. Rebuilding those carbs was a pretty cheap fix too. Good luck.

[Zeen]

[Paslode235]

What exhaust are your running?? If you are running an aftermarket super flow exhaust you will get poping do to there is no back pressure. If you have a stock muffler you won't get any backfiring unless there is something else wrong. I had that problem when I had an aftermarket exhaust. Get ride of it, my aftermaket exhaust fell apart after one summer and less than 5000 miles. Junk if you ask me.

[Bay Window Steve]

Sorry, I've been away for the weekend. It is an aftermarket exhaust, but has held up for the PO since '96. Anyway fouled plugs could cause my problems? I was concerned about bad gas too, since the bus has set since '02.
_________________
'73 Transporter - Driver
'69 Deluxe

Member: WTKHABG


Original Air Cooler Member