I have a 1981 Gazelle kit car built on a 1969 beetle chassis with a stock Bosch distributor.  New this year, its been loosing power at the top end of third and forth gear and then backfiring.  This only occurs once its been running for around 10 minutes.  It idles fine and will even red line in neutral without a backfire.  Dwell is 50 and points are new and set to .016".  I found some discrepancy about timing though.  Should it be at TDC or 7.5 BTDC?  When set to TDC it backfires at about 2900 RPM consistently so it is now set at 7.5 BTDC.  Thoughts on vapor lock?  I'm pretty sure my rear main seal is leaking some; could this some tie to it?  It has an aux oil cooler and even and electric fan to aid with circulation.

 

I know this isn't a purist VW but, my baby isn't feeling well and I'm dieing here.  Any help will be greatly appreciated!

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Marc

Can't give timing advice without knowing the distributor model. There are dozens & dozens of "stock Bosch" distributors, and it's not at all uncommon to find an engine with the "wrong" one installed. If it's a 1969 4-speed distributor (0 231 137 035, 036 or 039) the correct timing setting would be 0° static or at idle with the vacuum hose disconnected; it should pull 32-35° total if the advance mechanism is working properly...if it won't run right without additional initial timing, you should suspect a problem there. Simply sucking on the hose to the vacuum servo to see if it leaks would be a good starting point.

Your symptom sounds more like a fuel-supply problem, though. Does this kit use a stock Beetle tank? There's a screen over the pickup tube that will plug up with crud from a dirty tank - it'll fall away when the engine's off and there's no fuel demand, but quickly accrete again after a short period of use.

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Car wouldn't run for 5 seconds with the vacuum disconnected.  Looks like the Weber carb just stopped producing vacuum.  I swapped out the Weber for a 30 year old Solex that I had laying around and after a little coaxing it started.  I also opened the points up to .017" from .016" to change the dwell angle to 48 from 50.  Now I just can't get the solex to idle down to 900rpm so  I can set the timing correctly.  It hangs around the 1300-1500 mark.  Will the air/fuel mixture screws get me a reduced idle speed?

 

RFZ

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sounds like mixture... too much air... find the correct screw, bottom it out, then back out 2 turns, drive around, keep adjusting it till its right, get an engine analyzer to do this at home , or a portable tach. my 2 cents  oops...should have read the entire thread, yes it will make a change to the rpms, so will lostening the dist lock down clamp, and turn it till the timings right,  definately a fuel issue tho 

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