Tune up questions/problems

[Brent Lineker]

I have a hesitation and backfiring in the intake during light acceleration from say 2000 rpm up until 4000 or so.The car idles well and full acceleration runs great.I have put new rotor,cap,points and plugs in the past week,the ignition cables have about 8000 miles on them(2 years).The engine is a 75 911s with stock bosch cds,stock cap, rotor,ect.The plugs are gapped at .032.I am running 40ida webers,ssi's and 73 rs exhaust.The carbs were cleaned and new kit installed around 4000 miles ago,valve adjustment is around 7000 miles old now.what direction should I be looking,electrical,valves or carbs.I have never taken out the idle jets before,is this something that could be causing it,how about fuel filters or maybe the fuel itself?Should I go ahead and buy new cables and try that.Thanks for any ideas or feed back...Brent

[Por_sha911]

Start with double-checking your work. Make sure the wires are in the proper order and check that all the cables are firmly on the plugs and the dizzy cap... This is probably not the answer based on the symptons you gave but it never hurts to start with the basics. Also, look around to see if you have banged into and disconnected or broken any wires in the area.

[Brent Lineker]

Thanks John:I did check over my work and it looks fine,I took the idle jets out and blew them out and cleaned my K&N filters as they looked dirty,I then filled up the tank with 94 octane fuel as I may have gotten a bad tank of fuel earlier in the week.The car is a little better but does stumble occasionally around 2000 or 3000 rpm during part throttle conditions.I will change out the fuel filter next as the pressure guage on the downstream of the guage is reading 3psi and I believe 3.5-4 psi is optimal.I have never looked at the guage before so don't know what it was earlier.I have only had the car 3 months or so.

[Brent Lineker]

Well it seems I have it dialed in now.I changed out plugs,fuel filter,cap,rotor,points and cleaned out the idle jets and cleaned the K&N air filters and still had some part throttle backfiring in the carbs.I talked to George at Midwest Eurosport in Joliet who dilaed the carbs in before my trip from Chicago to Vancouver B.C.,he put me in the right direction.We are having cooler weather here now with lots of rain which translated into leaning out the carbs.He suggested turning out the mixture screws 1/2 turn to richen up the carbs and voila the car runs perfect now.I am a happy camper now,I put new hoses in last weekend from my heat exchangers so I now have heat in the cab and George also told me how to hook up my hand throttle.I must give a plug for him and his shop,they are great guys.

[Walter_Middie]

Brent,

Beautiful car, and great to hear you got it fixed yourself. We need more midyears in the PNW - I hope to see you on one of the next outings.

[Brent Lineker]

Thanks and I do plan on doing a few outings the coming year...