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Thu Aug 22, 2013 2:55 pm

ok i had my 912 professionally rebuilt , with the big bore kit , but it never ran as good as before the work , (it seems slower instead of faster) I checked and adjusted valve lash , put a flame thrower coil and dizzy on er , cleaned and sealed fuel tank (and lines) , cleaned and rebuilt dual webers 40 idf ,added a rev limiter , (set to 6100 rpm , now here is the mystery , with timing light hooked up correctly ,and dizzy set properly , both valves on #1 closed in compression stroke , dizzy rotor pointing at dizzy notch (#1 spark plug wire),so far so good right ? but the marks on the crank pully (degree grooves on pully) are nowhere to be found , in fact i believe there almost 180 degrees off , yet everything in set correctly , it starts easy idles fine , and runs , (just not the way it should , Has anyone ever incountered this senario ? It seems to lack low end power , and pops through the carbs . I think maybe , my only issue now is perhaps the carb sincronization , (but that timing light issue , I have never incountered prior ) any insight here would be greatly appreciated , thanks , Jim :?:

Thu Aug 22, 2013 8:08 pm

Plug wires on in the wrong order? Looking at the wrong rocker arm? When the line on the crank pulley is lined up with TDC you are saying that even through say 4 revolutions of the crank pulley, the dizzy never lines up with the line in the distributor body? What distributor do you have?

Thu Aug 22, 2013 8:16 pm

brojames wrote: put a flame thrower coil and dizzy on er ,
As in this one?

That's a clone of a Bosch 009 and only has 22* degrees advance. The 912 engine should have a Bosch 022 or 031 which has 32* degrees advance.

You most likely have the wrong distributor, no wonder why it runs like crap.

Fri Aug 23, 2013 4:28 am

jt912 wrote: Plug wires on in the wrong order? Looking at the wrong rocker arm? When the line on the crank pulley is lined up with TDC you are saying that even through say 4 revolutions of the crank pulley, the dizzy never lines up with the line in the distributor body? What distributor do you have?

no ,what i'm saying is every thing lines up properly on dizzy and wires , but with timing light hooked up and car running , the grooves on the crank pulley , are no where to be found (roughly some 180* off) and I know the dizzy is installed right ! the flame thrower, is the dizzy i have installed (as you pictured)and is the recommended dizzy , why would it not be the correct one? thanks for your response !

Fri Aug 23, 2013 5:40 am

you were recommended the wrong one. its for a VW not a Porsche.

Fri Aug 23, 2013 7:36 am

Something isn't correct. The crank pulley line will indicate TDC for cylinder #1. If the valves aren't closed when this is lined up you've got a bigger issue. If the valves are correctly closed when the crank pulley is lined up then you have a distributor issue. With the #1 valves closed and the crank pulley lined up, the timing mark in the distributor should be close to the the orientation of the rotor. I'm guessing the dizzy could be in 180 degrees off? None of this fixes the advance curve of your dizzy which WILL have large part to play in how well the engine runs. Do you have access to another distributor? 022, 031, 061, RSR0012?

Sat Aug 24, 2013 5:07 am

ok assuming It's the dizzy , which one would you recommend out of the 031 , and 0012 , for my application , and are they both centrifugal advance ? what about electronic ignition ?best place to purchase a good one ready to pop in and play ! thanks again

Sat Aug 24, 2013 5:11 am

I'd get a 022 or a 031. I have many customers that reported back the 022 provided the best performance with stock and big bore 912 engines.

I'm not a fan of points replacements but the Pertronix 1844 fits the 022.

Sat Aug 24, 2013 5:33 am

thanks again glenn !

Wed Oct 11, 2017 12:01 pm

haven't been on here in a while still not driving my 912 :( , the more advice i get the more confused i get, wish i knew 1 intelligent, trustworthy,porsche guy out there.The car starts and runs , but not well at all, and it smokes pretty bad, and backfires a lot, my thoughts ,dizzy, or wrong carb jets.any help would be greatly appreciated, this has been an ongoing issue for 4 years.

Wed Oct 11, 2017 12:38 pm

Was the case split when rebuilt as it sounds like the cam gear is off by a tooth or two so your valve timing is retarded causing the lack of power and popping through the carbs. :cry: . I've run an 009 with pertronix for years and my 912 with big bore kit screams. To use the 009 forget about the timing at idle just rev. the motor 3500 rpm and mark your pulley at 30 - 32 deg.s which ever runs the best without pinging. Your carbs might need to be rejetted for the big bore. Did they put shims under the cyl.s so you don't have too much compression, a must for todays low octane gas.

Thu Oct 12, 2017 5:15 am

not sure about split case , shims, but your the first one to mention this,interesting possibility ? I swapped out the dizzy for a supposed good used 022,is there any way i can verify its a good one, myself? also am pulling and cleaning carbs today for the umpteenth time ,as i am still leaning towards fuel problems, it runs way to rich.wish i knew the best jet combo for my application ? Thanks for your prompt reply

Thu Oct 12, 2017 7:59 am

update: pulled and cleaned both carbs, 40 IDF F11,jets are 45 idles,115 mains, while i was at it pulled and cleaned plugs, they are bosch super RO 182 W7 BC,gapped to .028,does all this sound correct so far ? thanks

Thu Oct 12, 2017 9:31 am

What other specs on the motor?
Bore
Stroke
Cam
Compression ratio

Have you verified TDC for #1?

Can you talk with the builder/mechanic?

Rev.

Thu Oct 12, 2017 12:15 pm

Is it rich at idle , top end or both? That the jets to go two sizes smaller. First thing to check on your dizzy is to hold the drive end and see if the rotor will twist some and spring back as people forget to add a drop or two of oil to the felt pad under the rotor, if it's frozen you might free it up by soaking the dizzy in a solution of 50% acetone-50% atf for an hour if that doesn't work it's shot and needs a rebuild or replace. Is the carb linkage synchronized? To check hold a plastic straw down the throat of a carb on each side and have someone slowly push on the gas peddle, both straws need to start moving at the same time or adjust linkage.

Thu Oct 12, 2017 1:38 pm

it is rich all the time, may have to find some jets, will check and lubricate dizzy, linkage is perfect, cleaned carbs today,filthy,dismantled,and cleaned every nook and cranny, lots of blockages throughout.plan to clean fuel tank and lines again, since its been sitting for a while,(what would be a recommendation)with tank in car i hope, fuel additive etc. I'm feeling pretty positive now, after todays progress, looking forward to starting er up again tomorrow, also i have the stack tube dial tool, to sync the carbs, thanks all for help and comments, will give update tomorrow .

Thu Oct 12, 2017 2:09 pm

While the dizzy is out you can check and see if the dizzy drive pinion was installed correctly. With the motor set with both valves closed on #1 cyl. (cyl. closest to passenger seat) and pulley set with "OT" lined up with case split, the groove in the drive pinion should point to #4 main bearing lock screw (bolt head in timing gear cover to the left and lower of case serial #. Put in a high quality fuel filter from tank to fuel pump and be sure to check float level as too high or a bad needle could be causing flooding and rich running.

Thu Oct 12, 2017 2:48 pm

thanks starbucket,and great info, will do , tomorrow, and yes both carb floats were set wrong, one was 8mm, the other was 16mm, set them both to 10.5 mm

Thu Oct 12, 2017 10:15 pm

Sounds like your jetting is the default weber setup. I had that and mine ran rich and back fired now and then. I kept thinking it was wrong even though shops would say that's how 912 run with Webers, well after researching the 912bbs I went with

Main - 130
Air Correction - 180
Emulsion - F7
Idle - 55
Venturi - 32
Accel Pump - 40

My 68 runs much better, not rich at all. Starts right up, no back firing. I run 031 distributor. Good luck.

Fri Oct 13, 2017 9:02 am

ok, i'm really at a lose, after everything i've done , it runs even worse, :( , i went to a couple trusted shops this morning , and was told to check a couple things no one has mentioned yet . #1,check compression, which being a rebuild with under 100 miles on it i ,never thought this could be an issue, #2 firing order, why would this change ? was told with rebuild and big bore kit, the firing order could be different, never heard this before but what do you think ? back to scratching my head, checkin things out this afternoon.