Need tune-up specs for '66 912:
 

Hi, I need the basic specs for a 1966 912 that is stock, I still need to check which distributor it has. I have already read that I need ~35 deg. total advance, so I need the following:

-plug gap and which plugs are prefered around here,

-dwell and point gap

-basic mixture adjustment (if there is such a thing)

-compression #s on a healthy, stock motor


Thanks a lot in advance for any help! :cool:

Buy the 912 book, it has everythng you need in it.

A good, really good 912 has 150 to 160lbs compression. Bottom line, if it accelerates ok and dosen't burn a visable ammount of oil, its probably ok.

Spark advance at 900 rpm about 10 degrees, not critical. At 3200rpm it should be maxed out. Some say 32 degrees, some 36 degrees. If it don't knock its ok.

My 912 race engine uses 36 degrees at 3000 rpm, reduced to 34 degrees at 8000 rpm. Compression about 220lbs, but cr is over 12:1. cr is also very dependant on cam used. Most important is that it is the SAME for all cylinders.

A leak down test is the best test. Anything below 10% is hunky dory. Up to 25% probably ok for any street car.
A racer will tear it down at 10%, a street car at 50%

Spark plugs, in general, 0.025", not critical with any high energy ignition.

Balance the carbs, then adjust the mixture for smooth idle, max rpm, reset idle and recheck.

Strictly from memory, no guarentee this is correct, I think the point gap, new points, is 0.016". Can't remember the dwell. I suggest dumping the points for the electronic "points". Much better, dosen''t wear. Check Crane UN-655-2310 from our esteemed sponser.

IIn addition to the last well informed previous post I would suggest checking the valves for clearance. You know, rotate the engine backwards and do it 1-2-3-4 order. As for balancing the carbs - can be a nightmare if you don't have a strong motor that runs well at idle. Nevertheless – (1) make sure float levels are ok (beg or buy) a float gauge - or make one - see UpFixen Der Porsche someplace in early books. Get also the little squirters measurer vile. (2) Make sure the volume is equal on all throats. (3) Now start engine – warm it up so it idles evenly. Disconnect one arm of the accel rod. Starting with the left carb – and the rear (remember rear is REAR – closest to you) throat, see what the volume of air is – then go to front throart – are they the same? If you don’t have a set of emission carbs (68-69) you will have to devise a delicate method to bend the shaft so the butterflies allow the same volume of air at idle – hold the back nut and twist the front – Ayieeeee – without mashing the butterflies. They are the same? (4) Good – now do the same with the right side. (5) Still disconnected, and by adjusting the idle screw – go left to right. Finshed? Good. (6) now adjust idle – follow directiection – think its unscrew and screw in until engine stumble then back out ½ turn. Do R side. As you get closwer the idle may go up – back off idle screw a tad. (7) go back to left side with air meter and see whats screwed up there – keep doing this process until all thoarts are even and happy. (8) measure arms and make adjust ments. DON’T forget to lub the arm in the front of the engine that the tranny to engine arm fits to AND the very hard to get to shaft. (9) go under the car to the tranny and make sure the bushings aren’t shot and like wise in the foot box. All done? You will have one sweet motor.
Onward
Doug

Oh oh oh - almost forgot - BEFORE doing all the messing around with the carbs - be sure there is a good seal at teh carb base!! Mayn gorillas tighten the little 12 mm (oh, you have 13s? Tut tut - not original heh heh) nuts and bend the fragile carb base INTO the soft gasket. Take a .002 or so feeler gauge blade and go around the base - especially at the middle point of the two attachment lugs. IF there is substantial air gap, consider taking carbs off and trueing up surface. Suggest emery paper, plenty of water, taped to a bif heavy mirror - or, in my case, an old quarter window. Plenty flat.
Onward
Doug

At the base of the carbs, you might have to use that ugly stuff called RTV to get a seal. If you do, use the stuff VERY sparingly, big lumps of the stuff dosen't help the air flow much, but its better than a vacuum leak.