912e Vaccum Advance

[Nige-912E]

I'll be installing my freshly rebuilt engine soon, this will be Rebuild Version 3.5 after a botched build from the original engineer, in and out twice to resolve the problems only to have number 3 piston melt after 250 miles, after a few solid recommendations and a new builder my new engine will be arriving shortly.

I have one question though, the engine is now running a pair of 40mm Dellortos and the standard efi dizzy with the vaccum hooked up to the carb outlet on number 4 cylinder. I'm alittle unsure as which connection to make at the dizzy end as I have two inlets. Do I use the outer connection and block the other, or will this cause a negative effect on the vaccum? Or should I switch to an 009?

[WFBowen]

Hey Nige:
I'd try your stock dist. first, although, as you mention, you can run an 009 with the dual carb setup. The vertical vacuum fitting on the cannister should (going from memory here) be your advance and the inner, horizontal fitting the retard. The question here is whether the vacuum port on the carb will deliver the proper amount to advance the timing, since the stock vacuum was taken from the single throttle valve with the vacuum of all cylinders. To be safe, on initial fire-up, I'd set the static timing (with the retard blocked) to factory specs. Then fire the motor & check just what kind of momentary advance you're getting & what the total (mechanical) advance is. If it's not off the charts either way, I'd stay with your stock dist. As for the retard, I don't think there's a proper (below throttle valve) port available on those carbs but I might be wrong.
As an aside, there's been a lot of discussion about this distributor on a 912E. I had a rock-stock 912E that had both +/- ports hooked up (maybe Calif. only?) Others say their retard port was always blocked & used only on the 914's. To make matters more confusing, the factory repair manual photos don't give a clear picture of the setup and it's obvious that at least some of the photos were thrown-in from the 914 service manuals (!)
As for the fried piston, did you ever find a clear reason for the motor's failure?
Bill.

[eki912]

I asked the same thing a while ago on 912bbs , got several different opinions how the vacuumhoses should be connected....

On my own car they were BOTH connected , one to the upperside of the throttleswitch , one to the lower side of the throttle switch.As there are 2 connection places.Worked OK.

Well , on another car I saw , no hoses connected to dizzy at all ! Worked just fine....

On another car , only one hose connected to throttleunit , other was not there at all , worked OK.

On another car , one hose to throttleunit , one to the EGR thingys .... worked OK.

Go figure ?

Anyway , do some research on 009 and T4 engine. They dont work too well together ( I have been told ). Recommended type for T4 is 050. Or go for these fancy electronic thingys....

eki

[Nige-912E]

Thanks guys for your responses,

ahhhh, its for 'retard' its all becoming more clear.

As you say Bill there is no port available for the retard side of things with the carbs I am running. Though both ports on the dizzy were used when I originally had the efi fitted, not sure where the retard fitted though, I have photos of the efi setup so should be able to report back.

I'm alittle worried as to whether its doing its job, as when I ran with this dizzy with the previous incarnation of the rebuild I had number 3 piston melt. Although this was obviously an overheating problem, temp gauge was well within limits, I'm slightly concerned that a lack of advance caused this, but then it could have been wrongly gapped rings or block jets on number three.

I know there varied feelings about 009, some people swear by them some don't, the guy that is doing the rebuild suggested I get an 009. I may do for initial running in and then have a play with the vac advance setup after a few hundred miles.

Thanks again
Nige

[WFBowen]

Nige:
You could always just use your current dist. without any vacuum for initial testing, then try to dial-in the vac advance once the motor's up & running. Also, does your dist's advance cannister hold vacuum? Off of what cyl. is the vacuum taken by the Dellortos?
Looks like it'll be a sweet motor when done.
Bill.

[Nige-912E]

Hi Bill

Will do, I'd prefer to keep the vac advance dissy anyway.

Checkout: http://www.myfonepics.co.uk/nige/

Show images of the engine under construction, balanced lightened flywheel/crank, balanced rods and pistons (96mm KBs) polished ports/combustion chambers. Sporty cam and a very clean crankcase.

Some shots of the melted/holed piston and then some of original install and stainless twin exhaust plus other random stuff.

Should be picking the engine up this weekend from Simon (engine builder), shame I didn't know of him when I had the engine rebuilt originally. He's known for turbo'ing type 4s, I would've been very tempted to go that route but spent most of my funds on the first crappy build.

You live and learn and its all sorted now.

Cheers
Nige