1970 911 T Timing Question

handleyb · 09-13-2011, 02:19 PM

When timing a 1970 911 T is the vacuum hose to the distributor left in place, disconnected, or plugged?

daniel911T · daniel911T's Garage

Are you absolutely sure it's a 1970T? I only ask because they have a vacuum system only for the overrun system on the Zeniths.

There shouldn't be a Vacuum line to the distributor on a '70T.

Post a pic please!

-Dan

FYI... I think all the early vacuum distributors are set with the vacuum hose removed. More experienced hands will confirm or deny.

handleyb · 09-13-2011, 05:26 PM

Yes the Manufacture ID plate says that it is a 911 T. Not sure if its the original distributor... but it's a Bosch 001.

daniel911T · daniel911T's Garage

Please post a pic. It would also be super useful if you could post the engine #. It's on the case, opposite the distributor, near the base of the fan. The number will be hand stamped, not cast.

I have a sneaking suspicion that you may have a 2.4 or 2.7 motor, or possibly a modified distributor. A pic of the distributor base, where the adjustment nut is, will answer the question.

Good luck!

Dan

daniel911T · daniel911T's Garage

Quote:

Originally Posted by handleyb

Yes the Manufacture ID plate says that it is a 911 T. Not sure if its the original distributor... but it's a Bosch 001.

BTW, definitely not original. The original was a 231 159 008 (if memory serves) in any case, 008 is the T dizzy.

Dan

handleyb · 09-13-2011, 05:50 PM

Chassis # 9110122657
Engine # 6107549

I'll work on the photos. Thank you !

handleyb · 09-13-2011, 06:37 PM

daniel911T · daniel911T's Garage

610 7XXX is a USA delivery 911T engine.

Little trivia:
6= 6cyl
1= 911T (E=2, S=3)
0= last digit of year. 1970

7 is the start of the engine series. USA Ts with manual transmissions from that year went from 5001-8001

The procedure for that distributor is to check and set the timing at 6K RPM with the vacuum line disconnected. On the T you should be setting it at 35 BTDC at 6K. It should sit near TDC at idle. With the stock distributor you would idle about 5 BTDC, but the vacuum system pulls you back a bit at idle. The 6K measurement is the gold standard.

When looking with your timing light at the pulley, 30 is the first mark, 35 is the second. I got my timing data from the Haynes manual. Many just set it straight at 30.

If you're curious: What you most likely have is a distributor from a 2.4 or 2.7 that's been modified. They came with a thicker shaft and a built in clamp, both of which have been modified or removed on yours.

I hope it works well! Please let us know! Also, to satisfy my curiosoty, could you please get a pic of the engine bay? I want to know what carbs you're using.

-Dan

gamin · 09-14-2011, 04:49 AM

I bought my 70T new and it does not have a vacuum distributor. I believe 008 is correct but I will check the manuals tonight. Again, no vacuum to the dizzy on 70T.

handleyb · 09-14-2011, 07:42 AM

Thanks for the info ! The car has Zenith Carbs.

daniel911T · daniel911T's Garage

Quote:

Originally Posted by handleyb

Thanks for the info ! The car has Zenith Carbs.

Is the overrun enrichment system still installed and working?

-Dan

handleyb · 09-14-2011, 10:00 AM

Dan,
The Auxiliary enrichment device is installed. Not sure if they are functional yet. I just picked up this car. It has been in a garage for the last 10 years. Not driven. I searched the forum and followed advise to get it up and running. It runs very rough and backfires a lot. I haven't adjusted the carbs yet. Waiting for a flow meter. Any advise on adjusting the carbs would be appreciated. I have a Haynes manual and a 911 project book and plan to use their instructions. I timed the car at idle but left the distributor vacuum hose in place. I'll redo per your instructions. Thanks again. Brian

daniel911T · daniel911T's Garage

If you want to have a discussion off the main board about bringing it back to life, feel free to contact me. I'll help as much as you need, or connect you to people who can.

As another idea, you could bring her back in full view of everybody, taking it step by step. I suspect others could use your experience in the future.

When you're ready to get into Zenith tuning, I have the full factory manual on those, digitally. I'll be more than happy to share, and/or provide advice. I've just had 6 Zenith carbs completely disected, cleaned, reworked, rebuilt, reinstalled, and very nearly properly tuned. I've learned a lot, and I'm happy to share!

It'll be good to know how she runs with the timing set right!

Last quick question: Can you please post a picture of what vacuum source the distributor is plugged into?

-Dan

handleyb · 09-14-2011, 11:26 AM

The vacuum hose from the distributor runs to a " T" connection with one hose connecting to the base of the left Zenith. The other leg of the hose runs behind the air filter housing and connects with the right Zenith at its base.

daniel911T · daniel911T's Garage

Quote:

Originally Posted by handleyb

The vacuum hose from the distributor runs to a " T" connection with one hose connecting to the base of the left Zenith. The other leg of the hose runs behind the air filter housing and connects with the right Zenith at its base.

So it's borrowing vacuum from the line that runs the overrun enrichment system. Should work well enough.

Trackrash · Trackrash's Garage

There was, as others have noted, no vacuum on a '70 T distributor.

The timing at idle, is listed on the engine tag on the fan housing, which is 2-4 deg ATDC. This was done for smog reasons. Your motor will idle much better with the initial timing set at around 5 deg, BTDC. The problem is the timing at 6000 rpm is what really maters. It should be 33-35 deg BTDC at 6k rpm. The stock distributors have way too much advance to be able to run 5 deg BTDC at idle and 35 deg at 6k rpm. So you may be lucky and have a distributor that is better than the stock one.

You should get the numbers off the distributor you have so someone can look up what it came from.

The purpose of a vacuum advance on a distributor serves two purposes. It allows more advance at part throttle and at idle when the vacuum is high. This allows smoother idling and more fuel economy during part throttle operation when more advance can be tolerated by the motor. During higher loads there is less advance.

If the car has not been driven you should clean out the entire fuel system, and replace the fuel filter. Check the tank for rust. Any rust in the tank and good luck getting it to run. Carbs are very sensitive to any contaminates.

daniel911T · daniel911T's Garage

Trackrash,

I got mine to run with a rusty gas tank! Not recommended, I have to go into my freshly rebuilt Zeniths to remove the last of the rust from the bowls this weekend. That crap got through 4 serial fuel filters!

My understanding of the vacuum dizzies was that under acceleration they were essentially mechanical advance. The vacuum system only kicked in under high vacuum conditions, like high RPM closed throttle, or idle. I thought it moved timing from where it would naturally sit, like about 5 bdc at idle with no vacuum, and retarded it to about 5atdc. Under acceleration it did virtually nothing, for cruise it retarded the timing a bit, then in overrun (closed throttle, high rpm) it retarded it a lot.

My understanding was also that it was emissions crap. All I know is that on my trusty old bug, when I ditched the 013 vacuum dizzy for the 009 mechanical dizzy it became a completely different beast! (I'm aware that the curve was also different.)

-Dan

Trackrash · Trackrash's Garage

Yes, there are some distributors that have vacuum advance and vacuum retard. Good luck with those.

handleyb · 09-14-2011, 05:29 PM

The distributor is a Bosch 0 231 169 001. Not sure what it came out of. I already drained the gas tank, changed the filters, new plugs, new oil, etc. When I went to buy new points, the ones for a 1970 T did not fit. I then pulled the distributor and matched contacts accordingly. I plan to recheck the timing tomorrow. Then on to adjust the Zeniths. thanks for your help !