Ignition timing questions........... built 2.7RS
09-03-2002, 02:06 AM
#1
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Ignition timing questions........... built 2.7RS
hello all!
My name is Edmond and I need a little help.
Before I ask I'd like to let you know that I could not find the answer to my question in BA's book or some of my other referances.
The engine in question is a:
911/51 case ['72T ]
'72 T heads machined to accept S valves with enlarged intake and exhaust ports
new Weber 40's set up as BA recommends
headers w/ duall out sport muffler
901-105-109-04
901-105-110-04 cams [ solex? ...early "S"?]
'72T distributor points, no vaccum advance
Speedatron High Energy ignition system. [ capacitive discharge I think ]
stock wires [ new ]
I fouled a plug and I thought I could get the engine to run better by adjusting the mixture screws on the carbs. Big mistake. I got these new carbs so out of whack I had to put the old carbs back on. The old carbs are ok but, have out of round throttle shaft holes.
I want to start from scratch and try to get this engine to perform as it should. So the first thing I want to do is adjust the timing. And this is my question. How many degrees btdc or atdc??
I just don't know. Should I time the engine as if it were a T, S or an RS??
So that is my question, where do I time the engine?
Also, when the motor was built it used w225T30 plugs [ reading from invoice ] are these Bosche plugs and are they a good plug for this set up?
Am considering a MSD ignition system and a set of Magnacor wires. [ which I WILL purchase from Steve Weiners Company ]
If anyone can help with my question and add any suggestions regarding my engine I would appreciate it very much.
Thanks for your time with this beginner.
Regards, Edmond
My name is Edmond and I need a little help.
Before I ask I'd like to let you know that I could not find the answer to my question in BA's book or some of my other referances.
The engine in question is a:
911/51 case ['72T ]
'72 T heads machined to accept S valves with enlarged intake and exhaust ports
new Weber 40's set up as BA recommends
headers w/ duall out sport muffler
901-105-109-04
901-105-110-04 cams [ solex? ...early "S"?]
'72T distributor points, no vaccum advance
Speedatron High Energy ignition system. [ capacitive discharge I think ]
stock wires [ new ]
I fouled a plug and I thought I could get the engine to run better by adjusting the mixture screws on the carbs. Big mistake. I got these new carbs so out of whack I had to put the old carbs back on. The old carbs are ok but, have out of round throttle shaft holes.
I want to start from scratch and try to get this engine to perform as it should. So the first thing I want to do is adjust the timing. And this is my question. How many degrees btdc or atdc??
I just don't know. Should I time the engine as if it were a T, S or an RS??
So that is my question, where do I time the engine?
Also, when the motor was built it used w225T30 plugs [ reading from invoice ] are these Bosche plugs and are they a good plug for this set up?
Am considering a MSD ignition system and a set of Magnacor wires. [ which I WILL purchase from Steve Weiners Company ]
If anyone can help with my question and add any suggestions regarding my engine I would appreciate it very much.
Thanks for your time with this beginner.
Regards, Edmond
09-03-2002, 02:55 PM
#2
RL Technical Advisor
Hi Edmond:
LOL,..As I saw my name in your post, I felt I'd better speak up,....
FYI, those are Solex cams.
I know very little about Speedatron ignitions but I will tell you that an MSD-equipped 911 with the proper wires & plugs gapped at .040, will not foul plugs.
The amount of ignition timing for these engines doesn't vary between T, E, and S variants, only the advance curve. Set your timing at 6000 RPM and make sure that you have 34-35 degrees, total. You may need to have your distributor recurved. Using your timing light, you can check the centrifugal advance mechanism and get an idea about shaft wear by observing any timing variations at 3000 RPM.
I'm a real fan of eliminating the points in these early distributors with the Pertronix, and using the MSD-6AL and Blaster coil for their ability to keep these engines running cleanly. This also permits the wide plug gaps needed for best power and idle quality.
Make sure that you have 3.5 psi of fuel pressure (no more!) and that the float levels are perfect.
Those W225 (old numbering system) plugs are too warm for that engine, but would be OK for setting the carbs as that's a lot of idling. I would use the Bosch W5DC in that thing for all around use and W4DC for aggressive track use.
My recommendations would be to get a solid ignition system that will NOT permit plug fouling no matter what, and then proceed to setup & adjust your carbs. Install the Pertronix, MSD & matching coil, some Magnecor wires, new plugs, (cap & rotor if needed) and you'll be set.
Hope this helps,
LOL,..As I saw my name in your post, I felt I'd better speak up,....
FYI, those are Solex cams.
I know very little about Speedatron ignitions but I will tell you that an MSD-equipped 911 with the proper wires & plugs gapped at .040, will not foul plugs.
The amount of ignition timing for these engines doesn't vary between T, E, and S variants, only the advance curve. Set your timing at 6000 RPM and make sure that you have 34-35 degrees, total. You may need to have your distributor recurved. Using your timing light, you can check the centrifugal advance mechanism and get an idea about shaft wear by observing any timing variations at 3000 RPM.
I'm a real fan of eliminating the points in these early distributors with the Pertronix, and using the MSD-6AL and Blaster coil for their ability to keep these engines running cleanly. This also permits the wide plug gaps needed for best power and idle quality.
Make sure that you have 3.5 psi of fuel pressure (no more!) and that the float levels are perfect.
Those W225 (old numbering system) plugs are too warm for that engine, but would be OK for setting the carbs as that's a lot of idling. I would use the Bosch W5DC in that thing for all around use and W4DC for aggressive track use.
My recommendations would be to get a solid ignition system that will NOT permit plug fouling no matter what, and then proceed to setup & adjust your carbs. Install the Pertronix, MSD & matching coil, some Magnecor wires, new plugs, (cap & rotor if needed) and you'll be set.
Hope this helps,
09-03-2002, 10:34 PM
#3
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Thanks Steve! Your input is GREATLY appreciated.
I'm a little nervous about taking my engine up to 6k without a load. But if this is how its done, I'll do it.
I forgot to say in my earlier post I have 2.7 RS p/c's.
I'm going to RennsportSystems to make my list and will be ordering very soon.
I've done some searching on this site and found that you are a quite a sharp fellow. And always willing to answer many questions. I think this is great. Hope to meet you some day and buy you lunch.
Best regards, Edmond
I'm a little nervous about taking my engine up to 6k without a load. But if this is how its done, I'll do it.
I forgot to say in my earlier post I have 2.7 RS p/c's.
I'm going to RennsportSystems to make my list and will be ordering very soon.
I've done some searching on this site and found that you are a quite a sharp fellow. And always willing to answer many questions. I think this is great. Hope to meet you some day and buy you lunch.
Best regards, Edmond
09-04-2002, 05:45 AM
#4
RL Technical Advisor
[quote]Originally posted by Edmond911T:
<strong>Thanks Steve! Your input is GREATLY appreciated.
I'm a little nervous about taking my engine up to 6k without a load. But if this is how its done, I'll do it.
I forgot to say in my earlier post I have 2.7 RS p/c's.
I'm going to RennsportSystems to make my list and will be ordering very soon.
I've done some searching on this site and found that you are a quite a sharp fellow. And always willing to answer many questions. I think this is great. Hope to meet you some day and buy you lunch.
Best regards, Edmond</strong><hr></blockquote>
Hi Edmond:
Happy to be of service, Sir,...
Regarding timing,....just quickly blast the throttle to 5000 RPM and watch the timing marks. Its done as a blip, not held there. All of the advance should be in by 4000 so 5K is sufficient to set the total timing.
I kinda figured that you had the 90mm 8.5:1 set.
I'm very pleased that you've found my advice helpful and to be of some value. Give me a call anytime you are planning a trip to Portland and I'd be happy to show you around.....
<strong>Thanks Steve! Your input is GREATLY appreciated.
I'm a little nervous about taking my engine up to 6k without a load. But if this is how its done, I'll do it.
I forgot to say in my earlier post I have 2.7 RS p/c's.
I'm going to RennsportSystems to make my list and will be ordering very soon.
I've done some searching on this site and found that you are a quite a sharp fellow. And always willing to answer many questions. I think this is great. Hope to meet you some day and buy you lunch.
Best regards, Edmond</strong><hr></blockquote>
Hi Edmond:
Happy to be of service, Sir,...
Regarding timing,....just quickly blast the throttle to 5000 RPM and watch the timing marks. Its done as a blip, not held there. All of the advance should be in by 4000 so 5K is sufficient to set the total timing.
I kinda figured that you had the 90mm 8.5:1 set.
I'm very pleased that you've found my advice helpful and to be of some value. Give me a call anytime you are planning a trip to Portland and I'd be happy to show you around.....
