Is my Distributor working ????

[flmont]

I have a 81' 3.0 911 ...I had my Dist tested due to the car breakes up around 2500-3K the shop tells me this..

Mech advance starts at 1800 RPM,and is all in at 2900 RPM,.Total of 10 Deg's...Vacume advance starts at 7" and is all in by 10"of vacume ...Gives 8 deg's both adv and retard.....

I set the timming at 5 Deg's BTDC...book states 25 Deg's at 4 K rpm ...So should'nt this be my problem ???? TIA FM

[stlrj]

Ask your shop if they are talking about distributor degrees or crankshaft degrees because 10 degrees at the distributor means 20 at the crankshaft.

Cheers,

Joe

[BURN-BROS]

Correct if I am wrong;
10 deg mech. adv
+8 vac adv
+5 static
= 23 degrees btdc looks close to me.

Did I miss something?

Aaron

[flmont]

Yes they were talking Dist spec's only from thier test unit.....dont I need something like25-30 Total advance...Thanks FM

[BURN-BROS]

Can you check timing yourself? Verify that you are indeed getting 23 degrees @ 4000. Adjust 2 more to get the 25. If you had some help you could map the curve by writing down the advance for every 500 rpms starting at around 1000.

[flmont]

Well my problem is the car breakes up at around 2500 to 3 K RPM...So I had the dist CK'd and of course I did'nt know how it all worked,So I needed to ask the question,..the shop guy asked for dist spec's and I did'nt know what they were. So,he said best he could tell me is what the Dist alone actually did...So if these spec's are close to the working spec's and it seems pretty close, then its another problem...I was asked to ck the coil aswell,When they get hot they can act-up,Or the throttle switch..??? The P-shop I took it to did not Ck those 2 things I know...??? Thanks so much for the insight..

[BURN-BROS]

Is the missing happening under load, when you rev the engine in neutral or both?

[flmont]

Both......FM

[BURN-BROS]

I wish I could help more. It could be weak spark or a problem with the cis. Maybe you could post more info such as if you have performed a tune up. What items were changed in the tune up? Maybe more will chime in to help.


Aaron

[flmont]

Well,.. fuel presure was good,..I will try the coil...Thanks agin FM

[emcon5]

Just a guess, what kind of ignition do you have? Bosch/Permatune/MSD?

Tom

[stlrj]

Your distributor seems OK. I would concentrate on an ignition problem causing the miss. How old are your ignition cables? Plugs?

Start with the simple things as your first option. You could alway pour ca$h down the black hole later.

Cheers,

Joe

[john walker's workshop]

msd units on sc's often fail as you describe. when you say "breaks up", does it pop and backfire, or just flatten out power-wise?

[flmont]

I have a Permatune...and yes it pops and backfires a little, pops and cuts out but can still run ...plugs are new...wires are very nice shape but I dont know the age...Thanks FM