Hello
I read the arctical on timing your car and I have a question.
I replaced the distributor with a pertronix ignitor II , coil and new wires.
The initial timing is 4 degrees- when checking the total timing with the vacuum line pluged and disconnected from the distributor the total timeing is about 28 degrees- I scored the balancing damper at 36 degrees and that mark never reached above 8 degrees ADC (retarded) ,on the timing plate- with the vacuum advace line connected the maximum timing is about 48 degrees- not 52 degrees

The vacuum line is port connected- and the new distributor has electronic mechanical advance-no springs.

So how do I get the total timing to 36 degrees to maximize the cars power and efficiency? can I advance the initial timing to 12 degrees instead of 4 degrees? or is there another way to hit the 36 degrees-

Vacuum advance is B-19 5.5" -8" @ 14-18 distributor degrees. Manifold vacuum is about 10 -12 " at idle.

Thanks
Ed

 

Looks like your electronic mechanical advance is not working- or very limited. You should be able to get 36* @ 3000 with no vacuum. Add the vacuum and adjust the can to limit to 52*.
The only reason you shouldn't be able to reset the initial timing to 12* will be is it's pinging. I'm running 18* initial, and 41* total on VP 110 fuel.

 

12° initial shouldn't be a problem. GM was very conservative with 4°. I'm using 16° initial instead of 8°.
But 36° total is the most important goal. ( Let's say 34 - 38° depending on heads, CR and other engine components ).
Check if you reach maximum centrifugal advance between 2500 and 3000 RPM.
Read your Pertronix notice to know how to set it. There must be a way to do it.
You have to be sure the centrifugal advance will not go any further after 3000 RPM.
You will need someone to read the tach when you reach maximum timing advance.
Maximum advance at 2800 RPM is a good & safe place to start.
And remember : Check your timing without vacuum advance ( plug the hose )

 

Just watch a tachometer or RPM/dwell meter (set on RPM) as you hold a timing light on the damper. Rev the engine slowly upward until the timing mark stops advancing, then take a reading of the RPM. If max mech advance comes in much over 3000 RPM, you will have to modify the advance system to bring it down to 2800-3000 RPM. On a standard distributor, that is done by putting 'softer' springs on the flyweights so that the weights get thrown out to their max limit sooner. You'll have to figure out what to do with your new distributor. Now rev it up again and adjust the distributor for 34-36 deg. advance at that max. advance point. When you let it go back to idle, it should be set between 4-16 deg advance. If it is and the idle is smooth, just leave it alone. Also, if your distributor does not require vacuum advance, just cap-off the carb port used for that and discard (or save) the vacuum line going to the dizzy. Lastly, if the advance at idle is above 16 degrees, you will have to make a modification to the (max) limit stop for the mechanical advance so that it can go a few degrees farther. Then you can readjust the dist position at max mech advance point and the ilde advance reading should be lowered in a usable range.

 

Thanks for the advise.
I was able to get the total timing to 36 degrees with a curb timing at about 17 degrees- who was smoking the funny stuff in the owners manual that states 4 degrees curb timing

I think that the maximum timing is about 52 or 53 degrees.
The vacuum skyrocketed on the intake and it setteled down nice and smooth at about 16" - it was very eratic prior to retiming.

I get no knocking or pinging - and what hidden power is now unleashed- I never knew the car had so much @#$#@$ and get.

I am getting just a little lurching at crusing speed- Think the carb may need alittle fine tuning. What do you think?

Ed

 

You can back off the tining 2* and see if that helps.
OR
See how much the advance can increases the timing, if 16* you can get a can that will be all in at 14* or 12*. PG.

 

Maybe a couple steps up on the jets. What carb?

 

If you're getting lurching at cruise, you probably have vaccum advance coming too early. Don't know what kind of vacuum can you have on your distributor and if it is adjustable or not ( but it should be on a Pertronix distributor ), but if you can, keep the same total timing you now have and just set the vacuum advance so it only comes in at a higher vacuum value. Do it step by step and try by driving. When the car stops jerking at cruise, you're all set.

 

You're the lucky owner of a '68 Vette. Do you have pictures of the beast ?

 

Your are in good hands with TimAt But with 10 to 12 Hg of vacuum and a total timing of 36* you want a vacuum can to match. You might want to try a B26 can. It stars at 5 to 7 Hg and gives *8 adv distr degrees at 11 to 13 Hg of manifold vacuum.
36 total
+16 crank
=52 total at cruise.

I would try this before you get into the carb. PG.

 

Hello
Well I figured it out- the idiots who made the pertronix ignitor II distributor II put a B19 vacuum advance on it- I have 12" minimum Vacuum at idle and that stupid thing has a 24* advance on it which makes my maximum at 60* not 52*. With it hooked up to manifold it makes the curb idle at 36* not 12* like it should be-hooked to port at idle has no vacuum timing increase.

Looked at the old distributor and it has a B1 on it- go figure!

I sent a nasty gram to corvette central for allowing pertonix to do such a stupid thing on their distributors.

Guess that I will need to change that one out to a B1 vacumm advance

 

Use the old distributor advance on the new distributor. You have the parts!

 

Yea I will have to look at the other vacuum advance - it was on a point type distributor- the new pertronix is all electonic except for the vacuum advance to keep the vintage look.
I did check the over all vacuum and it is about 22" before it bottoms out and kicks in the mechancial advance.

thanks
ed

 

Hello Fellow vette lovers

Well I took Corvette Central to task on the new pertonixs Ignitor II distributor they sold me that has a 24* vacuum advance @ 14" HG - ( for an old Impala not a vette) and they sent me Timing 101 and said it was " my " problem.
Well I responded to them that they must not understand what was written in the "Timing 101" that they sent me or the chevy specifications of 15* vacuum advance at 12" HG set forth in the Chevy manual for a 68 327 SB. Nor did they check their vender as to which vacuum advance they put on thier disrtibutors and selling them for 68 vettes.
I told them to put a B28 on a new distibutor and send it to me , then I would return the crap that they tried to represent for a 68 SB. We shall see what they do - I sent the sam E-Mail to pertronixs also.

It is sad that they do not understand the car as a whole and only push parts- parts that they should stand behind and meet factory specifications as least. So be ware when pruchasing parts for your Vette.

Ed

 

I would love to post pics of the 68 vette. the site will not let me post the pics- they are to big 1.3.mg- any suggestions?
Thanks
ed

 

Yes, you can create an account on Photobucket ( for instance ).
It's free. Then you can upload your pictures and sort them out in albums. Give them a name and a description if you want. Photobucket will resize them automatically if they are really big.
When you post a thread on Corvette Forum, just copy the link of photobucket pictures by pointing the mouse over the picture you want and select & copy the field named "IMG code" with a left mouse click & draw, syntax is something which looks like :

[IMG ] http://i300.photobucket.com/albums/......... /[IMG ]

and then paste the link into your post.
Remember that the link must always begin and finish with "[IMG ]" or people won't see the picture.

The pictures will appear directly in your post ! It's a kind of magic !

If you need or want to resize easily your pictures first to decrease uploading times, you can use a freeware called :
VSO Image Resizer. Here's the direct link to download it :

http://www.vso-software.fr/products/...ge_resizer.php

Now you have no excuse !

 

Hello
update - Pertronix sent me a message and they are going to help me figure out what went wrong with the distibutor I ordered.
Thanks
Ed

 

I have read this posting with interest. I Went through a similar situation. As you are see ing it's not a cut-and-dried deal. The only way to get the performance you desire is through trial and error.

 

Knowing what you are doing goes a long way, too.....

 

Hello all
Well the B28 vacuum advance did the trick - I took out the B19 corvette central put on their distributor and put on a B28- Total timing 36* w/o vacuum, 32* with vacuum and 52* maximum timing.

Pertronix people were real cool about the whole thing and that did not have anything to do with that distributor sold by Corvette Central- The pertronix ignotor II does work very well on the top end maximizing power and getting all the horse power out of the car between 2500 and 3500 rpm.

That is not my car :o, I took it out and it kicked @#$!$%- screamed through all 4 gears, laided a 25 footer at 2500 rpm with out breaking a sweat, idles and cruses smooth as a babies #%$%.

That car has never ran that well ever

well I am a believer of Timing 101 and it does work very well-

Thanks to all.
Ed