I have an aftermarket motor in my car, I didnt install it. I am going to check the timing and Im not sure it i should just go with what the manual says on the timing or should there be something else I should go by because this is not the stock motor??? It is a 350.

 

Are you experiencing any run problems or poor fuel economy?

 

Whats the block number, we can trace the year of the motor for you.

 

Do want to set timing to stock or for performance? They ware not the same. I don;t ste my timing at idle since I never drive at idle.

Here is a link to a good paper on timimg:
http://www.lbfun.com/warehouse/tech_...t%20Timing.pdf

Shoot for 36 degrees of mechanical advance, all in by 2500 rpm and another 16 of vacuum.

 

I will look for the block number, I have looked at it before and the numbers did not match any for a corvette.

I was looking for performance instead of stock...

I just checked the timing and it was around 10 degrees at idle.

 

Read Lars' paper that I linked to above. You don't drive at idle so why set your advance at idle. I have about 16 degrees at idle and 36 all in by 2500. Runs great.

 

These are the numbers on the block:

V1019TWZ

C85122916

 

as usual i feel inclined to chime in on this issue. information given on this forum concerning timing is mostly incorrect. respected members have been given idol status and therefore their information is being taken as gospel. you should never acheive 50+ deg. of TOTAL TIMING. your total timing should be 34-36 deg. total timing. this INCLUDES mech. AND vac. advance. you may check any other source of information ather than this forum and you will find i am correct.

 

Reb,

With all due respect, I have to disagree.

Total timing = initial timing + centrifugal (mechanical) advance. Vacuum advance does not factor into total timing since it is only in effect when vacuum is high and load is low.

Under WOT, vacuum goes to zero and so does vacuum advance and you have your 36 degrees of total timing. You only get the 52 degrees of timing under light load when the engine can tolerate more advance.

I stand by my recommendations above. I have used those setting for over 5 years with no problems. I have a ZZ4 clone that pulls hard to 6000 rpm, gets 20 mpg and has no issues with detonation and pinging.

For the OP, read this thread for more info:
http://forums.corvetteforum.com/c3-t...long-post.html

Another source of information:
http://rockridgefarm.com/vettdoc/Timing_101.pdf
I will trust the judgment of two former GM engineers over random internet folks.

 

sorry, ive been around engines and cars since i helped change reverse thread lug nuts on a dodge when i was 5. my 383 spins over 7000 rpms with no pinging and pulls like a raped ape. it did an 11 sec. 1/4. go get a dail back timing light and get back to me. i have built and helped build many an engine and repaired even more. my family has raced circle tracks for years and have been around many an engine/car builder and race shops. this forum is the only place ive even heard of 50 degress of anything. your own quote proves what im saying. forum members are ADDING vac. advance to what they think is their total advance, and this is how their coming up with advance #'s over 50. your own quote says NOT to factor this in. get a dail back timing light and use it to measure your advance at different rpms and DAIL IT BACK. this is how you measure and add your timing total. respectivly
and the engineer argument is lame, they didnt invent mech. or vac advance. this was created long ago. ive got engineers at my job who cant tie their own shoes

 

http://forums.corvetteforum.com/c3-t...long-post.html
This is an excellent explanation of timing.

 

I do have a dial back timing light. I have been using it for the last 8 years or so.

I set my timing as follows:

1. Disconnect and plug vacuum advance.
2. Set total timing (initial + centrifugal advance) at 36 degrees at 2500 rpm. My curve is set to that all centrigugal advance is in by 2500 rpm.
3. Initial advance is then about 18 degrees or so.
4. Reconnect vacuum advance to manifold vacuum (not ported).
5. Drive and enjoy.

You initially said that total advance includes mechanical and vacuum advance and now you say that my quote not to add vacuum advance is what you meant.

Questions, on your 383:
What is your initial advance?
What is your centrifugal advance curve? What rpm is it all in by?
Are you using vacuum advance?
If so, how many degrees of advance does the vacuum can add and at what vacuum setting?
Ported or manifold vacuum?

Just read the info here as well:
http://forums.corvetteforum.com/c3-t...ng-post-7.html
Very entertaining.

In that thread, you said:
Now, I pulled the instructions for the MSD 8394 E-Curve Distributor and found this:
http://www.msdignition.com/instructi...pdf?terms=8394

Note, they say total timing change is 34 degrees NOT total timing. So, if you run 12 degrees initial timing, you could have up to 46 degrees total timing by your own measure.

Just because MSD limits you to 9 degrees of vacuum advance, doesn't mean that you cannot run more.

 

this is great, keep it coming!!