Gain extra benefits by becoming a Supporting Member Click here find out how!

Classic Performance Products Classic Parts
American Auto Wire Classic Industries
Danchuk Catalog
Hellwig Products IncPerformance Rod & CustomJoin the Community today
Ecklers AutoMotiveNu-Relics Power Windows



Username Post: Ignition settings for 1970 Camaro LT1        (Topic#357914)
ranman 
"2nd Year" Silver Supporting Member
Posts: 10807
ranman
Loc: The cold wet and windy O...
Reg: 03-10-01
09-02-19 06:43 PM - Post#2774704    

Helping a friend tune his 1970 Camaro and me, not knowing much about engines with a little bit of cam... I'm curious about where to set initial and vacuum advance. Engine sticker says 6 initial.
The engine has roller rockers 1.5 and World products sportsman heads with a stamp saying 11.25 on it. Factory specs are 11 to 1 so whatever this is it's very close to stock. Cam is a stock LT1 with specs of .458/317 int and .484/346 exh.
We haven't begun the ignition timing so I'm looking where to start.
We are at 10 initial right now and I don't know what it has in the vacuum can. I haven't checked the mechanical advance either, but I think he bought an MSD kit along with his MSD6 ignition.

Any information would help and I'm also curious how much vacuum this engine should pull at idle
with the vacuum can hooked up.

~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~
If plants ruled the world, would they regulate oxygen?


 


Shepherd 
Frequent Contributor
Posts: 1848

Loc: Lake George, NY
Reg: 11-11-15
09-03-19 02:17 PM - Post#2774755    
    In response to ranman

There can be a lot of variables here, but for the most part, around 14-16 initial, 35 total at about 3000., with a properly set up mechanical advance.



 
japete92 
"5th Year" Silver Supporting Member
Posts: 1249
japete92
Loc: No. Virginia
Reg: 01-18-13
09-03-19 03:52 PM - Post#2774762    
    In response to ranman

Does this help?

http://www.superchevy.com/how-to/additional-tec h/1...

Pete













 
ranman 
"2nd Year" Silver Supporting Member
Posts: 10807
ranman
Loc: The cold wet and windy O...
Reg: 03-10-01
09-03-19 07:59 PM - Post#2774780    
    In response to japete92

I'm looking for approximate settings for that specific engine.... Not the factory settings.... Those were either 0 degrees initial (California) or 6 degrees initial (for normal states ) and who knows what was in the vacuum can. We want it to run good and factory setting weren't always designed for that. Looking for a starting point.
It's a 1970 Z-28 with the LT1 350 and 11 or 11.25 to 1 compression.
We have high octain non alcohol gas here.
No emissions stuff are on this engine. It runs the stock 4 speed manual tranny.

~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~
If plants ruled the world, would they regulate oxygen?


 
japete92 
"5th Year" Silver Supporting Member
Posts: 1249
japete92
Loc: No. Virginia
Reg: 01-18-13
09-04-19 08:31 AM - Post#2774811    
    In response to ranman

More info here:

https://www.chevelles.com/forums/13-performance /18...

Generically speaking (as a starting point for any sbc, not 'factory') 'Initial' at idle is the 'place' where you get about 24 degrees BTDC with the vacuum advance connected. Say for example; 12 initial, 12 vacuum, yields 24.

At about 3400 rpm, mechanical plus initial (vacuum is nil by then) of about 35 is a good place to be (very similar to what 'Shepard' suggested).

Without knowing how much your distributor and vacuum are adding, its hard to define the initial.

Hope this is helpful.

Pete





 
ranman 
"2nd Year" Silver Supporting Member
Posts: 10807
ranman
Loc: The cold wet and windy O...
Reg: 03-10-01
09-04-19 10:13 AM - Post#2774816    
    In response to japete92

My thinking is on a stock plain smooth running street cam. (grocery getter) 12 to 14 initial, and 8 in the vacuum can. 8 in the can lets you set the idle screw lower, meaning less of the transition slot is uncovered at idle. I was also figuring the total ought to be all in below 3000. 3400 seems a bit high.
I won't know the mechanical until I have some time to help him work on it.
I guess my confusion is, should this same initial and mechanical and vaccum be set just the same with the high compression and larger cam as it is with a grocery getter with 9 to 1 compression? I just haven't messed with an engine like this, so that's why I'm asking. I appreciate the advice guys.

~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~
If plants ruled the world, would they regulate oxygen?


 
Rick_L 
Honored Member
Posts: 27651
Rick_L
Loc: Katy, Tx, USA
Reg: 07-06-00
09-04-19 12:48 PM - Post#2774824    
    In response to ranman

The numbers you posted are pretty close. The final best settings are going to be based on your actual compression ratio and how good your fuel is.

If it pings you'll have to pull some timing out. If it doesn't ping you can try more initial and see if that helps or if it causes pinging.

Additionally, somewhere around 12° initial, you're going to have trouble with the engine kicking back against the starter, or just slow cranking, when the engine is fully warmed up. Just where that happens is a function of compression ratio and cam timing. The cure is 2° less timing.

Too much vacuum advance will also cause pinging. If that occurs you'll have to back off on initial timing or limit the amount of vacuum advance.

Don't get too caught up in setting idle timing using the vacuum advance.



 
ranman 
"2nd Year" Silver Supporting Member
Posts: 10807
ranman
Loc: The cold wet and windy O...
Reg: 03-10-01
09-04-19 03:58 PM - Post#2774835    
    In response to Rick_L

Thanks Rick, I just never messes with a true high compression engine. I still want to get the vacuum as high as I can. I think my gauge is off by 3 inches, so we may be close to 9 instead of 6 inches.We're at 10 degrees now and we have good gas. I didn't think we were going to get to 12.
It gas a gear reduction starter. I'm thinking maybe we leave it at 10 degrees and get the mechanical figured out, and all in by 2800 sound about right?
My 8 degrees was form ignition mans advice a long time back. That worked fantastic on my old 9/1 350 in my pickup.
I suppose maybe we could go 10?
I'll still have to figure out what his mechanical is. It's just hard finding time to play with it.

~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~
If plants ruled the world, would they regulate oxygen?


 
Mel Foye 
*VIP* Founding Member
Posts: 4877
Mel Foye
Reg: 09-29-00
09-04-19 10:17 PM - Post#2774852    
    In response to ranman

Hi big guy long time. I could not get detailed enough specs on an LT1 Camaro but did get for a 70 LT1 Vette. Stock is on the left and my recommendation on the right.
Initial 8° at 900rpm 12
1000 rpms centif starts
Max 26° at 3,800 22 by 2,800-3,000
Vac starts at 8 inches and
maxes at 15°at 15.5 inches I would start there but be open to reducing the number of °s if needed. Don't want to over advance part throttle because we would be bringing centrif sooner.
YMMV Mel




Edited by Mel Foye on 09-04-19 10:18 PM. Reason for edit: No reason given.

 
ranman 
"2nd Year" Silver Supporting Member
Posts: 10807
ranman
Loc: The cold wet and windy O...
Reg: 03-10-01
09-05-19 12:41 PM - Post#2774886    
    In response to Mel Foye

Am I that memorably Mel?
You said:
Vac starts at 8 inches and
maxes at 15°at 15.5 inches I would start there but be open to reducing the number of °s if needed. Don't want to over advance part throttle because we would be bringing centrif sooner."
Could you clarify that?
Vacuum should be 8 at idle and will get up to 15ish at some point? ...or at 15 degrees?
You guys are great. I have somewhere to start now.

~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~
If plants ruled the world, would they regulate oxygen?


 
ranman 
"2nd Year" Silver Supporting Member
Posts: 10807
ranman
Loc: The cold wet and windy O...
Reg: 03-10-01
09-05-19 12:48 PM - Post#2774888    
    In response to ranman

I need to find a good vacuum gauge because my Mightyvac and my tuneup gauge don't read the same...3 inches different, and neither are the same as one at a friends shop. Is there a way to hippy-calibrate a vacuum gauge?

In the mean time, I gotta get back to work. I'll check in tonight. Thanks again.

~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~
If plants ruled the world, would they regulate oxygen?


 
Mel Foye 
*VIP* Founding Member
Posts: 4877
Mel Foye
Reg: 09-29-00
09-05-19 07:20 PM - Post#2774916    
    In response to ranman

Of course I remember you. Who else signs in as ranman but writes as if he was rain man? Oh my that felt good!!!
With the stock settings of static/initial at 8° BTDC plus centrifugal of 26° you end up at 34° at 3,800 rpms. Then you start adding vacuum advance once the engine produces 8 inches of vacuum--- which it would reach as soon as it was running. When the vacuum reaches 15.5 inches this system would add a total of 15° degrees. Total of 8,26 and 15==49° at 3,800. At 900 rpms you would have 8+15==23° of advance.
With my suggestions you get 12+22 for 34°s again w/o vacuum advance but at 800-1,000 less rpms. So when your spark/flame front starts earlier in the
cycle to add 15.5°s may add up to be too much advance for that rpm. If so you can stick with starting moving that systems advance at the same amount of inches but limit the amount of its advance.
I know I went way more basic than you needed but I wanted to cover all the bases. The guys who really are expert can add their experience/knowledge.
I have found with vacuum gauges best to really see small changes get one that is at least 4" in dia.
Good to hear from you again. mel



Edited by Mel Foye on 09-05-19 07:24 PM. Reason for edit: No reason given.

 
ranman 
"2nd Year" Silver Supporting Member
Posts: 10807
ranman
Loc: The cold wet and windy O...
Reg: 03-10-01
09-05-19 08:35 PM - Post#2774920    
    In response to Mel Foye

Guys like you make us all look like experts. Too much info is better than not enough. I'll print the info so we'll have it on hand.......... I have CRS syndrome. Always had it but it's getting worse as time goes on.
I have to do hit and run with my internet use so pardon me for dropping in then running off so quick. Internet at home isn't working so well.

~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~
If plants ruled the world, would they regulate oxygen?


 
ranman 
"2nd Year" Silver Supporting Member
Posts: 10807
ranman
Loc: The cold wet and windy O...
Reg: 03-10-01
09-17-19 03:42 PM - Post#2775747    
    In response to ranman

Got the engine running with the carb issue fixed and the vacuum is now a steady 13.
I used my dial back timing light and found we have 18 inches in the can and 10 or 10.5 initial. We aren't gonna mess with the mechanical until we get an oil change done. Sounds clean and runs smooth. Still have a tiny fuel leak at the rear fitting even tho it's tight.

~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~
If plants ruled the world, would they regulate oxygen?


 


Icon Legend Permissions Topic Options
Report Post

Quote Post

Quick Reply

Print Topic

Email Topic

451 Views
FusionBB
FusionBB™ Version 2.1
©2003-2006 InteractivePHP, Inc.
Execution time: 0.07 seconds.   Total Queries: 16   Zlib Compression is on.
All times are (GMT -0800) Pacific. Current time is 11:47 AM
Top