International Full Size Jeep Association
Home Forums Reader's Rigs Tech Library Trail Stories FSJ-List
International Full Size Jeep Association  

Go Back   International Full Size Jeep Association > Tire Kickin' > General FSJ Tech

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 01-24-2020, 02:15 AM
Beach_Dude's Avatar
Beach_Dude Beach_Dude is offline
327 Rambler
 
Join Date: Mar 03, 2011
Location: Newport Beach
Posts: 565
MSD Timing Curve - questions

Getting ready to install the MSD 8519 to work in conjunction with the MSD 6AL and the TFI coil on my 1977 AMC 360.

I plan on running a little advanced, 11* since my idle seems to run best with ridiculous vacuum around 10-12*.

The 79 setup seems to be 0* @ 900 RPM and 19* @ 4,400 RPM. The vacuum advance starts at 3" @ 0* and peaks at 27* @ 11" in acuum.

MSD states the vacuum advance is maximum 10* at 15" of vacuum, which I assume is distributor advance, not crank? I'll call support and get an answer for you guys.

Here's the stock curve for the 1979 Duraspark ignition



Here are the curve options for the MSD distributor



I'm tied between the extremes.... graph A is stock for the unit and has the longest curve but put the limiter on at 18* since I'm running 2* more advanced to begin with.

Graph F has the lowest starting advance at around 800 RPM, but seems rather aggressive?

Anyone have input and knowledge of timing curves or MSD billet distributor setups?
__________________
1977 Jeep Cherokee Chief
360 w/ MC 4350
All stock but ignition and slightly modified suspection
Original paint, garaged/non-op for over 15 years
Reply With Quote
  #2  
Old 01-24-2020, 09:17 AM
wiley-moeracing wiley-moeracing is offline
350 Buick
 
Join Date: Feb 15, 2010
Location: arizona
Posts: 1,133
Its been awhile since I did mine, (many years ago), You have to know what your came specs are, carb your running, torque convertor lock up is, gear ratio/ tire size combo, weight and then start to dial it in with the correct curve. When you change the curve you will find you will need to change the carb jetting to compliment the curve.
Reply With Quote
  #3  
Old 01-24-2020, 09:50 AM
Beach_Dude's Avatar
Beach_Dude Beach_Dude is offline
327 Rambler
 
Join Date: Mar 03, 2011
Location: Newport Beach
Posts: 565
Everything is stock, carb, cams, TC, etc. except for the fact that I'm running 33s instead of factory spec tires, which were 31.4".

I have been thinking about uping my diffs, but doing this for now. Iirc the diffs are at 3.54.
__________________
1977 Jeep Cherokee Chief
360 w/ MC 4350
All stock but ignition and slightly modified suspection
Original paint, garaged/non-op for over 15 years

Last edited by Beach_Dude : 01-24-2020 at 09:56 AM.
Reply With Quote
  #4  
Old 01-24-2020, 10:48 AM
wiley-moeracing wiley-moeracing is offline
350 Buick
 
Join Date: Feb 15, 2010
Location: arizona
Posts: 1,133
The gear ratio is hurting you, causing you to rely on very low torque curve/ low power curve. If and when you change gears you will end up having to recurve again. Change your gears out to 4:10's and your truck will come to life and the stock curve will be good. With the stock cam/ carb etc. you want the power to come on around 800 and slowly go up, not aggressive. Only get more aggressive if and when you add higher compression and a more aggressive cam profile and a 4 bbl carb and intake otherwise it is all for nothing. The "B" curve looks to be your starting point, your motor will never see 6000 rpm and you want a slow rise on the curve with stock compression and torque.
Reply With Quote
  #5  
Old 01-24-2020, 01:02 PM
Beach_Dude's Avatar
Beach_Dude Beach_Dude is offline
327 Rambler
 
Join Date: Mar 03, 2011
Location: Newport Beach
Posts: 565
Thanks for that!

Just got off the phone with support and they said the vacuum of 10* is actually crank degrees, not distributor. Seems super low, but hey, why not. With that much spark, it should be more than enough.

I was going to do 3.73 to keep it closer to stock since I'm running 33s, not 35s, and won't go to 35s. This is a road car with light trail use, like once every ten years.
__________________
1977 Jeep Cherokee Chief
360 w/ MC 4350
All stock but ignition and slightly modified suspection
Original paint, garaged/non-op for over 15 years
Reply With Quote
  #6  
Old 01-24-2020, 03:52 PM
wiley-moeracing wiley-moeracing is offline
350 Buick
 
Join Date: Feb 15, 2010
Location: arizona
Posts: 1,133
I would still think at least the 4:10's would be better than 3:73.
Reply With Quote
  #7  
Old 01-24-2020, 04:02 PM
Beach_Dude's Avatar
Beach_Dude Beach_Dude is offline
327 Rambler
 
Join Date: Mar 03, 2011
Location: Newport Beach
Posts: 565
I'd go higher than 3.73 if there weren't so many freeways in the area.
__________________
1977 Jeep Cherokee Chief
360 w/ MC 4350
All stock but ignition and slightly modified suspection
Original paint, garaged/non-op for over 15 years
Reply With Quote
  #8  
Old 01-27-2020, 12:18 PM
Beach_Dude's Avatar
Beach_Dude Beach_Dude is offline
327 Rambler
 
Join Date: Mar 03, 2011
Location: Newport Beach
Posts: 565
So, anyone else familiar with setting the timing curves for the MSD distributor?

Ready-Run or not, they're all the same timing curves.
__________________
1977 Jeep Cherokee Chief
360 w/ MC 4350
All stock but ignition and slightly modified suspection
Original paint, garaged/non-op for over 15 years
Reply With Quote
  #9  
Old 01-27-2020, 01:47 PM
johnsonic johnsonic is offline
232 I6
 
Join Date: Mar 12, 2015
Location: Oregon
Posts: 245
It 100% depends on your setup. I'd start by trying to match the curve from the factory for your year (it's in the TSM). From there you can tweak it.

I have mine starting @ 19 degrees with the stop bushing limiting advance at 36 degrees at 3000 RPM. But I'm also running manifold vacuum and replaced the vacuum can with an adjustable one.

There really isn't a right answer here.
__________________
1984 GW
360
Comp 260H
Magnum Roller Rockers
Wiseco -21cc Forged Pistons
Performer Intake
Holley SA 670
MSD 8523
Dakota Digital custom cluster
Serehill headlamp harness
NWMP aux tank

1987 GW deceased
...but the parts live on
Reply With Quote
  #10  
Old 01-28-2020, 01:50 AM
FSJunkie's Avatar
FSJunkie FSJunkie is offline
The Nigel Tufnel of the FSJ world.
 
Join Date: Jan 09, 2011
Location: Not The Hot Part, Arizona
Posts: 3,994
Some years used a lower base timing setting like 0* with a high mechanical advance like 35* and other years used a higher base timing setting like 15* with a low mechanical advance like 20*.

The net result driving down the road at engine speeds above idle is the same. The only difference is one idles with more advanced timing than the other.

The base timing that you choose largely depends on what the mechanical advance curve looks like. More specifically, the maximum limit on the mechanical advance.

Generally, ideal timing for most AMC V8 is 5-10 degrees at idle and 30-35 degrees at 4000 RPM.
__________________
'72 Jeep Wagoneer Custom, 360 V8

I love how arguements end as soon as Ristow comments. Ristow is right...again.
Reply With Quote
  #11  
Old 01-30-2020, 09:09 AM
Beach_Dude's Avatar
Beach_Dude Beach_Dude is offline
327 Rambler
 
Join Date: Mar 03, 2011
Location: Newport Beach
Posts: 565
My biggest issue is that my other cars are zippy m series bmw and a daily driver 328i.

The torque feels great, but it almost always has... I feel like I'm missing some top end HP though.

Everyone says play with it till it feels right. Also, set it till detonation, then back off... i don't know why, but this goes against logic for me.

I ended up going with diagram C's timing curve since it matches the 10* mechanical advance at the same 2000 RPM, with the black bushing capped at 18* and 13* initial advance.

Should I try swapping swings and/or bushing to see what happens or should I call it a day and be happy?
__________________
1977 Jeep Cherokee Chief
360 w/ MC 4350
All stock but ignition and slightly modified suspection
Original paint, garaged/non-op for over 15 years
Reply With Quote
  #12  
Old 01-30-2020, 09:29 AM
babywag's Avatar
babywag babywag is offline
out of order
 
Join Date: Jun 08, 2005
Location: Land of froot loops and cukcoo-nuts, CA
Posts: 9,593
No harm in trying different springs.
Running manifold vacuum vs. ported will give a snappier throttle response.
Due to the vacuum unit being fully advanced @idle on manifold vacuum.
If on ported there is no vacuum advance @idle.
Age old debate/argument on that one though...
Easy to test and see what you/your engine prefers.

When I ran carb(s) I found initial in ~13* range to be best but honestly, it really depends on the engine.
They're all a little different and what works for one doesn't always work for another.
__________________
Tony
Reply With Quote
  #13  
Old 02-05-2020, 08:07 PM
Beach_Dude's Avatar
Beach_Dude Beach_Dude is offline
327 Rambler
 
Join Date: Mar 03, 2011
Location: Newport Beach
Posts: 565
I ended up with Diagram C, and then did the 19* bushing. Runs great, but not a single knock or ping! I even pushed the baseline to 15*.

Still no knock or ping.

I've even turned the dizzy over enough to get the idle to roughen out, and still no pinging that I could hear!

I just don't want some detonation occurring that I'm not picking up, go on a long drive and blow out my engine.

Ideas?
__________________
1977 Jeep Cherokee Chief
360 w/ MC 4350
All stock but ignition and slightly modified suspection
Original paint, garaged/non-op for over 15 years
Reply With Quote
  #14  
Old 02-05-2020, 08:13 PM
Mikel's Avatar
Mikel Mikel is offline
 
Join Date: Aug 09, 2000
Location: New Haven, CT
Posts: 6,287
Quote:
Originally Posted by Beach_Dude
I ended up with Diagram C, and then did the 19* bushing. Runs great, but not a single knock or ping! I even pushed the baseline to 15*.

Still no knock or ping.

I've even turned the dizzy over enough to get the idle to roughen out, and still no pinging that I could hear!

I just don't want some detonation occurring that I'm not picking up, go on a long drive and blow out my engine.

Ideas?






How's the performance?
__________________
1969 M715 6x6
1963 J300 Swivel frame
Reply With Quote
  #15  
Old 02-05-2020, 10:03 PM
Beach_Dude's Avatar
Beach_Dude Beach_Dude is offline
327 Rambler
 
Join Date: Mar 03, 2011
Location: Newport Beach
Posts: 565
Runs great... 22" vacuum, smooth idle, again, perf is great.
__________________
1977 Jeep Cherokee Chief
360 w/ MC 4350
All stock but ignition and slightly modified suspection
Original paint, garaged/non-op for over 15 years
Reply With Quote
  #16  
Old 02-06-2020, 04:10 AM
Mikel's Avatar
Mikel Mikel is offline
 
Join Date: Aug 09, 2000
Location: New Haven, CT
Posts: 6,287
Congratulations
__________________
1969 M715 6x6
1963 J300 Swivel frame
Reply With Quote
  #17  
Old 02-06-2020, 09:04 AM
Beach_Dude's Avatar
Beach_Dude Beach_Dude is offline
327 Rambler
 
Join Date: Mar 03, 2011
Location: Newport Beach
Posts: 565
Still a little concerned with the lack or pre detonation though.
__________________
1977 Jeep Cherokee Chief
360 w/ MC 4350
All stock but ignition and slightly modified suspection
Original paint, garaged/non-op for over 15 years
Reply With Quote
  #18  
Old 02-06-2020, 10:29 AM
Ristow Ristow is offline
 
Join Date: Jan 20, 2006
Location: The Great Googley Moogley Midwest.
Posts: 17,104
Quote:
Originally Posted by Beach_Dude
Still a little concerned with the lack or pre detonation though.






why? these motors aren't that sensitive to pinging. nothing about what you have tuned alarms me.



but if it makes you feel better, set your timing at 5 degrees,ported vacuum with the stiffest springs you can find.....
__________________
Quote:
Originally Posted by Hankrod
Ristows right.................again,




Quote:
Originally Posted by Fasts79Chief
... like the little 'you know what's' that you are.




Quote:
Originally Posted by Fasts79Chief
I LOVE how Ristow has stolen my comment about him ... "Quoted" it ... and made himself famous for being an ***hole to people. Hahahahahahahahahha!


→ Where the kids hang out...

fsjbuilder.org come for the mindless chat,stay for the hand drawn emoticons.

It's like you're unraveling a big cable-knit sweater that someone keeps knitting...and knitting...and knitting...and knitting...
Reply With Quote
  #19  
Old 02-06-2020, 10:29 AM
Mikel's Avatar
Mikel Mikel is offline
 
Join Date: Aug 09, 2000
Location: New Haven, CT
Posts: 6,287
Quote:
Originally Posted by Beach_Dude
Still a little concerned with the lack or pre detonation though.

I know some knocking is hard to hear, but it's not worth keeping you from enjoying your Jeep.
__________________
1969 M715 6x6
1963 J300 Swivel frame
Reply With Quote
  #20  
Old 02-06-2020, 02:59 PM
Beach_Dude's Avatar
Beach_Dude Beach_Dude is offline
327 Rambler
 
Join Date: Mar 03, 2011
Location: Newport Beach
Posts: 565
I'll just drop it down to 12* to play it safe.
__________________
1977 Jeep Cherokee Chief
360 w/ MC 4350
All stock but ignition and slightly modified suspection
Original paint, garaged/non-op for over 15 years
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Buick 350 overheating solved? 1969Wagon General FSJ Tech 17 03-27-2017 10:24 AM
which timing curve for stock 401 mattparliament General FSJ Tech 24 01-03-2014 10:48 PM
My stock timing curve. Millerluck General FSJ Tech 9 02-12-2006 10:57 AM
timing questions kreb General FSJ Tech 10 11-03-2003 01:31 PM
Couple of newbie engine timing and vacuum questions 79_Limited General FSJ Tech 0 09-22-2003 07:04 AM


All times are GMT -6. The time now is 02:58 AM.


Powered by vBulletin Version 3.5.4
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.
corner corner