Let's talk base timing theory. And how much timing I should shoot for.

Nikkormat · Post by **Nikkormat** » Tue Apr 11, 2017 4:14 pm

Lets talk timing theory for my next engine. .040 over 401 with 9:1 compression and a K8600 cam.

- Where should I bring the mechanical advance in?
Some on the internet say all in by 3000, some say at your target cruise RPM, some say by your peak operating rpm. What do you think?

- How much advance should I have at idle?
Total, including vacuum advance hooked to manifold vacuum. I can use an adjustable cannister to hit about any number. What should I aim for in general?

- Is it better to have more mechanical advance or more base timing?
If I have a target total mechanical advance number of say 32° is it better to have more of that curve be mechanical advance? Or initial advance?
The reading I've done suggests that having higher base timing vs. higher mechanical advance allows for better throttle response. Is that correct thinking?

az chip · Post by **az chip** » Tue Apr 11, 2017 6:14 pm

If the timing chain is ok, I think book timing or close to it.

Nikkormat · Post by **Nikkormat** » Tue Apr 11, 2017 8:40 pm

az chip wrote:If the timing chain is ok, I think book timing or close to it.

This isn't for a stock engine. And in my experience the stock setting gives too much timing if you have the wrong distributor. Wyatt's 360 has a distributor that gives 24° of mechanical advance. As that all starts to come in at 4000 rpm it pings bad with the stickered 16° of advance.

az chip · Post by **az chip** » Tue Apr 11, 2017 9:22 pm

Nikkormat wrote:
az chip wrote:If the timing chain is ok, I think book timing or close to it.

This isn't for a stock engine. And in my experience the stock setting gives too much timing if you have the wrong distributor. Wyatt's 360 has a distributor that gives 24° of mechanical advance. As that all starts to come in at 4000 rpm it pings bad with the stickered 16° of advance.

How would I know that? None of that info was in your first post. Start with a complete picture and we can get closer to a complete answer that you are looking for. Are you talking your 401? which 360 in your 18 FSJ's are we talking about? Can I buy a vowel?

Nikkormat · Post by **Nikkormat** » Tue Apr 11, 2017 10:17 pm

az chip wrote:
Nikkormat wrote:
az chip wrote:If the timing chain is ok, I think book timing or close to it.

This isn't for a stock engine. And in my experience the stock setting gives too much timing if you have the wrong distributor. Wyatt's 360 has a distributor that gives 24° of mechanical advance. As that all starts to come in at 4000 rpm it pings bad with the stickered 16° of advance.
How would I know that? None of that info was in your first post. Start with a complete picture and we can get closer to a complete answer that you are looking for. Are you talking your 401? which 360 in your 18 FSJ's are we talking about? Can I buy a vowel?

I'll re write the first post to make things simpler.

Nikkormat · Post by **Nikkormat** » Tue Apr 11, 2017 10:33 pm

az chip wrote:which 360 in your 18 FSJ's are we talking about? Can I buy a vowel?

And for your information I only currently have 1 FSJ with a 360 and my name on the title.

How many I've owned/played with or done the tune up on in the past few years is another story...

ghcoe · Post by **ghcoe** » Wed Apr 12, 2017 6:49 am

A lot of this is going to depend on your cam profile. When does torque come in? Where is peak power? Then gearing and wind resistance? Mechanical advance advances with no regard to outside inputs. Vacuum advance responds to loads, whether it be hills, wind and weight hauling. There is a ton of variables. Stock curves will caution to "safe" parameters and a lot of performance can be achieved with timing curve manipulations. Some of the equipment used to curve distributes are no longer easily available with the advent of electronic control. So at this point it becomes seat of the pants tuning. I do not envy that. I just went trough that on my 360 when I did the Ford Distributor, Chevy Module conversion. Lots of trial and error until it feels right. Is it right now? I do not know, but it feels good.

There is a app that can help https://play.google.com/store/apps/deta ... tion&hl=en . Find a stretch of road you can use to test your curves and keep at it until it is right. Start with just mechanical until you have no noticeable ping under hard acceleration , play with springs until you get the best results then detune 1-2 degrees to get you "safe". Next is vacuum, no ping then all is good. Ping then back off on timing a bit till it is good. This should get you close for normal driving, but may be still too advanced for towing and heavy loads.

Unfortunately there is no easy way to set a curve. Each engine has its own likes and dislikes as well as driving styles. Good luck.

REDONE · Post by **REDONE** » Wed Apr 12, 2017 8:57 am

Regarding vacuum advance, keep in mind that it was originally meant as an emissions control, not a performance addition. I just got the 401 in my dad's Wag dialed in by dialing it in with vacuum plugged. Once it was pulling max manifold vac at idle with no ping under load, I hooked up the vacuum to ported then I took it on I-70 on-ramps to test and tightened the vac advance 1/2 turn counter clockwise at a time until no ping from that either. All of our Duraspark dizzies have adjustable vac advance, which is nice. You can tell by whether or not the vac motor has a hexagon portion. My reman dizzy has a 2mm adjustment screw though, not 1/8".

EDIT>>> I built that 401 with 10:1 compression, performer intake and cam, and 600cfm 1406. It's tied to a stock TH400 with a stock stall torque converter and 3:31 gears turning 31s. It's a snappy driver but still a fully drivable rig. I probably could have messed with the mechanical advance but didn't feel the benefit was worth the hassle

Post by **fulsizjeep** » Wed Apr 12, 2017 11:41 am

Matt! That yellow 401 went in your Dad's Wag? <goody goody>

Post by **fulsizjeep** » Wed Apr 12, 2017 11:43 am

Why the heck is this thread in general chat? I have a vowel for that... OYE

REDONE · Post by **REDONE** » Wed Apr 12, 2017 11:48 am

fulsizjeep wrote:Matt! That yellow 401 went in your Dad's Wag? <goody goody>

Yep! But we shot it AMC blue, to match the rest of his Wag.

That other 401 I might build is the one that we took out.

Post by **fulsizjeep** » Wed Apr 12, 2017 11:53 am

That is cool as chit man. Just knowing it is on the road. YES!

REDONE · Post by **REDONE** » Wed Apr 12, 2017 11:57 am

fulsizjeep wrote:That is cool as chit man. Just knowing it is on the road. YES!

And it runs like an angry gorilla, with no heat issues, .060 over!

Post by **fulsizjeep** » Wed Apr 12, 2017 11:59 am

Chingus Domingus! It should.

ghcoe · Post by **ghcoe** » Wed Apr 12, 2017 4:10 pm

REDONE wrote:Regarding vacuum advance, keep in mind that it was originally meant as an emissions control, not a performance addition.

Not necessarily. It also helps for easier starts and better fuel economy. Been on cars before there was even a concern for emissions.
http://www.onallcylinders.com/2015/03/2 ... u-need-it/

68glad · Post by **68glad** » Wed Apr 12, 2017 6:31 pm

ghcoe wrote:A lot of this is going to depend on your cam profile. When does torque come in? Where is peak power? Then gearing and wind resistance? Mechanical advance advances with no regard to outside inputs. Vacuum advance responds to loads, whether it be hills, wind and weight hauling. There is a ton of variables. Stock curves will caution to "safe" parameters and a lot of performance can be achieved with timing curve manipulations.

X2. Give it what it wants.

http://www.badasscars.com/index.cfm/pag ... /prd76.htm

Full Size Jeep Network

Let's talk base timing theory. And how much timing I should shoot for.

Let's talk base timing theory. And how much timing I should shoot for.

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Re: Let's talk base timing theory. And how much timing I should shoot for.

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Re: Let's talk base timing theory. And how much timing I should shoot for.