Advance Springs arrived from Petronix today!Rick May want to help here!

[tonyiiiafl]

I received the advance springs for my FlameThrower distributor today with instructions from Petronics. However, I haave a question on the TAT for this against the instruction sheet.

I received 3 sets of springs, light, medium and heavy for the distributor. they list the advance curve (in degrees) as the following at those specified RPMS:

500 1000 1500 2000 2500 3000 3500
Copper 0 5 16 24 24 24 24

Silver 0 0 3 10 22 24 24

Bronze 0 0 0 3 10 18 24

These show a total of 24 degrees advance in timing. Question, if these are the advance in degrees, how do I get to the 30 total advance timing as specified with the springs sent? Do I instead of setting the idle timing at 8 degrees BTC set it at 4 which will give me a total 28 degrees TAT??

[2850Bounty]

Tony, can you link me to your other recent thread..... seems to me I went into this....... Maybe not.

Also, I can't tell for sure how your advance is aligning with the RPM to form a chart! Can you adjust those into a column format?

Example:
RPM.......... 500 .. 1,000... 1,500... 2,000... 2,500.. 3,000.. 3,500
Copper kit = 0 ....... 5 ....... 16 ....... 24 ....... 24 ..... 24 ...... 24
(w/ BASE = 8 ...... 13 ....... 24 ....... 32 ....... 32 ..... 32 ...... 32)
Obviously, the copper kit is out!
The limit may be workable.... but the curve is way off for marine.... it's even a little stiff for automotive, IMO.


Or

RPM..........Copper.... Silver.... Bronze
650 = ......... 0 ......... 0........... 0
1,000 = ...... 0 ........ 0 ........... 0
1,500 = ..... 5 ......... 3 .......... 0
etc.

And remember, these specs are likely minus BASE advance. So this is the distributor's mechanical advance only.... and your TA must work with your BASE setting.



Tony, if you know anyone who owns and would run this on their machine....., that would be my suggestion!


.

[tonyiiiafl]

Ok, let's try this then, the format looked good when I did it!



...RPM.......500..1000..1500..2000..2500..3000..35 00..4000..4500..5000

Copper....0.......5.......16.....24.......4.....24 .......24....24......24......24

Silver.......0......0.......3........10......16... .22.......24...24.....24......24

Bronze.....0......0.......0.......3.........7..... 10.......14..18......22........24

So, this looks like there is NOT enough TAT with any of these springs then?

[2850Bounty]

Originally Posted by tonyiiiafl

Ok, let's try this then, the format looked good when I did it!


...RPM.......500..1000..1500..2000..2500..3000..35 00..4000..4500..5000

Copper....0.......5.......16.....24.......4.....24 .......24....24......24......24

Silver.......0......0.......3........10......16... .22.......24...24.....24......24

Bronze.....0......0.......0.......3.........7..... 10.......14..18......22........24

So, this looks like there is NOT enough TAT with any of these springs then?

Add BASE to these numbers!
Tony, go back and look at my previous post.... apparently I was doing an edit as you were posting.

[The_Sea_Word]

Geez guys, 24 mechanical + 6 static = 30 degrees.

If your static is at 8BTC then your total is 32 degrees.

No vac advance makes it easy.

[tonyiiiafl]

Originally Posted by 2850Bounty

Add BASE to these numbers!
Tony, go back and look at my previous post.... apparently I was doing an edit as you were posting.

DUH! So it looks like the SILVER springs are my best bet. That would give me the 30 degrees TAT at the 3000 Revs. Now as we have stated in previous posts, the TAT is more important than the static timing. So i would be putting the springs on and seeing where I am at each RPM level.

[2850Bounty]

Originally Posted by The_Sea_Word

Geez guys, 24 mechanical + 6 static = 30 degrees.
If your static is at 8BTC then your total is 32 degrees.
No vac advance makes it easy.

Will, if it was that simple, I'd have not asked for more info!

Originally Posted by tonyiiiafl

DUH! So it looks like the SILVER springs are my best bet. That would give me the 30 degrees TAT at the 3000 Revs.
Now as we have stated in previous posts, the TAT is more important than the BASE timing. So i would be putting the springs on and seeing where I am at each RPM level.

Yes, you can map it out and put into graph form and look at it.
Without knowing the engine build, keep in mind that a TA of 30* @ 3k rpm may be a wee bit early.
If you ran a TA of 30* @ 3k rpm before, then you may be OK.

Tony, Make sure that the markings on the balancer are accurate.

http://www.summitracing.com/parts/MRG-1591/?image=large

Let us know how it goes!

[88fourwinns]

I think you need to know the advance curve that was specified for this particualr engine to be able to make a good choice....I have advance charts in my '88 OMC shop manual for all the engines..I know this is a Volvo though there may not be that much of a difference....for one thing the curves are different for different engines and also so are the base timing specs...

the 5.7 4bbl Cobra starts with 8 * base timing...

10* (18 total) of centrifugal advance at about 1800 rpm
12* (20 total) at about 2000 rpm
20* (28 total) at about 2900 rpm
21* (29 total) at about 3000 rpm and it stays at that level to the end of the chart at 3500 rpm....

the 5.0 2bbl Cobra has 10* base timing but the curve is lower and less steep...So I'd want to see if I could dig up the OE curves for that engine and see how this compares...
I checked my old 4.3 against the factory charts with it in the water so I could run it in neutral at those speeds and it's pretty much right on the specs (used an advance timing light I got when you could still set timing on cars....)

[2850Bounty]

A BASE of either 6* or 8* ....... or even 10* will usually work for the SBC marine.... They tend to start up on this much spark lead and idle just fine. 8* or 10* BTDC may be preferable.
The more important aspect of timing (regarding possible engine damage) is TA..... not only TA, but at which RPM TA comes full on! (Hence the curve!)
The curve is important!
Much is determined by engine build.... I.E., piston/head selection as per what the factory specified.
**Dished pistons and small chamber heads are best if this is held back some.
**Quench Effect piston, and the appropriate head chamber size, then this may be increased some.

2* too much TA, and/or being full out too early (even as little as 200 or 300 rpm), can cause detonation under the right conditions. This is what we want to avoid, yet get our best performance!

Specs for a M/C or OMC SBC may not be suitable for Volvo, or a custom built SBC, for example..... and visa-versa.

When/if in doubt, error on the lessor side of the scale, eliminating detonation.

.

[Bellingham_2850]

I couldn't see how the stock Pertronix spring kit (or a mixing the colors) could get me to the VP numbers:

Tony, here is the data I found for my VP AQ260A 5.7L engine (V/P manual):

RPM Advance (as seen with timing light)
600 8 (base timing)
900+- mechanical advance starts
1200 12
1600 16
2000 20
2400 23
2800 27
3200 30
3600 30
4000 29
4600 29


When I graphed this it was a very straight line. So be careful, not only is base timing and total advance important, but also how fast the advance increases (the slope of the line).

If you figure it out, I'll probably then convert over to Pertronix too!