Points Distributor - P30 Chassis BBC into C10 SBC

[Gromit]

This question is a longshot; but I never cease to be amazed with the savvy of the people on this site

So here goes with a really long post - and maybe someone will learn from my errors in thinking or by someone's insightful query or answer to this - and in my defense to what many will doubtless think is an overly long post let me please say ignition is really important and I think the more of us can master all the details the better.

What is the designed in curve for this 1973 BBC 454 Points Type distributor?

(I'm one of those diehard Points Distributor fans)...

I'm thinking of running the following Delco Remy V8 Distributor in my mostly stock or Stock Type 1970 SBC 350

Which has:

No stock emissions controls other than evap system for fuel tank and PCV valve hoses (as stock for that year)
Auto Trans TH350
Compression 8:1
Hydraulic Valve Flat Tappet
Lift is .450 Intake / .460 Exhaust
Duration @0.50" is 222 Degrees Intake and Exhaust
114 Degrees ATDC Intake and 114 Degrees BTDC Exhaust
Rocker Ratio 1.5 to 1
Holley 4160 List 3310-3
Edelbrock Performer 2101
Headers and 3" exhaust - all else stock

Part Number for the Distributor is 1112105 and Date Code is 3L15

I believe that this 3L15 date code translates to the year 1973 (from the first digit);

And then the "L" meaning "November" (because ignoring the letter "I") "L" is 11 digits from "A" - (hope that makes sense)

And the "15" in the Delco Remy date code being the day of month of manufacture (not necessarily date installed, though.)

So November 15th, 1973 and the 1112105 - rare as it is) seems as best that I am capable of determining - a part number for a distributor used in a 1974 P30 Motorhome (or bare) Chassis with a Big Block 454 Motor.

If this distributor were in a car or pickup by 1973 we would be well into at least the California emissions stuff -and starting to get complicated - but this was a commercial truck chassis so maybe not? I do see this distributor definitely used on a 1974 P30 Motorhome in the GM parts Wiki.

My understanding is that BBC points type distributors can generally be used in 350 SBC's - (but of course check the end play before running)..

My motor does currently run with this distributor - and the end play seems okay and if anything a little sloppy as was usual..

The distributor also has the following codes:

A - (Aluminum Housing)
S - (Single Point)
CL - (Cam Lubrication on Breaker Plate)
V - (Vacuum Advance)

As most of you know - Delco Remy Points Distributor Manufacturing Plant was closed down in the early 1970's with introduction of HEI - so most of the records and/or documentation or guidance for these later type points units was lost or is gone to the winds for these distributors...

But my worry in using this distributor in my 350 SBC is about the span of designed in vacuum and centrifugal advance - I've installed the stiffest available springs on the reluctor; and my vacuum advance can is an Eiclin VC1605 or ID #B-9

And this Vacuum Advance Can starts to move at 7 to 9 Inches of Mg; and with maximum advance of 10.3 Distributor Degrees at 16 to 18 Inches of Mg

So that is too stiff to consider using manifold vacuum directly to the can; because the vacuum advance will by no means be even close to being all in at the 10 to 12 inches of Mg that my 1970 engine can make at 650 RPM to 750 RPM idle; (not to mention being all in at two inches below that)..

So that means this VC-1605 vacuum advance by itself is capable of producing 20.6 Crankshaft Degrees of advance at the harmonic balancer (assuming my engine could even make 16 to 18 inches of Mg - which again it cannot).

I'm trying to work with what I have - so I plan to use ported vacuum for my existing advance can (and by "ported" meaning attaching the distributor vacuum advance hose above the manifold and at the carburetor - letting the motor idle with no vacuum at all sent to the vacuum advance can at idle RPM).

Also with the stiff springs on the reluctor that should mean there will be zero additional centrifugal advance at the 650 to 750 RPM idle (so the timing won't be hunting either from vacuum or from centrifugal advance).

In my rookie mind that means I should be free to set the initial timing to 8 BTDC; (compared to the stock spec 4 BTDC - because I have a Edelbrock Performer 2101 and Holley 4160 450 CFM 4 Barrel carb and headers - and because gas no longer has lead in it in 2015 and because folks have learned a thing or two since 1970 about idle cooling..)..

So theoretically my current best estimate of the curve for this distributor is that it would have 32 to 40 Crankshaft Degrees designed in at 4200 RPM (which is from a 454 L54 spec for a 1974 Chevelle).

So adding my 8 BTDC initial that would be 48 total advance Crankshaft Degrees of BTDC advance at 4200 RPM (which I can promise my engine will never see that kind of RPM unless the Cops are after me).. but anyway; any thoughts? I am a pencil necked accountant - so feel free to sharply correct any flaws in my logic - I won't be able to do much about it unless your neck is even skinnier :-)

[Grumpy old man]

You say it runs and drives currently ? Your way over thinking things put the shifter in D and push the go fast pedal !

[Gromit]

You got me there Grumpy; point taken and thank you; it does still help to hear it again so I'll try and unlax a little.

Overseas I heard that from different unrelated people and even strangers so that I knew it had in general to be very true - they would say "You are thinking too much!" (and I heard this more than once - so Yeppers!).