I'm going to adjust my timing from smog factory settings

[udidwht]

Good to see your coming along nicely, ive just finished the brake system and a new starter. The starter was real brain damage...I have a 81 454 in a 83 model yr, there is a difference between the two, it was a frustrating experience.

As to your recurve, I would not get caught in AFR'S...fuel injection may seem the same yet it is completely different. To over simplify one is forced induction and carbs are vaccum/ signal induction....meaning FI one can force the fuel induction and carbs require a rejetting..which can be quite frustrating. Above and beyond that RV engines are HEAVY DUTY CYCLE engines, which require entirely different AFR'S.  Trying running a AFR of 14 and you will burn up your engine in short order...think along the lines of 11/12 and some change.

Running 14:7 under excess load or WOT certainly will burn an engine up. The 'death zone' under excess load/WOT would be 14-15AFR. But at a part throttle condition/light load 16:1 is actually cooler than 13:1. One needs vacuum advance for lean cruise tuning. Or a digitally mapped curve.

Load = Throttle position

[Eyez Open]

I respect and understand your discipline of thought. I will also say I am by no means a blogger.

How I see afr would merely be a reflection of it's state of tune or better said the results. With one caveat and that would be how efficient the engine would be..aka making maximum power safely. Setting up a engine to run at 15/1 would be a disaster..But tuning a engine to maximize power and efficiency at all loads safely would be the goal. Checking the afrs would merely be the results.

Maybe trying to marry old school tuning to popular efi tuning. I need to think about that for a moment or two. Back to some simple concepts, base timing and mechanical timing are set in stone...there combined timing is always limited to say 36^, only under a low load or no load does vacuum advance come into play. A vacuum advance can/ system is a load compensator making it capable of advancing timing under no load or simply not functional under a load.


So far I've been able to run at 15 initial and 20 degrees mechanical, I limit the vacuum advance to 10 degrees. Meaning when the engine is operating under a load maximum advance is 35 degrees,when at cruise vacuum advance takes to to 45 degrees.  Not a rattle,not a ping just smooth butter. I've not had a chance to run in any mountainous areas yet or high elevation yet but that is coming.

With all that being said the carb did need a rebuild and some tweaking on the secondaries, but today it runs cooler and is a much stronger engine.

Each engine will respond differently,the engine I am tuning is a 454 low compression 7.5 ratio something and peanut port heads. Now change that up to a 5.7 engine with Vortec heads, the above timings will more than probably cause detonation.

[zMadMechanic]

@Winningbago 2 years later... what are your final thoughts??

[RockwoodMike]

If Winningbago comes back with an answer...that may not be your answer to use..

The true answer is........it depends...on what??

Timing is going to be different for...Compression ratio..thermostat temp..hotter engine will ping easier..

Carb jets..a carb with 74 jets will ping easier than one with 77 jets

Differential ratio..low gearing will be easier to get moving the RV than high gearing..

You need to buy Cliff Ruggles book on the Quadrajet carb..In chapter 2, he explains how the different systems of the carb works..

A typical Q-jet looks like a complicated convoluted mess..But in reality, it is a pretty simple thing to understand..

In his book, he said a simple sentence..in regards to timing..."Experiment"

With my 440 Mopar, this is my setup to start my experimenting..

20 degrees initial..14 degrees centrifugal..with light springs to have that 14 degrees at 2000..
and then PORTED vacuum to add 4-6 degrees for final cruising timing...

And I will see what happens!?!..My engine has a 9-1 CR..A Edelbrock 1905 Q-jet clone (equivalent to about a 1982-5 Q-jet)..The jets were 73 now 77 size (If I remember right)  Ruggles suggested I up the jets because of the extreme weight of the motorhome..

The problem with these performance engine forums (Olds, Buick, Chevy) is they are dealing in a different realm in comparison to  a 15-18K big fat motorhome..

The best that I understand in regards to timing for a motorhome is about 32-36 TOTAL timing..Because of the extreme load the engine is under even just cruising down the highway..

Experiment..

[udidwht]

Remember...

Load = Throttle position

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