If you're dizzy is curved to all in at 3000 you won't be all in at cruise speed unless you have pretty low gears. Even small pedal movement will drop vacuum and retard spark.
ok u are cruising with say a 308 diff around 2700 a 355 close onm 3000
Considering the curve is elipical and the top is close to horozonal then at least 90/95% of the cent is all in...say 2900 of 3100 rpms and 34 degs
So there is around 30 degs there
Now cruising with a bit of a cam at those rpms u will have 15 1/2 to 18 deg of vaccuum.
And considering the VA will be all in at something below 10 or 12
there is another 12 degs there
Now u are sitting right on the limits of the 40/42
Not have AFRs correctly set and increase speed a couple mph ....u are over into dangerous area...And the sad part is u will not know it untill something fails in the engine over time
This will then be blamed on the engine builder or part failure... NOT the tuning specs established when the engine was dialed
I'm not familiar with knock sensors that work with non computer controlled engines?
u do not need a computer controlled engine to fit knock O2 imap or throttle position sensors....
And data loggers are used extensively in the racing world but can be expensive.
No they are not.. this is the 21st century....the computers that put the man on the moon cost millions.. today we have more computing power in our smart phones
My data logger paid for its self just in the savings in fuel in the 1st 6 months
The other terms you're tossing out such as TPS, Map, MAF and O2 are used in EFI setups not much for carbs
Really? any techo on a dyno will hook up these to your engine if they know what they are doing.. and if the dyno is too old then they will have a modest data logger like an innovate unit that will do all that... on non EFI, carbed, non computer engines.
This is the 21st century.
Power is efficiency... and so is economy which is why carbs have idle , cruise/economy and power circuits separately... and the dizzy also has power (cent) idle (initial+VA) and economy/cruise VA separately
Something so basic that most ppl just cant seem to under stand....
Old school we would advance until detonation and back off a couple degrees.
yep.. keep in mind I have been messing around for over 40yrs now..
A note on that "old school" BS
Advance an engine and it sounds
more powerful... put it on the track and it is slower... its like an optical illusion....something we stopped doing in the late 70s early 80s.
The best position is to retard ill withing a couple degrees there is a noticeable drop off in power (measured distance/stop watch) and economy.. then increase 2 or 3 degrees.
look we spend thousands building the engines ,10s of thousands on the car.. 1000s on the tools in the workshop, then when it comes to dialing the engine into the car we choke on a few 100 dollars for a data logger... but are quite willing to spend even more on a dyno tune which simply tunes to the best of what is in the current carb/ dizzy settings and stil not have the full potential.. usually not even close
I just dont get the above logic.. doesnt make even basic common sense... for a few 100 bucks.
And to clarify something else
Dailing an engine in
...that is establishing the tuning pionts ... like the tuning specs in the workshop manual u tune the car to for best performace/ economy
Tuning an engine
... that simply re setting , if required , the carb , dizzy to the specs established from the dialing in
or as most tuners do... set the engine to the best they can with the current carb/ dizzie setting in the engine.. which are usually way wrong... patching maybe a better term.
So ppl have a choice.
Spend a small fotune on the car... then at the end spend weeks and money making do with what u have.
Spend a few 100 dollars, have a very nice tool in your arsenal in the tool box, and dial the engine in in the same manner as car manufactures do to get the ultimate performance/ economy
And get over the 'old school' "Im not interested in economy BS" dial the engine correct in and 'unfortunately' u get the dreaded "ecomomy " thrown in for free.
Old school tuning mid 14s 18 mpg to 21st century tools [email protected]
mph and 18mpg to 32 mpg couple road trips and paid for the data logger.
I now use it with a couple m8 setting up their cars , and even on our old 1912 to 1951 vintage British technology cars.
Before simply ordering a given VA.. u NEED to estblish your best engine specs
The carb AFRs in ball park
The mixture/ idle speed/ butterflies sorted
Then find the best STABLE idle advance setting
The best total advance setting.
Then (if no knock sensor) adjust the VA vaccuum characteristics and the nuber degs in it and the cent to suit and stil be under 40/42 degs
ANY ONE of the above changes will change the vacuum characteristics of the engine which will most properly mean the VA canister u get will be the wrong specs.
How to change degs in the cent, change degs in the VA how to change the vaccuum start AND the vaccuum stop points in the VA I have described many times in these forums over the yrs.
If u cant be bothered to read (not skim) all of the above u have no interest in getting your engine to run as well as it could.