max compression on pump gas\steel cylinder head\241 @ 50 cam

[1wild&crazyguy]

T67, Another thing to consider is the timing curve. Once the engine goes into ping or detonation, it won't "get out" until you let off. However minor changes in the timing curve, meaning the rpm points at which the advance comes in, can stave off the first signs of it and thereby stop it altogether. Also, ping and detonation come from liquid fuel, not vapor. So anything you can do to help make the mixture more thorough the better. I've found by slowing the advance to bring it all in by say 3000 rather than 2400, and using the power valve ratings rather than the acc pump or jetting to richen things I can tune ping away without any loss of response or power. Not all engines need the standard "34-36° all in by 2400" deal. Many open chamber combos relly don't.

just the ones with proper combo of octane/cam timing/compression.
yes there are a lot of...in a sense, crippled combinations out there.

later total advance deals in less initial load vs timing.
closely related - detonation problems with too Numerically low 'gear' for the cams rpm range while having proper/recommended comp ratio.
you usually see like 'more timing' with a slight retard at/about a certain rpm where it can occur unbeknownst -circle track stuff.

 

[dgc333]

The only purpose of advancing the timing is to light off the mixture early enough so that maximum cylinder pressure occurs around 20 degrees ATDC. When this happens the engine will generate it's maximum torque and provided the highest efficiency. To little timing and the max cylinder pressure occurs late and to much timing it will occur early, either case the engine does not produce max torque.

"octane/cam timing/compression" are only a piece of the equation; the velocity of the mixture entering the engine, the temperature of the mixture entering the engine, the finish on the surfaces of the combustion chamber, the temperature of the surfaces of the combustion chamber all play just as important a part in what an engine needs/can tolerate for timing. The 34-36 number is gets you into the ball park, after that only testing of your particular combo will maximize the engines output.

As moper stated anything you can do to make the mixture more homogeneous will reduce the tendency to detonate and will also reduce the amount of timing required to obtain max power. It is this principle that makes modern high swirl, closed chamber heads so good at resisting detonation and why they require much less timing than older designs.

 

[1wild&crazyguy]

when you have a smaller combustion area,it's herded into a smaller more controllable area which mixes 'still'-from squish -it's burns faster/more even-takes less time, less need to for earlier ignition timing to get all spent.
Larger 'open chamber' is the opposite, except at the point the octane no longer resists combustion 'beyond it's compressible/combustible limit' and pre ignites where ever in the chamber space it wants [hot spots-sharp edges], & however early and then crashes into the flame front/ignition caused by the spark plug-2 fronts crashing into each other,pre ignition

this why I say to cut the chamber to the bore size, because the damn chamber edges hang out into the bore and become...'hot spots'.

A few others including myself seem to be the only people doing this, hmmmm....that sux for the rest who aren't getting it yet.

dave, you say the magic # is 34-36*, but then say as long as you mix the fuel super duper you make more power and need less timing to make max power.
See, when the fuel is better mixed/homogenous, it burns faster which will put the psi on piston sooner=less timing required.

Funny how all my engines run best with only 32*...

And btw, I heard 15* or just after TDC, buts whats a few degrees...lol

'tubulence' also mixes, but there is a fine line and from where it starts.

compression also does some mixing, the more compression , the less need to intro more turbulence , and we talking about raising the compression.
I wonder how much port induced swirl is going on in a nascar motor.
Any rpm beyond idle and you can bet there is plenty of velocity.

Cooler fuel-denser , but what if it's hot/thin air out? lean it some, I see not much there when it comes to keeping the ping monster away, but I work areas before that..

to me, timing is combo specific, I do agree there is a window of a generalized setting, but for the most part, what happens as you raise the timing-rpm/speed go's up=I think thats hp. I mean john doe's 7.9-1 318 likes 38* total, while jane doe's 9.2-1 318 likes 32*-lower compression =less cylinder turbulence 'at least on that end' longer to burn it all.
Just thinking out loud here, bouncing some sht around n such..

 

[T67POWER]

Less combustion area(smaller) = more atomization (stirring effect)and higher efficiency=LESS TIMING.

Large combustion area=less atomization and less efficiency=MORE TIMING.

I am going to check my cylinder pressure again on both my 318 and 360.
I will use a different gauge this time.
They both checked out to 148psi to 150psi and it's making me wonder if the gauge is bad.
Two completely different engine combination's and the same pressure???
Going racing tonight and will be changing some plugs, so it's a great time to re-check it.

 

[crossram383]

crossram...

185 on 87.
That's not to bad.
What is your timing set at????

It's around 36 degrees . I put light springs (really light) and recurved the distributor . Something like 16 initial 36 total all in by 2200 rpm.
Had MP 590 solid in motor ( way big for my combo...but all I had at the time ) car would run 110 in the quarter no matter what gear 3.54 or 4.88 or timing setting from 32 degrees to 38 degrees . Best time was 12.5 @110 with a 1.6 or 1.65 sixty foot (can't remember).
After swapping cams gauge pressure went from 160 psi with .590 cam to 185 psi with .528 cam . Way more bottom end performance with smaller cam with no perceivable loss of top end power .It's a much better match for the rest of the combo.
I haven't taken it to the track yet to see what it runs with the small cam but the car is violent off the line.....Hopefully it'll break into the elevens !!!

 

[dodge freak]

I did one up on Mopar, I delay full advance until 3,500. Got a msd e curve dist. Do have 25 degrees at idle and all 10 more in at 3,500. Its a real cool dist. Try to have just 10 more degrees come in starting at 1,250 rpm and all 10 in @ 3,500 with springs and weights, LOL.

The e curve dist is all electriconac, has many timing curves you set by 2 tiny dails. I firqure better to be extra safe. At 3,000 rpm it was fine.

 

[moper]

T67, Pressures in any engine are only based on three variables: Stroke length, ring/valve sealing, and the intake closing point. So any two engines could have exactly the same readings regardless of the cam/displacement. I've run big block open chambers at 185psi with no trouble. I've also had quench-built closed chamber iron heads that had 190psi that were prone to ping without careful attention to setup. It also means in terms of pressures in the cylinder in relation to the burn and piston/crank angle that different strokes require different amounts of lead to have the cylinder reach peak pressure on the piston top when the crank is around 18° past TDC. The longer the stroke, the longer the piston stays at TDC before moving away and the longer there is for pressure to build before the crank is in the best position. Some 3.31 engines running open chambers may like 40°, some 4" engines may only like 28°... Nevermind adding altitude, fuel type, and convertor/gearing into it. Back when he was new and less educated RyanJ used to used blue dye to simulate and watch liquid flowing through his port and valve job. He used to post on Moparts to more experienced guys to work things out. It was wild to see what minor adjustments in the porting or seat/back-cut angle could do for getting a poorly mixed liquid into the chamber to burn effectively. It's the liquid fuel that is the problem with open chambers, plus as 1Wild says all that dead space above the top ring and between the bore/chamber edge/gasket ring.

 

[djwhog]

yep all that Moper says affects what is called burn time, and that is what detonation is all about, exploding or burning aka preignition before the correct time. to give a short reply.

many many variables, of course anything that make heat adds to the condition.

 

[1wild&crazyguy]

Less combustion area(smaller) = more atomization (stirring effect)and higher efficiency=LESS TIMING.

Large combustion area=less atomization and less efficiency=MORE TIMING.

I am going to check my cylinder pressure again on both my 318 and 360.
I will use a different gauge this time.
They both checked out to 148psi to 150psi and it's making me wonder if the gauge is bad.
Two completely different engine combination's and the same pressure???
Going racing tonight and will be changing some plugs, so it's a great time to re-check it.

smaller tends to deal in the closed chamber bracket, so it's QUENCH that aids cylinder mixing.
High compression also causes turbulence/mixing...