496ci revamped

Speedlink1973

Well-Known Member
I haven't been on here for awhile
I've remodel a house and built a house
Since my last post.
But last week I made a few minor changes to the old 496.
It is now supercharged because of the belt drive I installed, I had to modify head mounting plate, instead of 3/4" it's 1"5/8
 

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Speedlink1973

Well-Known Member
Soooo...
I have some interesting results.
I'm a bit baffled on a issue
I have 3 different pulls one is N/A
Two under boost
N/A 40 Degrees of timing
One 26 degrees of timing under boost
So I adjusted timing only to 32 all in at 3k
But pulling 2 degrees for every lbs of boost
Now my issue is rpms
I pull timing motor will not rev.
I'm going to go with a colder plug
And I'm running e85.
I put Timing back in I can rev 6500
I take it out it's flat at 5800 ish
Here's a plug from number 2 cylinder
I put anti seize on threads it's not oil.
 

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Speedlink1973

Well-Known Member
Just wanted to make clear about afr and e85 + pro flo 4 , I posted this a few post back.
 

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Speedlink1973

Well-Known Member
OK I did get an answer,
Two different things going on
Issues is resolved with great results.

So one was plug gap, it's now at .020 from .040
I did need one stage colder plug as well
I sent a message to Richard holdener
And he emailed me about it.

Finally get a track day this coming Wednesday!!
 

Speedlink1973

Well-Known Member
It's official a 10 second car still tweaking it I think I can get it to 10.5 next up is chipping away at short time.
 

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Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
index.php


CONGRATS ON THE PROGRESS YOU'VE MADE!!
that's impressive in any street driven car/truck
 

Thunderbolt

Well-Known Member
10 sec street car is impressive :like:

This is interesting, (i also run E85 and a blower, sbc 350) does this mean that its harder to ignite later because the air fuel mixture is more compressed? Seems logic but never heard of this scenario.

I know spark gap often needs to be reduced under boost, thats a no brainer.
What type of ignition system do you have?
I run 30 degrees of timing locked out (tried 35 and 40 also), NGK XR5 plugs .040, never been on a dyno, seems to work ok, but who knows? :thinking:
 

Speedlink1973

Well-Known Member
10 sec street car is impressive :like:

This is interesting, (i also run E85 and a blower, sbc 350) does this mean that its harder to ignite later because the air fuel mixture is more compressed? Seems logic but never heard of this scenario.

I know spark gap often needs to be reduced under boost, thats a no brainer.
What type of ignition system do you have?
I run 30 degrees of timing locked out (tried 35 and 40 also), NGK XR5 plugs .040, never been on a dyno, seems to work ok, but who knows?
Well information I gathered from Richard holdener And David Vizard, it all boils down to physics and chemistry
high compression +e85.
Fuel is not a very good conductor of electricity including gasoline, keeping in mind you are using 28 to 30% more fuel and 50% more with methanol. It's harder for electricity to travel from the electrode to ground strap, because the space in between has fuel and air molecules that are so compressed that the electricity has trouble pass as easily across longer distances.
My best explanation.
 

Thunderbolt

Well-Known Member
Yes, im fully aware of the physics that makes it harder for the electricity to make a spark jump across.
It was the fact that it could spark at say (just an example) 40 degrees, but would struggle at say 20 degrees, assuming its because the piston is higher at 20 degrees and more compression is made at that time, that was interesting to hear.
 

Speedlink1973

Well-Known Member
Yes, im fully aware of the physics that makes it harder for the electricity to make a spark jump across.
It was the fact that it could spark at say (just an example) 40 degrees, but would struggle at say 20 degrees, assuming its because the piston is higher at 20 degrees and more compression is made at that time, that was interesting to hear.
It definitely was interesting.

Sorry for the long explanation, but Grumpy told me along while back that when you post stuff, to explain it as well as possible
Because it's a public forum and not everyone knows or see the big picture.
Especially when you start getting chemistry and physics.
 

Speedlink1973

Well-Known Member
10 sec street car is impressive :like:

This is interesting, (i also run E85 and a blower, sbc 350) does this mean that its harder to ignite later because the air fuel mixture is more compressed? Seems logic but never heard of this scenario.

I know spark gap often needs to be reduced under boost, thats a no brainer.
What type of ignition system do you have?
I run 30 degrees of timing locked out (tried 35 and 40 also), NGK XR5 plugs .040, never been on a dyno, seems to work ok, but who knows? :thinking:
Another thing to keep in mind
My compression ratio is 11.5: 1 with a 210-215 psi compression test for each cylinder. So my effective compression ratio is about 16:0 :1 under 5lbs of boost
Which comes out about the same as say 9.5 :1 under 12lbs of boost.
I'm currently running what came with my pro flo 4 efi , which is basically a msd distributor and a blaster 2 coil.
I pull out 2 degrees of timing per lbs of boost 38degs total all in at 2800 so 28 degrees under boost
 

Speedlink1973

Well-Known Member
At the wheel it made 610 but the torque is crazy 6.5 lbs of boost
750ish at the flywheel
 

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Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
it would make sense that a highly compressed mix of alcohol laced petroleum (LIKE E85) ,(not a great electrical conductor, but a reasonably good heat absorbing mass) of molecules, even though its gaining heat through compression, and that alcohol/air and petroleum mix of compressed atmosphere gases, which must be moving rapidly moving, and being heated by mechanical, compression, as its being compressed and forced into an ever shrinking and thus a smaller/denser area, thus packed rather densely would require a smaller gap so that the electrical arc between the spark plug electrode and ground strap would require both higher volts to jump the gap and more amps to build the required thermal heat to ignite the gaseous mix that might be effectively at least partially insulating the plugs electrical gap, there's roughly a .50 thousands of a second, time frame between ignition and the flame front crossing the cylinder, at least up to about 3000 rpm, once the rpms exceed the approximate 3000 rpm level the combination of rapid compression and turbulence starts to increase the burn speed, that's why you don't need to keep increasing the ignition advance on the distributor past the 3000 rpm and the ever shorter time due to the faster rpms compensates.
(one reason E85 is less prone to detonation issues is ethanol alcohol is harder to ignite due to compression heat)
keep in mind at idle, (lets say 750 rpm)(remember every other time the piston hits tdc is the compression and ignition cycle) thus at 750 rpm you need an ignition electrical arc 6.2 times per second at the spark plug, for the flame front to have time to fully ignite the cylinder, at idle but by 7000 rpm you need roughly 58 times a second.
remember any pressure over the piston before TDC reduces power, and you make power with pressure above the piston as it travels down forcing the crank through the connecting rod on the crank journal , but the pressure drops rapidly as the volume , of burning gases providing that pressure above the piston increases, and the fuel/air mix burns out.
chart3e1.jpg


obviously the type of fuel and the volume of fuel effects the burn characteristics
typical gas burns out before the piston has dropped more than about 25-30 degrees
nitro methane burns longer and provides more total pressure per gram of fuel so it continues to burn to about 50 degrees past TDC.
engbalq5.gif

Cylinder-Pressure-lLrg.gif

 
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