Detonation in my 59AB engine

[Mart]

You're overthinking it. Back the timing off.

[Ol' Ron]

60cc's is a small chamber, especially with a HI lift cam. What cam are you running??
Gramps

[rotorwrench]

I don't know how many states are affected but there is gasoline produced for winter time operations. I know it was used in Colorado when I lived and worked there. If the weather would get real warm suddenly while this fuel was still in use, there were vapor lock problems and also problems with the dreaded ping under acceleration.

[qmdv]

Originally Posted by Ol' Ron

60cc's is a small chamber, especially with a HI lift cam. What cam are you running??
Gramps

Not sure about the cam as it had no marks. My dad's old buddy Kong Jackson put it on a lathe to check lift and overlap and said it would be a good street cam. Intake has .301 lift and Exhaust has .345. Not exact but real close. One of my sons was using my dial indicator as a toy so a Vernier caliper will have to do. Ordering head gaskets from Van Pelt this morning

To retard spark I am assuming loosen the screw and move it counter clockwise.

[flatjack9]

Yes

[qmdv]

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Originally Posted by flatjack9

Yes

Do you know how many degrees each mark is

[47topless]

http://www.vanpeltsales.com/FH_web/f...str-timing.htm

[Zeke3]

I am guessing each mark is two degrees. Based on a diameter of 4.00 inches. the marks for two degress would be a 0.070" apart, a little more than 1/16". This dimension would vary based on the circumference of the distributor where the marks are located.

[Ol' Ron]

Yes, That sounds like a mild cam, The Max#1 has .350 lift. I think. So the 59cc chamber might be possible.
Gramps

[tubman]

I agree that that sounds mild, not much more than stock. But I didn't think that it is not lift that effects the compression, but duration. A longer duration would result the intake valve opening earlier causing bleeding off compression resulting in a lower effective combustion ratio.

Or do I have this wrong?

[cadillac512]

Originally Posted by tubman

I agree that that sounds mild, not much more than stock. But I didn't think that it is not lift that effects the compression, but duration. A longer duration would result the intake valve opening earlier causing bleeding off compression resulting in a lower effective combustion ratio.

Or do I have this wrong?

Pretty close- increased duration closes the intake later and that's the thing that affects cylinder pressure at low speeds. You're correct about the increased lift- more lift alone will not affect compression.



Terry

[vilanar]

And more lift causes ex valves to hit the head if chamber is that small.... although it don't look that small...

[Ol' Ron]

There is two types of compression. One involves the closing of the intake valve and it has a different name, and is not the compression ratio of the cylinder. I think the L-100 knocks about 2 points off the actual ratio. Getting told for this stuff, hurts my head!!
Gramps

[Brian]

static and dynamic

[cadillac512]

Originally Posted by Brian

static and dynamic

Exactly.

[qmdv]

Did the tin foil test. .070 is what I measure. I am assuming the gasket goes on v notch to the rear. That is lettering up. Best 515G head gasket.

[Brian]

v goes to front, not that it matters for your tinfoil test

[qmdv]

Well here is the latest and greatest. Put the head back on and turned the adjusting screw on the advance break of the crab dist. down 5 full turns. did a test run and the detonation is almost not detectable. And that is if I really get in to it. It will only do it in a drag racing mode. And this is with 91 octane non eth gas. I have a spare crab dist am going to send it off to third gen automotive and have it gone through and have different weights installed so that the total advance is not as much. When it gets installed I will give a full report

[Brian]

The distributor you get third gen to modify will fix your detonation...using the '68' advance curve is a far better solution than either retarding the whole distributor, or cranking down the vacuum brake...

[40 Deluxe]

Originally Posted by Pete

Consider this. Locally, gas is roughly 6 bucks a gallon right now.
Alcohol is roughly 70 bucks a barrel. (1.27 a gallon) But you need roughly 3 times as much alcohol for proper mixture. 1.27 x 3 = 3.81.
Looks to me like burning straight alcohol is a fairly good bargain for a flathead Ford engine running Stromberg carbs. They can be converted to alcohol with nothing more than a few drills.
As a side effect of converting to alcohol with no other mods, you gain about 10% hp. You will need to replace the rubber hose at the fuel pump with a neoprene one but you should have done that for gas anyway.

Oh, I forgot to mention, the exhaust from alcohol smells even better than that from av-gas....

Don't forget, if you're cruising the drive-ins you need to pay road tax on that alcohol!