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Discussion Starter #1
I am looking for a starting base line for Ignition timing on My 489cid bbc. i am running a MSD ready to run dizzy and timing is not locked out.

I just want a place to set it now while i can run it on the trailer and test and tune on the water. Once I insall the pump I will not be able to play with it on the trailer, With out the headache of disconecting the drive line.
 

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Discussion Starter #5
I have a 489 with iron headed closed chamber heads, a tiny ass 256* @ .050, 12.5 to 1 pistons and run it on 87 octane. Do you think that 36* totall will work for me as well? :)eh:)
gn7 will You elaborate. I am just looking for a place to start. A place to set it before I get to the lake. Its a fresh motor and has not been on the water Yet.
 

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gn7 will You elaborate. I am just looking for a place to start. A place to set it before I get to the lake. Its a fresh motor and has not been on the water Yet.
I can't give you a place to start. Now if your just trying to light it off in the drive, 28 works no different than 38. Once you set the idle, I doubt you could tell the difference between the two. But if your looking for a setting to run on the water as a starting point, the fuel octane, manifold/carb(s), cam, head type(open/closed) material iron/alum are alll things you kind of need to know to make a reasonable intelligent guesstament



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Discussion Starter #9 (Edited)
Explain what? I'm the one asking the question. I need the explanation
What are Your thoughts on a starting point?
 

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Discussion Starter #10 (Edited)
I can't give you a place to start. Now if your just trying to light it off in the drive, 28 works no different than 38. Once you set the idle, I doubt you could tell the difference between the two. But if your looking for a setting to run on the water as a starting point, the fuel octane, manifold/carb(s), cam, head type(open/closed) material iron/alum are alll things you kind of need to know to make a reasonable intelligent guesstament
489 C.I.D.BBC Full roller.

.030" over bore

Scatt 4340 forged crank,4.25" stroke

Splayed main caps /w ARP main studs

Eagle, 6.135" forged H beam rod's

SRP forged pistons, 17.00cc dome
Block,zero decked

Bullet roller cam, duration- in. 264/ex 273 @.050, lift - int .720/ex .710, 108 seperation

Morel pressure fed solid roller lifters

Cloyes hexadjust double roller timming set

AFR 325cc aluminum heads, milled, .030 for compression bump

Crane gold rockers,1.8 int.,1.7 ex

Edelbrock TR2 tunnelram

two 600 cfm holley carbs

100 OCTANE

Any thing else? Oh yea Here is the cam card.

 

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Discussion Starter #11 (Edited)
No skiing or tubeing, jet boat ,73 kona, friendly river racing.
 

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Shorten the curve way up,like 22-24 intial and 34 total. Make a custom stop bushing if you have to. Or just lock it out and see how it starts. That combo will love 34 degrees locked. But for now I think there is 22-24 degrees built into that dist. so set it at 8-10 degrees initial. But its not going to idle well.
 

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489 C.I.D.BBC Full roller.

.030" over bore

Scatt 4340 forged crank,4.25" stroke

Splayed main caps /w ARP main studs

Eagle, 6.135" forged H beam rod's

SRP forged pistons, 17.00cc dome
Block,zero decked

Bullet roller cam, duration- in. 264/ex 273 @.050, lift - int .720/ex .710, 108 seperation

Morel pressure fed solid roller lifters

Cloyes hexadjust double roller timming set

AFR 325cc aluminum heads, milled, .030 for compression bump

Crane gold rockers,1.8 int.,1.7 ex

Edelbrock TR2 tunnelram

two 600 cfm holley carbs

100 OCTANE

Any thing else? Oh yea Here is the cam card.

Nice Job

I see you put a few bucks in that,but I would spend a little more

If you have a chance to run it on the dyno, I would for peace of mind

I would start at 34 make a couple pulls check the jetting and recheck the valve settings

And add a degree of timing at a time and watch the dyno #

Good luck with your project
 

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I am looking for a starting base line for Ignition timing on My 489cid bbc. i am running a MSD ready to run dizzy and timing is not locked out.

I just want a place to set it now while i can run it on the trailer and test and tune on the water. Once I insall the pump I will not be able to play with it on the trailer, With out the headache of disconecting the drive line.
gas or alcohol? blown or normally aspirated? put it on a dyno. you won't be sorry
 

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with the 100 octane, if you were running it at the drags, I would try 38, easy. But for a river deal I would start with 34 as a start. Like Big Steve said, if it was on a dyno I would find max HP and then run it on the river minus 2*, knowing you could run it at max HP for short runs.

34 is a good safe setup for that, with maybe a little left on the table, but it affords you a cushion.



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Question-- Say the engine makes 750 HP with 36 degrees. About how much HP is it losing with each 2 degree taken out.

Sorry for the thread jack. Just always been curious.
 

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Its going to depend on the engine, mainly the combustion chamber/piston dome configuration and the camshaft. some may lose a little, while others will lose more. But if it maxs power at 36, I would tend to run it at 34* if I wasn't racing it just for the cushion in temperature or octane change. If you dyno it at 65* and a engine temp of 140*, who knows if it is going to be happy with a 110 intake and the engine at 160. Throw in a slight dip in octane, and your getting edgy.

If you can't control every aspect of the tune, and control the fuel quality like fresh drum fuel, its best to play it safe. No matter, the HP isn't that great in 2 degress from max HP.



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Personally, I wouldn't try to guess that deal without going on a dyno. Or at the very least at a track. Camshaft profile plays a big part in the timing.
Think about 2 cams having everything the same except the LSA. On is 106 with an earlier colsing intake but ton more overlap than with a 114 LSA.

Or 2 cams with the same LSA and 10-15*difference in the .050 duration.

Is it 110 octane race gas or 116. Is it C16 or Q16?
Is it a Ford with a 70cc chamber or a Chevy with a 118?
did you get to 500 inches with a big bore, or a long stroke?

'What would you run the timing at in 470 BBC with 12 to 1 and 12lbs boost on race gas? You would be amazed!



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Question-- Say the engine makes 750 HP with 36 degrees. About how much HP is it losing with each 2 degree taken out.

Sorry for the thread jack. Just always been curious.
Some motors not much. Some motors, well, you wouldn't believe the difference....not just on top end but through out the whole rpm range.

Tunnel rams like a lot of initial timing. So do large overlap cams.
 
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