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Old 03-25-2007, 09:20 AM
Tyler
 
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79 T/A w/Olds 403

hi guys, i just want to say thanks alot for all the help and advice, if it wasnt for this site i wouldnt be where im at... just have a few more questions..heres what i've done so far,
Its a olds 403 hooked up to a th350 w/stock converter..
#7 olds heads w/ 62cc combustion chambers
comp cam Kit-part # CL42-229-4 advertised 268-268
edelbrock 3711 performer intake
hooker competition headers
flowmaster header back 2.5" exhaust
installed 3.08 rear end
stock qaud jet carb
stock pistons, rods, and crank

so here are my questions..what am i looking at for compression ratio? what should i set my timing advance to in degrees to get the most power from these combos? should i run stock plugs or a colder set? and would it be safe to run nitrous in this motor? or would it shatter the rods?

thanks alot guys...very much appreciated...but if nothing else could you please help me with the timing?? the book says to set it at 20 degrees btdc at 1100 rpm?? is this where i should set it or should i go a bit more? thanks alot again..

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Last edited by Rough-Rider; 03-25-2007 at 09:25 AM. Reason: wasnt finished srry...
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Old 03-25-2007, 01:51 PM
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stock pistons = stock 403 Olds pistons or stock 30 over cast rebuilder pistons ? ask over at www.realoldspower.com
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Old 03-25-2007, 02:00 PM
Tyler
 
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stock meaning the pistons that came with the motor from factory.

hmmm...i'll try and make an account over there, c what happends...but if neone can help please reply..
thanks
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Old 03-25-2007, 03:21 PM
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you will be happy you ask around over at realoldspower.com if nothing else do a search there for 403s b4 signing up.


Mr. Olds at realoldspower.com knows loves / builds and races 403s heres his web site. http://www.fcrparts.com/





Mustangsaly
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Old 03-25-2007, 04:16 PM
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The timing spec that "the book" suggests is for a specific stock emmisions controled Olds Engine. Once you change things you will need to fine tune the timing to suite your particular build. Once you change the camshaft the motor is no longer "stock".

I would suggest something like this.
14 to 16deg initial timing at idle. (600rpm vac adv disconnected).
32 to 36deg total mechanical advance maxed at 3000-3200 rpm. (16 initial +20 deg mechanical advance)
An additional 12 to 15deg vacuum advance at highway cruise (part throttle light load driving)
I would suggest a 9.5 to 9.8:1 compression ratio for your cam and pump gas (92 octane)

Then for up to 180 hp nitrous shot on 92 octane gas . retard the timing by 6-8 deg. (2 deg/ 50hp)

The stock factory OEM recomeded spark plug heat range is for general driving on a stock low compression motor. If you are racing the car you want to install a slightly cooler spark plug. about 3 heat ranges cooler.
@ 100 to 150hp nitrous shot this plug will be fine.
For 180 to 250 hp nitrous install an even cooler, non- projected tip type plug. Always use the best available octane pump gas when using nitrous.
If you need more octane than whats available at the pump, mix your fuel with 110 octane unleaded racing gas.
Use 110+ octane race gas for anything over 180hp.
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Old 03-25-2007, 07:23 PM
Tyler
 
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awesome f-bird, thats what i needed..but the only thing i question on that is this, do i retard the timing 6-8 degrees from the initial 16 degrees btdc, making it 10 degrees btdc? or is it retard the timing from zero degrees making it 6-8 atdc??

if that makes sence..
thanks alot
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Old 03-25-2007, 11:22 PM
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There are two ways to do it. The cheap way and the best way.
The cheap way is to just retard the timing 6-8 deg by adjusting the distributor timing 6-8 degrees less than normal prior to a nitrous run.
The better way is to employ a electronic switch controled adjustable ignition retard box (MSD) to allow you to retard the spark 6-8 degress when ever you activate the nitrous injection.

The 6 to 8 degrees comes off the normal 16btdc timing.
In that case (without a retard box) you would simply set the timing at 8 to 10 deg BTDC. instead of 16deg BTDC at idle.
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