347 timing and carb - Forums at Modded Mustangs
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post #1 of 29 Old January 6th, 2009, 08:00 PM Thread Starter
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347 timing and carb

i built a 347 stroker does anyone know what the timing should be around.
would a holley 670 carb be enough cfm.
the cam is a .498 lift flat tappat.
i have a problem with backfire through the carb
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post #2 of 29 Old January 6th, 2009, 08:02 PM
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the backfire through the carb is usually a timing issue what do you have it set at now ?
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post #3 of 29 Old January 6th, 2009, 08:15 PM Thread Starter
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it was set a 35, but somone told me to set it at 28 so i did and the motor hesitated so bad at idle it stalled out. at 1000 rpm
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post #4 of 29 Old January 6th, 2009, 08:39 PM
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sounds like some one may not have broke the cam in right...uh-ohhhh.. I like about 16-17 initial and 34 total, all in at 3,000. It really depends on the engine where it will make the most power, but you should be able to set the dizzy at 16* and it should run good.

A bigger motor with a lot of parts they said would make me go faster......
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post #5 of 29 Old January 6th, 2009, 10:50 PM Thread Starter
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i broke the cam in right
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post #6 of 29 Old January 6th, 2009, 10:51 PM
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16* and tell us how she runs

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post #7 of 29 Old January 6th, 2009, 10:54 PM Thread Starter
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16 at base timing
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post #8 of 29 Old January 6th, 2009, 10:58 PM Thread Starter
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i want to make sure i'm doing the timing right.
how do you set the timing
u close your vac advance and set it to 16 correct
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post #9 of 29 Old January 6th, 2009, 11:00 PM
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correct.

A bigger motor with a lot of parts they said would make me go faster......
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post #10 of 29 Old January 6th, 2009, 11:04 PM Thread Starter
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so what should the total advance be around
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post #11 of 29 Old January 6th, 2009, 11:07 PM Thread Starter
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i was thinking of changing my diaphragm spring to a lighter one. the motor also has a hesitation at take off
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post #12 of 29 Old January 6th, 2009, 11:10 PM Thread Starter
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and or try a different jet size
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post #13 of 29 Old January 6th, 2009, 11:17 PM
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you may not be getting enough fuel into it as well through the accelerator pump circuit. is your carb a vacuum secondary?
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post #14 of 29 Old January 6th, 2009, 11:42 PM
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Quote:
Originally Posted by PANAMACITYMUSTANG View Post
i built a 347 stroker does anyone know what the timing should be around.
would a holley 670 carb be enough cfm.
the cam is a .498 lift flat tappat.
i have a problem with backfire through the carb
Every engine is different so timing for one 347 could be much different from what your 347 likes. The car size is good for what you have.

My daily driver has 16 cylinders and 4400hp @ 1000 rpm....


***1988 Mustang GT - Stock....almost
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post #15 of 29 Old January 7th, 2009, 12:41 AM
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Total advance should be somewhere around 34* at about 3200 rpm . That's just a guideline tho you gotta try adjusting it to what your motor likes before you start to get detonation
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post #16 of 29 Old January 7th, 2009, 06:14 AM Thread Starter
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i just changed the pump cam i put the green one in in pos #1 and it seemed like that a little bit and yes it has a vacum secondary. the carb i have is the holley truck avenger 670.
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post #17 of 29 Old January 7th, 2009, 06:18 AM Thread Starter
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is this true, to set timing for best performance advance the timing until you start to hear the motor pinging then retard the timing 2 to 3 degrees
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post #18 of 29 Old January 7th, 2009, 07:24 AM
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Originally Posted by PANAMACITYMUSTANG View Post
is this true, to set timing for best performance advance the timing until you start to hear the motor pinging then retard the timing 2 to 3 degrees
on a carbed engine a good way to do a base timing is to turn it till it idles the highest then back it out 2*. you can use a vaccume gauge to help.

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post #19 of 29 Old January 7th, 2009, 08:14 AM
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on a carbed engine a good way to do a base timing is to turn it till it idles the highest then back it out 2*. you can use a vaccume gauge to help.
This old guy that work for my dad told me when I was a kid the same thing only he said 5*, and this old fart could tune anything
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post #20 of 29 Old January 8th, 2009, 05:19 PM Thread Starter
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well i got a chance today to mess with the timing i set base at 16 and i put a light spring in the dizzy and changed to a green pump cam hole #2 shes really close but she still popping through the carb
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