400 SBC Timing Specs - Team Camaro Tech
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post #1 of 13 (permalink) Old Oct 29th, 09, 10:46 PM Thread Starter
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400 SBC Timing Specs

406, flat tops, bottom end stock otherwise, mild cam, 487x heads, performer intake holley 750 vac sec., 4 spd. msd hei stock config., what would you guys recommend my total timing to be set at? i was thinking somewhere in the 32 to 34? what rpm would i bring it in at 2500 to 3000? i dropped my dist in, fired right up ran smooth with a 600 holley, havnt pulled timing yet, just drove it to see how it did, had a popping in mid throttle, left as i reached redline, thought it was lack of fuel, swapped to 750 still pops a little, so im going to try to dial timing in and go from there. any other ideas?

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post #2 of 13 (permalink) Old Oct 30th, 09, 03:35 AM
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Re: 400 SBC Timing Specs

About 12 initial and 36 total should get you close.

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post #3 of 13 (permalink) Old Oct 30th, 09, 04:37 AM
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Re: 400 SBC Timing Specs

there is alot of variables like your cam timming etc.
best bet is to experiment and find out what your motor likes best.
there really isnt no magic number to set the motor to.


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post #4 of 13 (permalink) Old Oct 30th, 09, 08:00 AM
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Re: 400 SBC Timing Specs

Start by setting the mechanical at 36 degrees at 3000 rpm and let everything else falls where it falls. After you set the mechanical, attach your vacuum advance to manifold vacuum.

Good luck!
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post #5 of 13 (permalink) Old Oct 30th, 09, 08:36 AM Thread Starter
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Re: 400 SBC Timing Specs

do you guys think the popping is a timing issue?

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post #6 of 13 (permalink) Old Oct 30th, 09, 08:44 AM
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Re: 400 SBC Timing Specs

Quote:
Originally Posted by cfauver View Post
do you guys think the popping is a timing issue?
Certainly could be,the first thing you want to do is baseline the timing (as long as your valves etc. are adjusted correctly, otherwise that would be first).
What cc are those heads? If they are a smaller chamber, like 64cc, your compression could be up there in a touchy zone on pump gas with flat tops, watch out for detonation. But as was mentioned cam timing etc play a big role in the timing and tune, so knowing that would help.

I think 35-36 total is a good start.

Sean

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post #7 of 13 (permalink) Old Oct 30th, 09, 04:39 PM
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Re: 400 SBC Timing Specs

Popping u say at mid throttle....this when u back off a little?
If so this is classic indication of a a lean out...usually a vac leak.

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post #8 of 13 (permalink) Old Oct 30th, 09, 11:32 PM Thread Starter
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Re: 400 SBC Timing Specs

got timing set tonight. drove car, accel several times hard only popped once or twice, new carb, checkes set screws when i got back they were only out about 1 turn. turned them out to 1 1/4 to 1 1/2, will try again tommorrow. runs strong, think it needs a little more fuel.

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post #9 of 13 (permalink) Old Oct 31st, 09, 04:22 AM
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Re: 400 SBC Timing Specs

Try shooting some ether around the manifold when it's running - just stay away from the distributor with it - if you have a vac leak it will rev up when you spray it.

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post #10 of 13 (permalink) Old Oct 31st, 09, 01:46 PM
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Re: 400 SBC Timing Specs

Quote:
checkes set screws when i got back they were only out about 1 turn. turned them out to 1 1/4 to 1 1/2, will try again tommorrow
Carbs are 2 separate carbs in 1
1/ the idle circuit that has no effect once off idle rpms
2/power circuit that is shut off at idle
Dont confuse the 2.

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post #11 of 13 (permalink) Old Oct 31st, 09, 07:10 PM
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Re: 400 SBC Timing Specs

My 406 runs 16* initial and a total of 36* and I use ported vacumm which is a whole other issue with many opinions. I've done both, I just prefer the ported over manifold for having a lopier idle with the cam I run. As was said earlier, you get a starting point and find what your motor likes, and yes it sounds like you are running lean, check your plugs to see.

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post #12 of 13 (permalink) Old Nov 1st, 09, 08:00 PM
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Re: 400 SBC Timing Specs

Quote:
Originally Posted by cfauver View Post
got timing set tonight. drove car, accel several times hard only popped once or twice, new carb, checkes set screws when i got back they were only out about 1 turn. turned them out to 1 1/4 to 1 1/2, will try again tommorrow. runs strong, think it needs a little more fuel.
You should use a vacuum gauge to adjust the idle mixture screws (warmed-up, normal idle rpm, adjust for highest steady vacuum).


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post #13 of 13 (permalink) Old Nov 1st, 09, 10:22 PM
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Re: 400 SBC Timing Specs

The popping through the exhaust is likely a vacuum leak.
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