timing? - Team Camaro Tech
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post #1 of 6 (permalink) Old Jan 23rd, 09, 02:12 PM Thread Starter
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SS
 
Join Date: Jun 2002
Location: U.S.
Posts: 535
Question timing?

I am looking for some opinions for timing specs/curve for my current combo.

What should initial and total be?

I realize this is relative; but in speaking with someone very knowledgeable they stated that less total is actually preferred due to better efficiency and better peak rpm. (34* vs 36*total) especially for 406 due to piston speed etc...

Current combo is 406, 72cc sportmans, XS274 237/[email protected]
108lsa-Manual trans, 3.73s

Current timing is 16 at idle with 4* in vac advance can( so really 12* initial)

total of 36* all in by 3k.

I am going to be having it recurved or just and more vac assisted timing for more initial or timing at idle and cruise would exceed 40* which should help mileage: shooting for more like 16-18* initial (so 22* or so at idle) with probably 6-10* in the can and total between 34-36*
I am looking to help cruise economy and fine tune things.

I am going to keep the vac advance which is connected to manifold vac (I know this is somewhat of a debate).

Does this seem logical?

additional input please

Thanks, SS

406, TKO 600 and 12 bolt posi.
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post #2 of 6 (permalink) Old Jan 25th, 09, 04:31 AM
 
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Re: timing?

Well your total and your initial sound about right. It's trial and error i guess.
all in at about 3k sound about right too. The better heads you have, the less advance you need.
The only thing that sound off is your vacuum advance. Why is it backed of to just 4 degrees? that means your engine will only be seeing about 38-40 degrees at cruise. But if it likes 34-36 at wot, it most likely handle about 50 at cruise. So you should try turning up your vacuum can. aim at around 50 with with vacuum. So if you run 34 total, start having your can give 16 degrees. That will probably give you better idle, and better throttle response.
But it only works if you keep it hooked up to manifold vacuum. Thats where the difference between manifold and ported lies. No sense in running ported as far as I am concerned.
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post #3 of 6 (permalink) Old Jan 25th, 09, 04:55 AM
 
Join Date: Jul 2008
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Re: timing?

Well your total and your initial sound about right. It's trial and error i guess.
all in at about 3k sound about right too. The better heads you have, the less advance you need.
The only thing that sound off is your vacuum advance. Why is it backed of to just 4 degrees? that means your engine will only be seeing about 38-40 degrees at cruise. But if it likes 34-36 at wot, it most likely handle about 50 at cruise. So you should try turning up your vacuum can. aim at around 50 with with vacuum. So if you run 34 total, start having your can give 16 degrees. That will probably give you better idle, and better throttle response.
But it only works if you keep it hooked up to manifold vacuum. Thats where the difference between manifold and ported lies. No sense in running ported as far as I am concerned.
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post #4 of 6 (permalink) Old Jan 25th, 09, 04:29 PM Thread Starter
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Re: timing?

I am staying with manifold vacuum.

I agree that I need more timing for cruise etc, and a some additional at idle.

The distributor was curved for my last cam, I had the crane adjustable can added and switched to manifold vacuum vs. ported.

I am not sure why he set it up with so little vac advance?

Last cam was [email protected] and this one is 237/241

and same person is saying I now need more vac advance. NO complaints in performance or the quality of their work, just would like to clean up cruise and idle tuning.

I could just add the stock vac can again I believe it has 12*, I don't remember why I switched or put the adjustable cam on the plate in the correct position on the crane can?

10* from can would give my 22* at idle and 44-46 at cruise and (34-36* total).
Thanks for the response

406, TKO 600 and 12 bolt posi.
railing68 is offline  
post #5 of 6 (permalink) Old Jan 25th, 09, 04:35 PM Thread Starter
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Re: timing?

oops

406, TKO 600 and 12 bolt posi.
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post #6 of 6 (permalink) Old Jan 26th, 09, 06:00 AM
 
Join Date: Jul 2008
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Re: timing?

Just stay with the adjustable can and bumb it up to give 16 degrees. See if it works.
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