Timing For 400

rstockbridge · Sep 4, 2018

Does anyone know what the timing should be for a 400 with a 727 auto, headers and cam with the following specs:

Cam Style:Hydraulic flat tappet

Basic Operating RPM Range:2,000-5,800

Intake Duration at 050 inch Lift:227

Exhaust Duration at 050 inch Lift:241

Duration at 050 inch Lift:227 int./241 exh.

Advertised Intake Duration:279

Advertised Exhaust Duration:296

Advertised Duration:279 int./296 exh.

Intake Valve Lift with Factory Rocker Arm Ratio:0.486 in.

Exhaust Valve Lift with Factory Rocker Arm Ratio:0.473 in.

Valve Lift with Factory Rocker Arm Ratio:0.486 int./0.473 exh.

Lobe Separation (degrees):107

Camshaft Gear Attachment:1-bolt

Computer-Controlled Compatible:No

rstockbridge · Sep 4, 2018

Forgot to mention: it has a Weiand aluminum intake manifold as well.

Don Frelier · Sep 4, 2018

That's a tight lobe separation angle looks like a thumper cam or something similar. You will likely need to restrict the mechanical advance amount and run 15-20 degrees initial and 35-37 total.
I would start with no vacuum advance and then try that after you get it running well.

rstockbridge · Sep 4, 2018

Don Frelier said:
That's a tight lobe separation angle looks like a thumper cam or something similar. You will likely need to restrict the mechanical advance amount and run 15-20 degrees initial and 35-37 total.
I would start with no vacuum advance and then try that after you get it running well.

Ya, it's a Thumper Cam. Thanks for your suggestion. I'll give it a try.

Bill Monk · Sep 4, 2018

I agree with Don, my bet is you will settle in between 16 & 18 with a total of around 36

Cranky · Sep 4, 2018

What kind of cranking PSI is it producing? Usually the less it is, the more initial and sometimes the more total it will like. Experimenting with it will usually tell you what it likes....

Bee1971 · Sep 4, 2018

Cranky said:
What kind of cranking PSI is it producing? Usually the less it is, the more initial and sometimes the more total it will like. Experimenting with it will usually tell you what it likes....

I agree

Iron heads lower compression 36-38 Degrees Total

Aluminum heads high compression 32-34 Degrees Total

My 10.5 to 1 Compression 200 PSI Cranking 383/432 Stroker with Edelbrock 75cc Heads really seems to like 15 Initial 32 Total on the street
Running on 91 octane no ethanol

I did experiment with 34 and 36 total , I guess in reality short of a dyno or drag strip there is only so much you can do with your *** dyno meter and acceleration / burn outs and I got a slight part throttle ping the higher I went but nothing under wide open acceleration

71charger_fan · Sep 4, 2018

I ran my 400 at 36 degrees total and it was a slug. I eventually wound up at 52 degrees total.

Cranky · Sep 4, 2018

71charger_fan said:
I ran my 400 at 36 degrees total and it was a slug. I eventually wound up at 52 degrees total.

I've had the pleasure (more like displeasure lol) of tuning on two low compression engines that ended up liking 50 total! One was a 440 that ran in the 12's with lousy traction and the other was a 318 that ran 13.50....

wyrmrider · Sep 6, 2018

man you do not need that extra long exhaust duration with headers (even with a bad flowing exhaust LA head)
which weiand?
did you say what your compression mechanical and cranking is?
don't make me guess
what heads
what cam
what pistons
trans and gear
weight
suggestion to getting it running best w/o vacuum advance is spot on
did you say what carb?

Timing For 400

rstockbridge

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rstockbridge

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Don Frelier

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rstockbridge

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Bill Monk

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Cranky

Banned Henchman #27

Bee1971

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71charger_fan

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Cranky

Banned Henchman #27

wyrmrider

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