How much initial and total for my cam?

[matt030305]

hey all, I was wondering if anyone can help me with timing my new 408 Stroker motor. Here are the build details-

2001 magnum block- 408 Stroker with forged pistons, I-beams, crank (apprx. 10.5:1)
Trickflow 190cc heads
Harland sharp 1.6 ratio rockers
Edelbrock rpm air gap intake (gasket matched)
750 cfm Holley carb

Cam- COMP Cams 20-813-9 specs:

I know high performance engines need very specific timing to get all the power out of it. If someone could school me and get the timing dialed that would be greatly appreciated!

 

[RustyRatRod]

Timing is so specific, it's different for each engine. If we get some compression test numbers, we can get a LOT closer with our "guess".

 

[matt030305]

Timing is so specific, it's different for each engine. If we get some compression test numbers, we can get a LOT closer with our "guess".

I’ll try and run some compression tests tomorrow morning, it’s a fresh rebuild with less than 10 miles on it

 

[crackedback]

18-20 initial and around 32 total on pump swill for a starting point

 

[Demonx2]

My 10.5 CR (actual measured CR) 408 with Eddy heads, Super Victor intake, and 251/255@.050 SFT cam runs 14 initial and 34 total. It has an 8" 5000 rpm stall torque converter.

 

[AJ/FormS]

My 10.5 CR 408 with Eddy heads, Super Victor intake, and 251/255@.050 SFT cam runs 14 initial and 34 total. It has an 8" 5000 rpm stall torque converter.

I run about the same in my 11.1Scr, Eddie-headed 367, with a 230/237/110 cam, 276/286@.008/straightup
but I run 87E10, so all in is around 3400 , and with a manual trans/3.55s

 

[matt030305]

Thank you guys for all the feedback, I’ll try 14 and up. I’ll see what it likes. Just got the engine back into my car and trying to get all the fine tuning done.

 

[autoxcuda]

That cam is sorta close to the Comp solid flat tapped I run in my 416" stroker with eddie heads. Same duration at .050 and centerline. I have 9.7:1 measured compression.

I run something like 30 total and about 16 initial. No vacuum advance. 91 octane pump gass

If it's a brand new rebuilt motor. I would be like 28 degrees total just to be safe during break in. Play it safe.

Then after 100-200 miles, up the total until you hear pinging and back if off a couple degrees.

 

[33IMP]

I agree with autox.
I'd be conservative to start, break it in for a couple hundred miles with 30 total (or less) and get comfortable with the way it behaves.
Then bump timing up a couple, see how it feels. Likes it? Give it a couple more.
Do you have a timing tape? You'll probably need to chart the advance in the distributor to see what your timing curve looks like.

 

[Bewy]

It is going to be a looooooooooot more than 14*......My guess, for best idle quality & tip in response 30-35*. You do this my using manifold connected vac adv [ MVA ]. Don't ask your mechanic about it, you will just get a strange look...

 

[MOPAROFFICIAL]

Probably around 24 initial

 

[Bewy]

To determine optimum idle timing is quite easy:
- warm up engine & adjust carb for best idle quality
- start with factory initial timing 8-15*, not critical
- engine idling, in gear if auto, loosen dist clamp & rotate dist SLOWLY CCW [ advances the timing ]. Keep going until you get the highest rpm/smoothest idle. Toggle dist to make sure.
- now check the timing. It will be more than 24*, my guess mid 30s. A 440 I did with a slightly smaller cam reqd 42* for idle. A smaller engine & bigger cam will require more timing all else being equal.

You achieve this by using an adj vac adv unit connected to manifold vac. Examples above, here are some more...

www.hotrodders.com/forum/vacuum-advance-hooked-up-directly-manifold-bad-47495.html Scroll down to post #6

 

[like_A_pike]

Keep us updated OP I’ma following your progress.

I’ve the XE275HL in a 372, ported J heads & high stall. But a mopar performance electronic ignition straight from the box and tuned by ear. It does 1/4 in 12.7seconds like this. I’m Gonna start with the FBO wheel before welding any slots, play with springs, 72-79jets, extensions, orange acc cams, and a 9.5” power valve. I’m after shaving that 0.7 off simply by power tuning…

I’m well broke in however. I’d echo the easing into it sentiment.

 

[matt030305]

I’ll be trying some things in the following weeks, tried timing it at around 16 degrees initial and around 36~ degrees total. Hard to tell if it likes it or not. Trying to chase a rough idle condition right now (most likely just carb tuning)

The car refuses to idle smoothly, I have a hanging idle problem (when revved, stays at around 1500 rpm for a second then comes back down slowly) I’m going to try playing around with the throttle blade positioning to see if that helps.

Specs on carb: Holley 750 cfm with a fresh rebuild

Vacuum secondaries, electric choke, forgot the jet size but I have the paper somewhere that stated the jet size.

Any help with this as well would be greatly appreciated as I’m trying to get this car in a state where it isn’t a headache trying to take it out for a drive! Thanks