Right now I'm running 12* initial, light advance springs and about 16* mechanical advance (have the longer duraspark advance slot). I've calculated my compression at around 10.25:1. Comp XE 262 cam makes the dynamic compression live able with vacuum advance hooked up I had to back initial down to 8* to stop the ping so it's been disconnected.

I have FiTech EFI on order which will be controlling the timing. I'll lock out the mechanical advance. I believe the EFI setup can add 16*. What timing curve/ total timing has worked best for you? I know conventional wisdom says you want all advance in below 3500 or so...

 

You want it in as quick as it will take it without detonation. To many variables. One thing, you want to tune it with the same gas you will always run in it. You can make a stop for the vac advances arm in the housing and tune it back if you don't have an adjustment screw in the end of the canister.

 

Also, that cam has a 4 degree advance, you could set i up straight at 110 degrees by retarding it 4 degrees with an adjustable trimming gear to free some dynamic compression to avoid some detonation...

 

16 deg mech. will only add up to 28 degrees total. Not nearly enough. Unless your talking dizzy degrees instead of crank.

 

10-14 base, 32 mechanical all in by 2500, and 52 total at lean cruise. All ballpark figures.

 

Well I think that would be too much total. I have a 435hp (on paper) 400ci @ 1 mile above sea level and about 9.8:1 compression. I run 12-14 initial, 25 mechanical and 10 vacuum. Total (no vacuum) would be about 38 with weak springs. This is too much for 91 octane so I solved that problem with a Snow Performance water/methenol injection system.

 

Hmmm tfs195 alloy heads 9.73cr./ 8.27 dcr .043 squish, 92octane. Works for me. You need around 52 at lean cruise for economy. Some will take less total mechanical depending on detonation resistance. If you don't tighten the deck on these engines they rattle with very little timing, losing power and efficiency. 10 degrees in distributor is twenty on the crank and that would put you there with high cruise vacuum. Idk. 12 initial plus another 20 at 2500 is 32 total mechanical, add another 20 with a 10 degree can. Comes to 52 total at 2500 rpm and high vacuum. Seems real standard timing too me.

EDIT- Coming back a few yrs later I was wrong, so wrong. My timing now is 16* base plus 12* mechanical for a total of 28* (TFS195Powerports). On top of that I have 16* vacuum advance for a total of 44*at cruise.

 

If the heads are aluminum and or have a quench area you can get by with another full point of compression over stock. Same on the timing. The 2V stock heads like lots of timing.

 

As for aluminum heads with squish and modern combustion chambers, they allow a extra half point of dcr over iron closed chamber heads. 8.5 vs 8.0. The closed chamber heads have a good squish area but they are iron. NOW open chambers you lose some more maybe a quarter point or so and that's if your using Tim's pistons. Now with any other piston, it sits too low, and none of this applys and you have a ping monster. So, if you have a tight deck and closed chambers and your dcr is below 8.0 you should be able to run normal timing on premium fuel, if everything is perfect. I would knock a quarter point off the max dcr (7.75dcr)to be careful and start with 10 to 14 base, add another 20 by 2500rpm and a total of around 52 at lean cruise and adjust from there. Your engine will tell you what timing and fuel it likes, you just have to listen. Now with timing, base timing is a compromise between easy starting when hot and idle quality. Total mechanical is based on max power and total with vacuum is for economy. If it pings when you put your foot to the floor, back down on the total mechanical and leave base and vacuum alone. If it pings at light throttle your vacuum timing isn't coming out fast enough and that needs to be adjusted without changing base, mechanical or total vacuum. (Usually with a Allen wrench in the vacuum canister, clockwise to drop it out faster and counter clockwise to have it hang in there longer). All this assumes your running the right air fuel ratio also. I hope I'm not being confusing.

 

Ran your specs in Wallace racing calc. 408, xe262 with 57degree intake closing and got 8.65dcr. If this is true it won't run on pump fuel without pinging. Even retarding that camshaft 4 degrees (it's now strait up) intake closes at 61 degrees and a dcr of 8.42. Over the edge even with modern alloy heads, unless something other than pump fuel is going to be run.

 

Never mind, I read your build thread. Good luck with your ping monster.

 

I can't say enough about Snow Performance water/methenol injection.

 

Yes, because nobody had a successful higher compression 400 before Tim Meyer's pistons came out

I don't have a pinging problem currently. I am asking since I will have greater control over timing what would be optimal. Good luck with your carb

 

Thank you.