Timing Suggestions for best Performance

[Dons67]

I'm a bit of a rookie when it comes to specifics so I usually research the site for the right direction and I need some help with the proper timing on my fresh engine re-build (or at least a good place to start)

he's what I put together:

350 - .40 bore with JE forged flat top pistons and is running a 400 crank

Brodix Aluminum Heads 102100
70 cc chamber - 200cc intake runner - 2.020 in intake valve with a 1.600 exhaust - max lift .575 in

Lunati Cam and Lifters, Hydraulic Flat Tappet, Duration 268/276, Lift .489/.504,

1.50 ratio Aluminum Roller Rockers

RPM Air Gap Intake



Holley 750

Using a stock HEI distributor with the Acell Super Coil nice plug wires and the E3 plugs in the gap that Brodix recommended for the heads.

I know I could have went a lot more aggressive on the cam but wanted to keep it more road friendly and as built it should be an animal between the 1500-5500 rpm range.

What is the best way to get the timing perfect? And where is the best place to start? Right now it runs fine for a bit then when she gets up to operating temperature she seams to bog down.

Thanks in advance for the help,
Don

[John Wright]

I would start with 36° total timing, all in by 2900-3000 rpm. You may be able to try a few more degrees but 36° is a fairly safe place to start with 93 octane and mild compression.

[Dons67]

i've read that most advances will push 16-18* of advance so should i start out with 18* BTDC when I set the timing at idle without the vac plugged in? that seams like a lot.

[John Wright]

Most likely you will have to work with the mechanical and vac timing to get it all worked out....stock HEI stuff can have crazy timing curves that end up with 54° or more total while cruzing.

[Dons67]

Thanks for the help John --- not to sound like an idiot - but how would i go about adjusting the vac timing? - car has a 200r4 and 4:10's in the back so cruising should be around 2600 rpm @ 65 mph so I don't anticipate the engine being rev'd up past 5,500 very often (if that even makes a difference)

[John Wright]

You can swap the vac can for an adjustable....may have to redrill the plate to limit the amount of travel and/or change out the weights and springs of the mechanical advance to get it to come in when you need it. If you had a dial back timing light, you can unhook the vac can(plug the vac line) turn the idle way down to get the timing steady(no mechanical)....gradually speed the motor up and watch the timing mark move...this will show you how much mechanical advance you have to start with...you will have to work with it to get it where you need it. I'd start around 12° initial timing(probably could use more like 14-16 but start around 12), then add in the mechanical advance on top of that and see where you are...You "could" do without the vac advance, but the vac advance helps you while cruising burn a little cleaner and get a few more mpg. Kick it and the vac goes to nothing, so you really don't worry about the vac advance except at part throttle(ie cruising). If the thing is detonating while cruising, then you will have to limit the amount of vac advance you're getting. Lighter cars with a lower rear ratios can bring in the timing a little quicker than a heavy car with tall gears.

[Dons67]

that helps a lot -- thanks for sharing

[Vegas69]

Leave it at 34-36 degrees total timing. You MAY gain a few horsepower with more but it's not worth the potential trouble with heat and poor gasoline.