injected BBC timing

Looking for opinions on ign timing for a 509 bb chevy. Alky hat inj on tunnel ram, MSD 7 box, 1.76 glide 4.30 gear in an altered. Anyone with anything similar to compare?

 

timing

I think I ran somewhere between 30 + 32 depending on conditions. Don

 

Had a S/C dragster with that set-up, 7AL2 with a crank trigger. Like Don 30 - 32 degrees. 7.90 no stop & 8.90 on the stop.

 

The big deal is going to be the cylinder head. Alcohol likes a fair bit of timing. I have never had 32 do anything on my dyno with a standard head. The only way 32 is feasable for the stuff I have run on the dyno is if the stroke is in the 4.5 range. Plus the amount of compression is also a big factor. All of my 4" stuff likes to be at 36. Some of the larger chambers like to be 37 and even 38. Big chief and other pro stock style heads like 30-31 for a 4" and mid range size bore with a standard 13.5-14.8:1 compression.
But, I would figure 36 will be where you end up with a typical head. But a little more info will help.

 

i ran that same motor years ago in a dragster with a msd 7-al 2 with a dual point dist. now depending on your fuel system look at the plugs more timing more fuel
36* to 40*

 

Just to clarify this is non-blown, the stroke is 4", the heads are Brodix bb xtras 325 on the intake side, and comp is 13.38. We currently run it at 40 deg. basing off old carburated 468 combos we used to run. They always liked 40 on gas. Am I pounding on bearings etc. for no reason? The car seems like it could use less timing at the big end. It goes 1.10 60' 5.0's @ 134 in the 1/8 and
8.0's @ 164 in the 1/4.

 

Ran the same combo except mine was a 540, (4.25 X 4.50) last year. crank trigger, 7-al box with the msd hvcII coil. I ran the timing between 36 and 38, but we were anywhere from 5000 ft to 7800 ft corrected. Ran a couple of 7.99 - 7.98's at 5200 ft. Pulled motor down this winter, and bearings looked like new. A guy I know that has run a ton of injected bbc's told me that anything over 38 was too much. Just my 2.

 

I am not a genius when it comes to injected BBC's on alcohol, but I have a dyno, and that helps. Plus, I have probably done 20 in the last few years, and just put another Crower stacked 540 on the dyno yesterday. Plus this is the engine combo I have raced with for 15 years.
I have NEVER had one run its best at 40. Not with a 4" stroke and a pretty good piston diameter. I would guess that combo would like 36-38, in fairly standard air. My Brodix heads always liked about 2 degrees less than my dart/merlin/RHS/etc. (go figure) I would need dripping humidity to make my tune up need 40 degrees. But even at 40, the bearings should not be taking a beating. Are you sure that 0 on the damper is true DTC? That is a good place to start. Next, how does your oil look when you go to change it?
I would start at 36, then go from there if you had that thing on my dyno.

 

The bearings look great and the oil looks fine too I was just saying no sense pounding on them any more than necc. Plan on taking it out again this weekend for some testing and just thought I'd start with timing changes and see what it likes.

 

timing

You probably are right, with the 36 degrees.The old paper work showed 38 degrees on the dyno, with highly modified heads. on a 496. but I really find it hard to beleave 40 degrees. How much do you need to retard the timing so you don't break the starter when it kicks back. Sorry for the 30 thing. Don

 

On our 489" BBC alky on injected, got my best MPH at 40* advanced, started out lower and added little at a time, our combo is a 4.25 crank & 4.28 bore w/ 15:1 compression.

 

I also have a 565 ci chevy with dart 360 heads ( fully ported ) injected on alky using a sheetmetal intake and a bird catcher. I have run 4.66 in the 1/8 and 7.35 in the 1/4 with my old FED at appox 1750 lbs with a glide (1.80 low) and a 4.10 rear with 33in tires. I ran appox 36 to 38 deg timing and it never got hot. Hell my radiator was an oil cooler with a fan hid in front of the motor under the body-work, and I drove it all around the pits (half filled block also). Hope this helps. Jody

 

next question... what difference using zoomies compared to colector headers?

 

Less power with the zoomies and weird sounding.

 

um, good idea. What oil cooler did you use? Pics?

 

Just a few thoughts,

Just like different heads Conv. to a 12° will have different timing requirements, on a conventional head timing requirements will vary (albiet to a far smaller degree) depending on the head and the dome on the piston, that is large bore engine with a large chamber CC with a large dome with deep valve pockets and sharp edges will require more timing than a smaller chamber with less dome on the piston. Along those same lines the temperature will play a big part also, and that is where the big changes come into play, as the engine builds load and heat going down track the amount of timing required to reach peak pressure at the correct crank angle will become much less.

Remember the only purpose of spark advance on a NA engine is to adjust peak cylinder pressure to the correct crank angle, what I mean by this is that on a power adder engine you can usually add more fuel and oxygen to the mix (if you can burn it) and adding timing often allows you to do this, on a NA deal with a set amount of oxygen, I feel a lot of guys try to add too much timing and fuel and all they wind up with is a poor burn and a lot of milky oil and engine wear.

 

Derale (I think ) AN 8 fittings are best with the fan mounted to the cooler.