Wich hei springs to use?

[Ypsik10]

Got a summit advanced curve kit wich springs should I start with? Has double hump 461 heads comp 268h cam.

 

[SkinnyG]

Likely just a light spring and a medium spring. Don't use the weights.

But check with an advance timing light to be sure.

 

[74 Shortbed]

All depends what the curve is now then go by the chart, no matter what there will be some trial and error to get the optimum performance, every application is different..

 

[gmmatt81]

I think medium springs will work fine, best to try this first.

 

[75gmck25]

All mechanical in by no more than 2500 rpm should work if you have a reasonably loose torque converter. You may want to even try setting it up for closer to 2000 rpm all-in. You can use a dial-back timing light to measure your current advance and see how fast it comes in, then adjust springs to get what you want.

You may also need to tweak your setup to get the mechanical plus initial to a total of about 36 degrees. I would start with 12 degrees initial, and bump it up until just short of pinging.. Somewhere around 16 should work. Then adjust mechanical advance to get the rest of the 36 degrees.

Bruce

 

[HotRodPC]

All looks like good advice above. Also agree, don't use the weights. Unless you're going to be a full race engine and want all your advance while stalling out on the tree, and no vac advance, don't use those weights.

 

[Ypsik10]

All looks like good advice above. Also agree, don't use the weights. Unless you're going to be a full race engine and want all your advance while stalling out on the tree, and no vac advance, don't use those weights.

Why not the weights?

 

[HotRodPC]

Notice the shape difference. They'll allow more timing. Not only allow more timing, but make the advance come on quicker if springs were equal on both sets of weights. That kit is pretty much for full race tuning with no vac advance.


You don't want to much advance. It'll just ping like hell and you'll melt pistons eventually. No more than 36 degrees full advance with both mechanical and vac advance combined.

 

[SkinnyG]

You want no more than 36° mechanical advance. Vacuum advance is separate.

You should run about 12° vacuum advance if you have no EGR (this is additional advance), 14° if you do.

That could give you 48° to 50° FULL advance when cruising. Vacuum advance is gone when you open the throttle for power.

 

[HotRodPC]

That's new to me. I've always thought 36 degrees full and total advance is all you'd want on the street.

Though I'm totally aware of not getting any Vac Advance at WOT. That's where the long debate of where to hook the Vac Advance hose to. Ported Vac or Non Ported Vac?

 

[74 Shortbed]

That's new to me. I've always thought 36 degrees full and total advance is all you'd want on the street.

All depends on what the motor can handle with the compression and fuel being used and the load put on it, every vehicle/application is different and you don't know until you try it, 12* initial and 36-38* all in by 2800-3000 is average starting point for mechanical, average 15* on the vacuum at cruise then go from there, if it works you can try squeezing a little more like having the total come in at 2500, if that works step up the initial a couple degrees and see what happens and so on, "ONLY" the motor will tell you what it needs period. On my beater the best I could get is 14* initial, 37* total in by 2700, 15* vacuum for 52* at cruise, only thing I have to run a colder plug in the summer when the temps get up around 110*, OH, and that's with 87 ethanol skunk piss, now my nova that's a whole different story...