Mechanical advance Spring Question

[saludora]

Hello I recently rebuilt my 440 6 pack motor and have it back in the 70 Bee. I used a 512 stroker kit, aluminum heads, and the cam is a Comp Cam mechanical roller,Adv.Dur. 286 Int./292 Exh.;V.Lift .576 Int./.582 Exh.;Lobe 110 deg. My question is what springs would be recommended I use with this build on my MSD 6al2 ignition and mechanical advance distributer setup. ANY HELP is appreciated I'm not to savvy when it comes to the electrical world of anything lol

 

[bm02tj]

It depends on what RPM your motor wants full advance

 

[coloradodave]

Compression ratio, rear gearing, tire size, available gas octane, etc. need to be figured in. On a new motor it's always wise to be conservative with the initial timing, total timing and the advance curve. If it's an MSD Pro Billet distributor I would start with the factory set-up, which should be the stiffest springs (silver) and the blue advance stop bushing, which will give you 21* of mechanical advance, all in by 4,000 rpm. If you set your initial advance at 13-14*, you get a total of 34-35*. This is a very safe tune for firing and breaking in a new motor. After the motor has been broken in and it's got some miles on it you can begin to alter the total timing, initial timing and lower the rpm at which the timing is completely in. The MSD manual has good suggestions for doing this. BTW, there is no perfect tune that works for every motor, but there is a perfect tune that will work for your motor...
I recommend reading all you can find on ignition tuning and then experimenting from there. Listen carefully for "pinging" under heavy acceleration. It'll let you know when you've gone too far... Good luck. Feel free to PM me if you have questions.
Dave

 

[saludora]

The Roller cam is species 3000-6500 range of that helps at all I have a 3000 stall converter

 

[saludora]

275/60/15. 392 gears auto, 92 octane non ethenol, 10.5 to 1 with alluminum heads

 

[saludora]

Adv.Dur. 286 Int./292 Exh.;V.Lift .576 Int./.582 Exh.;Lobe 110 deg complete mechanical roller camshaft

 

[Crackedback]

Let the engine tell you what it wants for initial/idle timing.

If it's a pro-billet distributor, the bushings they provide only allow down to 18* mechanical advance. Lots of times that's too much mechanical to hit the total timing number desired.

I have 10* and 14* bushings to allow for more initial advance on the billet distributors. They are much less expensive than others out there.

 

[coloradodave]

I'll stand by my post #3 above for a new motor, regardless of the build. The factory MSD set-up will get it started and is good for the initial driving/leak checks, etc.. Plenty of time down the road for experimenting with different tune-ups. I'm sure the end tune-up won't be what you start with.

 

[oldmanmopar]

You want the motor to start at around 19 - 21 degrees advanced. your total timing 34 -36 degrees should be all in "off idle" or at "2000 rpms". anything between could cause timing to fluctuate at idle and cause rpm fluctuation . Your problem is you need and advance because of the 6AL. if you had a digital 6 unit it would do the advance for you and you could lock your distributor. A digital 6 retards the timing 15 degrees for start up and automatically advances at 800 RPM's. This can be done easily with your distributor with a little work. My compression ratio is over 12-1 My distributor is locked at 34 I can run my car on pump gas on the street. The High stall low gears and no traction on the street never loads the motor. At the track my son leaves just off idle and it don't skip a beat. Everyone has their own method. this always worked for me with large cam motors. 15 degrees of travel all in at 2000 or lock it up and buy a digital 6