5.0pntydrpr

Hello all,

I have recently installed a vortech v1 s-strim supercharger into my 66 fastback.

The engine is a 5.0 from an 89 GT with the following mods:
Comp Cams XE270HR cam
GT40 iron heads
Weiand Stealth intake
holley street hp 650 carb (list 82651) ((Wonderful blow through carb btw))
Hooker long tubes with 2.5 inch dual exhaust with magnaflow mufflers
stock 289 distributor with pertronix ignitor I and flamethrower coil

Question is: I know I have to retard my ignition timing for the added boost (about 8~10 psi), and I'm shooting for 10* initial timing with about 24~26* total timing. This would put me at 14-16 mechanical advance degrees. The slots available on the breaker cam assembly are 10L and 15L both yielding 20* and 30* respectively. I really need a 7L to 8L slot to achieve my desired mechanical advance limit. Does anyone sell a breaker cam assembly with these slots? Should I modify mine by welding and grinding? JB weld (I'm thinking not)?

Let's hear your advice, experiences, recommendations etc. Thanks in advance (pun intended)

Oh, and my fuel system is more than adequate.

67mustang302

Get a real ignition system first. The chamber in a high performance engine, especially a blown one, is very hostile to creating a spark. You need a system with ***** that can give an adequate spark, otherwise at best you'll be cheating yourself out of a ton of power, and at worst you'll have issues (stumbling, roughness, misfires, blowout etc).

The problem with most distributors these days, is the engines need like 15-25 at idle and anywhere from 20-35 total depending on the setup. And you just can't get that with most distributors.

A blow through will be more favorable to timing because of the evaporative cooling. A blow through carb without an intercooler is actually more thermally efficient than a port injected car with an intercooler all else being the same. ~25* total is a good starting point, but you'll need a dyno to really know what your combo wants. Or run it at the track and check the plugs.

5.0pntydrpr

What kind of system would you recommend? The flamethrower coil is advertised at 40,000 volts... is this inadequate?

67mustang302

To actually get 40kV of output you need like an MSD 6/Dig6 and HVC-2 coil. That's what I run on my n/a setup.

You don't have big heads, so cyl pressure won't be insane; an MSD 6 and HVC should work fine. It partly depends on what features you want and how much you want to spend. Rev limiter or no, boost retard controllers etc etc (really a must actually, then you can have your proper timing at cruise and pull it under load). The MSD-6-BTM has a boost retard built in. More bells and whistles is more money.

On coils in general, the voltage is their max voltage they can handle, not what they produce necessarily. Those coils won't make their max voltage without a box.

On a side note, those heads will hold you back a fair bit. And they're iron, so you have a higher risk of detonation; so be conservative with your timing. Not bad mind you, you could still probably make enough power to break the block even with a conservative tune.

What's your compression anyway?

5.0pntydrpr

My compression is right around 9:1.

I recurved my stock dizzy to 20* mechanical advance with 10* initial. Honestly, if the 289 K code engines with 10+:1 compression can run their dual point distributors with a paxton supercharger blowing through a carb, then my current distributor should be able to work. I completely understand about an adequate spark, but my current ignition setup should have enough "*****" as you say.

I put in AP103 spark plugs gapped at .034 and it runs well now, just rich at idle (still working on that one).

My current problem is a slight exhaust backfire at about 4,500 rpm, I'm hesitant to advance at all for fear of detonation...

Iskwezm

I keep my timing locked at about 18*. I could run more timing but dont want to risk detonation.You could also get a timing module to pull timing based on the amount of boost so you can run more timing so the power isnt so sluggish.