Im planning on buying a vortech supercharger... if i can run a decent amount of boost. How much boost can i run safely? Im using iron heads and have a compression ratio right at 9.4:1... if i can only run 3lbs it wouldnt be worth it. It comes with a 9lb pulley.

Also how much timing do you retard per pound?

I plan on later adding meth injection but it will be a while.

 

u should be able to run 9psi with no issues just watch the timing and meth wouldn't hurt

 

Thats exactly what i wanted to hear, how much should i retard timing? And i know there is a way to lock out a vacuum advance distributor. How would i go about doing this?

 

Timing is really dependant a lot on your setup. The general rule of thumb (as I've heard) is 2 degrees per pound of boost. Honestly, instead of getting rid of vacuum advance all together, I'd go with an adjustable Boost Retard unit.

I can set mine from zero to 3 degrees of retard per pound, and I don't lose the function of a vacuum advance for street driving. But yes, on most aftermarket distributors you can lock out the vacuum advance if you want.

 

I called vortech today and they said i would be fine running up to 10lbs and timing is 1 and a half to 2lbs per lb of boost. So i think i would be safe running 20 to 21 degrees all in

 

WAIT

IRON heads, 9.4:1 compression, Is this the same car:
355sbc,th350, 3k stall, 4.10 gears...


Your full throttle timing without any boost is probably around 35* no?
Have you ever been to a chassis dyno and got a look at the torque curve? and played with the timing?

With that compression, and those heads, I would want no MORE than about 15* of timing on 93 octane at 10PSI. And 10psi might be seriously pushing it! The stall and gears will "help" but I am really worried about those heads heating up. Install colder plugs and run an intercooler and 10 would probably be ok. But if you are thinking hot air right out of a compressor and into the engine... 10psi of boost and 20* of timing is sure to put a hole in something. You really need to fine tune it on a dyno, start with about 10* of timing and slowly add until torque is smooth (set smoothing to zero) and stops rising. I bet that will be around 14*. Then pull it back a degree or two for safety (hot days, bad gas, uphill, etc...)
I recommend an oil cooler also to help with temps
If the heads are very old, and the combustion characteristics are poor, meaning there is 70's or 80's technology and a weak spark, then the timing figures could be off. Older engines with older technology in the combustion chamber typically require a bit more ignition timing, usually because flame propagation is poorly managed.

METH injection is a great thing, but it can fail without notice, leaving your engine in a dangerous situation. I would stay away from any extra moving parts where possible. If you like alcohol switch to E85- then your 10psi is acceptable, with 15* of timing, even non-intercooled.

As for power output, at 10psi figure you will gain about 50% additional horsepower at the wheels.

 

In the back of my mind i was still kind of worried about it. I will just make the switch to e85 since im having the carb shop do the carb.

 

Regardless which fuel you go with, so long as air temps are kept in check, the engine will take as much boost as you can throw at it. Meaning if your roller assembly is cast and is only good for up to say 500 horsepower naturally aspirated, then as long as your air temps are kept in check, the engine will take as much boost/horsepower as it was designed to handle. Once air temps increase though, the pistons and rods heat up, and the excessively heated metal is easier to bend during quench...