Hey there guys. I am lookig to maybe run a small supercharger (or maybe some nitrous) but timing seems to be the issue. Here's the specs on my motor 9:1 comp/ 320-330 hp/ hypertectic pistons/ 350/ 4 bolt main/ 600 cfm edlebrock.

My question is about how much timing will I have to pull for about 5 or 6 psi out of a 144. Everyone says you have to pull a little bit but how much. I know these cause a lot of heat so I would probably have to retard it a little more than usual. I run an untouched hei distributor. Pretty sure it has about 24 mechanical degrees of timing. My initial timing is 10 degrees. Could I retard the timing by just lowering the initial timing or would that set my idle timing way too low?

As a reference how much would I have to retard the ignition if I had an intercooled 5-6 psi?

Oh and the reason it's such a big deal is I have to stay on pump gas and I'm kinda don't want to change the springs on my distributor. I will if it's better tho!

 

Does anyone have any prior boosting/ Timing experience to help me out?

 

Normally when this question is asked you are talking about total timing and that will vary depending on timing. You need to understand all the things that make up your total timing. You can not run a vacuum advance for obvious reasons. Are you running weights? Any type of MSD box?

If you think your just going to bolt a stock GM ignition system on a small bock and retart the timing a couple degrees and run it your about 10 hours of research away from being ready for boost. All the reseach in the world is not going to answer your question, it just going to explain the tests you need to do to come up with a setting. There are just to many varibles. How good is your intercooler? how rich is your carb? Sea level?

Boost and NO2 do not really hurt motors as much as you think, it is when the timing and fuel raito is not setup right that does the damage.

 

Supercharging increases the effective compression ratio. A 6 PSI boost will make your 9:1 compression look like 12.5:1. Depending on the supercharger you plan to use the spark advance curve will be different. A roots blower builds pressure immediately and will require less initial advance than a centrifugal type, which needs to high RPM to build boost. Total advance should be somewhat less for the roots blower as it thends to heat the air more. Intercooling helps a lot, but is difficult when using a blower. You could start by retarding the total advance by about 10 degrees and and advance it one or two degree at the time till the engine starts pinging. Additionaly, the fuel mixture will need to be enriched substantially to both provide the necessary fuel and to cool the mixture under load. This will get the engine running but it won't be right without a lot of trial and error. A dyno tune will be very useful, unless you are good at reading spark plugs. The easiest thing would be to find a kit that includes all you need to get the thing working properly.

 

@gorn I thought the only two things that affect total timing were initial and mechanical. I did not know that vacuum couldn't be used, but that only comes into play under cruising speeds so it doesn't really matter too much. I run a stock hei distributor. I've heard good initial timing for a stock 350 is about 7-10 degrees. If I chose ten and my mechanical(weights) had 24 degrees, added up I would end up with 34 degrees total timing(if I went with 10 degrees initial) please correct me of I'm wrong, but the only reason I would need to retard the ignition is to stop it from predetonation. Now my question is, if I end up after boost getting around an 12:1 compression ratio, how much would I have to retard my stock 34 degrees of timing without detonation on 91 octane. I don't see why I can't use a stock ignition. I can change the timing curve to almost anything I want using different springs and I can change how much mechanical timing I want with weights. The only reason I asked if I could simply retard my initial timing was because first off I don't know what the lowest amount of timing a 350 can idle at, and second of all I don't know how much total timing I need to take out in the first place. For example if I only needed to take out 3 degrees of timing, I'd simply retard the initial timing because I'm pretty sure the car would still idle fine, and it would also give me a total timing 3 degrees less. If I needed to take out a total of 10 degrees, I'm just guessing a car cant idle with 0 degrees timing, so then I would leave initial at 10 and just get different weights to take away from mechanical.

If I were trying to run a na motor at 12:1 cp ratio on pump gas, would I have to retard the ignition as much as a 144 supercharged motor at 12:1 cp on pump gas?

I don't know any other way to ask this but how much does richening the carb help with detonation. What ways other than retarding timing can I help stop the detonation with such a high compression ratio and only 91 octane? I want to do anything I can to give it good manners

 

Woops I thought I could change the amount of overall mechanical timing my switching weights, but I guess that just changes the curve alOng with the spring