best timing for super charged engine

[insomniacshotrods]

Hi all, Finally got engine to where it will start and run but have no idea what to set the timing at. Ive got a timing light coming that has the advance setting for it ,so i can set up which springs to put in if i knew what to put in that is. A guy at a car show with a blower motor told me 26 initial and 34 total in by 2400 rpm anyone else with numbers? Ive been told all kinds of things and am getting confused. Engine is a 355 sbc,dished blower pistons,mild blower roller cam,64cc dart aluminum heads shaved 10 thousands if that matters. Msd ready to run distrib,no box or boost retard. Stock pulleys on 6-71 blower 5-6 pds of boost. Thanks a million Eric

 

[sstock]

That is a rediculous amount of timing for a non intercooled blower. Personally would not run more than 18-22 degrees total at full boost. And that is to start with. If it rattles back it off even more. Watch out with too fast a curve because that blower can make full boost at lower rpms. I would still make sure you run a vacuum advance on top of this though. If you run a boost retard then you can set it up with more timing similar to a normally aspirated motor.

 

[RPM]

Mine will make 10-12 lbs of boost. I run 40 degrees. I tried 34 an it had no power and it would over heat.

 

[Lee_in_KC]

Mine is 18 initial, 36 all in by 2500 rpm, per Pat Ganahl's recommendations. No vacuum advance, no boost retard. I have a vac/boost gauge and have only seen positive boost a few times. To see boost on the gauge I have to keep my foot in it and get above 5000 rpm. At highway speeds (2200-2400 rpm) the gauge still shows a little vacuum, although a lot less than if it were normally aspirated. I'm running the drive 1:1, which according to BDS's chart should make about 7#, wide-open throttle at 6,000 rpm. The most I've ever seen on the gauge is 5#.

 

[sstock]

Mine is 18 initial, 36 all in by 2500 rpm, per Pat Ganahl's recommendations. No vacuum advance, no boost retard. I have a vac/boost gauge and have only seen positive boost a few times. To see boost on the gauge I have to keep my foot in it and get above 5000 rpm. At highway speeds (2200-2400 rpm) the gauge still shows a little vacuum, although a lot less than if it were normally aspirated. I'm running the drive 1:1, which according to BDS's chart should make about 7#, wide-open throttle at 6,000 rpm. The most I've ever seen on the gauge is 5#.

Lee, something is wrong IMHO, you should see boost at full throttle immediately after dropping the hammer on a positive displacement blower at low rpms.

 

[railroad]

Your compression ratio has a big affect on how much adv you can stand. Naturally you need to run 90+ octane. The next factor you need to know is how much max boost you have. I have a Kenne Belle with 9.8 comp ratio and 10 lbs of boost. It has been a while, but I think I am running 19* adv. My son just had an Edelbrock SC installed on his 08 Mustang GT. The turner said he put in 17* at 9 lbs of boost. I do not see how anyone is getting by with anything over mid 20s unless they have very low comp ratio and less than 5 lbs of boost. You can always work your way up, but detonation damage under boost comes in milli seconds. I would start low and conservative and check your plugs often while tuning. Be aware of what mild detonation looks like on your plugs. A wide band sensor and A/F ratio gauge would be invaluable. Most dyno shops have them. I have an Innovate model with the screw in sensor. They also have the tailpipe sniffer type. Go ahead and get you a good vac/ boost gauge. I found out that autometers are terribly inaccurate. Whatever you buy, try to verify accuracy against other gauges. The screw type blowers have to be under load to make boost, no driveway tuning. Need a good co pilot to tune, if dyno is not an option.

 

[Lee_in_KC]

Lee, something is wrong IMHO, you should see boost at full throttle immediately after dropping the hammer on a positive displacement blower at low rpms.

Can you explain your logic there, Steve? My understanding is that the boost curve follows the rpm of the motor. I have seen a graph illustrating this, maybe in Pat Ganahl's street supercharging book.

I found out that autometers are terribly inaccurate.

Awww poop! Mine is an Autometer.

 

[Lee_in_KC]

Did a quick google search for a boost curve chart and found this one. The MangaCharger is a 6-71-type blower, while the ProCharger is a centrifugal supercharger.

 

[old round fart]

I had a 10 lb. gauge that stayed at 0 until you opened up a little and pegged when you planted it!

 

[RPM]

My motor has an 8.2-1 compression ratio and it has SRP blower pistons in it. So I could run a little more boost and a little more timing. It also has the MSD boost retard on it. Another thing is cam choice. A cam for a blown motor is a little different that a naturally aspirated cam

Here are a couple of links with some really good info.

http://www.blowerdriveservice.com/techcharts.php
http://www.blowerdriveservice.com/faq.php

 

[Lee_in_KC]

Hey Ron, I don't know what you did to your motor, but it just sounds nasty!! I garan-damn-tee I ain't gonna race you for pink slips!! (Does anyone outside of California understand what a pink slip is? It's your title. You race for pink slips, the winner gets title to your car! We actually did this in the 60s in SoCal!)

 

[insomniacshotrods]

Ooops my gauge is auto meter as well. Love your car Lee, will you be at the NSRA in springfield again this year? Seen your car there last year ,but didnt get a chance to meet you. What ever my timing is at now the car fires right up and idles great so im guessing im in the ballpark on intial timing. Thanks so much guys for the input,guess its just something im gonna have to play with and see which combo works for my setup. Im used to bigger problems with this car so this is nothing lol.

 

[Lee_in_KC]

Yep, I'll be down there this weekend! I was gonna ask if you were coming. Please check in with me if you see me!!

 

[insomniacshotrods]

Will do. I was going to try to get mine done for it but after hearing of the entry fee ,and cost of gas for my truck with the trailer .We are just going to take my buddies 27 t roadster. That way we can split the cost of the entry fee and you get two admission tickets . Im about 1 hr from Springfield but i hope to have it ready for next year for sure . I better start now if i know me lol. Got any pictures of you car you could send me? Cant get a big picture on this site. Cant make my mind up on color,flames or no flames ect. Yours reminds me of mine and might help me make up my mind. I was going with synergy green at first then rat roaster green, now synergy green again. But for now im just going to shoot it with semi flat black, but would also consider strongly gloss black with flames.

 

[railroad]

Let me give the reason for the autometer gauge evaluation. With the internet connection a lot of the 99 Mustang Cobra owners were able to relate and compare mods. Thanks to Ken Christley of Kenne Bell we had the opportunity to have a KB supercharger for our cars. Ken notified us, if we would put up $500 deposit and he got enough to justify fabing up the kit, it would be developed.
Long story short, we got the kit. Ken spoon feed us all the ins and outs as we installed the kits and dealt with our own issues.
The kit was designed to boost to 9 lbs. Immediately reports of boost being all over the place 6, 7, 8, 9, 10, 11 lbs. Ken told us the gauges would vary widely, but sometimes you miss those things. Anyway, what better gauge is there than Autometer. After some gauge comparisons and returns for calibrations everything seemed to calm down and get back to hot rodding. My boost gauge was one that was in the ball park.

 

[insomniacshotrods]

Sounds like a bad a$$ mustang. Im a chevy guy but i do like the mustangs alot,except for the 95 my wife owns that i have to work on lol. I love the sound of them with flow masters,standard shift and throw in a turbo or supercharger man thats sweet and hard to beat. Thanks for the info on the gauge.

 

[PotvinGuy]

My setup is similar to yours; crate SBC, 8.5CR, 6-71 at 1:1. I run 20 initial, 15 vacuum and 15 speed, in by 2500. This gives easy starting with a hi-po starter, great idle at 35 and cruises in the 40's. The expression "blower motors need lots of advance" is a bit misleading; it stems from the fact blower motors are usually low compression, and any low CR motor is going to need more advance, with or without a blower. The blower itself doesn't come into play until you load the motor and get into boost, when you might need some boost retard (boost retard is just an extension of vacuum advance; more manifold pressure results in higher chamber pressure which needs less advance because it burns faster).

Manifold pressure (termed boost when it exceeds atmospheric pressure) increases with load; RPM has little effect. And with a big motor in a little car it's hard to get much load on the street, but on a chassis dyno I've seen 10# of boost. See http://www.tbucketeers.com/threads/timing-for-dummies.12177/ for a timing primer.

 

[Gerry]

Hey Ron, I don't know what you did to your motor, but it just sounds nasty!! I garan-damn-tee I ain't gonna race you for pink slips!! (Does anyone outside of California understand what a pink slip is? It's your title. You race for pink slips, the winner gets title to your car! We actually did this in the 60s in SoCal!)

I do I watched 2 lane blacktop
G

 

[Lee_in_KC]

It has been brought to my attention that there is a TV show called "Pinks" that is all about racing for pink slips. Well, I don't watch a lot of commercial TV, so I didn't know. I'll be in the garage if you need me...