SN2000 HO installed on 406 SBC

[Buck-Strickland]

Thank you to those who answered my questions.

I got to a point in the installation of the SN 2000 where I could take it for a spin.

Back ground on the Car and Engine:

1972 Olds Cutlass
TH400 (low gear set) and 3.90 rear gears. Est. 3650lbs with driver, car was put on diet.

Engine:
406 cu. in. Small Block Chevy
9.6:1 Compression ( Forged SRP pistons)
Edelbrock Performer RPM heads
Howards Hyd. Roller cam, 230/232 Duration @0.050, 0.510 Int. 0.530 Exh. Lift, 112 Lobe Sep

3200 Stall converter

Previous best E.T. NA was 12.41 @ 106 MPH, 1.66 60ft on drag radials (AFR 12.3 with 33 degrees of timing)

I installed the blower and took it for a test run down the street. Wow, lots of pull in the mid range. Makes 5psi instantly and holds well past 5300rpm (my shift point). AFR is in the 10.72 to 11.72 towards the upper RPM. No third gear pull, so can’t say how it will really work until I get it to the track in June.

I backed the timing down to 23-25 total, put in colder plugs (0.038 gap)

Blower is a SN2000 with the HO impeller and 34-35 in/lbs of turning torque with seals in. I have 75% plus belt rap with a 4.5” (4.35 on the ribs) blower pulley and a 7”(on the ribs) crank pulley. Shift point normally around 5,600 max (shift light set @ 5,300). I have a cooler, but it’s not installed yet. It will be before I drive it to the track.

I made the brackets and collected misc. parts to build my own blow through kit. Mind you the pictures are of it installed, but I have some more finish work left to due on it.

I’m hoping to pick up 5/10ths, I would really like to run a 11.99.

I though I would share this with folks. I know most of you are Mustang guys, and thought that some others might be interested in a non Ford application. Nothing wrong with the Fords or Mustangs, I like them too.

Check my Album for pictures.

Any advice on tuning would be great or other suggestions too. Issues I’m over looking? Thank you all!! This forum is great.

[Buck-Strickland]

Oops, Picture would be nice.

[JPJP]

Beautiful...........and keep us posted on your track times!

[pavement pounde]

Nice numbers and nice looking, try to get 12.0 a/f ratio and gain some more power.

[Buck-Strickland]

Thanks.

I am a little concerned about 12.0 AFR; carbureted setups tend to have inconsistent cylinder to cylinder distribution. Unlike the MPI systems. So, since the AFR sensor is a cylinder bank average I tend to lean towards the rich side. I will watch the plugs and see if I can creep up to 12.0 AFR.

Looks like first week of June or possibly a weekend this month I may get to the track and take a hit on it.

Sorting the timing has proven to be the most difficult part so far. HEI's are not very modification friendly, plus they tend to have too much timing in the distributor. Last night I made some limiters for the advance mechanism, but it was 1 a.m., so couldn't fire it up and check the total. Previously to get 25 degrees total I had to crank the initial down to 3 degrees, the cam does not like that low initial. I should be able to crank it back up to 13-15 initial now with total limited to 25.

The track will help me tune it better, I'm afraid the fuel system may be marginal at the top end. I may need to add an electric pusher pump near the tank.

I had not run one of these Paxton’s before; I am amazed at how quiet they are. I really cannot hear a difference between now and before. (Unless you stick you foot in it, then the motor just sounds mean. :angry:)

[Buck-Strickland]

Well, I was hoping to have some time slips today, but I took the car for a shake down on the freeway and discovered why my AFR was rising so fast in the upper RPM. Discovered that my boost referenced Carter 130 mechanical fuel pump could not keep up with fuel demand. Note to anyone trying to use this type of system, get a fuel pressure gauge to watch the pressure rise with boost. Mine would spike then start to drop fuel pressure with rpm. Ordered a piston style mechanical pump from www.racepumps.com hopefully this will take care of the problem.

I had not seen the flow charts for mechanical fuel pumps. They are rated at free flow, 0 psi, but when you start raising the fuel pressure the flow drops dramatically, I mean a lot. Even the big Holley 225 pump at 11psi only puts out like 35gph.

If I did not like electric pumps so much I would have gone to the Aeromotive A1000, as that seems to be the pump of choice for the carbureted blow through crowd. I like the concept of the Race Pump, plus it's upgradable for cheap, and Howard the owner is way helpful.

Thank goodness for Wide Band sensors.

I will let you know how this works out, should have all parts collected by end of month.

[pavement pounde]

The wide band is my best tool I ever bought and the hammer my second best

[Buck-Strickland]

Well, installed the Race Pump and Race Pump regulator with boost reference and idle bleed. Really nice products, the regulator and the pump are top notch. This system has no issue with fuel pressure, or volume for that matter. Took it for test drive this morning and the fuel pressure was the base 7psi plus whatever boost was at any given point. My AFR in high gear went to 9.6, from 11.7(and rising) with the other pump. After I make some passes I will re-jet the carburetor and shoot for 11.5-12 AFR. .

Also, installed BOV in the mean time. See picture.

Going out Wednesday to the strip, hopefully I get to make a full pass. It’s hard to tell how the system works on the street. Unfortunately it will be very hot 85-90 degrees

Looks like I get around 6psi of boost at 4k rpm, then drops after 5500rpm to 4psi.

[Buck-Strickland]

[pavement pounde]

Nice, you have a lot of beltwrap to around the blowerpulley, nice.
it is not nessesary to put a filter on the bov, becouse it wil never suck up air from outside.

[69fury]

NICE BUILD! What fuel are you running? Can you give some specs on the carb (type,CFM, jetting)

-rick

[Buck-Strickland]

Hey Rick,

4778 Holley 700CFM DP Carburetor Jets Primary: 72 (w/PWV), Secondary Jet 95, 0.110 needle and seats, 0.028 F & 0.031 R squiters, Nitrophyl floats, timing 23-25 total by 3000 rpm. Champion RC9YC spark plugs gapped to 0.038 (which may still be too much, will see, anybody have a suggest here that would be great.)

91 octane with splash of 100, so pretty much 91 octane.

I will be running it at the track this evening for the first time. Hopefully things workout okay. I will be checking plugs and the Wide band AFR. I think it may be on the rich side now with the new fuel sysem.

[69fury]

how rich is showing on the wide band? you shooting for about 11.5:1 afr? sounds 'bout right, but i'm not sure what the grace window is for your amount of boost.

[Buck-Strickland]

Update:
Took it to the track last night, not super excited, but I have some tuning to do which should reap benefits.
NA best was 12.42 @105.6MPH AFR 12.2
Last night it went 12.16 @110.4MPH, 5-6psi boost through the traps, AFR 9.00 middle of track to 10.2 at the end, VERY rich, 26 degrees timing total.
It is a different beast; it took a new launch approach to get my 60ft’s back in the 1.6’s (on Drag radials). I need to rein in the optimal shift point now, because it did not like my prior NA shift points. Also it felt like the first 1,000’ it was not really moving then the last 300’ it was pulling really hard (also when the AFR started to get into the low 10.0-10.4 above 5,000rpm and out of the 9.0-9.7 range). The super rich condition in the lower RPM may be why it was sluggish.
So, I think I will pull some jet out and try again in a week or two. Perhaps shoot for 11-12 AFR range.
Anybody have any dyno experience with super rich vs. leaner conditions, perhaps I’m giving up some power?

[69fury]

yes we see big gains on the dyno when the tune gets more crispy- lean is mean, but fat is happy. But with boost you really need to get it up to the 11.5 range as a good ball park goal. extreme rich can wash cylinders down and even lift ring lands (witnessed that first hand leSigh...)

I'd expect some good gains once you get the a/f right. you may also want to pull some gear out of it, depending on what you're running now, vs. your final power increase. But i dont recall if you posted your tire dia and how that's working for ya?

what rpm were you going through the traps?