high speed help

im running a 555 bbc that is 12.4 to one with dart 345 heads with 2.30 valves . some mild clean up work is all and port matched. cam is a 720 lift with 277 and 284 at 50 . i have a 14-71 ssi blower and a buzzard from enderle. it has a k valve and a 990 pump that was taged at 15.8 at 4000.my nozzles in the hat are 8 .044s and 4 .040 in the blowermy ports are .052 .050.048 .046 front to back. i run mud drags and only run 200 ft at a time i made some test passes and ended up with a 160 main pill in the main. run pretty good. now in wanting to turn the high speed on next. where do i start at on a main pill and hs pill. i was thinking around a 110 to 125 main and a .090 hs.what are your thoughts

 

I have a similar combo, 480 cubes, 25lbs boost, 990 pump, similar cam etc...
I had to install a pump sizer to bring the main jet size down from 150 to 100. (easier to tune)
Pump sizer poppet opens at 30lbs and has a 065 pill.
I run a highspeed set at 50lbs with a 083 pill.
Total pill area 0.01656sq"
2 x #42 and 6 x #40 nozzles in hat
8 x #50's in ports.
None in blower.

I suggest you start by fitting a pump sizer at 40lbs with 050 pill, and a high speed 60lbs with 090 pill. then work your way up in pill size from there.

But I'm no expert...just a guy thats learning as he goes.
Cheers

 

Not being familiar with Sand Drags, I don't know how much the engine is loaded vs. 17" wide slicks grabbing on concrete. We ran a manual leanout (1979-80), and often in 1/8 mile races, did not even "throw the switch". Back then many people had a tendency run BBCs too lean. Also in 1980 my car was geared higher (Lenco) than most AA/DAs. I only had a 110 pump and 8-71 (~40% OD) 442" Rodeck (~11-1 compression) with only hat nozzels (055-058s) with ~100 main jet (Birdcatcher)~40 deg adv (Super Mag II). D port aluminum (solid) heads and custom intake made a big difference in fuel volume (w/ standard iron heads and Cragar intake I used ~125 main jet).

 

I would not use a high speed. ust make sure your blower can make enough boost and leave the line 55 to 6500 rpm. I ran the earthshaker about 10 years ago. High speeds burn up parts if not used correctly. I used to beleved in high speed not long ago untill we started making power. If you spin the blower up make sure you richen it up. A 160 main is to lean for that combo with any kind of real boost. You should have 40 to 45 lbs of boost at 6500 rpm and depending on corrected alt. temp. water gains. etc should have from a 85 to a 100 in the main if you can achive the 40 lbs of boost. Spark is a big factor also that I hope you are looking at. You never mentioned what you have for spark. You should not be that lean because pump psi at the finish line. Bottom line is we need more info to correctly help you. Thats my take

 

ok i can give most of the imfo. i have a msd 20 mag set at 35 degrees timing. all just checked out over the winter. blower is a ssi f rotor with top and bottom mods. fresh has 4 1/8 mile passes before i got it. was done at ssi. i run a scs gear box with one gear set-up for what track i run and have a crower slipper clutch. i have it with a 50 thousands airgap and 26.7 grams per finger weight still think i need more weight .car moves at 2300 idles at 1600 barrel valve leakdown at 78 percent. 2600lbs car with driver , hooks really hard . we run mud or dirt drags 200 ft is longest down to 100 ft. motor is based on the dart big m block. billet crank , child alberts rods custom j-e bloer pistons.12.4 to 1.total seal rings. crank support on front to help motor live.miledon gear drive. heads are dart 345 that i had run on old motor . need to get them gone but funds dont support that thought yet. 2.30 1.88 valves with a mild clean up and port match. new 990 pump tag said 15.8 at 4000it was 2512ft the day we was making some passes .not good hook in the track. 30 over on the blower as a stating point . i had a 10-71 hi helix before on this motor turning 50 over made 28lbs of boost this blower makes 32. i have pulles to 65 over . just dont want to kill the motor to fast

 

Id send the blower to jr at RBS superchargers. If you are spinning the blower at 50% and only making 32 lbs of boost there is something wrong there. Spinning my blower at 32 % this weekend I made 42 lbs of boost. Thanks Jr. Keep 1 thing in mind. Spinning the blower harded will take hundreds of hosepower for only a few more lbs of boost. Now if all you can make is 28lbs then set your high speed at 55 lbs (should be 1 thick and 1 thin shims). I would put a 95 in the main and a 75 in the high speed. Start leaning out the engine from there and keep a close eye on the egt temps. If you can get better boost than no high speed and start with a 70 main. Again watch the exaust temps. Boost is everything on an alky engine.

 

i turned the 10-71 50 over the ssi only turns 30 over and made 35lbs .ended up with a 115 main and a 100 hs and it burned to the face of the plug not over the sides.