Ron Pope Motorsports                California Custom Roadsters               

any guidance on 471 blower tuning

Vegas T

Vegas T

Supporting Member
Supporting Member
Just bought a 471 blower and 750 carb from Big Al's Toybox. Anyone got any tips on tuning it? The carb is supposed to come ready to run but I'm not sure on timing and the other specifics. It's going on a 350 GM crate motor with 8.5:1 compression. Not a radical motor and the blower is underdrivin 15%. Any info would be appreciated, I've seen some of your guys blower setups so I trust your input more than others.....
 
Lee_in_KC said:
Huffer boy here. Underdriving a 4-71 by 15% on a 350 will not produce any boost, according to Blower Drive Service's chart...

attachment.php


How did you arrive at 15% under?
Click to expand...

I wondered about that also. I have a 6-71 on a 355 with 10% under and it will make about 10 psi boost
 
Sorry guys, Its not 15% its 12% and that was recomended by Big Al at Big Al's Toy Box...
 
RPM said:
I wondered about that also. I have a 6-71 on a 355 with 10% under and it will make about 10 psi boost
Click to expand...

I'm running my 6-71 at 10% underdriven too. Runs great with no blower lope. You shoul dbe able to run between 4 and 6 lbs of boost. That's what those little Weiand 142 make and they're made for stock small blocks.
 
slap that 471 on the motor put the carb on and fire it up, depending on your altitude i really don't think being @ 15% under your going to get anything but hell it will look awesome, stock create motor you can run it @ 5% under and have no problem. The reason i say that is you will be so scared when you hit the gas that you will never hold it to the floor, Boost is calibrated @ WOT about 6000 rpm i know the only time you will hit that is when you go up in smoke. Put the blower on and carb and fire it up. It will work just fine, when you save a little money buy another pulley and get yourself to 6 or 8 under driven and go have fun, then save money for tires because you will need them.
 
Nas T said:
slap that 471 on the motor put the carb on and fire it up, depending on your altitude i really don't think being @ 15% under your going to get anything but hell it will look awesome, stock create motor you can run it @ 5% under and have no problem. The reason i say that is you will be so scared when you hit the gas that you will never hold it to the floor, Boost is calibrated @ WOT about 6000 rpm i know the only time you will hit that is when you go up in smoke. Put the blower on and carb and fire it up. It will work just fine, when you save a little money buy another pulley and get yourself to 6 or 8 under driven and go have fun, then save money for tires because you will need them.
Click to expand...
Dito! Put it on, then fire it up is the only way to tune it. Should be alot of fun to drive!
 
Boost Daddy said:
Dito! Put it on, then fire it up is the only way to tune it. Should be alot of fun to drive!
Click to expand...

Hey, these guys have given you sound advice. A 6-71 on a goodengine with 6 to 7 PSI.....it'll feel like a jet. 8-10 PSI....you'd sware that they've stuffed you into the space shuttle. crank your engine up, have your timing light out and shoot for about 8 btdc......and see how it runs. Mess with your timing just a touch at a time......its like vitalis or brylcreme.....a little dab will do ya....
After you've run it a little..... recheck your intake and water inlet bolts..... :cool:
 
Another Huffer boy here. Sounds to me like what you have is a great starting point.

A sure way to test things is to visit a quarter mile dyno and measure your performance, then start messing around with your jetting etc.
 
your suppose to back the timing off .. i think its 1deg per lb of boost, it might not be that critical with the smaller amount of boost, but i would back it down a few degrees to start nonetheless.....
is this kit you got the wieand 4:71 box kit, it is 12%underdriven... should make around 3lbs of boost. its gonna wake that motor up for sure.. if anything i would see what jets are in the carb and write them down, then go up a couple jet sizes, then bring the jets down a size at a time as needed


and i would hit the nearest chassis dyno for a few good pulls with a wide band o2 sensor in both pipes...
 
If you back the timing down much you will cook the headers and possibly the exhaust valves. This causes the fuel charge to burn late and it gets blown out into the header. I know I done it. I was running total advane at about 32 deg. It burned the ceramic off the headers and wanted to run hot all the time. Bumped the timing to 38 and what a big difference it made. Runs cool now and quit burning the headers. I also put a MSD boost retard on it.
 
You can adjust it from 0-3 deg for each lb of boost. I have it set on 1.

The blower likes lots of timing at low RPM. So run a lot of initial advance then retard at higher RPM and more boost. I run about 18 deg initial.
 
he doesnt have a boost timing controller... hence backing it off 1deg. per lb of boost to start... dont know if it would be that critical with 3lb of boost..

but with 3lb of boost its not going to kill him, and help him when he starts getting boost to the engine in the upper rpms... its kinda like nitrous at that point. if i put a 100hp nitrous kit on a car i will back the timing off 2deg, now if i have a timing contoller, you can leave the initial timing where its at and back the total advance off a few degrees..




with 10lbs of boost or more it will matter..
 
RPM is right. Run as much timming as you can down low then use the msd boostmaster as you build boost to pull timming out. You will also get more mile per hour with doing that. BLOWER+T=:lol::lol:
 
I would really like to put a blower on mine but the cost for one is basically out of reach for me at this time
Unless some one knows how to get the high cost of one ?
 
"roughly" speaking 10 lbs of boost will double the HP on the engine. A mild 350 making 300 hp will make about 600 hp with 10lbs of boost.

600hp in a short wheelbase 1800lb car is a hand full. But lots of fun.
 
RPM said:
"roughly" speaking 10 lbs of boost will double the HP on the engine. A mild 350 making 300 hp will make about 600 hp with 10lbs of boost.

600hp in a short wheelbase 1800lb car is a hand full. But lots of fun.
Click to expand...



Yep....a handful......and take BlownChebby's advice also. If you got a MSD with a soft touch Rev Limiter.....SET IT.....cheap insurance. You can get two identical engines, running every thing the same, same blower, cam, and both will run different.
Me myself personally, I run as much timing as I can get away with....(blowers seem to like it), then I come up until it just starts to labor ever so slightly, then I go from there.................
 
You must log in or register to reply here.

Similar threads

PotvinGuy
Timing for Dummies
2
Replies
22
Views
10K
Island Girl
Island Girl

     Ron Pope Motorsports                Advertise with Us!     
Back
Top