guys, got my motor broken in and nailed it a couple of times- if i floor it at low rpm(below 3k) to the floor, i get a bog, then it takes off in boost. previously i had a roots on this motor, and it never did that, is this normal w/ a carbureted blow thru turbo application? engine is a 383 chevy, has twin t3/t4's, brodix track 1's, victor intake, and a solid roller(600 lift, 246/254 duration, 114 center), qft 750 blow thru carb, timing is at 20 deg base/ 38 total, and an msd 6 btm pulling out 6 deg under boost(i'm only running 3 psi now).has a tremec 5 speed w/ 4.10's, is there something wrong w/ my setup, or is that the way it is and i need to bring the throttle in easy?? bottom end off idle torque is non exsistent(doesn't feel like the car would break the tires loose anymore unless its in boost!! thanks!!!

 

turbo spec?

 

i believe they were .57/.63 ar

 

Have you tried different pump cams and squirters ?

 

that i didn't, i did have a lil stumble at tip in rite off idle, the carb currently has 31 squirters in it w/ pink cams

 

??

57mm, .63 turbine housing ?
what wheel ?

 

that i don't know, how do i tell?

 

Measuring compressor inducer, and turbine exducer is a good start.

 

had the same problem, needed alot more fuel from the squirters.

 

^^^^

 

+1 on the pump cams and squirters

Do you have w/b , what does it say ?




Gino

 

besides what has been said already.....why are you pulling 6* for 3 psi??? I wouldn't pull any for only 3psi!

typical that I have seen in less than 1* per pound of boost. I would try leaving the timing in it, or at least only pull 3* from it.

 

Pink cams are garbage, throw them away. You need the pump 'all in' in the first 50% of throttle opening; pink cams are linear from 0%-100%. You don't need any pump shot when you go from 3/4 to WOT. Try the orange or green cams.

 

the QF carb is one size fits all-now you have to dial it in for your setup-as said, prob wants more fuel untill the boosters are flowing-not sure what all the specs are on the carb, but i like the green cam, #1 hole, maybe go to .035 squirters, some other stuff-a stick car/big cam isnt as forgiving as a tq converter, so your tuning is a little diff-try little stuff first, one change at a time, write down your changes so you can go back if needed

 

thanks guys, next time i have the downpipe off i'll measure, i also go to 35 squirters and toss the pink cams, i haven't hooked up the wideband yet, so i'll do that next, great website and thanx for the help, i'm wondering if i should change the cam or continue playing w/ it?

 

change those 4.10s to some 3.23s or 3.55 gears also

 

IMO blow through will like more squirter and pump cam than roots. I'd try the Orange cam and a squirter up around #36 maybe #42.

 

Just a few humble suggestions.....agree with knocking a bunch of gear outa that thing cuz turbos make torque and need to be lugged
I have a 385" w/G.M. fastburns and a box stock C&S 800 aerosol; BW s475 @ 8psi for 93octane....also my cam is ultra conservative Comp 12-253-4 w/1.6 rockers
to kick the lift up close to .500...I guess I figured since this was my first blo-thru a [email protected] cam would have good manifold vaccum for low end throttle response
having 210cc intake runners and a victor jr.high-port on a 9:1 engine and the turbo will cram the shit in as neccesary. Also the fastburn springs w/105@seat &280 open
work just fine with a 6500 max.. I'm not sure but perhaps you wouldn't need all the additional pump-fuel shot if the booster signal was better :noidea:

 

i currently have 600 miles on the new combo since december, and i'm getting ready to change the cam. all i can say is i would never recommend comp cams to anyone!!! they are clueless(at least their tech line is). i finally got tired of the lack of torque(at 70 mph in 5th at 2500 if you have to go up a hiway overpass you have to increase the throttle quite a bit, another example, at a traffic lite i almost have to boost the thing to keep up w/ normal traffic(over half throttle). i'm tired of the idle as well. i locked the timing at 34 deg and it helped alot, but it still sux. i talked to crower and bullet cams at the suggestion of some friends and both companies agreed the cam profile was totally wrong! they recommended almost 15 deg less duration(both companies were around 236 @ .050, crower had 1 deg less duration on the exhaust, bullet was 4 deg), w/ lifts of aprox .575. i called comp again after talking to both companies(comp initially said the blower cam would be fine in this combo), when i confronted them w/ the new information, they changed their story,and maybe there are some things wrong w/ that cam for my application,but they'll charge me less for a new one, and next thing they tell me is they don't make a turbo profile for sbc??????? wtf!!! he says they can try to grind a cam w/ the same lobes that i currently have but put them in different spots???? i can't believe them, never again will i buy a comp cams product. i'm leaning towards bullet, which is the old ultradyne cams,what do you guys think?

 

After reading what you have, I think if I'm not mistaken you have a .57 wheel and its the .50/.63 AR twins, did you get them from Ebay? As far as cam goes I would go with one of our sponcers if your going to do a custom grind they know their shit and won't put you in the wrong direction you want something in the range of 112-114 lobe seperation and 216/224@50 duration. ** Just example ** But the cam shops will hook you up from this site, so take what I say with grain of salt, so to speak. lol As far as your gear someone already addressed the issue gear needs to come down for turbo ride. But I'd take Cat and Erics advice to a Tee with carb tuning these guys know their stuff and on their game. I've actually learned alot from them just from reading these threads, lol But good luck man, pop in that different bump stick and see how it works for ya. Just get that gear down turbo's like load. Sorry just to make something clear looks like all the information in this thread is really good, Thank god for the Turbo Forum!! lol