Blow through problems

[camcojb]

Well you're right. I think mods to a carb should be done by a professional....but what about when that "professional" doesnt come through...then its in your own hands, and thats where i am.

AFTER i took it upon myself to modify the metering blocks CORRECTLY, did mostly jet changes to get where i am...and i drive my car 4/5 nights a week.

-Carm

the reason I mentioned it was because Procharger tells everyone that a switch to solid floats, milling the choke housing, and jet changes will be all that's needed. I've been there, done that and it simply wasn't true for me or anyone I've done or participated in, which is several.

A guy is better off spending $375 for someone like SDCE to fully mod your carb. I've had him do two for me in non-efi builds and both were spot-on right out of the box. Had perfect manners everywhere, actually ran as smooth as efi in my opinion. Just didn't get the mileage of a good efi system.

This was no slam on you, you obviously have a handle on it. But most simply get frustrated trying to make their setup run right following ATI's advice, and there's almost always a lot more modding required. Making the decision in advance to get the carb correctly modded up front saves a lot of frustration and is well-worth the money.

Jody

[Adam's 55 Chevy]

CSU would not finish my carb until I had furnished them with all the cam specs of the engine. They could have given me anything but this shows the level of preperation a carb needs to have for a blow thru application.

[Supervette]

I went to a car show this weekend and met up some other guys doing similair procharger set ups. They told me to ditch that ignition with the springs and weights, and go with a programmable digital 7 with boost retard curve. They said this would clean up the launch of the car a lot. The extreme velocity carb hat with dropping the secondaries down 5 jet sizes and giving the idle circuit more fuel seemed to help out a lot. Surging is almost gone and little blurps on throttle are much more crisp.

First things first is a innovate wideband system. then digital 7. Hopefully this gets me to where i need to be. Other wise I might have to look into the FAST system more seriously. Can a fast system be used with a digital 7. The good news is I have an extra labtop sitting around the house waiting for software! I was on their site and the program looks very extensive. Whats the learning curve on it?

[Turbo Hen]

I use the digital 7.....its VERY easy to use & EXTREMELY user friendly.

if you goto MSD's website, download the "ProData" software & start playing with it....you can know it inside out before you even buy the Digital 7.

-Carm

[bigdaddyvu]

I have a turbo charged camaro with a blow through holley 750 dbl pumper. I have or had similar problems with my setup. when you get a holley style carb or have one modified make sure it has neo fill floats or they will collapse under pressure, remove and mill choke, anti blow power valve they like to rip apart under uneven pressure, modified air bleeds, vacuum fittings on all extrenal throttle shafts bushing and having a vaccum line attacted to the plenum ( holley style carbs always leak power at the throttle shafts) special metering block gaskets (rubberize coated style) seal off all unused vacuum fitting with epoxy or solder don't use rubber cabs or vacuum lines with a bolt stuck in it. reduce your primaries and inrichen your secondaries. and mod your metering blocks. or you can buy a carb already setup for blow throughs for atleast 800 bucks. and another thing check the nuts and bolt on the carb they like to loosen up with the hot and cold ( i blew a gasket on my float bowl cuz one bolt was loose)

I also use a aeromotive fuel pressure regulator. with a progressive line signal. run your pressure at least 4 psi and should always be atleast 4psi above boost psi or the boost will push the fuel back into the tank (4 psi @ idle no boost psi to 18 psi of fuel 14 psi of boost)

I use a mallory hyfire vi 685 advance box. it features boost psi retard. beings everyone knows you can't run a advancing dizzy on a boosted engine or detenation occurs (hestitates or popping just before boost). i modified a hei dizzy with a lockout advance and have it set at 24 degrees i use the hyfire feature by using a stock gm map sensor and hooking it up to the plenum now i can retard the timing. basic rule for boosted is for every pound of psi retard the timing a degree or two. and since i have the dizzy solid advance i also use other feature the under 500 rpm to retard timing to get the engine started easier.

if you don't believe me read the book Maxinum Boost by corky bell

i have a 86 z28 junkyard 350 s-10 headers flipped, t-70 turbo, ford power strok intercooler, holley 750 blow through, spohn 8 point roll cage 6 point legal, sub fram, and other misc stuff. 4000 dallors get me going 10.69 @124 mph in a qtr

[Supervette]

Nice! I believe you.. I gotta get rid of this ignition system this week. Msd digital 7 for sure now. Also the innovate wideband is it okay to run one band and switch it to the other side for tuning.. I can't see spending an extra $400 for another sensor.

[slocobra]

try www.theturboforums.com and check in teh carb+boost forum. there you will find everything you ever wanted to know and alot of guys that will help you even though you have a blower

[Supervette]

Okay so i decided to stick with the blow through setup. I purchased the innovative wideband today and sent in my specs for the csu carb. Its six weeks out though. Im gonna finish installing the rack and pinion setup and then install this wideband and let the car sit for a bit until i get the carb done. He says that I should also do the boost retard curve 38 to 40 degrees and then slowly drop degrees of timing as boost comes in.

[whytry]

Kevin told me the same thing, Lock it out @ 40 and retard with BTM, but I am finding out the BTM is not as accurate as the dial indicates....

[WELTERRACER]

Im running a procharger prepped holley 750. 75/85 jets.. it runs very good, probobly not perfect by some of your standards but very good.. (i gave someone on the site a ride in it and i think he was impressed)

I am running 36degrees total timing and no cintrifical advance..

[Supervette]

Well Im back with an update. i had a carb worked over by Kevin at CSu and I must say im very happy with it so far. I brought it down to the dyno and it idles nice and has a wonderful wide open throttle with some minor jet changes. Now that Im out on the street. Im noticing I have a lean spot on partial throttle. When I bring the rpms up slowly get ready to crack on it at 3200 to 3500 and my wideband starts to show a lean condition. i think this attributed to my pump cam. I have the green ones in there now at position one. Im not sure which way to go from here. I had it sneeze once on me. Now I just cruise around watching the wideband so I dont make it sneeze. Anyone have any ideas on what type of pump cam to put in this. Maybe I need a bigger shooter possibly. Any ideas would be appreciated.

Almost there Mike

[Supervette]

I changed the pump cams to the brown ones from the green ones and she launched perfect. wheels and procharger spinning. A shout out to kevin and CSU for the help with the e85 conversion. Time to go racing!

[Supervette]

oh yeah and Hi tech motorsports for there dyno time and knowledge. They have some of the best facilities I've seen. great people to work with.

[NEokcTERROR]

I am glad you got this all worked out. I read this post thoroughly and kept thinking I was going to have to post. "STOP DROPPING JET SIZES that's not where the problem is." Kevin did mine and so far 3 years later so good.

I thought at one time I had a carb problem when I tried lowering the boost. I took the carb apart and stood in awe of the modifications. I have over 20 yrs experience with Holley carbs and I have to say Kevin's attention to detail and phone support are second to none. I would say the phone support alone is worth the expenditure on the carb. Got any RWHP numbers with new carb yet?