Blow through problems

[Supervette]

This is my first blow through system. I have a procharger D1sc with a 12 rib setup running 12 lbs of boost. When your crusing around town it feels like its surging. Or like a bad miss that never goes away, but when i get on the throttle it smooths out??? I have 15 degrees initial, and about 33 total. I know the timing is right on par. My compression is about 8.25 to 1. my jets could possibly be to big 80s and 90s. It ran find on the dyno but they had an MSD digital 7 and i only have the 6 could that be another reason they could go in and program the curve and i can't. Can they also lean the system out with that digital 7. Cuz i think im running way to rich right now. Any feedback would be awesome.

[camcojb]

This is my first blow through system. I have a procharger D1sc with a 12 rib setup running 12 lbs of boost. When your crusing around town it feels like its surging. Or like a bad miss that never goes away, but when i get on the throttle it smooths out??? I have 15 degrees initial, and about 33 total. I know the timing is right on par. My compression is about 8.25 to 1. my jets could possibly be to big 80s and 90s. It ran find on the dyno but they had an MSD digital 7 and i only have the 6 could that be another reason they could go in and program the curve and i can't. Can they also lean the system out with that digital 7. Cuz i think im running way to rich right now. Any feedback would be awesome.

who did the carb prep?

Jody

[Supervette]

a buddy of mine did. I just went in and knocked the primaires down to 77s

[camcojb]

a buddy of mine did. I just went in and knocked the primaires down to 77s

any idea what mods he did? No regular (even talented) car guy that I know can do all the mods needed to get the carb to run right with that amount of boost. In addition to jetting, milling the choke housing, and solid floats you need the metering blocks completely re-worked, probable booster mods or swap, bleeds need work, etc. You really need a good shop who does the blowthrough carbs to do it.

What you're describing sounds just like what mine was like when I did the mods myself as per Procharger. I could cruise great but no wot, or great power but the cruise was all goofed up.

Jody

[Supervette]

the mods are as follows. Ported power valve restriction orifice. solid nitrophyl floats, it has epoxy in certain areas to stop boost leakage, Nothing has been done to the air bleeds though.

I just went out and gave her hell and the low end to mid range feels great but then it starts to feel like its hesitating and falling flat up top. Like it wants to go but something is stopping it

[Supervette]

choke tower was sawed off as well. But im starting to wonder if efi is really the way to go or not. ive also been hearing these holley 750 double pumpers can't handle that much boost. I wish fuel injection wasn't so expensive.

No one really knows blow through carbs around here in Mn that I know of except for the guy that put mine together. I really dont have anywhere else to go

[Supervette]

Cool website by the way!

[camcojb]

choke tower was sawed off as well. But im starting to wonder if efi is really the way to go or not. ive also been hearing these holley 750 double pumpers can't handle that much boost. I wish fuel injection wasn't so expensive.

No one really knows blow through carbs around here in Mn that I know of except for the guy that put mine together. I really dont have anywhere else to go

we had a 750 prepped by http://www.sd-concepts.com/ on my friends 406 at 14-15 psi and he made over 700 rwhp on pump gas, no intercooler. He went to EFI for mileage only, the carb ran flawless everywhere.

Jody

[69Bbird]

CSU is a good place to mod your carb. I had the same problems when I was running a carb with my procharger. I did all the mods myself and could never get it to run right. I ended up going to efi best thing I could have done. My car would lean out bad at wot with the carb. It would be wise to get a wideband afr gauge or you might pay the price.

[shmoov69]

any idea what mods he did? No regular (even talented) car guy that I know can do all the mods needed to get the carb to run right with that amount of boost. Jody

Meaning?

I do agree however, it would be best to send it off to CSU or somebody that does carb mods for blowthru.

[Turbo Hen]

You need to get yourself a wideband 02 system........that takes the GUESSwork out.

Surging while a VERY light cruise is probably you idle circuit....you'll need to play with your adjustment screws.

-Carm

[Supervette]

Let me pick your guys brain one more time. What if the carb was fine since it did run good on the dyno and did pull 700hp. Could i have blown head gaskets. Blown but not leaking coolant into the cylinder. These heads were suppose to be oringed out for 30lbs, but what if?

[camcojb]

Let me pick your guys brain one more time. What if the carb was fine since it did run good on the dyno and did pull 700hp. Could i have blown head gaskets. Blown but not leaking coolant into the cylinder. These heads were suppose to be oringed out for 30lbs, but what if?

doubtful. An engine dyno runs it at idle and then under load through the rpm range. It would not see a light cruise condition on a dyno. I'm still guessing it's lean, and highly recommend a pro doing the carb mods.

Jody

[Adam's 55 Chevy]

CSU are building a carb for me which will run up to 24lbs boost but most likely stay at around 16lbs. I would say that even dealing via email their attention to detail and customer needs is second to none. A properly built carb is cheap insurance over a home built one leaning out and damaging your engine.

[Supervette]

So I leaned it out quite a bit and it seems a lot more responsive i brought the primaires down from 80s to 77s and the secondaries from 90s to 85s. Im guessing though since i was so rich that i might of fouled out a plug. I think im going to replace them all and get a wide band and putz around a little bit before i make any decisions. While im playing around with that Im gonna get a custom hood down so the blower will clear. I found a sweet 5 inch cowl for it!


wide band http://www.fuelairspark.com/WhatsNew/

anyone have experience with one of these. Im almost wanna go with a whole fast setup next year if i cant tune the carb. I could start with this.

[Supervette]

http://www.fuelairspark.com/WhatsNew...-FuelMeter.jpg
i meant this link.

[Turbo Hen]

With a wideband, you'll be able to get the carb dialed in just like the other THOUSANDS of people out there! Dont give up, it aint that hard trust me.

The FAST system is nice....how about looking into something that will datalog....Innovative or AEM.

-Carm

[shmoov69]

PM me if you are going to go with the FAST stuff. I have a good friend there that may help you out some.

[camcojb]

With a wideband, you'll be able to get the carb dialed in just like the other THOUSANDS of people out there! Dont give up, it aint that hard trust me.



-Carm

trust me, he ain't gonna get there with just jet changes. And I know few people who can (or should) do their own metering block mods, bleed changes, and booster swaps.

Jody

[Turbo Hen]

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