Ok my car has been back up and running now for a few months but due to the body work I have not driven. The motor is fresh and I have more lift on the cab. The heads and intake were also opened up. My problem that I have now is (and didn't have before) when I open the acc. the car sounds great however when I open the throttle quickly it has a short hesitation and then comes up. When I was taking the car to get the body work done I got it in the street and opened her up. same problem hesitated then just screame. any suggestions.

Corey

WWhat kind of carb?
Hesitation if you ease down into the gas while cruising?
Hesitation if you mash it wide open fast from a dead stop?
Hesitation If you mash it wide open fast while cruising?
If you sit still in gear stall it up tight then mash it fast does it hesitate?
Does it spit back when it hesitates?
Have you touched carb or timing?

It is a Holley 750dp ms I have not touched the carb since freshening up the motor! Same jets etc. the only thing I did was set the floats. On the rebuild I opened up the heads and intake, larger cam and electric fuel pump with regulator. I haven't actually got to go out and cruise with it so I don't know if it is a cruising thing also. But it occurs when you crack the throttle wide open quickly either setting in the garage running or when I went to load it on the trailer I pulled it out in the street stopped and then just mashed the throttle it hesitated then started screamin'.

Corey

[This message has been edited by SUPERSONICBLUE70 (edited December 22, 2004).]

Opening up the cylinder heads, and using a larger camshaft will decrease the low speed air velocity. If that is all you have changed, and the weather conditions were similar to the last time you ran the car you’re accelerator circuitry is most likely too lean now. First make sure your butterflies are set in the proper position. Once you’re verified that, you’ll most likely need to go to a larger squirter nozzle.

------------------
Thank you,

Technical Support @
Barry Grant, Inc.

BG Fuel Systems, Demon Carburetors,
Nitrous Works, & Rush Performance

Tech @ BG I am kinda glad you chimed in. Instead of going through this old carb and setting it up the way I want it I was almost leaning towards a Mighty Demon 825 but am a little scared with all the talk on the boards lately what kind of garuntee do you give on the carbs and can you hook a brotha up.

Corey

ps thanks for the other info. I will check out the butterflies and increase the squirter size. Would the accelerator pumps help any if changed to a 50cc.

<font face="Arial,Verdana" size="2">Originally posted by Tech @ BG:
Opening up the cylinder heads, and using a larger camshaft will decrease the low speed air velocity. If that is all you have changed, and the weather conditions were similar to the last time you ran the car you’re accelerator circuitry is most likely too lean now. First make sure your butterflies are set in the proper position. Once you’re verified that, you’ll most likely need to go to a larger squirter nozzle.

</font>

What he said. Lower velocity requires more fuel.

Corey,

All of our carburetors come with a 90-day warranty against manufactures defects. They all come with a tuning DVD, and in depth instruction manual as well. Being a manufacture all sales go through our distributors, who do you normally purchase your performance parts from? As far as the 50cc accelerator pump goes, it’s hard to say without know more about the combination. We do not find the need for them on any of our small flange carburetors that we build. If you decide to purchase a new carburetor please contact our technical department directly at (706) 864-8544 before so we can make sure to get you into the proper carburetor.


------------------
Thank you,

Technical Support @
Barry Grant, Inc.

www.barrygrant.com
BG Fuel Systems, Demon Carburetors,
Nitrous Works, & Rush Performance

Well I would like to find a dealer local that I could go through instead of jegs or summit so if there are any dealer in the Des Moines, Iowa area-50317 I would prob go there or a buddy is starting his own buisness and may be interested in becoming a dealer. If my buddy wanted to become a dealer who would he contact.

thanks,
Corey

Corey,

Check with the guys over at JR Motorsports. Your buddy would want to go through one of the two step warehouses.

------------------
Thank you,

Technical Support @
Barry Grant, Inc.

www.barrygrant.com
BG Fuel Systems, Demon Carburetors,
Nitrous Works, & Rush Performance

<font face="Arial,Verdana" size="2">Originally posted by Tech @ BG:
Corey,

Check with the guys over at JR Motorsports. Your buddy would want to go through one of the two step warehouses.

</font>


Ok I will check with the JR guys they are only about 5min away from where I work Thanks for all the input.

Corey

Corey,

Thank you, if you've got any questions on tuning or setting the carburetor up please let us know. www.barrygrant.com (http://www.barrygrant.com) or (706) 864-8544.

------------------
Thank you,

Technical Support @
Barry Grant, Inc.

www.barrygrant.com
BG Fuel Systems, Demon Carburetors,
Nitrous Works, & Rush Performance

Just a couple of thoughts for you. I have had the same prob + fouling. First the position of the idle screws is critical. I tried to lean it as much as possible to kill the foul...can you say stuuummmble. So make sure they are out far enough. I think the increase in squirter is a good idea helped me. The accellerator pump was a waste for me. Another thing is to make sure the rod to open the back is in the position that opens the back barrels at the same time as the front. This will help getting the gas you need in opening, or at least on mine with a .555 lift and 260 duration mech cam on a high compression 355. The other thing I did to save a few $ is taking the baseplate from my 850 Holley and modifying it to fit on my 750 Speed Demon....Wow this marriage is very hot...but I still have to change plugs every 500 miles or so, but it was not built to drive in the city ..cooler plugs may be my answer. Good luck it took me 4 years to get the carb set right, but I did not know about this site then either.

z28smokin thanks for the info I am going to try the bigger squirters in fact I think I have some in the garage but I have to wait to get the car back from the body guy to do anything. Just for you all who might be interested here are the specs on the cam.

Internal Duration @.050" 258
External Duration @.050" 268
Internal Lift 560
Exhaust Lift 580
Lobe Separator 106
Advance Internal Duration 296
Advance Exhaust Duration 306


Corey

I have an 850 dp on my 350 it took a little while to get it right but its right,
my cam is almost identical to yours
255 / 266 @ 50
.555 / .572
105 LCA
my timing helped as well i think timming is critical to prevent stumble with a cam like that i set my total at 36 and my initial is at 22 with no vac advance and the total is all in by 2800
I put a power valve in that is borderline ready to open (it would if my car idled down any) i idle at 950/1000, the rear i plugged the p-valve and installed 87 jets that made a huge improvement from primary transition to secondary, and finally i put a 50 cc accel pump front, 40 squirter rear 37 front

mwilson thanks for the tips I may try that out on the carb before I do anything because I do have the squirter sizes at home in the garage. Now if my buddy could just finish the body work I would be good to go.

Corey

Hey Mwilson, It appears our motors are very similiar. Have you had any problems with fouling? My plugs last about 200-500 miles. What type of plugs are you using. Tell me about your idle screw settings please. From what it sounds I need to put in bigger squirters, kill the rear power valve bigger jets in the rear as well. Then tighten the idle screws. The car runs great other than the changing of the plugs.

I did have fouling problems then i changed front metering blocks with a carb that had the largest idle feed restictors i could find
then i even put 3 or 4 strands of speaker wire in the ristrictors (found that in a book
called "Super Tunning and Modifying Holley Carbs" Ill check later but i believe my plus are R-44T