Carb tuning questions??

[Gus68]

I will deffinetly (sp?) let you guys know. BIR is a little far for me, we usually go to Thunder Valley in Marion SD. Anyone else ever heard of it?

[Speedster]

So have you put the new carb on? if yes did it fix the problem or is it still there?

[grandville455]

I will deffinetly (sp?) let you guys know. BIR is a little far for me, we usually go to Thunder Valley in Marion SD. Anyone else ever heard of it?

Cool I Have a friend that races there.. Has A big 71 4 door grandville, and a blue 70 GTO Or lemans too?

[Gus68]

Well..... Didn't go too well. Last year with my old 830, my car ran alot of 11.95s and one 11.93. On saturday it started out with a 12.57, I thought, it's hot and that was my first pass. After that it ran pretty consistant 12.47s. I guess I was ok with it being cansistant, but what happened to my 11.90s??? I talked to a few guys that said that the air was crappy and that everyone was a little slower. But HALF A SECOND???? I could see running 12.20s or 30s. I should also say that early on that day in the staging lanes, I couldn't get it started, acted like it was flooded, I finnaly did get it started and made a pass. When I came back I checked the float levals, the front was ok but the rear was WAY high so I lowered it and it never happend again that day. The next day was a mess, I was in the staging lanes and it died, had a hell of a time getting it started (seemed flooded) I got it going and made my pass, 13.37!!! It launched ok (not the best) and acted like I was pulling an anchor!!!! checked the floats again, they were fine, made another pass, 12.74. Came back and put on my old reliable, (my edelbrock 750 I ran years ago and never had any problems). I figured it might not run no 11 b ut atleast it will START! Made a pass and it was WORSE, 14.32!!!! just about died when I launched and felt like the E brake was on!!!! SOOOOOO....... Here's our thought. I have a holley mechanical fuel pump, that I think is going bad and putting out too much pressure, or it is getting hot and putting out too much pressure. I should also say that after I made my pass with my edelbrock and shut it off, I could not get it started again, smelled like fuel BAD. So now Im REALY scratching my head. God I love cars!!!!!

[Speedster]

sounds like it is dumping fuel in while your shut off? I have a couple things i do if i think it's flooded.
1. floor the pedal and dont let up while cranking and that works pretty good
2. spin the motor over a couple seconds and then hit the ignition switch.
being slow you might might be really fat(rich) if the air is really bad?

[grandville455]

Well I went to dragtimes.com and yes weather was over 3000 ft DA... I inputed your time and guessed at your mph of 108 and at sea level the car would have ran 11.87. Now thing is when did u run the 90's last year? Dates, etc, then go to that website and click on tools and then DA and u will see what the weather was from then also. Where was your 830 carb? didn't bring it along? How did the car run on the street with the new carb?.. I run my holley both in the middle of the sight glass i know holley says at the bottom ,but it is what works very well for me and my car. Where was the jetting on the 750? On the fuel thing sounds like it was vapor locking in the heat!.. I would get a electric and be done with the mech! Is your tank sumped?

[Speedster]

grandville455 thanks for that website. i went there and plugged in my new best run from this weekend and now i know why we ran that fast. my density altitude was -62 feet below sea level. my relative density 100.18 percent.

[grandville455]

grandville455 thanks for that website. i went there and plugged in my new best run from this weekend and now i know why we ran that fast. my density altitude was -62 feet below sea level. my relative density 100.18 percent.

yw! that site is pretty accurate also! yea -62 is damn good air!

[Speedster]

the next day we raced and i fiqured it must have been pretty bad cause we were a tenth off? 675 above sea level about 730 ft swing.

[Gus68]

I don't remember what the air was like when I ran the 11.90s, but I remember that my buddy who has a weather station saying that it was pretty good. I did'nt bring my 830 cause I broke an ear off the base plate earlier that week, but I did bring my old edelbrock AFB and I had simmilar, almost worse problem with that carb. That's why im thinking its a fuel pump issue. I bought a fuel press regulator and a press. gauge. I'm gonna mess with that this weekend. I remember when I put my pump on that it put out 9 psi, which at the time was ok for my AFB carb. I guess that that is too much for a holley? What should the press be? About 4.5 to 6? I am thinking that 9 is alittle much but when it got hotter that the press went up and made it worse. When I put my new carb on last week, I messed with the idle alittle and it ran great, I went out of town and ran it through the gears and it ran good. Of course you never have problems at home, only when you get to track!!! And no my tank isn't sumped, I still have the stock pickup in the tank with the sock removed. I'm not a big fan of electric pumps, I've always thought they wern't too reliable on the street. What do you guys run???

[Speedster]

9 psi is too much. holley says max 7 1/2 psi min 6psi. i think too much pressure blows right thru the needle and seat?
mine is set at 7+ and will drop to around 6 when you first hit the gas but im using a holley blue electric fuel pump and it is loud.

[grandville455]

My car runs around all the time at 9 psi and I don't have any problems , But I would try and get it closer to 7-8. U can get away with more pressure if u run the bigger seats, but then u need the volume to match it!... The carter electric pumps are great and use the fuel to cool them just like the intank ones in our cars now. I run twin electrics(4594 and a 4600) y blocked in back feeding a modified carter mech with a 14 psi diaphram!.. Over kill I know, but it works and pumps 2 gallons in 30 sec with the electrics alone! I still think u were vapor locking

[Gus68]

So do you think I was vapor locking in the tank or the carb? How do I prevent it? I have a wooden spacer and a heat sheild under my carb. I am guessing the mechanical pump is getting hot from the motor, but how can I prevent that?
I just like the simplicity of the mechanical pump and I have seen lots of other guys running them, so what gives? If I do run an electric pump, what is a good reliable one for decent money?

[grandville455]

Well did it ever do this before with the other carb? have u ran it when it was hot before?..I would try the other carb again if the answers are no above. RobbMc Makes a very good Mechanical pump if u want to stay that way! Look them up.. Tell Him Darby Sent ya. How are your lines ran etc? pics?

[wikd69]

Dunno if it's an issue for you, but I'm always having to tweak the throttle cable and bell cranks to get full butterfly opening in my carbs. that might be something to check...