camaro98rs

iTrader: (2)

Hey guys i took my car to the track for the first time since switching it over to a carb set up and i picked up right where i left off with the efi except i picked up a full mph. I am running a holley 780 vacuum secondaries with a proform main body and my racing buddies are telling me i need a bigger carb cause we have it jetted 84/88 and the air fuel looks good and it picked up with this jetting but they think going to an 850 with mechanical secondaries will work better. what thoughts do you guys have on this?

here are the motor specs.
forged 346
heads are 853's with 54cc chambers and cnc ported they flow about 320 on the intake with 2.08/1.60 valves
232/238 .620/.612 112+3
victor jr with holley 780
th400 with transbrake
9 inch with 4.56

richard david

850 would work great on it. That is what i have on my 346 and it loves it.

speedtigger

iTrader: (16)

How big is your converter and what does your time slip look like?

camaro98rs

iTrader: (2)

I know for a fact that the converter is totally wrong for the car since it is built for nitrous and a 408. in my car when i take away the 2 step and hit the transbrake it goes to 3500. I will take a picture of the time slip and post it on here when i get home from work tonight.

camaro98rs

iTrader: (2)

here is what my time slip looks like

60" 1.690
330 4.878
1/8 7.486
mph 93.88
1000 9.735
1/4 11.626
mph 119.33

and the next day after a front jet change during our 1/8 points race

60 1.655
330 4.836
1/8 7.450
mph 92.76

speedtigger

iTrader: (16)

The reason I wanted to see the timeslip and know the stall RPM is the fact that you have a vacuum secondary carburetor. When you have a stall converter bigger than 2500, mechanical secondary carbs are the way to go. If you go to a 750 or 950 mechanical secondary carb, I think your 60' times will improve a lot. In fact, I bet your car will run much harder the whole pass. And you will like the way it feels on the street better too. I would not be surprised if it ran at least a full 2 tenths faster.

camaro98rs

iTrader: (2)

cool thanks for the info. i fully panned on going to a mechanical carb but this one was a free be from my dad. So your thinking i may even need a 950 vs the 850?

speedtigger

iTrader: (16)

You could use either one, but I am not a fan of the 850 on a small displacement street engine. The 850 based Holleys are different from the 750 and 950 in that the venturis are larger. For this reason they can be fussy down low. I have had both a 750 HP and a 950 HP Holley on my car and there was next to no measurable difference in the performance after extensive testing. Maybe a couple hundredths.

camaro98rs

iTrader: (2)

thanks for the info agian im learning more since this is my first carbed car. I did forget to mention that this will be a drag race only application so im not worried about the streetablity of it.