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850 hp dp question

4K views 14 replies 5 participants last post by  vinniekq2 
#1 ·
I was wanting to see if anyone had a similar set-up to see where your carb adjustments were or if anyone had some ball park ideas. The problem is when nailing the gas from a dead stop or rolling and nailing it dips off for about a second and then she's gone. Just a 1 sec of drop off hesitation. It is a 69 Chevelle 496 bbc turbo 400 with 4.10 gears. The motor was dynoed before it was put in the car at 648 hp and all adjustments were made. there was an issue with the carb after being dynoed and an 850 hp double pumper was installed although I was told from the shop all adjustments are good I went back through everything and have it pretty straight other than the carb. Timing is spot on. Only prob is the hesitation when first stabbing it also feels like the motor has a little more grunt in it, but its being held back just a little. Carb set up pink accelerator pump cams set on #2 was on #1 spot on carb. 78/78 on primary jets 86/86 on secondary jets 4.5 PV in primary and plugged PV in secondary (vac is 6") squirt nozzles are 28 primary and 29 secondary. In thinking slightly bigger nozzles? Any ideas? Really just trying to fix the 1sec hesitation, but trying to give as much info as possible. Thanks!
 
#5 ·
Once I get it worked out it should run perfect. It runs and drives great, but that slight hesitation when stomping the gas is a little aggravating. It's almost like it starved for gas for a split second which made me think the squirters might be to small.:confused:
 
#11 ·
You are running almost the exact same setup as I am. Except mine is in an 81 GMC truck, and you have a Chevelle.
I have an 850 Mighty Demon carb, and I had all kinds of trouble with it, but it's sorted out now.
I have the same vacuum as you, and I also have a 4.5 PV in it. That's exactly what you need.
My timing is 18 init and 36 max.
Our jets are the same too. I'm running same intake as you. ( awesome choice )
Your hesitation is most likely caused by a lean hit when you dump it hard.
I would just make sure you have no play in your accelerator pump linkages, and then start going bigger on your squirters.
Also make sure you have your fuel bowl levels set good.
I'm sure you got your idle screws dialed in.
Sometimes them squirters just don't get that shot in that big hole soon enough.
I never had a hesitation issue, I was always on the other side of it.
I was constantly pig-rich until I got it all dialed back.

BTW... what do you run in the 1/4 mile? I'm just curious what that setup can do, since I have not been able to get mine on the track yet.

:cool:
 
#13 ·
I don't have a 1/4 mile close by, so I drove it up to our 1/8 mile track and ran it. Fully trimmed out chevelle it ran a 7.2 which if you convert is around 11.2's in the quarter the 60ft was horrible though I really feel like I can squeeze a flat 7 or a 6.9 out of it which in a quarter should put me at high 10's. at least that's my goal I ran the 7.2 on street tires. She is really strong motor is 95% there except for that quick dip off the line then she haulin grass!! Let me know what you run when you run it! I would like to see how close they are. I'm going to get some slicks once I get the carb squared away and run it again that 7.2 was only the second run at the track after I got the motor in. I think that's pretty good! Any thoughts?
 
#12 ·
when I ran an 850 on my 67 Camaro 355,I was at S.I.R. and I had #78s in the primary side.It was horrible,,,, I had also forgot my jets at home.
The engine didnt stumble but did not make any power and would not rev out. 80s are minimum for me,I would throw a set of 81s in to start.
Thats a small carb for a 496,there should be no hesitation issues at all
 
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