Well kids I got up to the Esta Drag strip and was thoroughly impressed, not at the low 15 second times but the fact that it was done with the 850 Holly DP on my intake, I have a 750 single pumper being rebuilt (it's off a 71 Corvette 350) so that being said hopefully I'll drop into the low 13's high 12's once I'm not drowning my poor 358 with gas.

 

umm what type of heads do u have im pretty sure a 750 is still to big for ur motor,,,id check out a 600 dp with your setup

 

Your engine isn't drowning in gas just because you have an 850 on it.

 

Hell you might hit 10's with that full race cam..

 

I gave up on trying to get the 850 I had to run right. Was crap on the street and crap on the strip at launching. Went back to a 750 and got much better throttle response, much better drivability, ET's dropped and MPH went up. Still messing with the 750 but it's getting closer each time, can't wait till the weather cools down to maybe get into the low 11.70's on the motor.

 

I'm using some Dart 2.02's and I'm not sure the cam specs(most of the work was done when I bought it) but it's fairly large but I have the same problem as Evilcartman my launch is horrible, but once I was out of the box and hit 2nd she took right off like a rocket, now that I think about it my neck still hurts from yesterday. And Apieron the smell of raw gas commin from the pipes bad enough where your eyes burn and water is a good indicator I'm drowning it.

 

It sure is, but it's not drowning because it's an 850. It's drowning because it's not tuned.

 

It's drowning because it's too much carb, the Holly 6213 Spreadbore 800-850 CFM Carbs are big block carbs and as I stated before I have a small block

 

No it's not. Overcarbureting gives the engine too much air, not too much fuel.

If it's actually rich at WOT (burning eyes don't tell you much about what's happening off idle) you could lean it out to perform just fine. You'll have better street manners from the smaller carb, but it's not going to be a magic bullet.

 

put smaller jets in it lean it out and it will run better still throttle response will suck...its not rich cause of the cfm of air but the fact that they have large jets apeiron is right...

 

You can get the A/F perfect, but the large throttle bores of an 850 are not meant for a lower revving 350ci class motor like you have. Throw that 850 on a 600hp 406 and it would work good - obviously...

 

Thank you paul finally someone listened, apeiron, that carb is jetted down as far as it can go, 1 still burns your eyes, 2 bogs down in 1st, 3 fumigates the area with black smoke no not a puff a fog, an 850 big block carb is too much for about anything under 383 cibic inches,

 

Aperion knows that 850 cfm is too much air for your engine, he's simply trying to explain to you that your 850 could be jetted properly to work decent on that engine.. throttle responce would still suck because it move's too much air, yes.. nobody is arguing that.. but there is nothing special about the amount of air the carb can move that makes it unable to be jetted properly to the engine.. Also the term "big block carb" makes you sound a little silly.. If I have a 427 sbc should I put a "small block carb" on it?

 

Sounds more like a flooding problem then.

 

Heres a good one for reading

http://www.gofastnews.com/board/tech...big-350-a.html

Seth

 

a carb isnt going to pick up 3 seconds unless something is seriously wrong with the carb.
while an 850 is too big for your setup, it can me made to run very well with the proper tuning.
youll pick up some drivability with the 750, but its not gonna make it any faster ET wise by a large margain.

 

What I said was the carb that came with the car is a Holly 850 DP, which after some research I found it was "designed" for big block. Now the 1050 King Demon carb is a very popular carb however I've never seen a street/strip small block with one, many street/strip big blocks and bunch of very high dollar small blocks (supercharged mainly) but everyone at the track that looked at my car and played with the carb have all said it's too big, too much fuel and too much air even at full lean, and I never said I will run 12's with the 750 but I am losing 2-3 seconds when she bogs down out of the hole with it' huge black cloud behind it, hell my Banks tuned duramax doesnt even smoke that much, but anyway the Z is gonna be down for a while I sheered my clutch rod swivel off and bent the clutch rod so I am yet again awaiting more parts, once the 750 is on and I get a chance tyo run her again I'll let you guys know what improvements it makes. till then keep it under 100. Oh and by the way Bigseth that article is a pretty good one but we're comparing about 30+ years difference in technology.

 

if its bogging and making black smoke, that has nothing to do with the size of the carb.
a 390, 500,600,650,750 will do that if not tuned properly.
positively the 850 is too big for the motor to run at optimial, but it should still get down the track and drive without the mentioned affects.
you could put a 1150 on it and it will run fine when tuned.
just cause its an 850, doesnt mean its pushing 850cfm down the motor.
the motor is only going to suck in as much air as it needs.
im interested in the results...

 

What size jets are currently in it primary and secondary? What other sizes have you tried?

 

The jets I believe are 55's I think I might try dropping the power valve size in the primary from a 6.5 to a 4.5 and see where I am with that, the 750 is out of a 72 Vette with a 350 but I'm still waiting for it to be finished, my guy is switching the factory holly body to a proform without a choke as this car wont ever see 32 and below temps, there was a guy there at the track with a similar setup only using a 670 DP and he was in the low 12's with a really sucky *** reaction time 1.000 and slower so I'm pretty confident I can get her under 12 but right now it isnt going anywhere s I broke the clutch rod swivel the other day and am waiting for a new one from classic parts of america, so the car is sitting in the garage lookin all sad cuz I cant drive her and it's been gorgeous outside eh thats the name of the game I guess.

 

Changing the power valve isn't going to do anything, your vacuum is 0 at WOT.

 

i doubt ull hit 12s with just changing ur carb. and reaction time has nothing to do with e.t....but neways this carb ure gonna run is a vacum secondary carb? is it a 4160 or 4150 carb?

 

i think a holley jet starts at 64 or 65?

 

Holley jet sizes start at 20. The gasoline jet assortment kit starts at 64.

 

Igotta355z28 no neither carb is vaccum secondary, both are mechanical secondary, and apeiron I think you should read the Holley DP tuning thread on this sight, sofakingdom begs to differ, so think what ya want but the proof will be in the time slips, take care all

 

I've read it. You're not understanding how your carb works.

 

if indeed he does have 55's in it..... its way to lean.... which would explain the bog off the line.

 

and the way I'm reading it he has 55's on the secondaries too?

 

Does lack of air velocity mean anything to you?

WOT off the line ,850cfm potential flow and nowhere to go .
His is air flow is zilch , fuel is dropping out of suspension and he just dumped a **** load more in with the sec accel pump.Carb will be seeing weak vac signal due to low velocity/
Would run faster with a 450cfm due to better bottom end response more than compensating for lack of top end.

 

I think you have a jetting problem. Pull your front and back fuel bowls and check your jet sizes. Start out with a 76 in the front and the back. Check your power valve and make sure it doesn't have a block-off valve. If it has a power valve, your 76 jets become 86 jets (it jumps 10 jets sizes with a power valve). Make a hard run then shut off and check number 1 and number 8 plugs. See if they have cleaned up. You want your plug to look like a brown paper bag. You may have to jet up or down, but you want the plug to look like a brown paper bag.

 

im not sure if thats worded right or not.

if it DOES NOT have power valves, you want to square your jets.... meaning run the same size front and rear.
if it has a power valve in the front, then you want to stagger your jets.
usually a 6-8# spread. 10 is pushing it, but it all depends on what the motor likes.
76's may be a bit rich, but its a good starting point.
going by the info in his sig, id go 72/80's as a starter, or 80's all around if its got block off plates.