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What is a good street carb?

36K views 174 replies 17 participants last post by  Dajerseyrat 
#1 ·
What street carb would you recommend for a fairly angry 383 Stroker with a 600 lift cam and about 11:1 compression? Currently it has a racing carb on it that is about 850cfm with mechanical secondaries. In this set up it like to load up and foul out plugs at idle or part cruising. Im looking to tame the car down a bit for the street, not a daily driver but a weekend warrior. Im looking for something I can install and drive out of the box with the minor adjustments..

Recommendations and why?
 
#130 ·
So I finally worked out a boatload of other issues on the car and got it running and on the street. There was an issue with the fuel cell deteriorating and sending crap into the entire carb so I cleaned and rebuilt the entire fuel system.

The car starts right up and idles nice at around 850-950, timing set to 32-34 degrees fixed. However after driving for a while i noticed the idle was hanging up at 1300-1500 and the car would break up if I tired to lug the engine at low speeds coming off a stop. I was also starting to get lots of eye burning smoke from the exhaust and in the cabin. Not clouds of it but a nice haze, that smelled like fuel.

Also one other thing I noticed is that on occasion the float bowls, despite being set properly will overflow. Fuel seems to blow by the bowl after sitting overnight and dribble out. The needles and seats are brand new as well as all the accelerator pump stuff.

It seems like the fuel delivery is not consistent with this carb.

Please help me and talk me out of fuel injection at this point..
 
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#134 ·
Carb is idling like crap after driving for a few minutes, running pig rich,burns my eyes cruising in it. But when I go WOT GOO LAWDY LAWDY this car is FAST!!! I pooped my pants from 3500-6000 rpms...

But the RPS are hanging up down low cruising so something is up with the carb..Help...
 
#135 ·
So can anyone assist me in my dilemma at this point? I have done as most suggested.

1) Set timing- 34 degrees with no advance (its locked out)
2) fresh plugs
3)cleaned out carb very well
4) took for a highway cruise it loves 3300+ RPMS

The issue is when I come to a light the car seems to load up a little, and burn my eyes with rich raw fuel. Something is dumping a little too much fuel at idle and just off idle.

If I lower the Idle screw anywhere below 1000 rpms it runs like **** off idle and burns my eyes and the transition between idle and throttle is a nice dead spot where it wants to die completely.

when Raise the screw to 1000 rpms it runs fairly well, but the idle adjustment screws do nothing, I can completely close them and the idle picks up...

I have 7 psi if fuel pressure and a 3.5 powervalve
I was thinking of lowering the fuel pressure to 5.5 psi but then dont know if it will starve up top..

Or I was thinking of lowering the powervalve to 2.5
 
#136 ·
To much fuel pressure is pushing the gas past the floats.
You will never be able to adjust the idle until it's fixed.
Get the higher pressure float needles, stock are good for only 5 psi max or get a fuel regulator.

No need to change the power valve unless it's ripped and causing the flooding problem.
It will not starve at higher rpm's either with less pressure. I'm running quad's with only 5 psi, it's the Flow that really count's

I like setting the float to where the gas just trickles out when I bounce the front end a little.
Make sure you have around .015 gap on the accelerator pump arm when fully open ( check when shut off)

Change your oil once you get this fixed.
I recommend fixing the advance unit since this is not a race only car
set the timing to 12* initial and 36* total
 
#137 ·
I recommend fixing the advance unit since this is not a race only car
set the timing to 12* initial and 36* total

Actually, it kinda is a race car that I drive on the street. The cam is a .600 lift. Look at the first 2 pages for the engine specs. The distributor is fixed at 36*. As for the Needle and seats , I am running the 110's and believe that my float level is fine just under the sight glass. (unless it is changing when I drive.)


Another culprit I suspect due to the idle adjustment screws not really doing much, is the Idle Air Bleeds. Im thinking of installing larger ones to lean out the idle circuit this way I can lower the Idle adjustment screw. As of right now I believe I am ideling off of the primary metering block and too much of the idle transfer slot is exposed. The issue is when I try and close the primary throttle blades to get it to idle off the idle circuit, the car will not stay running, it gets too rich. Then I wind up almost fully closing the idle adjustment screws, and the car idle picks up, but then starves and dies out. I cant seem to find a happy mid way point between the idle adjustment screw and the idle mixture screws..Leading me to believe I need larger Idle air bleeds..
 
#138 ·
You are trying to have the best of two worlds so you need to tune in the whole combination for both.
The 850 is a big carb for that motor and just changing the bleed screws/seats won't help it either.
No reason that can't idle at 650 rpm when tuned in.

quote: idles good at around 850-950, timing set to 32-34 degrees fixed worse when it gets some heat, because when cold it needs to be rich.

Borrow a smaller carb like a 750 and you will notice a difference.

You can always change the carb & distributor when you go racing but then again why.
It's combination, combination, combination and tuned in combination .

Like I said before along with the other's in this posting fix the timing, locking the advance out don't help on the street.

F-BIRD'88-ap62-Techinspector gave some very good info and are some of the best on this site, along with many others I did not name.
 
#139 ·
You are trying to have the best of two worlds so you need to tune in the whole combination for both.
This is exactly what I am trying to do...But i cant seem to get the specific answers for my specific combination.
I took the previous advise:
-Timing
-New plugs
-Float level
-Needle and seats
-powervalve replaced (3.5)
-Jets down 2 sizes
-Idle transfer slot Not over exposed ( car wont idle unless I expose it more)
-idle mixture screws- not responsive
-fuel pressure 6 psi

It seems as if I am ideling off the main circut and dumping fuel as I drive, the RPMS's occasionally hang up, and when I come to a light sometimes it idles fair, some times it dies from being too rich.

The carb is running overly rich and I want to know how to fix it, I cant get a straight answer..I covered the basics as advised, but something is just off in the carb itself. I feel that because sometimes it runs ok and sometimes it runs like crap.

The 850 is a big carb for that motor and just changing the bleed screws/seats won't help it either.
Every calculator I do for my motor tells me 850 or a 950, even on Holleys website with the interactive carb selector. 383 stroker motor+ 7500 rpms.If I go any smaller will i hurt the motor running lean?


No reason that can't idle at 650 rpm when tuned in.
So how exactly do I tune it in at this point? What is dumping fuel into my engine on the carb? What do I check and how? What if the float level is inconsistent and rising as Im driving?
 
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#145 ·
I was toying with the idea of a cam swap but someone on the thread said it would screw up my compression ratio and cause detonation:confused: Is that true?

I want to change the cam, and intake manifold for sure, the way this car is now id WAAAAAAAY to aggressive for me. I also might swap out the Jerico, the darn thing sounds like a dump truck shifting anything less than WOT..

I do have a nice little 355 10.3:1 with a lunatti Cam .517/543 lift 239*/240* sitting in my garage. It was the last engine my dad ever built before he died of cancer, and I have been toying with the idea of throwing it in. I will have to lower the steering rack about an inch to fit a conventional Oil pan, or if it is not too much work I can convert my dads engine to a dry sump. That motor should make the car go decent. drop a nice 750 cfm on that too... Would that be all round better street motor?


But I am with you on this whole "modified race carb" that seems to be tinkered with beyond belief..

On a side note, I did lower the fuel pressure to about 5.5, and change the power valve to a 2.5, and it seems a little bit better but not much...I still leave the car smelling like raw fuel...LOL..My wife wont come near me..(perhaps thats not a bad thing..)
 
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#146 · (Edited)
Did you get that Racemaster full race (on/off) clutch sorted out?
Yup, I wound up with nice Centerforce single disc sprung hub with a standard 33lb flywheel, no lightweight crap.. Very easy to drive.

Which cam do you have in mind? and what should I check with my Valve train to see what needs to go with it? Also, what about a better matched intake?

This is the cam in there now.

The push rods say 7.800 and a part number of 0408 on them
The rocker arms are Crower and say 1.50/.150 RH on them
 

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#150 ·
When you say measure the venturi, do you have an illustration of exactly what points to measure from? Do you also need the baseplate openings? I removed some of the smaller jets from the blocks but they were not stamped. Also this carb appears to not have removable idle air bleeds like a Holley would..:confused:
 
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#149 ·
Not sure..If I wind up selling the engine and trans combo, I may go with a fuel injected LSX engine and 6 speed. But who knows..For now the set up is staying the way it is. I may swap a cam or the engine to my 355 over the winter, but that will require some fabrication and altering the position of the steering rack.
 
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