OK I hate to do this but I really want to get some opinions on what I am thinking for a new carburetor. Anyways, here goes...

Background info: I have an 81 with a BluePrint 383, TKO600 five speed, 3.54 gears. Stock 255/60-15 tires, stock suspension for the most part if that matters. Motor should be putting out around 440 HP. Mild/performance cam, 10:1 compression etc. Right now I am running an Edelbrock 800 AVS2 which runs fine. I have no complaints with it really. I just want to see if I can find something better, for some nagging reason I feel like I am leaving some power on the table, so to speak. Quickest 1/4 mile run was 14.0 at 105. So no problems really and this is sort of just to change things up a bit too. The Eddy 800 is a mechanical secondaries they say. I have never had a Holley on the car and would like to try one out. So I am leaning toward a 750, 4160 adjustable sight (model 80508S >> https://www.summitracing.com/parts/hly-0-80508s). This is actually what Blueprint recommends. Right, so I should probably just go with that. But there is this little nagging thought (another) that says I should go with a double pumper - 4150 in 750 cfm. I want to limit the decision to one of these two, unless there are real good reasons to include any others. But it gets too hard to make a choice when you get too many variables also.

Here is what I want from it. First off, this is a street car which will see maybe occasional run down the strip but I want maximum performance on the street (which sometimes is a drag strip) and I don't care about gas mileage. I want it to be the fastest it can be. Does that mean the double pumper?

Fire away!

 

What distributor, timing, vacuum advance are you running? Is the carb tuned? Have you checked it with a wide band? I would even consider throwing it on a chassis dyno to make sure everything is optimal before spending money on another carb.

 

I vote vacuum secondaries if your majority of driving is on the street. You go to Thompson?

Steve O.

 

youre not getting 440hp if you are only at 105. I was over 400hp in my 327 and was getting 108hp with a about a 10:1 total rear. My best was 13 flat spinning the tires in the first 2 gears off the line. My car should have easily been in the 12 if I could get it to hook even just a little. I would see what your first gear and final gear add up to and post what your cam is. I dont think changing the carb is going to do anything if the rest of your set up isnt giving you the best torque you can use

 

Admit to liking Holly carbs just can't see any signifcate change to your power or ET by changing the carb not to mention all the cost to do it
the new 800 avs2 should
be a good street carb.

 

You might give Holley tech services a call, tell them what you are running, your style of driving and what you are looking for.
They may or may not recommend the change, or they might send you to another direction altogether.

 

The TKO has a 2.87 first gear, and with the 3.54 diff it should work out to 10.16:1 in first gear, which is pretty close to what they say is ideal.

Scotty

 

that gearing should feel really good off the line and out of corners. How does you car feel when you come out of a corner or off the lights. Do you get a gentle push or good snap? Does your rearend break free when ever you get on it out of a really slow turn like onto a street from a side street? Does it spin easily in the first 2 gears if you are really on it and are popping off the clutch?

 

Distributor is MSD 8360 (think that's the one) timing is right on, they say 32-34 at 3000 which is what it is. Light springs. I have not checked it with a wide band although there really isn't much adjustability in the Eddy 800 per the chart. Which ever way I go, I do want to have it dyno tuned sometime this summer.

 

Yep, once or twice maybe a season. It's pretty close to me.

 

That's the thing - I can't spin the tires. It is very close to 10:1 total gear with the TKO and 3.54 rear so that should be perfect.

 

Yes it should. Although I'm not worried about swapping on a new carb, need to try something!

I might do that.

More like a gentle push, and no it doesn't easily spin in first gear let alone second. That's sort of why I think I'm missing something.

 

Did you degree the cam when you installed it? Is it a compcams? Have you tried increasing your timing to 38 all in?
Is it a roller, flat tappet, solid or hydraulic? Does it run real smooth?


Im asking because the cam could be installed advanced or retarded. If its retarded you arent even in the 30's. If its at zero then maybe your motor wants 36, 38 or even 40 degrees. Maybe its just too small of a cam. I would think you would be .580 or bigger with 240 or greater duration

 

cam was installed when I bought the short block. I installed the valve train and heads. It’s a roller cam. Yes it runs smooth.

 

Look into your timing see if it's advancing in distributor like it should set the initial timing higher make the timing come in at a quick rate, check something as simple as maybe throttle cable slipping not opening the carb correctly. This just sounds more like an advance problem to me you have enough gearing and engine displacement it should easily spin the tires off the car in low gear for sure.

 

I will check those things for sure. Pretty sure I checked the throttle cable but I'll check it again to make sure it's not slipping or something. Problem is, right now it's like 0 out so I might have to wait a couple weeks for some warmer weather to open the garage. I've been working in there doing cutting for the kitchen project.

So when we say 'it should spin the tires off' how hard should I have to beat on it to do that? I suppose if I revved it up and dumped the clutch it might spin em but I am hesitant to do that with the weak Dana 44 rear end. But the drag strip times are what they are and I was on it full throttle the whole way. Maybe the tires are just real sticky haha. They are Cooper Cobras about 4 years old.

Sounds like you guys are saying it's not the carb. Hmmm

And much thanks for all your opinions, it is appreciated.

Jim

 

You know the Q-jet is such a good street/strip carb I'd try to find a 76-78 Q-jet if you want a good carb. Then let Lars rebuild it and you'll have a winner of a carb. With 440HP and a manual with 3.55 gearing you should be spinning tires without effort.

With my TH350 with 3.55 gearing a 350CI making 440 HP I can hardly not spin the tires in 1st gear. In 2nd gear if I hammer it the tires break loose also. Same setup as yours 255/60-15 tires. Your 383 should be developing more torque than my 350 as well.

 

If you can find a trusted tuner, I would engage them to set a baseline and then tune/dyno and make adjustments to reach your specified goals.

 

Just as a sanity check, I checked WallacwRacing/et-mph-hp calculator. Assuming your car weights 3,400 and you weigh 200, a trap speed of 105 mph yields 321 hp. Don't feel bad, my car only works out to 364 hp using 3,350 + 200 and 110 mph.
Remember that crate HP numbers are Gross. We usually are talking Net, so that brings you down to 400, at best. But realistically, I think you are below that. For comparison, I have a stock C5, with a manual trans, 350 net HP. Rolling in first gear and nailing the gas pedal will cause wheel spin, particularly in cold weather.
Your car might benefit from a properly set up Holley carb. Your ignition timing is critical. After that, maybe your cam is too mild. What about the heads? I assume you have headers and full duals. It never ends.

 

Car weights 3100 with a half tank of gas. Just had it weighed last summer.

This is the motor: https://www.summitracing.com/parts/m...make/chevrolet

And this is the carb: https://www.summitracing.com/parts/edl-1913 for reference.