Zerocyde

In a few months I'm pulling out my 305 tbi and putting in a carbbed 383. I'm all for it, and even though I love the durability of fuel injection I'm really excited to learn carbs.

The only problem is that everyone keeps telling me that I'll have issues daily driving something that I want to be able to take the track sometimes, and beat imports off the line at red lights. Something about how you 'load up the carb?'

From what I gather, you can load your carb up (load it with fuel I'm assuming) a lot so that you can launch hard, but that will make regular driving bad somehow.

So, am I right to be worried about having trouble setting my carb to launch well AND daily driving it? Thanks for any discussion!

Info in case it is neccissary:
Will be a 383 with some sort of 4bbl carb. I've yet to look into exactly which carb will fit my needs. (any tips on that VERY welcome, lol) it's a manual, T5 right now but t56 or something as soon as I can find one around my area. Rear is 3.73. NO power adders, just basic open air element and cowl hood. Exhasut-wise I'll probably just get some dino don's headers and y-pipe, run 3 inches along the stock route but maybe add an electric cutout between the headers and y-pipe.

Apeiron

Carburetors have been around since the mid-1800s, most of the driveability issues were sorted out in the first hundred years of development.

Look for a Holley-type 750 DP. Properly tune it and set your ignition curve, and you won't have any issues daily-driving it.

blue85305

Agreed, I daily a carbed car and don't have any issues.

Zerocyde

You can set an ignition curve with a carb? That sounds like something you would do with an ECM.

//<86TA>\\

iTrader: (14)

sure you can, its all done with the dizzy
i dont DD my carbed car, but could if i needed too and would have no problems. Only issue would be the lack of a choke, so starting it when its cold is a little tricky.

Zerocyde

So, by "set ignition curve" are we talking simply advancing or retarding the timing?

Also, what is "dding" your carb? All I can seem to find is that it somehow involves some device with 4 thermometer looking things.

Apeiron

Setting the curve means setting the rate of centrifugal and vacuum advance. DDing is "daily driving".

anesthes

iTrader: (12)

What 'worked' on mine was pretty lame, IMO.

1) I had to set my INITIAL advance to around 24 degrees. The car absolutely will not idle with less than 20 or so degrees of advance, regardless of the AFR.
2) I plugged the vac advance into the ported port, however I'm sure it's going to add too much advance at cruise, so I'll probably have to limit it with a stop.
3) with 24 degrees initial, I had to put a screw in the arm on the dizzy to limit the mechanical advance to around 10-12 degrees.
4) I still have to play with the spring combo, to get full advance in by 3000. It seems to come in around 2200 even with the 'heavy' springs.

So I don't know. It 'works'. I have to play with the throttle to start the car, and hold it for about 60-90 seconds until it will 'warm idle', although that might be corrected by a choke or fast idle spring or something. But in my defense, a lot of guys run holley DP's with removed chokes so.

Once 'warm' it idles steady bumpy at 11-12hg of vac, and a throttle 'snap' will bring it to 4500 without hesitation.

The mechanical dizzy is a lot of work. On previous EFI builds, I'd spend 10 minutes with the lap top dialing in the advance curve and not get my hands dirty..

-- Joe

Apeiron

Using a stock can, or aftermarket?

Which spring set are you using? Stock weights? You can take some mass off the weights if they're still coming in too soon. Are you pinging at WOT?

A choke would fix that. A lot of guys do run without chokes, but most of them have to feather the throttle to warm it up as well.

What cam do you have?

They're more tedious than setting the curve digitally, worse if you're doing it on the car and you don't have access to a distributor machine. It's not too bad with a little practice and experience, but even still I decided to use an electronic distributor the last time around.

anesthes

iTrader: (12)

Mr. Gasket can. I know I can adjust the 'rate', however there is no limit. I'm going to cut a slot put a screw/nut combo to limit it.

Have not done any WOT blasts down the road. I have the car apart right now for paint, but I'm running procomp weights right now. I'm going to compare them to some mr. gasket weights to see which is heavier. I'm running fat black springs. I tried the spring combo and weight that Mr. Gaske recommended but it still comes in a hair early.


Yeah I figure that's just how it is. I have a mechanical choke carb, but I might graft an electric choke to it.

XR288HR on 110* lsa

-- Joe

pancherj

Joe - That cam has the same duration @.050" as mine...but with a little more advertised and a lot less lift. My cam is on a 109LSA. I idle at 13" (1000RPM idle in gear), but I only have 350 cubes. What is your compression?

My timing curve right now is 22 initial, 15 mechanical (all in early...2500 RPM). With vacuum advance, I idle and cruise right around 52* (manifold vacuum source). I have 10.8:1 compression and run 92 octane gas. No sign of detonation and the car runs strong (11.89 @ 114 last time out). With that cam, don't be afraid of a lot of advance at cruise and idle.

Apeiron

Crane used to make a little cam plate you could put in to limit the amount of vacuum advance. I don't know if it's still available.

I wouldn't worry abut slowing the rate of centrifugal advance. The XR288 is a pretty big cam. It's not going to have any power that low, so you won't be spending any time down there under load anyway.

In my 84, I have an XR282 with a 3000 RPM stall. The engine is never below 3000 RPM under load, so I don't care much about centrifugal advance. The timing is locked at 34 degrees, with IIRC 12 degrees of vacuum advance added on top.

anesthes

iTrader: (12)

10.8:1 on 412 inches. 900rpm idle. Manual trans. Sounds like your cam has a little faster ramps.

Have not had any cruises. Just a bit concerned with pinging under cruise/light load. Though, it's a 4spd 3.73 car (no overdrive) so it will probably always be tached up a bit..

-- Joe