Carb recommendation - 66 SBC 283 engine

[Nick_nl]

Are you really sure that the intake doesn't have any leaks? The rpm uses 1205 gaskets, this is huge for a stock 283 head.
If the leak is in the valley area you might be pulling oil into the combustion chamber. I have used the 2703 intake with smaller ports on a stock 283.

[rgalajda]

#1 Do the spark plugs have have the correct heat range? R45 ac delco would be correct. .045" max gap
#2 I no you ohm metered the wires . Try wetting the wires . Start the car in a dark shop and look for spark leakage ( try a light load on engine ) # 5 & 7 wires if not separated can crossfire easily.
#3 an HEI system will experience a dwell time of 10 to 15 degrees at idle and will increase to 30 to 35 degrees by 2,500 to 3,000 rpm.The vacuum advance connects to the pick-up coil; those leads have a tendency to break from movement. This usually causes the engine to sputter, backfire and possibly stall at light load, though it will run fine at idle or full throttle. Makes contact and then not as vacuum advance moves. If this occurs, a quick diagnostic step is to disconnect the vacuum line so the advance does not function to see how the engine runs. I used to pull on those wires to see if they break.
Those chinese HEI usually have a cheap module that will not experience proper dwell like an AC delco 990 module or the new 1906 ac delco module.
Another point of interest is the pickup coil in some of the offshore distributors. If you grab it with your fingers it will be loose and rock back and forth.

The intake manifold
large runners and no crossover to heat the carb that already has a slightly large primary for a 283 low compression engine and rich jetting 570 brawler. The heated crossover helped atomize the fuel. Smaller runners keep velocity up for that tiny engine.
570 Brawler
Its a little large for the application. Venturi ,Transfer slot, and metering fuel. I would at least jet it down .OR send it back. The AVS with annular primaries would have been better

[bigblockmark]

Another update, kinda.

Got a new HEI distributor today and installed. Took it for a test drive and it did not "sneeze" out the carb or backfire out the tail pipes once. But it never runs bad at first after I clean the plugs, so maybe too soon to tell.

If I floor it from a dead stop it will die. Will start right back up. Maybe 570 carb is too big. Adjusted the Brawler secondary vacuum adjustment screw in and out to see if it was tipping in too soon or not soon enough. No real difference. From a stand still at normal acceleration and cruising around town it is almost normal but still no ball of fire.

I am going to put it back on the scope after I look at the plugs and see if the secondary firing voltage is what I think is low at 3000 volts. I have seen 5-7000 before with stock HEI on stock engines.

Still have to deal with the "cheasy" choke mechanism. and maybe accelerator pump linkage.

[GTO Geoff]

I can buy Chinese HEIs here for $60 for a SBC, $80 for other brands. They are very well made, have used heaps of them, never had a problem. Probably made in the same Chinese factory as brand name HEIs, price tripled.....
Plus, the Chinese HEIs come with a steel dist gear for use with steel roller cams.

[rgalajda]

[rgalajda]

[GTO Geoff]

Yes, used heaps, lost count, in the double digit numbers. Fit them to engines I build & recommended them to others.

Well aware of the different composition of dist gears. Steel gears. Melonizing is a form of nitriding & can only be done to steel, not cast iron.
I have had one in my own car now for about 5 years. Has a custom ground Comp Cams steel roller cam. Driven weekly except in wet weather. I check ign timing about every 3m. If the gear[s] wears, timing will retard. Last time I checked, it had advanced a degree!!

These dists are well made, nothing wrong with them. I strip them to change the centri curve. They are lubricated in the places where they should be [ shows attention to detail ]; the weights, centre plate are either chromed or black oxide coated. Originals were uncoated & free to rust. The adj VA units are also superior; Crane & Accel VA units have a spacer inside the spring that limits travel & can actually lock the thing solid! Pathetic idea! These do not have the spacer...

As I stated above, you can be sure these are made in the same factory as brand name stuff. I have compared side by side a MSD Dyna Force starter with a Chinese starter; Chinese unit even used the MSD instruction sheet with the MSD logo blanked out! They looked identical, same red colour. What was NOT identical was the price: MSD was triple the price. I have also used a few Chinese starters, with no problems.

[bigblockmark]

Malibu came back last night. Owner is satisfied now. No backfires or sneezes. Still weak on full throttle acceleration, but said that was normal for a long time. Just going to try and improve the choke function and maybe rejet smaller if plugs are still rich.

So the injection I was task with removing when it first came here was not the problem. Both carbs I tried seem to not be the issue. And the charging system not functioning at times was also not it. Timing was not it. Compression and timing chain were not it. 6 volts to the original HEI distributor was not it My scope did not really help either this time, except maybe I should have paid attention to the low firing voltage at idle. The new looking distributor (7 year old but barely run) must be it as another new one brought it out of its funk.

Thanks for all the suggestions along the way.

[Right hand drive]

That’s great. Seems you have got to the bottom of it.

Another tale of the problem with the carby is the ignition.