Carb recommendation - 66 SBC 283 engine

[Nick_nl]

Just a few thoughts.
Has the engine been rebuild?
283 pistons are not that plenty full and most rebuilder pistons are not the correct 1.8 inch compression height but shorter.
Also to keep the compression up the 283 used a shim head gasket.
If the engine has been rebuild using the rebuilder pistons without decking the block and with the generic thick fel pro head gasket the compression will be way down. My engine was done this way.

Does the 66 already have the aluminum distributor? The cast iron ones have a different vacuum advance that uses a screw in metal line. It might be leaking.

[bigblockmark]

Thanks for the tips on the pistons. This is a 1 family owned car from new. Original 283 never been touched other than the 4 barrel Edelbrock air gap intake manifold for the injection conversion and a HEI distributor. Engine is tired and I feel a miss. Will get it on my Snap On scope Monday and see if i can find if a cylinder is weak.

[bigblockmark]

Did some tuning on the 283 with the 670 Avenger this evening. On the scope it looks good on the idle circuit. Cylinder balance check is OK. Odd cylinders/even cylinders is OK. Carb balance side to side is even. A/F screws out 1 turn is what it likes. Highest vacuum at 800 is a steady 18" at that setting. Either way on the screws it drops RPM. Initial timing is set at 12 degrees and is 22 degrees with manifold vacuum to the distributor can. Carb seemed responsive to throttle in the shop. Took it for a test drive and it popped and cracked and would not accelerate hardly at all. Throttle linkage is not right either.

Maybe this carb is the issue. It was a "give me" along with an old Edelbrock 50 that was toast. I rebuilt it and did not see any thing wrong with it. Never had it on a known good vehicle yet. Just a test to see what carb should be on it maybe.

Owner is good with buying a new carb, but the only other one i have hear is a 1906 Edelbriock 650 and I think it may be too big. I like the looks of a 4150 dual inlet carb on a vintage muscle car.

Now what?

[GTO Geoff]

You have answered your own question: you have the 650 Edel, why not try it?

I presume being 650cfm [ & not 600 ], it is the AVS version. AFB or AVS these are EXCELLENT carbs. And not too big. The regulated secondary air flow means the carb will only deliver the flow that the engine wants. And another advantage over brand H [ & clones ]. Brand H has 1 9/16" primaries. 6XX Edel carbs have smaller 1 7/16" pri for better throttle response. If this carb is fairly new, it should have annular pri, another benefit.
750 QJs were used on the Pontiac 230 ci inline 6 engine, so I do not see a problem.

[bigblockmark]

Thanks. The reason I hesitated to try it is it's new in the box and I keep one of those in stock for people on a weekend who forgot to order from Jegs and Summit and need a carb right now. 1906 is the newer style AVS2. Retails for $389. If I try it and it does not help the issue, Which may not be the carb on it now. I is now no longer new so I can not sell it at full price. if I don't use it o this one. And i have not checked yet, but it may not have the lower hole for the transmission kick down rod. Before I do that, I am going to check with my friends and see if I can borrow a known good small carb to verify the present carb is the problem.

[gntkllr]

"670" Street Avenger, by their venturi and bore sizes, are a 600 (that should work real good on a stock 283), frequently come with a host of issues, and can be dialed in like any 1850/etc to smarten them up.
They usually have PIAB's on the big side, like ~0.080", the metering block/s might contain bleeds way-up-high-in-the-dog-legs that were originally meant to work with "emulsion" tubes (where the newer/present metering blocks haven't got tubes), and sometimes have 0.100"+ ("reverse-idle" size - standard are 0.063") idle mixture screw tip orifices and/or also short/blunt nose "reverse-idle" idle mixture screws (standard are longer, sharper tipped), and also sometimes include both "4-corner idle" secondary idle discharge orifices below the secondary throttle blades AND constant idle discharge orifices (meant for "2-corner idle") directly below the secondary transfer slots... speaking of transfer slots - check their widths and lengths...
Check for other ridicularities like passage drillings below air bleed/s that are smaller than the damn bleed/s, missing/incomplete passages, machining debris, etc...

A potential good starting point "recipe" for good 600 VS function, stock or mild combo, and if with "4-corner idle":
IFRs: P 0.026" (down low); S 0.026" (down low - or 0.031" up high)
IABs: P 0.070"; S 0.063" (0.028" if with "2-corner idle")
MABs: P 0.028"; S 0.025"
Transfer slots: P & S 0.024-0.026" width; P ~0.240" and S ~0.180" lengths - if wider/longer, install 0.081" TSR's...
Secondary constant idle feed orifices below transfer slots: Blocked
Up-high metering block dog leg bleeds: Blocked if "emulsion" tubes are not present...
"Emulsion" bleeds: Two 0.028" per barrel in "old school" Holley vertical locations
Jets: P #65; S #70
PVCRs: P 0.046"

[bigblockmark]

I changed the spark plugs and it is better, not great. At least it is derivable now at part throttle. Still a dog at rapid full throttle. Gave it back to the owner and he said it runs better than it ever has since he has owned it. it is going to get a new carb next. After looking thru several outlets I find the Holley carbs in 600 and smaller size are few and far between. Like none almost. Best option I found in stock so far is a Quick Fuel BR-67253 570 CFM. Edelbrock 500 CFM 1403 is next option.

[rgalajda]

Could this be an example of a carb being blamed for a bad engine tune.
''Original 283 never been touched"
''I changed the spark plugs and it is better, not great.
"Gave it back to the owner and he said it runs better than it ever has since he has owned it.

Personally I have not used a scope since the 80s. Apparently that didn't help either

[bigblockmark]

I rechecked the ignition system today,. It has a newish HEI distributor. Everything inside looks brand new. Ohm'ed the plug wires All about the same 1500-2000 depending on length.It has new plugs I just put in. Took a chance that the 670 Avenger Holley carb was the issue. Got a new Holley Brawler 570 CFM today. If anything it is actually worse. Back fires at idle. Give it any gas and it flames out the carb and dies. Not even driveable. It has felt like a miss at idle since it came in, but all cylinders show about the same on the scope. Almost like it has wires crossed, but they are not. Timing has been from 4* to 14* initial and another several with distributor vacuum advance hooked to manifold vacuum. Showed 18" vacuum at idle steady before I changed carbs.

Damper could be slipped?, in cap brand newish coil could be bad?? No lifter noise. They have not been adjusted recently. 150# compression. What else am
i missing?

[Right hand drive]

Time to go over some fundamentals like confirming tdc on balancer, no cam lobes are wiped out, springs are ok, HEI getting full voltage, blocked up exhaust...?

Things that fresh plugs make a difference.