Need a plan - component selection for restoring 68 340 that runs on 91 oct

[autoxcuda]

68 style AVS.
340 and 383 have smaller primary’s than the 440 carbs. Rated 625 cfm in some places, less in others.

Here is what the 1968 and one adjustment screw look like.

The 2 lead idle screw plugs have be removed on this. Doesn’t mean they were able to turn them.... Or broke the flathead slots off trying

This is what the more common 69-71 looks like:

 

[Mattax]

Interesting, but yes the signle screw is an air bleed adjustment for fine tuning to hit that emmissions target.
Pretty sure its in the FSM but its also here: 1968 Chrysler Imperial Carburetor Service And Repair Highlights from the Master Technicians Service Conference Session 243
I think internally the passages and restrictions are the same in '69 even though the 'limiter' screws are visible on it.
The factory Holleys are similar in this respect for these early emissions years.
Here's a couple with '70 Holley list 4668s being discussed
661 Throttle blades
List-4668

 

[moper]

There are a lot of threads on the subject of camshafts and compression ratios, but I haven't quite found one that shows comprehensive approaches to this question:
From a standard bore 1968 340 block, what are the cam, piston et-cetera selections to get an engine that runs great on California's 91 octane fuel and is as close to original 1968 4-speed as possible? This is for a 68 Barracuda 340 Formula S convertible. I'm trying to keep the restoration as close to original as possible. So, I'm starting with a 68 block and X heads, standard crank and connecting rods. I need pistons and camshaft. I'm interested in what your recommendations are, so please share.

I'm sure you've already noticed by asking the world, you get a bunch of varied approaches based on individual experiences. Here's mine:
Pistons - I'd run the KB243 hypereutectic pistons. Make sure your builder understands the gapping instructions.
Heads - The X heads are pretty good aside from the exhaust side which is serviceable but a little short of "good". I'd rebuild them with unleaded seats on the exhaust side, guides or guide inserts, and a valve job all done by a shop that uses modern high end equipment to cut the seats. I'd install 2.05 intake valves to avoid new seats or sinking the 2.02s. Anything your read about "feeling soft" down low is a bunch of BS. You can mill them to reduce the chamber size but I'd only do it enough to clean up and flatten the head gasket surfaces.
Cam shaft - The exhaust side and manifolding is not the best case solution, but it is what you have and the blowdown can help those work. I would talk to Dwayne Porter, at Porter Racing Heads in VT. He does a lot of high powered stock appearing cams and I don't think as long as you're forthcoming with him he will steer you wrong. A custom cam will outpace a shelf grind, but if a shelf grind is the budget you're adhering to - the Comp XE262 is a great all around camshaft and inexpensive, in addition to being able to use a lower price point single spring.
Edit - on the block - I have all mine align honed and square decked. Most small blocks are "tall", which would only serve to help the static compression ratio by lowering slightly - so rather than blueprint I'd have them square deck it just to flatten it up. Not set to blueprint height. That should end up around 9.5:1 static with most common head gaskets.

 

[Hank’sFS]

So, right moper. I got a couple of things out of asking the world - experiences and education. The education is incredibly helpful, the experience and banter has been fun. The latest discussions on the carb are going to hit me at some point near the end of the process. I have a feeling that I will be back on with a new thread when tuning the AVS is the job in front of me.

 

[Wyrmrider]

Hi Moper excellent advice on the heads and os valves I like the higher end dura bond sintered seats for non TI valves
We looked at the Comp 256, 262 and 268 and 274HL unfortunately comp does not make a Mopar HL version of the 256, 262 or 268 and I'm not about to support a cam company that does not support me. Plenty of other good cam companies out there, as you mentioned. I won't leave torque on the table. With a HL version I can use one size shorter and still have more area under the curve- unless you are maxed out on compression- which is not the case here.
Comp also has NO Mechanical Flat tappet cams for Chrysler except some old Top Fuel grinds. Johnson makes Everybody's HR conversions
I'll pass

 

[mopowers]

Hi Moper excellent advice on the heads and os valves I like the higher end dura bond sintered seats for non TI valves
We looked at the Comp 256, 262 and 268 and 274HL unfortunately comp does not make a Mopar HL version of the 256, 262 or 268 and I'm not about to support a cam company that does not support me. Plenty of other good cam companies out there, as you mentioned. I won't leave torque on the table. With a HL version I can use one size shorter and still have more area under the curve- unless you are maxed out on compression- which is not the case here.
Comp also has NO Mechanical Flat tappet cams for Chrysler except some old Top Fuel grinds. Johnson makes Everybody's HR conversions
I'll pass

You realize Comp can grind custom cams, right? Just because it's not an off the shelf grind doesn't mean they can't provide it to you.

 

[Mattax]

Can they? Or are they limited to their lobe library, as considerable as it is? Otherwise it means considerable time developing the ramps, etc, no?

 

[Wyrmrider]

That's the problem with comp
No solid masters in their lobe catalog for Mopar/AMC/IHC at all and no MOPAR hyd shorter than the XE274HL
They do have some Jeep lobes but they are designed for a bigger base circle- no Idea how they would work on a MOPAR
in any case there is a gap between the largest Jeep and the XE274HL
When asked for a custom Comp has come up with their CHEVY Extreme lobes IDK how that works with the heavier MOPAR valves