‘68 383 Cylinder Head Advice

[71SandbugCharger]

Hey, happy Sunday! Looking for some advice for a future effort (maybe).

I’ve got a 68 383 big block.
Details:
2-22-68
2468130-12 LL

The existing cylinder heads:
Right (Starboard)
3462346 - ‘71-73 2.08/1.74 valves, 79.5 cc or .81.5 cc
3022

Left (Port)
4006452 - 76-68 2.08/1.74 valves, 83.1 cc
2126

This is going to be a nice build on a ‘71 Charger SE (727, TTI headers 8 3/4 Sure-Grip). I’d like some great performance, but it is going to be a street driven hot rod. Mild, but able to roar!

Advice needed. Change the heads, or keep them as they are and why? If change for betterment, what do you suggest?

Thanks!

 

[BSB67]

400 block/stroker crank/TF heads.

Just getting a head start.

 

[496 polara]

440 source,sidewinder,Edelbrock E street,etc. for a typical flat tappet hot rod type build.

If your heads are ready to go then use them unless you have cash to burn. If they need reworking then I would consider upgrading.

 

[Jerry Hall]

I would try to use a matched pair regardless. 68-70 engines came with 906 heads. 452's are the same as 906's, but with hardened seats. A 452 on one side and a 346 on the other just doesn't agree with my thinking. With a performance build you can increase compression by approximately 1 by going with a closed chamber head, like the 516s or 915s. Then there is the aftermarket aluminum options. Just my opinion.

 

[440 4 speed]

Entirely depends on what you want. Normal driving, not racing at the strip etc I would go with a pair 452’s. The cheapest probably.

 

[440 4 speed]

Entirely depends on what you want. Normal driving, not racing at the strip etc I would go with a pair 452’s. The cheapest probably.

 

[69 Sleeper Bee]

My experience has been unless you are looking to have original or period correct heads the $'s you spend on the machine work, hardened seats,new valves & springs etc. on those you may as well go with aftermarket heads that will flow way better than stock and be equal $ wise in the end.
I do agree I don't like mismatched factory heads but that is just me and my OCD

 

[Geoff 2]

Depends on the budget....
Biggest improvement would be a stroker kit.

 

[DanielSlocum]

2 452 heads would be a great start for a low budget driver build. In reality they are 88-90 cc,So pick your pistons and gasket thickness accordingly to achieve the desired compression ratio. Some published cc numbers are NHRA minimum specs which are less than as cast to allow for milling/chamber equalisation etc.

 

[71SandbugCharger]

Thanks all! At this point I'd rather mate another 4006452 cylinder head with the one I have, so I put a WTB post for a right-side one!

I figure if I win the lotto then I'll buy all new!

 

[moparbob500]

Hey, happy Sunday! Looking for some advice for a future effort (maybe).

I’ve got a 68 383 big block.
Details:
2-22-68
2468130-12 LL

The existing cylinder heads:
Right (Starboard)
3462346 - ‘71-73 2.08/1.74 valves, 79.5 cc or .81.5 cc
3022

Left (Port)
4006452 - 76-68 2.08/1.74 valves, 83.1 cc
2126

This is going to be a nice build on a ‘71 Charger SE (727, TTI headers 8 3/4 Sure-Grip). I’d like some great performance, but it is going to be a street driven hot rod. Mild, but able to roar!

Advice needed. Change the heads, or keep them as they are and why? If change for betterment, what do you suggest?

Thanks!

View attachment 1832948View attachment 1832949View attachment 1832950

My . 02¢ would be a pair of 452's - for the unleaded garbage' @ the pumps ~ i believe the intake port floor is also lower in the #346 head (i think, it's been a few years now...) You could also scratch up a pair of 516's -& use factory 2.08 int. & 1.74 exh. -& that will raise your 8.2:1 - 400 engines at least a 1/2 pt. (Head gasket thickness will gauge that) & you will want a shim kit for under your rocker shafts (Mancini Racing ) to get some pre-load off lifter - gain you some RPM - & better off idle throttle response ~ sorry long winded - you have endless possibilities -- loose the 346, again my preference unless any one else wants to chime in on using 346's ( there's a pair on my Dad's Duster -& i could feel a difference in the drivers seat

 

[DanielSlocum]

At the risk of being overly argumentive.........346s and 452s have the exact same ports and flow equally. 452s likely have a few ccs more chamber volume and induction hardened valve seats which is why i suggested getting another 452.
When you do the math on the 400s actual compression ratio it comes out to only 7.6 or 7.7 rather than the falsely advertised 8.2. An 80cc 516 or 915 and a .020 steel shim gasket will get you to 8.2 with no quench [stock pistons]. Heavy milling of said closed chamber heads [.060] will get you to a respectable 9:1. Just saying.

 

[71SandbugCharger]

Thank you and appreciate the help!!!! Hopefully, I will find some 516 or 915's, or one 452 from the WTB section or Spring Fling this year! I'm also looking on FB marketplace, but it's a beware market!

 

[RemCharger]

At the risk of being overly argumentive.........346s and 452s have the exact same ports and flow equally. 452s likely have a few ccs more chamber volume and induction hardened valve seats which is why i suggested getting another 452.
When you do the math on the 400s actual compression ratio it comes out to only 7.6 or 7.7 rather than the falsely advertised 8.2. An 80cc 516 or 915 and a .020 steel shim gasket will get you to 8.2 with no quench [stock pistons]. Heavy milling of said closed chamber heads [.060] will get you to a respectable 9:1. Just saying.

Well said. I actually raced a 440 with both of those heads on lol. It was a chrysler fix back in the day. And currently putting my street 383 back together with .060 milled 516s. The problem with that is you're also reducing your valve to piston. Can't get crazy on the cam.

 

[PRHeads]

Basically, all the common passenger car/light truck BB heads have the same intake ports from 71-78.(346/902/975/452).
The 452 has its own exhaust port that has a taller floor(but doesn’t really flow any different).
Running a 346 with a 452 is of no concern.

None of the other open chamber heads have intake ports like a 906……which are the same as a 915.

 

[RemCharger]

I believe there is a 250 head in 68 that was the same as a 906.

 

[PRHeads]

The 250 head is basically an open chamber head with the flat intake port of a 516(which is flatter than the 71-78 intake ports).
It also has the 4 accessory bolt holes like a 516.
I don’t recall if the exhaust ports are like a 516 or the later style.

It’s def not like a 906 head

 

[RemCharger]

The 250 head is basically an open chamber head with the flat intake port of a 516(which is flatter than the 71-78 intake ports).
It also has the 4 accessory bolt holes like a 516.
I don’t recall if the exhaust ports are like a 516 or the later style.

It’s def not like a 906 head

Thanks! No need to think about those then!

 

[PRHeads]

If I had one 452 and one 346, and I was worried about the 346 not having hardened ex seats…….I’d just have the 4 ex seats installed.