What piston for my 383 build?

[__Larsson____]

The easy button for a warmed up 383 is 2315’s and either Stealth heads(80-81cc)or the 75cc E Streets.

That’s for combos that aren’t going to be using a cam that needs valve pockets.

Would the XE268H need pistons with valve pockets?

 

[PRHeads]

It should be fine........ if you don’t do a bunch of milling.

 

[__Larsson____]

It should be fine........ if you don’t do a bunch of milling.

Wont do any milling, just want i to run, be a dailydriver and do some brunouts from time to time =P

 

[BSB67]

My stock uncut 906 heads both CC’d at 91CC’s

Of course, because they are not new

 

[Kern Dog]

The easy button for a warmed up 383 is 2315’s and either Stealth heads(80-81cc)or the 75cc E Streets.

That’s for combos that aren’t going to be using a cam that needs valve pockets.

For a 3800 lb car with a 727 and 3.23 gears, what cam would be a good choice if a man wanted to make a high 13 second 1/4 mile time?

 

[Kern Dog]

Of course, because they are not new

Man, your posts have really been confusing me lately. How could a "not new" head actually measure a larger volume ?

 

[1 Wild R/T]

Man, your posts have really been confusing me lately. How could a "not new" head actually measure a larger volume ?

Because the valves are sinking....

 

[451Mopar]

This thread is busy, and most of the compression ratio numbers thrown around are based on "spec" or average dimensions.
One thing not mentioned is offset grinding the crank, different rod lengths, and custom pistons. Milling was mentioned a bit, but all that costs extra $$$ and may not make that much of a difference for a daily driver, but might be worth it if trying to make the most power for a specific combination.
Just trying to say that there are many different ways to change compression ratio.

Generally speaking, when planning an engine build everything is a compromise.

Kern Dog posted:
"For a 3800 lb car with a 727 and 3.23 gears, what cam would be a good choice if a man wanted to make a high 13 second 1/4 mile time?"

That sounds like you need about 300+ HP at the tires, and about 360 crank HP at sea-level standard pressure and temperature.
Next, what track / City / Altitude / air pressure and temperatures are realistic when running 13 second ET's?
For example a 13 second car at sea-level is more like a 15-second car at Bandimere here in Denver?
Or, in other words if you want to run 13's at a mile high + altitude, the engine would need to be built more like a 12-second at sea-level engine, maybe 100 HP more than what is required at sea-level.

Next, need to check if the heads can flow the cfm of air required to make the power, and it looks like 200+ cfm of head low will work, so the stock heads would be OK, but improvements in the head flow may mean a milider cam would get the job done, where a larger cam may be required with lower flowing heads.

Camshaft, determine where you want to make power in the RPM range, and what should the torque / power band look like?
Then cam lobe profile for valve train stability and durability.

Along with the cam selection, the compression ratio is considered along with the fuel octane being used.

 

[Kern Dog]

My understanding is that with the flow rates of stock iron heads or in my case, amateur ported heads, the BB Mopars often peak in the 5200-5500 rpm range. This would lead me to pick a cam that peaks a little higher, maybe 5800. I'm not interested in a cam that peaks at 4500 or at 6500. Trouble is, what works for a 440 may not be as good of a match for a 440. Yeah, the heads may be the same but the bore and especially the stroke is different. Looking at online lists, I recall that cams for Big Block Mopars are grouped together like 383-440.
This seems like they paint these engines with a broad brush.
I have heard that it is best to err on the small side with unknown combinations. I've ran four of the Mopar Performance cams...The 280/474 in a stock piston 440, the 284/484 in a .030 over 440, the 292/509 and the 528 solid in my 493. I've also ran 2 Comp Cams XE285HLs, both went flat!
The most power that I have made was with a Lunati solid....316/326...261-271 @ .050. A bit soft off idle in my 493 but it really scrammed from 2800 and up. It would be a poor choice for a 9-1 383 with stock heads though.
I may choose a cam milder than I've used before but still bigger than any stock cam. That is fine.... Plus, this engine probably won't be the only one I'll have in this car. I may switch to a 440 or maybe even a 3G Hemi someday!

 

[Bee1971]

Okey, new question!

What type of pistons should i use for my -68 383 with 906 heads, XE268H compcam, will the
Speed-Pro Forged Pistons L-2315NF 30 work? Or the KB Pistons?

This should not be a crazy HP motor, just enough to work good.

I ran the Speed Pro 2315 pistons in my 1971 383 for twenty years with 906 Heads and the Mopar 284/484 Camshaft , zero issues

Right up until I decided to install the E Street 75cc Heads with no other changes a few years back

Three intake valves kissed the pistons within the first week

My lesson learned with larger valves

 

[BSB67]

The easy button for a warmed up 383 is 2315’s and either Stealth heads(80-81cc)or the 75cc E Streets.

That’s for combos that aren’t going to be using a cam that needs valve pockets.

That's a match made in heaven. Zero deck, Quench, all the head a 383 would need, perfect compression ratio, and weight reduction. In the right B body you could get this combo on the edge of 12 second ets in full street trim

 

[BSB67]

I ran the Speed Pro 2315 pistons in my 1971 383 for twenty years with 906 Heads and the Mopar 284/484 Camshaft , zero issues

Right up until I decided to install the E Street 75cc Heads with no other changes a few years back

Three intake valves kissed the pistons within the first week

My lesson learned with larger valves

You've post this before and remember it well. This is one of those posts that has very useful info. Did you do any measuring with this or another cam?

Before you posted, I was sitting here wondering if a cam like the MP 280 cam would clear. Valve springs matter too. The 383 can rpm pretty good.

 

[BSB67]

My understanding is that with the flow rates of stock iron heads or in my case, amateur ported heads, the BB Mopars often peak in the 5200-5500 rpm range. This would lead me to pick a cam that peaks a little higher, maybe 5800. I'm not interested in a cam that peaks at 4500 or at 6500. Trouble is, what works for a 440 may not be as good of a match for a 440. Yeah, the heads may be the same but the bore and especially the stroke is different. Looking at online lists, I recall that cams for Big Block Mopars are grouped together like 383-440.
This seems like they paint these engines with a broad brush.
I have heard that it is best to err on the small side with unknown combinations. I've ran four of the Mopar Performance cams...The 280/474 in a stock piston 440, the 284/484 in a .030 over 440, the 292/509 and the 528 solid in my 493. I've also ran 2 Comp Cams XE285HLs, both went flat!
The most power that I have made was with a Lunati solid....316/326...261-271 @ .050. A bit soft off idle in my 493 but it really scrammed from 2800 and up. It would be a poor choice for a 9-1 383 with stock heads though.
I may choose a cam milder than I've used before but still bigger than any stock cam. That is fine.... Plus, this engine probably won't be the only one I'll have in this car. I may switch to a 440 or maybe even a 3G Hemi someday!

Your observations are correct. A simple, generally correct relationship regarding cams, heads, carbs, and RPM between a 383 and 440 is to simply multiply by the ratios of their displacements. If a combination of parts makes peak power at 5500 rpm in a 440, that would be 6300 rpm in a 383. Obviously there are other factors, but this is not a bad rule of thumb.

My 383 has home ported 906 heads, MP 280 cam, and 1 5/8" headers and can run in the 12s.

 

[Bee1971]

You've post this before and remember it well. This is one of those posts that has very useful info. Did you do any measuring with this or another cam?

Before you posted, I was sitting here wondering if a cam like the MP 280 cam would clear. Valve springs matter too. The 383 can rpm pretty good.

That’s exactly what happened when I installed those E Street Heads

It RPM ed very very well with that combo

 

[PRHeads]

For a 3800 lb car with a 727 and 3.23 gears, what cam would be a good choice if a man wanted to make a high 13 second 1/4 mile time?

If I wanted to increase my possibilities of meeting that goal, I’d run a small solid cam.
The modern faster rate hyd cams seem to create too many problems for what’s available nowadays for hyd lifters.
So, to just sidestep that whole situation...... I’d make it where I didn’t have to rely on them functioning as well as they’d need to for me to be happy with the upper rpm capabilities of the motor........ by not using them.

Most of the faster rate lobes make pretty good power(even when the lifters are annoyingly loud)....... up to the rpm limit of the lifters......and then it’s game over.

The best article I’ve seen about this situation, where they didn’t gloss over it or sugar coat it, was the old MM article Dulcich did on the “mild mannered mauler”...... around 2005 iirc.

 

[BSB67]

If I wanted to increase my possibilities of meeting that goal, I’d run a small solid cam.
The modern faster rate hyd cams seem to create too many problems for what’s available nowadays for hyd lifters.
So, to just sidestep that whole situation...... I’d make it where I didn’t have to rely on them functioning as well as they’d need to for me to be happy with the upper rpm capabilities of the motor........ by not using them.

Most of the faster rate lobes make pretty good power(even when the lifters are annoyingly loud)....... up to the rpm limit of the lifters......and then it’s game over.
.

Especially with a 383. Having a fast rate hydraulic give it up at 5500 in a 383 is a terrible thing. Its simply cutting that motor off at the knees. Put a mid rate solid cam in it and let it eat.

 

[PRHeads]

I did a cam swap in a 383 a few years back.
The motor had been recently built..... a pretty nice build with ported big valve heads, custom quench dome pistons, 1.6 rockers....... and a fast rate hyd cam.
The owner was happy with the power, but not at all happy that the party was absolutely over at 5500.
I put in a solid cam and was making dyno pulls to 7k, with peak power happening at 6600.

Most any kind of hot rodded 383 will easily make power to past 6k if the valvetrain is up to the job.
That’s a very very rare occurrence if you’re running a faster rate hyd cam.

 

[PRHeads]

That's a match made in heaven. Zero deck, Quench, all the head a 383 would need, perfect compression ratio, and weight reduction. In the right B body you could get this combo on the edge of 12 second ets in full street trim

Add in a nice little SFT cam, nice intake & carb, headers ........and it’s an easy 425+ hp.

 

[wyrmrider]

anybody else use an "isky tool" on those ft pistons
XE268 is for a chevy, right?

 

[BSB67]

anybody else use an "isky tool" on those ft pistons

That is exactly what I'd do too if I'd want to run a bit more cam. Put as little relief as needed. I'd bet a 0.090" would clear just about anything a street guy would use. The kb400 has a huge 0.265 x 2.360 relief. . That's why they need 0.200 dome to get back to net zero volume.