Think I found why my car's a gutless turd.

[RemCharger]

You don't see that I'm using an endoscope to see how far in the hole my pistons are, and using a .060" wire to estimate the measurement? I thought I explained that. Using 2.5D is .150". Do you think 88CC is a poor estimate for a 906 combustion chamber? This is what that comes out to.

View attachment 1873885

My mistake. I was thinking 440.

 

[68-500]

Regardless of the actual deck clearance you obviously have to much for a performance camshaft. I don’t know your bank account or power goals but if you can swing some pistons with CH that puts you near zero deck and a hone job you would have a much better foundation to build on.

 

[68-500]

My mistake. I was thinking 440.

I thought the same at first.

 

[V_TastyTacos_V]

That’s got to be the lowest CH 383 piston ever made.

A Silvolite 1271 replacement piston has a CH of 1.848, which would theoretically put them at .0865” down the hole……..which works out to 7.8-7.9cr with a .020” gasket and 88cc heads.
And those aren’t any type of performance parts.

Pistons .150” down the hole on a 383 is not a foundation I’d be building upon.

For reference, the Silvolite replacement 400 piston would be .122” down the hole.

Any idea if the shortblock is supposed to still have the factory pistons in it?

The guy I got the car from was a Chevy guy and knew nothing other than Chargers are cool. It was sitting for 18 years before that, and it's a '70 motor in a '69 Charger. Have no idea other than what I can see. That is a .060" wire. Looks easily more than twice it's thickness from piston to head gasket, doesn't it?

 

[PRHeads]

It certainly looks like it’s significantly more than .086” based on that wire being .060”.

Maybe there were pistons made for super low CR for use in industrial applications(no idea if they exist or not, just throwing that out there).

 

[V_TastyTacos_V]

My mistake. I was thinking 440.

Even low compression 440s have some balls to them. I've had several 440 cars, but this is my first 383, so I have no idea what they are supposed to do. I would think the bore stroke ratio would make it a high RPM HP machine having a shorter stroke than a 350 Chevy.

 

[V_TastyTacos_V]

It certainly looks like it’s significantly more than .086” based on that wire being .060”.

Maybe there were pistons made for super low CR for use in industrial applications(no idea if they exist or not, just throwing that out there).

Here's what the piston top looks like. Matches NOS pistons I've seen. Would have thought they'd have valve notches.

 

[33 IMP]

Search IQ52's build of a low compression 400 for ideas. I don't remember if it's here, or on A-bodies.
And I do believe in your borescope photos..... but I'd probably pull a head anyway, just to make sure of the deck height. (If the piston is not at exact top dead center, it'll look way down the hole)
Actual measurements are MUCH more valuable than guesswork.

(And if I was to replace a 7 1/2 to 1 piston in a 383, I'd sure consider a stroker kit)

 

[PRHeads]

Would have thought they'd have valve notches.

I’m not sure about some of the early stuff, but from 65-78 the only BB engines to have valve pockets would be 70-up 6-bbls.

If the pistons are down as far as they appear to be, there isn’t really a cheap & easy solution for that.
Other than perhaps finding a used shortblock for a reasonable price that’s not whipped or seized to the point where it would be okay with a quick re-ring job

 

[RemCharger]

That’s got to be the lowest CH 383 piston ever made.

A Silvolite 1271 replacement piston has a CH of 1.848, which would theoretically put them at .0865” down the hole……..which works out to 7.8-7.9cr with a .020” gasket and 88cc heads.
And those aren’t any type of performance parts.

Pistons .150” down the hole in a 383 is not a foundation I’d be building upon.

For reference, the Silvolite replacement 400 piston would be .122” down the hole.

Any idea if the shortblock is supposed to still have the factory pistons in it?

Pretty sure those are the pistons I have in my street 383 from back in 93. I ended up getting some 516s worked on and milled .060. With an xe284 , in a 4000lb w/ driver charger ran a best of 13.1 at 105. That engine in the polara would pull a 12.50 for sure. Definitely not turd material. It showed 325 rwhp way back in the day. The valves were getting quite close with the milled heads

 

[RemCharger]

I'd probably pull a head anyway, just to make sure of the deck height. (If the piston is not at exact top dead center, it'll look way down the hole)
Actual measurements are MUCH more valuable than guesswork.

Good advice

 

[PRHeads]

A compression test would probably shed a little light on just how low the cr is.
7:1 and any cam that had any kind of lump to it would likely pump under 125psi.

I remember trying to “tune up” a rebuilt 360(that as it turned out had about 7.5cr) with an Ede Torker plus cam in it.
All holes real close to 110psi.
Yes, it was a dud.

 

[V_TastyTacos_V]

A compression test would probably shed a little light on just how low the cr is.
7:1 and any cam that had any kind of lump to it would likely pump under 125psi.

I remember trying to “tune up” a rebuilt 360(that as it turned out had about 7.5cr) with an Ede Torker plus cam in it.
All holes real close to 110psi.
Yes, it was a dud.

125-130psi

 

[polyjohn]

Very impressive times for smog motor compressions indeed!
Yep my mates car ran 12.50 with a crane 480 cam and 8.5 to 1 smog pistons.

But it hit a wall after that, it wouldn't get better, I guess that the lack of comp?
Fitted the old sixpack pistons now with the four cut-outs and a 509 purple.

Everything old is new again...
More comp around 10 to 1 ish...

 

[AR67GTX]

Even low compression 440s have some balls to them. I've had several 440 cars, but this is my first 383, so I have no idea what they are supposed to do. I would think the bore stroke ratio would make it a high RPM HP machine having a shorter stroke than a 350 Chevy.

I have always thought the same about the short stroke 383. But in reality it just doesn’t seem to be the case. It’s a good engine, but no Mopar answer to the high winding 327 or 350 Chevy. I’m not enough of an engine guy to fully understand why - I guess the heads and valves are too limiting. But my 64 383 Sport Fury still managed to embarrass a number of so-called Musclecars on the street back in the 60s - at least up to 85/90 or so.

 

[33 IMP]

I have always thought the same about the short stroke 383. But in reality it just doesn’t seem to be the case. It’s a good engine, but no Mopar answer to the high winding 327 or 350 Chevy. I’m not enough of an engine guy to fully understand why - I guess the heads and valves are too limiting. But my 64 383 Sport Fury still managed to embarrass a number of so-called Musclecars on the street back in the 60s - at least up to 85/90 or so.

That's my impression too. At least the head part. (Valves should be okay, bigger than stock 327/350 valves)
906s are even more limiting on a 440.
I've got a set of 25 year old oob small block Chevy heads(or is it 30?) that well out-flow any non-maxwedge stock iron Mopar wedge head. Even with a 440-length crank, it will out-rpm the great majority of 383 mopars.
(Engine Masters did a test of a 383 Mopar vs a 383 Chevy. Mopar won, by virtue of the low-end torque it made. Peak numbers, and rpm, were virtually identical.)

 

[V_TastyTacos_V]

That's my impression too. At least the head part. (Valves should be okay, bigger than stock 327/350 valves)
906s are even more limiting on a 440.
I've got a set of 25 year old oob small block Chevy heads(or is it 30?) that well out-flow any non-maxwedge stock iron Mopar wedge head. Even with a 440-length crank, it will out-rpm the great majority of 383 mopars.
(Engine Masters did a test of a 383 Mopar vs a 383 Chevy. Mopar won, by virtue of the low-end torque it made. Peak numbers, and rpm, were virtually identical.)

The Mopar had 50ft-lbs more torque below 400rpm, then matched it on up. Grew up hearing longer crank makes more torque, but this is the opposite, and giving up nothing for HP. I see head porters and engine builders feel sorry for us that the "good" aftermarket Mopar heads flow well for small block Chevy heads.