Engine Stamp Pad Questions

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matthon

matthon

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Looking to buy a 383 from a friend, cast in 1970, appears to be a stock 4 barrel, crank drilled for 4 speed with correct early bushing. It s/b 8.5:1 compression.

On the pad below the distributor is:
G383, assembled in 1971, 383.
Next is assembly date, don't recall what it was, I'm dumb and didn't take a pic.
There is a maltese cross, my understanding is .001" undersize main bearing journals.

There is also HP for High Performance.
I don't recall anything else at the moment.

I've read many posts where people state 2 barrel 71 383s got a cast crank, Allpar states: "In 1971, the year also saw the use of a cast iron 383 crankshaft as a cost saving measure, on automatic-transmission cars." No mention of carb.

Can anyone explain exactly what was different on an HP engine?

What is the purpose of undersize main bearing journals?

I know pulling the pan and looking at the crank will solve the cast or forged question, but is Allpar correct?

I don't believe the 8.5:1 comp is a deal breaker, just looking for a good engine, but what would it take to raise comp to the 1970 spec of 9.5:1?
 
The factory Maltese cross just meant the crank was nicked or had issues from day 1, had to be machined .010 under to clean up. I have read that most 4 speed cranks were steel. The small bit of literature I have for '71 shows both 2 and 4 bbl 383's w 8.5 comp. Depending on what heads you go w and intended purpose, pistons may be the best way to get good compression.
 
I believe the heads are stock 346.
My goal is to keep it simple, change gaskets, check the cylinders for compression and with an inspection camera, maybe pull the heads just to be sure, and make it run.

Is 8.5:1 bad compression? It has a stock 4 barrel intake, but no carb, I have an Edelbrock RPM intake and a 750 holley, will those not work well with the current compression?

Can anyone comment on what HP means?
 
There is no exact measurement with the maltise cross. It just means the crankshaft is undersized SOMEWHERE. Either rods, mains or both. Could be .001" Could be .030". I've torn down enough to know. Undersized is all it means. Also, don't be surprised to find rods "numbered" with playing card suits. Hearts, clubs and the like. Seen it a lot.

Nothing wrong with 8.5 compression or a cast crank if it has both. Build it. It'll be a good engine.
 
RustyRatRod said:
There is no exact measurement with the maltise cross. It just means the crankshaft is undersized SOMEWHERE. Either rods, mains or both. Could be .001" Could be .030". I've torn down enough to know. Undersized is all it means. Also, don't be surprised to find rods "numbered" with playing card suits. Hearts, clubs and the like. Seen it a lot.

Nothing wrong with 8.5 compression or a cast crank if it has both. Build it. It'll be a good engine.
Click to expand...

How about the main saddles.
 
I need a runner for now, would build it later when I have more $.
He has two 383s. This one is very clean, pulled the valve covers, exhaust manifolds, that was it. The other is covered in grease, rust inside exhaust ports, didn't bother looking at it any further as the first looked like it would easily run.

Not worried about cast or forged, just curious.

I would like to put the rpm intake/holley on it since I have it.

I was not familiar with what undersized actually meant, I take it you would need to know where exactly in order to get the proper bearings. Interesting.
 
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matthon, let me toss this out there, even though I'm not an expert, and if I'm wrong then everybody can correct me.

The problem I have had with those 8.5:1 engines is that they originally came with open-chamber heads, which worked OK because the compression was low, but when you mill the head to raise the C.R. you don't have enough quench and will get bad detonation. So maybe you will have to change to closed-chamber heads.

So if I am wrong about this, then feel free to fire away. I know I need to learn more about this stuff.
 
Are you sure yours is not a steel crank? I copied and posted my experience with drilled cast cranks. This I posted first on here in 2007.


I thought I'd relay an experience I had with cast cranks drilled out to work on 4sp and auto apps. In 1972-1976 I worked as a mech. at a shop in Tampa Fl. We did all the main. and repairs on all Hillsbourgh county Sheriff cars. At that time we used Wheeler Engine rebuilders for 383 400 440 complete long blocks. I installed a 400 long block in a 72 Coronet and as soon as I cranked it, it had a rear main leak. Well I wound up installing 2 new rear main seals, pulling the transmission twice tring to figure out where the hell the leak was coming from. After many calls to the rebuilder, I finally had a chance to talk to a man on the assembly line. He said and I quote " Oh hell, All of those cast crank engine were suppose to be pulled off the shelfs" He went on to tell me that Wheeler came up with the idea that if they were to drill the back of all cast cranks, that they could then use one part number for standard or automatic applications. Sounded good, but there was one big problem, The cast cranks were to pourous and oil would find its way under preasure and leak thru the bearing surface and leak out the center of the crank! Since this was an automatic Cop car, the fix was clean the center of the crank, fill it with JB weld, and drive a flat type Freeze plug in the end. Well that fixed it, after 2 weeks of hell tring to find the leak. So if your thinking of drilling the end of the cast crank to accept the long input shaft of a 4 sd, Be Warned.
 
Bill Crowell said:
matthon, let me toss this out there, even though I'm not an expert, and if I'm wrong then everybody can correct me.

The problem I have had with those 8.5:1 engines is that they originally came with open-chamber heads, which worked OK because the compression was low, but when you mill the head to raise the C.R. you don't have enough quench and will get bad detonation. So maybe you will have to change to closed-chamber heads.

So if I am wrong about this, then feel free to fire away. I know I need to learn more about this stuff.
Click to expand...

I think that's probably pretty accurate. All this quench stuff is much ado about nuthing, IMO, unless you're running a ragged edge street engine, or an all our race job. People latch onto something and cannot let go. The 383 "is still" a big block. It's gonna run like one.
 
H.P. means high performance so it's a Magnum or Super Commando engine.
It would probably be originally out of a Challenger, Super Bee, Road Runner or 'Cuda. (or any other car that had the ''N'' as the fifth digit in the V.I.N.)
That being said, it would PROBABLY have a forged crank, but you never know.
 
The difference between a 383 "R" engine (regular fuel) and a 383 "HP" engine (premium fuel) is , as you may know , is the compression ratio . The "R" engine has dished pistons to run on regular fuel . From your description you have a "HP" engine . It's just fine as long as you use 93 or better fuel . I would pull the heads to see if it has hardened exhaust seats . this is important if you want to run pump gas . good luck
 
OK. So HP for 1971 means High Performance, labeled a Magnum or Super Commando engine, for a 1971 Road Runner/'Cuda/Challenger/Charger/Super Bee, with a Holley 4 barrel, 8.5:1 compression, 300 gross horsepower, 410 gross torque.

Basically, HP was for the engine in the super cars of the day, not granny's station wagon.

It also seems to make sense what Allpar has listed regarding the crank, that starting in 1971, the cast iron 383 crankshaft was used as a cost saving measure on automatic-transmission cars. HP or not, in 1971, a forged crank was used if it's for a 4 speed.

The chart on the Allpar link below shows the 1971 383 had a Holley 4 barrel and was standard in the Road Runner and 'Cuda. Only year for gross and net numbers.

Based on the links below:
1970 had two HP 383s, both with 9.5:1 and a four barrel, one with a Holley. There was also an 8.7:1 non-HP 383 with a two barrel.

1971 had one HP 383 with 8.5:1 and a Holley 4 barrel. There was also a two barrel non-HP 383 with the same 8.5:1.

Starting in 1970 compression was lowered, to cut back on emissions, and to run on regular gas, meaning lower octane gasoline, not unleaded fuel.

Starting in 1973, exhaust-valve seats were induction-hardened to allow use of lead-free fuels.

So, if my 383 checks out, and can easily become a runner, my Edelbrock/Holley combo should work fine, and if I get my 915 heads back together it should raise the compression and increase flow - or it needs more work to run and the same applies.

Thanks again FABO!

The Mopar (Chrysler, Dodge, Plymouth) B series V8 engines: 350, 361, 383, and 400
Mopar Chrysler Engine Specifications - MyMopar.com
MOPAR MUSCLE | 383 CID B Big Block Engine
 
It looks like there's a digit before 23, paint not scraped off, possibly a 9. So month/day.

Is that a C or 0 before the HP?
Can't find info on it, what does it stand for?

20181125_191452.jpg
 
For what it is worth my 72 400 was out of a 4 speed car and came with a forged crank. supposedly all 400's had cast cranks. I am willing to bet yours will be a forged crank as well if it was mated to a 4 speed.
 
From the GG book I found:
C = Special crankshaft + pistons
If that is a C, looks more zero-ish, and really faint. The so-called 9 looks faint too.
 
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