Stock-ish 383 Build

-
carfreak6970

carfreak6970

Well-Known Member
Joined
Jul 25, 2014
Messages
545
Reaction score
196
Location
Pittsburgh
It has come to the fun part engine work on the car I'm working on. It is an original 383 4 speed with a 3.23 Suregrip in the 741 case but the engine is out of a 70 Polara. The engine is the 2 barrel version and according to the data books it has an 8.7 C.R.

What I would like to do is set this motor up as a street motor that may see the track once in a blue moon (being honest here). It will be used as a fun cruiser with stop light brawls and hard pulls in and on the high way. I would be keeping the 3.23 in the rear with maybe switching to 3.55 a couple years away. I will be running a stock iron 4 barrel intake with an AVS or maybe a Holly. I am going to be running either the TTI or Schumacher (didnt decide which yet) headers. I would like to build this engine pretty close to the 68 version with a little bit of a hotter cam. Right now the engine is the stock bore but will probably need to be bored out. I will be running the stock valve train as well.

I would like to run around a 10 to 1 CR and have some good low and mid range power, but still has a little top end. Sadly I dont know much about the heads as I didnt measure the chambers, but I am fairly certain the heads I sent to the machine shop are the ones that came on the engine originally. However, what pistons should get me to my goal?

As for cam selection I did some searching here and found a few ideas, and went on COMPS website and found a couple more. I am going with a hydraulic flat tappet cam. Of the following cams, which would help me reach my goal of a great street motor that has a distinguishable idle and makes good all around power?

21-406-4

21-600-5

21-670-4

21-306-4

21-237-4

21-225-4

21-305-4

Would anyone have any other suggestions that I may have missed? I obviously want to make as much power as possible, but this is going to be a street motor. With what I am working with here, what kind of horsepower and torque numbers can I expect from a build like this?
 
Is it going to be an 8.7:1 engine or a 10:1 engine? Really need to know that to make a cam suggestion.

Also, you have some conflicting goals going on. Distinguishable (Lopey?) idle, tall gears, good low end and top end, mostly street machine, etc.

Both of those headers are quality and have their place. For you application I'd most likely go with the schumachers. As far as carburation the holley is the way to go IMO.
 
Rocco, I think he asked which pistons should he go with to make 10:1 compression, but I'm about to give my own somewhat hare-brained response here in a second...
 
OP: First off, you don't *need 10:1 static compression in a 383 for a decent daily driver...read some of IQ52's posts about making power with lower (read: 70's emission standards friendly) compression. You can have a hp/ci 383 with 9:1 or less as long as the heads support the desired power output and you match the rest of the package with that level. Besides, factory CR ratings were optimistic at best. Also, taking into consideration that you want to run a factory iron intake, and you want (from what I can see) what sounds like a factory Magnum 383, with headers, and a slightly bigger cam but using stock rockers, you won't need much cam to make it run well.

That being said...

Off the shelf pistons available for the 383 are desperately lacking in variety and those available are pretty heavy generally speaking compared to newer engines. They also have thick rings which produce more friction than newer offerings. Now, for all those conditions mentioned, KB makes a couple of decent offerings for a decent price that will suit whatever need you have for your pedestrian 383. They have a flat top with very large valve reliefs and a dome with the same reliefs.

Here: Chrysler : United Engine & Machine Co. Incorporated, Performance Pistons

For a everyday driver which will never see a power adder, or possibly a little bit of nitrous, I'd probably say these are your ticket.

As far as the cam, I'm with rocco on this one, figure out what static compression ratio you actually want your engine to have based on the not-so-dizzying array of pistons available. That means you'll need to actually measure whatever heads are on the engine if you plan to reuse them, or map out the actual volume of another head which you plan to use. Either way, you need to measure and find out actual numbers, not just what "the book says"...

But, if I were to go with a general cam recommendation, something in the vicinity of 215-230 @050 with about 480"-500" lift, and a 110 LSA...not hot, but still more than enough to make and keep your low end decent enough to not feel like a dog out of the hole with stock converter and 3.23s--and again, the heads have to support the cam and vice versa

And you need to keep your budget in mind here too...just slapping together an engine often ends up in disappointment and deflated goals.

If I've confused more than helped, I apologize...
 
I am not entirely sure of the differences between the base 383 and the higher compression one which is why I stated the engine came from the factory as the 8.7 CR one.. but to answer your question I'd like to run close to the 10 to 1 CR. But I am guessing from the responses so far that may not be the best route.

I will try and see if I can get information on the head type and chamber sizes So I can effectively get the CR for a proper cam selection.

I appreciate the responses
 
Pistons which came from the factory regardless of year are pretty much irrelevant as you'll very likely be replacing them. All heads, post '68 were open chamber anyway, and usually measured somewhere north of 88cc...so unless you run a dome or shave the heads to a point where you're hurting them, you won't be making a true 10:1 with a 383 and factory open chamber heads anyway, sorry...
 
okay thank you for the suggestions.

Looking into this further it does appear that the 10 to 1 CR would not be achievable. I still dont know the chamber sizes but I called the machine shop asking for the head's casting numbers in hopes of getting a ball park on the sizes. They informed me the casting numbers were 3769902 & 3751213. So one of them is the 902 head but what is the other one? It doesn't follow the 916, 906, 346, 902, 975, and 452 convention.

So I guess the chambers are in the 88cc ball park. which get me in the low to mid 9's CR.
 
...with a dome...

here's some more info on casting numbers:

Mopar Casting Numbers - MyMopar.com - Mopar Part Numners

it says your 213 castings are from a later model motor home? My guess would be sometime during the life of that engine the heads were swapped, as the factory castings, even for a 2bbl Polara, should've been 906s or possibly 346s

tellin' ya man, you really need to look up some of IQ's builds and not get hung up on SCR, except to choose a suitable cam and match ICL to make the most of the SCR you do have.
 
txstang84 said:
...with a dome...

tellin' ya man, you really need to look up some of IQ's builds and not get hung up on SCR, except to choose a suitable cam and match ICL to make the most of the SCR you do have.
Click to expand...

I appreciate the heads up. If I cant get 10 to 1 that's fine. But as you stated I still need to know the SCR to choose a suitable cam, which is what I am trying to do. I was just using the 10 to 1 as a goal and ultimately get a cam. But now knowing that the SCR is somewhere in the mid to low 9's it impacts my opinions on cam selections. Im trying to just figure out what my cam selection is.
 
But yes I was informed the heads were changed at one point. As this engine came out of the 70 polara my dad had since 71. And I was aware this engine should of had the 906 heads, which is why I called the machine shop to confirm.
 
so someone played the old switcheroo with your heads. Now before I put a nickel into those heads I'd be looking at a set of 440 source stealth heads for 1,000. That kills 2 birds with one stone for you. You get a ready to run set of heads and you get the SCR you want.
 
Very true...the source heads are advertised at 80cc...which would get him into the low 9:1 range with the KB flat tops, or about 10.2:1 with the KB domes. And even with the flat tops, a 383 with the 440 source heads should motivate a 4 speed A body pretty damn well, even with 3.23s
 
roccodart440 said:
so someone played the old switcheroo with your heads. Now before I put a nickel into those heads I'd be looking at a set of 440 source stealth heads for 1,000. That kills 2 birds with one stone for you. You get a ready to run set of heads and you get the SCR you want.
Click to expand...

This is the route I'm going eventually. can't beat the price
 
Though tempting those 440 source stealth heads are, I am going to have to pass. Really not in the budget at the moment. I am just trying get this thing on the road. Initially I was after the 10 to 1 SCR, I will be okay with the mid to low 9 SCR if that is what the equipment I have is good and reliable for. I am just trying to get an idea on pistons so I can get the ball park SCR to help me narrow in on the cam that would best suit my application.
 
carfreak6970 said:
Though tempting those 440 source stealth heads are, I am going to have to pass. Really not in the budget at the moment. I am just trying get this thing on the road. Initially I was after the 10 to 1 SCR, I will be okay with the mid to low 9 SCR if that is what the equipment I have is good and reliable for. I am just trying to get an idea on pistons so I can get the ball park SCR to help me narrow in on the cam that would best suit my application.
Click to expand...
Are the heads you have now good to go? If they are I wouldn't bother with the aluminum heads yet. But if they need machine work and all that, by the time that is said and done you probably wouldn't be too far off from the price of the 440 source heads
 
Does this engine currently run?

How much do you estimate reconditioning your heads and buying the valvesprings and hardware needed for your new cam will cost you?

I'm going to seriously recommend you itemize EVERY piece of hardware and get an estimate for all of the machining and other labor you will require.
 
It's been probably 6 years since I had any heads rebuilt, but at the time it was $550 to have my machinist perform a 3 angle valve job, clean, inspect, replace stem seals, .004" clean up cut, reassemble and pressure test...the guides were good, and no hard parts replaced...YMMV
 
txstang84 said:
It's been probably 6 years since I had any heads rebuilt, but at the time it was $550 to have my machinist perform a 3 angle valve job, clean, inspect, replace stem seals, .004" clean up cut, reassemble and pressure test...the guides were good, and no hard parts replaced...YMMV
Click to expand...

now add to that springs and retainers, etc
 
The verbal quote I received was about 1400 for the machining of the the block and all of the head work.

I was informed these heads did have some valve work done in the past and the engine did run when it was pulled about 18 years ago. it was having oil pressure problems that we believe the cam bearings were going out. The clearances and journals on the mains and rods all measured out to be within specification.
 
You must log in or register to reply here.
-

Back
Top