383 specs
 

Hi guys...

We're just about to overhaul my 70 Challenger's 383ci 4bbl engine. We'll bore it .03 over and use either hypereutectic or forged pistons. I'd like to increase the comp ratio a little, but it turned out it's not as easy as it seemed to be at the very beginning...Diamond talks about ratio's of up to 10.7:1 with 72cc heads.

Now a couple of questions :confused:
-Do you guys know, what size the stock cast 383 heads are?? And btw, is a bore of 4.280 already an oversize?

-Would you take forged pistons or do you think the hypereutectic (keith black) will do??

-What other brands would you suggest - JE, Manley,...and where can I get them??

Well, as you can see I'm still kind of confused and try to get an overview, I really appreciate your help!!

Greetz, if your heads are stock 73 383 heads they are 79.5 cc and your 383 will have a bore and stroke of 4.250 x 3.375 and I would avoid Keith Black pistons and go with a forged TRW, but the boys will have other options/suggestions, that's what's great about this place.

Wow, this was fast ;) It's not a matching # engine, so the heads might be of a later model, I'll try to find out more...they're still in a pretty good condition and there is just one valve that needs some work!
79.5cc will give me a comp ratio of around 9.0:1 with a 3.375 stroke...I saw a table with higher comp rations with a 3.750 stroke, which is probably a 383 block with 440 rods?? Would an application like that work with a 383 crank?

If the heads are earlier 383 they could be 73.5 cc. These heads would have 2.08/1.74 valves and would be a closed chamber head.Check out 440 Source on the web, they have rotating assemblies that you can drop right in.

g'day chally
4.280 is all ready + 030 , daimond will make a custom forged +040 for around $800 or you can go +060 for $650 . this piston is to suit a 440 rod , which has a better rod ratio . ( slows down piston speed , better bore angle , better mid - top end power .) if its not a huge horse power engine you could use a 440 source std replacement rod with 7/16 arp rod bolt for $270 .
there high compression piston would be around 10 - 1 comp with 79 cc heads . if you pm me your email i'll send you some e mails from marshall @ campbells who's been very help full . on this subject . after reading on here & talking to blokes over here i wouldn't use kb's for street uses .
gota go mate cya good luck iam building my 383 as well right now .
ps those 440 source rods would need little end bush to suit . 990 chevy pin or buy some 440 rods with 990 pin .

I have seen, and may have thrown my input in as well, a thread that some people have been talking about Keith Black pistons. I myself do not care for them. I like Eagle, they are a good quality but you'll pay for it too. I have heard TRW is a good one to go with as well. I would stick with forged pistons and rods.

i agree with all of them boys, if you are gonna hammer on it use forged. me i like trw,s and ross pistons. gl and welcome to the shop

@ deadkelly - you got mail ;-)

I checked out Eagle, TRW, Ross and Diamond...seems all to be pretty much the same. I was already about to order the Keith Black hypereutectic's, so I gonna think things over.
Here is a table I found recently - http://www.diamondracing.net/MoParSection.pdf
They distinguish between a 3.375 and 3.750 stroke. At first, I thought it has s.th. to do with the rods - 383 vs 440, but according to this table, both strokes are available with both rods...although the C.D. changes significantly!
I'm so confused ;-)))
In fact, the higher comp ratio could be achieved with the 3.750 stroke...but how????

Thx again guys...

Maybe through another crankshaft? :)

you could if you had a longer or shorter throw crank.

Oh my, I was probably a little confused, but I think I got it now :rolleyes: Stroking the engine is probably the only way to increase the comp ratio...the 3.750 stroke will be achieved by a 440 crank, that will fit in the B block after some machine work. The Diamond pistons will perfectly work with 440 rods, the new stroke and a .990 pin...
Thx again to deadkelly...Campbell is probably the place I should go :)

try to avoid the keith black pistons

You can raise your comp ratio also by decking the heads, I don't know if thats the way ya wanna go ? There's more than one way to skin a cat.:D

Now im a lil confused? is all you want to do is raise your compression you dont have to stroke it just to raise the comp ratio. or do you want to stroke the motor? what ratio are you after. and what heads do you have. do you have the casting numbers?

The car is in a garage with a friend right now...where can I find the casting numbers? Well, at the very begining we intended just to overhaul and check the engine, exchange some gaskets and check the cylinders and pistons for any wear. It turned out, that the cylinders need to be bored. As I was looking for new forged/hypereutectic oversize pistons, there was no brand with a comp ratio of more than 9:1 with stock heads. I thought the easiest way might be the application mentioned above - I would be able to achieve a ratio of more than 10:1 and increase displacement.
Overhauling and nitrify the old crank over here, is at about the same price as a new 440 crank ordered in the US. So I could either keep the engine almost stock, or throw in 500 bucks for the 440 rods and gain lot's of power...hope there won't be a rude surprise.
What else could I do?

Pull a valve cover and look at the head between the valve springs on the webbing of the casting, your numbers will be there. ( head #'s )

wow i looked online also not much out there. you can call summit racing and they can usually find what you are looking for. (1-800-517-1035). also 426 wedge was the same bore i just dont know the pin height diffrence is. also ross will make you custom pistions to your specs. there around $100 to $140 a piece their # 1-800-392-7677:)

Thx man! Summit seems to have complete Federal Mogul 383 rotating assemblies, but I didn't call them yet.
I'm also in touch with Campbell right now, they offer forged stroker kits for a reasonable price. I have absolutely no experience with strokers, how they fit and on what I actually have to focus. I hope these kits are already balanced and ready to drop in.
Oh yeah, btw I found the casting number - 3462346! Seem to be somwhere between 78 and 82cc...

70chally you can check these sites out but you have to look into them and you can find almost everything on you car (original) that is but like heads,blocks,and enter your vin #s and see what ya' got
Mopar VIN Decoder

Mopar Casting Numbers - MyMopar.com - Mopar Part Numners

Mopar Codes - MyMopar.com - Mopar Part Numbers

MyMopar.com - MyMopar Tools/Reference

Those heads are the "346" heads with 2.08/1.74 valves and a cc of 79.5. Check out 440 Source.com also Greetz.

stroking isn't the only way to raise compression

true. you can raise the comp with out replacing the pistons. mill the heads and use shim head gaskets. but that just ups it by a few point.
if you do stroke the motor becarefull if you go to big you gotta use an external oil pick up and they run $350 to $500. so talk to whoever you are buying the kit from and comfirm everything! and if they chamfer the bearings for? have you checked out the440source.com ?

Sorry, have been away a couple of days...I had a chat with a good friend, the mechanic who's working @ my car. He told me, if I wanted to stroke the engine, I should be looking for a complete and already balanced kit, as it was too much work and probably too complicated over here to find good machine shops, able for such a job. They can hone and bore blocks, overhaul and repair valves, etc...but balancing and trimming a crank/whole rotating assembly seems to be too much.
So, I had a look around...440source.com and Campbellenterprises offer complete and (internally) balanced high comp 438ci stroker kits. I understood, that there is no further balancing required and all kits are ready to go.
Do you guys know more about the complete kits - does internally balanced mean, that there is no further work and balancing required?

Greetz, from what I know of them, it's install and go.

The difference between the two have do do with whether there are weights externally on the torque converter and harmonic balancer, or whether it has been done internally on the crank. I only point this out as you will have horrible vibration issues if you mix and match parts. So you will need neutral balance parts and that's it, for "extra" work.

can you stroke a 383 to 438 safely though?
isnt that why they came out with the rb block?

It's just crazy, there are even 383-484ci stroker kits out there, but if it's safe with a B block...??? Stroking the engine was just an idea, but in the meantime I heared of so many problems.
The 3.750 crank needs to be machined, the mains turned down to the B block size. I guess this is already done, but probably the counterweights need to be trimmed down or heavily chamfered so they'll clear the main webs.
I think I'll just order some standard forged TRW pistons and I should be somewhere in the 9.8:1 region with my 346 heads.

yes, just like cammando pointed out, internally balanced means just that its done! put it in the block check clearances and go. Some 383s were externally balanced (i think) this means if there is a weights on your torque converter you got to take them off. and get a different harmonic balancer. or it will eat your transmission up.

Seems the stroker project is cancelled, just got a set of .03 oversize TRW pistons today ;) Next week, the block will be bored, the crankshaft machined and nitrated and then everything reassembled. Hope it'll all work!

good luck finishing the rebuild:D