383 vs 396 rotating assembly
Thread Starter
Burning Brakes
Joined: Jul 2013
Posts: 963
Likes: 57
From: Vancouver, BC
383 vs 396 rotating assembly
Hey guys,
I know we got into this discussion a little in my previous cam choice thread but I wanted some more info. Basically my motor is either going to get a 383 or 396 balanced rotating assembly but I want to go with the one that is more reliable. From what I have read online and through the forums is that the 396 is really pushing the limits of a 355 block and there is more potential for failure as opposed to a 383. I also gather that installing a 383 is much easier than a 396 since its basically unbolting the old and installing the new, whereas with a 396 there is much more involved. I saw some kits online at cnc and i'd like some input as well as to whether these are any good. My build as it sits is as follows:
-stock 355 block
- rpm air gap
- brodix 200cc aluminum heads
- 1.6/1.5 roller rockers
- comp cams 275DEH-10
- holley street avenger 770
- msd 6al
- hei distributor
- TH350 fresh rebuild
- aluminum rad with dual fans
https://www.cnc-motorsports.com/1-40...p-pistons.html
https://www.cnc-motorsports.com/eagl...p-pistons.html
I know we got into this discussion a little in my previous cam choice thread but I wanted some more info. Basically my motor is either going to get a 383 or 396 balanced rotating assembly but I want to go with the one that is more reliable. From what I have read online and through the forums is that the 396 is really pushing the limits of a 355 block and there is more potential for failure as opposed to a 383. I also gather that installing a 383 is much easier than a 396 since its basically unbolting the old and installing the new, whereas with a 396 there is much more involved. I saw some kits online at cnc and i'd like some input as well as to whether these are any good. My build as it sits is as follows:
-stock 355 block
- rpm air gap
- brodix 200cc aluminum heads
- 1.6/1.5 roller rockers
- comp cams 275DEH-10
- holley street avenger 770
- msd 6al
- hei distributor
- TH350 fresh rebuild
- aluminum rad with dual fans
https://www.cnc-motorsports.com/1-40...p-pistons.html
https://www.cnc-motorsports.com/eagl...p-pistons.html
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
The 3.875 stroke crank in a stock block question is based on solely how much trial fitting and machining you want to do. I don't think it is worth messing with for 16 cubic inches. Period. You will never notice the difference.....
Jebby
Jebby
Thread Starter
Burning Brakes
Joined: Jul 2013
Posts: 963
Likes: 57
From: Vancouver, BC
Sticking with a 383 that has a 3.750 stroke crank would eliminate the trial fitting and machining correct?
Intermediate
Joined: Feb 2015
Posts: 41
Likes: 14
From: NC
I finished just my 383 and you definitely don't just bolt in a 3.75 stroke crank in a stock 350 block there is a lot of clearance work to be done, you might come out better to buying a 383 long block and go from there.
Thread Starter
Burning Brakes
Joined: Jul 2013
Posts: 963
Likes: 57
From: Vancouver, BC
Could you elaborate some more in terms of what clearance work you had done? did you buy a kit or did you piece all the components separately?
Thread Starter
Burning Brakes
Joined: Jul 2013
Posts: 963
Likes: 57
From: Vancouver, BC
Also can someone explain to me why the CR for the kits on cnc vary so much? I've seen 11.3:1 with flat top pistons, 12:1 with dome pistons and 9.5:1 with dish pistons. Im assuming I should stay below 10:1 if I want to run normal pump gas that is 91 octane?
Last edited by titanle; Oct 2, 2019 at 11:31 AM.
Drifting
Joined: Dec 2011
Posts: 1,743
Likes: 289
From: Chardon Ohio
10:1 compression is a good number for a street engine, you just need premium gas. This is what I have in my 383. I think any higher than that gets a little tricky - have to be more careful on other things.
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Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
Yes you have to fit, check, clearance cant just slap them together. Ill always choose the bigger ci.
If you do a 383 youll still be happy but youll never regret a longer stroke. Reliable isnt a concern...machining and assembly is everything. If you arent "that guy" who starts it up cold and revs the pee out of it, long burnouts donuts for you buddies i dont see why it wouldnt last.
Get a good oil pan.
Id run a little more cam with the 396
If you do a 383 youll still be happy but youll never regret a longer stroke. Reliable isnt a concern...machining and assembly is everything. If you arent "that guy" who starts it up cold and revs the pee out of it, long burnouts donuts for you buddies i dont see why it wouldnt last.
Get a good oil pan.
Id run a little more cam with the 396
Last edited by cv67; Oct 2, 2019 at 12:06 PM.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Remember...the 400 came stock with a 3.750 stroke crank....there is very little, if anything to do.
The 396 is going to require a .900 base circle cam too.
The 383 might not if the rods are cam clearanced.
Jebby
Last edited by Jebbysan; Oct 2, 2019 at 12:19 PM.
Le Mans Master
Joined: May 2002
Posts: 5,086
Likes: 786
From: Lebanon Township New Jersey
[QUOTE=titanle;1600249621] I also gather that installing a 383 is much easier than a 396 since its basically unbolting the old and installing the new, whereas with a 396 there is much more involved.
You're not talking about a 396 big block, right? A 396 small block installs exactly the same as a 383 small block.
-
You're not talking about a 396 big block, right? A 396 small block installs exactly the same as a 383 small block.
-
Thread Starter
Burning Brakes
Joined: Jul 2013
Posts: 963
Likes: 57
From: Vancouver, BC
[QUOTE=BKbroiler;1600250291]
Yes a 396 stroker kit as opposed to a 383 stroker kit for my SB350.
Im definitely not that guy, I just like to let loose and go fast on occasion. Any suggestions on oil pans? If I went with a 396 over a 383 what cam would you recommend? I have hydraulic flat tappet now, Id like to keep it that way instead of spending even more to get a roller cam and having to change other components to roller from flat tappet.
I have 91 octane readily available and some stations have 94 octane. I'd like to remain in a somewhat safe CR hence why I didn't want to go beyond 10, but if I can get away with even a little higher like 11 I wouldn't mind as along as its still relatively conservative.
I also gather that installing a 383 is much easier than a 396 since its basically unbolting the old and installing the new, whereas with a 396 there is much more involved.
You're not talking about a 396 big block, right? A 396 small block installs exactly the same as a 383 small block.
-
You're not talking about a 396 big block, right? A 396 small block installs exactly the same as a 383 small block.
-
Yes you have to fit, check, clearance cant just slap them together. Ill always choose the bigger ci.
If you do a 383 youll still be happy but youll never regret a longer stroke. Reliable isnt a concern...machining and assembly is everything. If you arent "that guy" who starts it up cold and revs the pee out of it, long burnouts donuts for you buddies i dont see why it wouldnt last.
Get a good oil pan.
Id run a little more cam with the 396
If you do a 383 youll still be happy but youll never regret a longer stroke. Reliable isnt a concern...machining and assembly is everything. If you arent "that guy" who starts it up cold and revs the pee out of it, long burnouts donuts for you buddies i dont see why it wouldnt last.
Get a good oil pan.
Id run a little more cam with the 396
I have 91 octane readily available and some stations have 94 octane. I'd like to remain in a somewhat safe CR hence why I didn't want to go beyond 10, but if I can get away with even a little higher like 11 I wouldn't mind as along as its still relatively conservative.
Last edited by titanle; Oct 2, 2019 at 12:43 PM.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
You need to try out the online compression ratio calculators. They are easy to use now and will answer many of your own questions. I like the one UEM has on their website and you can shop their pistons also with their published dish volumes. Some of the volumes may seem difficult at first but take your time and sort them out. Once you nail all the volumes numbers the calculations go as fast as you can enter them. Once you master the static compression ratio then move onto dynamic compression ratio which uses your cam intake closing angle which may take some time to noodle out but that's how it's done so you need to bite the bullet and master this.
Hope this helps more than it hurts.
Hope this helps more than it hurts.
Thread Starter
Burning Brakes
Joined: Jul 2013
Posts: 963
Likes: 57
From: Vancouver, BC
You need to try out the online compression ratio calculators. They are easy to use now and will answer many of your own questions. I like the one UEM has on their website and you can shop their pistons also with their published dish volumes. Some of the volumes may seem difficult at first but take your time and sort them out. Once you nail all the volumes numbers the calculations go as fast as you can enter them. Once you master the static compression ratio then move onto dynamic compression ratio which uses your cam intake closing angle which may take some time to noodle out but that's how it's done so you need to bite the bullet and master this.
Hope this helps more than it hurts.
Hope this helps more than it hurts.
Thread Starter
Burning Brakes
Joined: Jul 2013
Posts: 963
Likes: 57
From: Vancouver, BC
That is a good idea but I have too sunk into this engine. Unless I can list the entire motor and recoup my money, I don't think another engine is in the cards at this point in time. Considering everything on the motor aside from the block is brand new and probably has less than 150 miles on it.
Thread Starter
Burning Brakes
Joined: Jul 2013
Posts: 963
Likes: 57
From: Vancouver, BC
Based on my current setup and wanting to have a forged crank and run on 91 octane pump gas, this is what CNC recommended to me:
https://www.cnc-motorsports.com/sbc-...gle-62010.html
Any thoughts on this kit? Is it a good option or would it be overkill and I don't need to spend that much?
https://www.cnc-motorsports.com/sbc-...gle-62010.html
Any thoughts on this kit? Is it a good option or would it be overkill and I don't need to spend that much?
