Hi everyone. I'm trying to build a budget 383. It's for my 4x4, so
don't need oodles of top-end horsepower. Just lots of low-end grunt
I'll probably go with a compression ratio around 9:1 or so. But I wa
wondering what cam and heads would be good for this. What have you guy
used and recommend? Any help would be appreciated. TIA.
Eagle52's Profile: http://www.4x4kingdom.com/forum/member.php?useridView this thread: http://www.4x4kingdom.com/forum/showthread.php?t "7
The way we used to make 383 SB long ago was pretty simple and cheap to
do. There is no need to buy a crate or kit to do it. All you need a a
400 SB crank, rods (if you plan to use stock 350 pistons) and the
dampner and fly wheel or flex plate for a 400 SB. The reason for the
dampner and fly wheel is that the 400SB is externally balanced while
that 350 is internally balance (they are both just as smooth as long
as you have right dampner and flywheel on 400 SB) If you simply use a
400 crank and rods in a existing 350, you will have a 377. If you bore
it out 030 over you will have a 383. Again these are with stock parts
and stock 350 pistons with 400 rods. If you plan to by aftermarket
pistons you can get them with a pin bore further up in piston to let
you use longer stock 350 rods with a 400 crank. THe crank will drop
right in and a stock 400 crank is rock solid up to about 6000 RPM or
so (some go a lot higher but I tend to be conservative) The modern 383
crate motor is a bit of a bastard engine in that it uses a non stock
stroke (3.80 vs 3.75 on old 400SB) so it limits interchangabilty of
cheap off shelf parts. THe 400 crank in a 350 was a very popular mod
long ago for many years. Another old mod was a 350 crank and rods in a
400 SB which made a 372 (or a 377 if it was bored 030 over) and was a
popular on drag strip because it let you use longer 350 rods in a 400
block and let to wind it up a lot higher safely.
Guess again. Some very rare blocks may have some minot clearance
issue that you can fix with a die grinder but it is bascally a drop
in. Same journal diameters and the 400SB is basically a 350 block with
siamized cylinders to take a 4.125 bore. Where some get into trouble
it that they do not use right rod/piston combo. A;sp some forget to
use the dampner and flywheel or flexpalte from a 400 on it. The 350
stuff will bolt right to it but engine will not be balanced (the 454,
8.1, 400SB and Dmax are all externally balanced) The only other no no
is some old 327 blocks because most of them though they had a 4 inch
bore like a 350, they had smaller bearing journals. There was also 2
Chevy 302's The 67 had a different crank diameter than 68 through 70
because 67 was based on old 327 block and 68 on on new 327 block that
had bigger journals and later morphed into a 350. And while the 67
302 basically used a 283 crank in a 327 block the 68 to 70 used a
crank unique to 302 large diameter journal blocks. The 307 was nothing
more than a large journal 283 block with a 327 crank and a 305 is a
smaller yet bored block (3.74 vs 3.875) with a 350 crank. That is
way the SB got so popular because most of the parts swap out to make
different versions of engine. It was a clever design.
You might want to reread the book your pulling your data from. The mains
on a 400 crank are .200 larger than the 350 crank. 400 is 2.650 and the
350 is 2.450. No way in hell you are going to drop that crank into the
block without cutting it. The same problem exists if you attempt to put
a different crank in a 400 block. TRW makes a bearing kit specifically
for that. Part number used to be M53564P Those were a thick shell insert
that made up the gap.
You can also make the 383 handle higher rpms by using 5.7 rods and
pistons with a deck of 1.425. Gives a better rod angle and allows it to
produce more torque at lower rpm. Great for a marine engine. Oh I
noticed no mention of head modifications if you don't use 400 heads. If
you don't you need to drill the steam holes in the new heads, unless you
like cracked blocks and blown gaskets.
You are correct sabout one thing, I have seen 400 cranks both ways in
main journal diameter. As you said if you use a 350 crank on a large
diameter 400 block like you said it is easy to get proper bearings. As
far as a large journal 400 crank in a 350, no need to bore block out.
All you have to do and have crank mains turned to proper size which
any competent crank shop can easily do. Bore the saddle larger is not
a wise idea or very viable
Not a factory cast 400 crank. GM has NEVER made one. After market billet
can be purchased with 2.450 mains BUT only if you spec it that way. The
HT383 that GM is selling uses a custom 3.80 stroke 2.450 main steel crank.
Oh and I never said to bore the saddles. I said "No way in hell you are
going to drop that crank into the block without cutting it". Although a
good line hone is a very good idea, especially on the 4 bolt blocks
since they usually have the rear main pounded out from the heavy use in
Of course having actually built at least 50 383s might mean I don't know
anything about them.
The main journals need 200 thou turned off to make for a drop-in. Add
THAT to your copy and paste file.
I made a 334 with a 305 block and 400 crank/rods/flex plate/balancer
with stock pistons I selected for 9:1 compression and some kind of RV
cam (was a long time ago now and the memory is not flawless). I went
to the local Head Rebuilder and told him what I was making and he sold
me low compression heads with oversize valves (1.9/1.6 comes to mind
as the bore size limits the od of the valve head or it will contact
the bore). It ran like a scared rabbit and pulled strong in our 86
Chevy auto/TH350 I never found out the rear end ratio but I passed a
chick in a red car and she tried to catch us. Lost her on "moose
hill" when the engine valve floated at 160 kmh. We slowed down and
she never came to the top of the hill. I laughed and said she was
probably at the side of the road kicking her car :)
I used basic math to select the pistons and the head rebuilder came
through with a set of heads. The machine shop had some cams to choose
from and I went with a middle of the road RV cam with .442 lift. Had
mild lop at idle and I used to go slowly through the parking lot and
set off car alarms with it.
Ran the stock 4 bbl. and dual exhausts with the cats removed and a
free breathing air cleaner.
It was a long time ago and can't remember any more details at the
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