want to build a 391 ci sbc !!!!!! [Archive] - Chevy Nova Forum

: want to build a 391 ci sbc !!!!!!


chevyIIheavy
24th-May-2009, 11:09 AM
hey guys i could use some help i would like to build a 391 or 396 sbc i would like to use forged pistons and forged i beam rods and a forged 4140/30 non twist steel crank im using a i peice rear main seal block its never been touched its still has a 4" bore. im going to be using this motor mainly for drag racing and a little street i would like to keep the compression down to 11.1 to 1 so i can run pump gas, will be going with a solid roller i havent decided what duration or lift yet but i would like it to go to 7500 or 8000 rpms also im going to be running dart pro 1 platnium heads prolly with 200 or 215 cc intake runners and 64cc combustion chambers, maybe running a pro products super victor type manifold.

what do you guys think? maybe you guys could help me choose a cam ( solid roller only ) or give me better advice too
thanks jim

bowtie0069
24th-May-2009, 12:17 PM
Why do you want to turn it to 8000? With the 3.832" stroke it's not necessary to buzz it that high, and with only a 200 or 215 head it won't make power up there anyway. Is that a 4 bolt main block? As far as I know there are no Off the Shelf cranks made with that stroke; it's made by offset grinding a 3.75" crank down to 2.00" journals and using small journal rods. It's easier to do a 388" (387.77") using a 3.800" crank which is available from several places.
I've used both in the past. What size rod do you plan to use? That will determine what Off the Shelf piston you can use(unless you plan to have them custom made) Using a 3.800" stroke with a 5.85" rod gives you lots of pistons to choose from, but there are fewer choices of rods in that size.

388 Recipe List
Mahle #SBC250030F05 Pistons w/rings.........................$614.99
Scat #4-350-3800-5700-L 4340 Forged Crank...............$525.00
Scat #2-350-5850-2100 4340 Forged H-Beam 5.85" rod..$399.00

From flatlanderracing.com

chevyIIheavy
24th-May-2009, 12:32 PM
thanks mike i dont why i want it to go that high i was going to use my 4500 stall converter and 4.30 gears maybe 7500 rpm then using a 27 or 28 inch tall tire. the block is a 4 bolt main out of a early 90s fullsize chevy van/pickup its never been touched thats what i wanted to do was use a 3.75 crank and have it turned down for the rods or would it be cheaper to go with a 388 i just wanted to get as close to 400ci as i could i was going to do your garden varitey 383 but everyone in there mother has one i wanted to go bigger with what i have do you think the h beams would be a problem inside the block my machinest said he do it but he recomended i beams instead i dont know though

chevyIIheavy
24th-May-2009, 12:37 PM
something else is i have a pair of stock sbc chevy rods ( 5.7 ) what can i do to them to make them work the thing is i may use some nitrous :yes:

tnblkc230wz
24th-May-2009, 01:12 PM
Won't a 3.875 crank and a 4.030 bore get him to 396? People are doing this with LT1s and LT4s.

chevyIIheavy
24th-May-2009, 01:22 PM
Won't a 3.875 crank and a 4.030 bore get him to 396? People are doing this with LT1s and LT4s.

:yes: :yes: :D :D thats what im shootin for

Little Red Wagon!
24th-May-2009, 02:31 PM
One question.............why a 396sbc?

chevyIIheavy
24th-May-2009, 02:40 PM
i wanted to be different i mean i dont mind doin a 383 i just want more cubic inches and to be different :yes:

levisnteeshirt
24th-May-2009, 05:25 PM
i've saw a couple of those 391's , seemed to do pretty good,,

i'd look at this cam if it wuz me and i had a 391 on my mind


http://www.lunatipower.com/Product.aspx?id=1809&gid=250

bowtie0069
24th-May-2009, 05:56 PM
use my 4500 stall converter and 4.30 gears maybe 7500 rpm then using a 27 or 28 inch tall tire

With a 28" tire (same gear/tire I use) that would be over 140 mph.

use a 3.75 crank and have it turned down for the rods or would it be cheaper to go with a 388

Unless you can find a crank in that stroke it would be cheaper to buy one off the shelf. One big plus to using the small journal is the rod can be smaller on the big end--depending on what rod you use. On my 391's I ran stock small journal 327 type rods prepped by Louie Unser's shop--dirt cheap and never failed--I did have a totally stock small journal rod fail after a 9000+ rpm oops! in the waterbox!! With the stock type rods, one of my 391's needed NO clearance work at all.


i have a pair of stock sbc chevy rods ( 5.7 ) what can i do to them to make them work the thing is i may use some nitrous

I used them for many years and many bottles without problems.

Won't a 3.875 crank and a 4.030 bore get him to 396?

The only pistons I see for that combo are cut for 18 heads. UPDATE: I found some Ross pistons for that stroke.

If you go with the 388, you can get pistons from Mahle, J.E., Manley(cheap too), Probe(very light and cheap), Ross.........

do you think the h beams would be a problem inside the block

I just did a 383 with 6" H-beams and it just needed the usual clearance.

chevyIIheavy
24th-May-2009, 11:00 PM
well mike since you have actually built 391s would you give me a parts list so i can go from there maybe do a cheap list and an expensive list or am i asking for to much :eek: remember this is a fresh block stock deck height and its never been bored i mean its got the 4" bore and never been decked

im really tryin to shoot for 396 c.i. that would be way cool

bowtie0069
25th-May-2009, 01:36 AM
well mike since you have actually built 391s would you give me a parts list so i can go from there maybe do a cheap list and an expensive list or am i asking for to much

I used a Chinese cast crank in my last one, with small journal 327 rods, and KB155 domed hyperutectic pistons, 283@.050 ancient Crane solid roller, old AFR 220's w/58cc chambers (13.8-1), Victor Jr./850 Holley and Hooker 1-7/8" headers--it ran 10.25/131 on motor only in a 71 Nova.

Ross 90261 pistons are forged but have big domes. 391 choices are much more limited, you'll have to do some shopping.
Contact these guys, they first put them together back when they ran Standard Crankshaft in L.A. http://www.larrysperformance.com/

levisnteeshirt
25th-May-2009, 02:50 PM
if you go the small journal route , i noticed these rods on sale the other day

http://www.racingjunk.com/category/1294/Rods/post/1521750/Eagle-H-Beam-Rods.html

1969NOVA1
10th-September-2009, 10:03 AM
I had a 391 sbc about 7 years ago. The thang ran & pulled hard!!!!!! I never revved it up past 6300, didnt need to.......I was whipping everything around town!!!!!! I Ordered the rotating assembly from Speed-O-Motive. Check them out.

levisnteeshirt
10th-September-2009, 06:54 PM
with the 327/6.0 rod piston , 1.385 comp height , 5.7 small journal rod , 3.832 offset ground to small journal rod , comes out perfect to a 9.001 total deck , cut the block to 9.001 and ur there ,

Paul Wright
10th-September-2009, 11:04 PM
As a reference Flatlander (http://www.flatlanderracing.com/crankshaft_services.html#offsetgrinding) charges $200 to offset grind a 383 crank up to 3.84". Add that to the cost of the crank and it may be better to get one with the right stroke from Scat.

The small journal rod will greatly reduce grinding the pan rail for clearance.
Using off the shelf pistons is cheaper than custom pin heights.

Building an engine to some specific cubic inch number for emotional reasons doesn't make sense especially since no one can "see" your displacement.

Just get some 396 decals and build a 383.

bowtie0069
10th-September-2009, 11:32 PM
The last 391" I built had a cast crank from Speedomotive--it was several years ago, but the finished crank was less than $350. My buddy put it in his fixture to measure it and was awestruck..it had the closest tolerances he had ever measured, and he used a lot of expensive Callies, L.A. Crank Krytonite, etc.....No telling how long it would have taken the abuse I gave it since the car was sold soon after the 10.25 pass at Carlsbad.

slow3oh
11th-September-2009, 12:07 AM
if you want to be different do a 377 instead of a 383

Paul Wright
11th-September-2009, 07:41 AM
if you want to be different do a 377 instead of a 383
Or do a 396 instead of a 307. Or do a 399. I'll bet nobody else has done that.

bowtie0069
11th-September-2009, 11:24 AM
The other way to build a 391 (4.145" x 3.625") makes a nice piece. My buddy used to shift his at about 8700--ran 9's N/A, drove it on the street, but the 1000lb. valvesprings were hard on parts.

bowtie0069
11th-September-2009, 11:39 AM
How about 387.7"? (4.030" x 3.800") Ohio crank gets $495 for the crank. Use 5.85" small journal rods, and a piston from any 6" rod 350 combo.

Granny 67
11th-September-2009, 11:51 AM
Competition Products makes a rotating assembly fully forged for a 391/396. Nothing special for 1500. Check it out.

tnblkc230wz
11th-September-2009, 02:13 PM
Isn't a 396 4.040*3.875? The LT1/4 guys use this combo.

bowtie0069
11th-September-2009, 03:23 PM
Isn't a 396 4.040*3.875?

In this case it refers to a 4.060" x 3.832" combo.

Paul Wright
12th-September-2009, 04:43 PM
Or a 4.060" bore with a 3.824" stroke.

MarkW
12th-September-2009, 05:13 PM
How about a 408? http://www.carcraft.com/techarticles/ccrp_0908_chevy_350_engine_build/index.html They put crap heads and a small cam on it but the short block looks pretty strong.

chevyIIheavy
12th-September-2009, 06:03 PM
wow i totally forgot about this thread ...:yes: well anywho thanks for all your imput fellas but me and my father have decided to go even bigger 420+ cubes , we will be using a dart lil m block with a 4'' stroke forged crank , h beam rods and a bore of 4.155 to start with :devil: im shooting for 600+ hp n/a and then maybe spray a tad in it :devil:

Novaman Oscar
12th-September-2009, 06:58 PM
wow i totally forgot about this thread ...:yes: well anywho thanks for all your imput fellas but me and my father have decided to go even bigger 420+ cubes , we will be using a dart lil m block with a 4'' stroke forged crank , h beam rods and a bore of 4.155 to start with :devil: im shooting for 600+ hp n/a and then maybe spray a tad in it :devil:

is this gonna be a separate block? or u got all of the stuff already?

chevyIIheavy
12th-September-2009, 07:02 PM
is this gonna be a separate block? or u got all of the stuff already?

ive got the block , but no other parts .......... the block was 2500 bucks from my machineist, it hasnt been touched , i soaked it in oil and its in a bag on my engine stand for storage :yes:

Novaman Oscar
12th-September-2009, 07:05 PM
ive got the block , but no other parts .......... the block was 2500 bucks from my machineist, it hasnt been touched , i soaked it in oil and its in a bag on my engine stand for storage :yes:

dam 2500 buck!!, what ya gonna do with old block?

chevyIIheavy
12th-September-2009, 07:09 PM
dam 2500 buck!!, what ya gonna do with old block?

well if i play my cards right i will have three running motors 420 + , current 360 , and a 383 :yes: so if one breaks i can install the other just so i can still race

Novaman Oscar
12th-September-2009, 07:15 PM
well if i play my cards right i will have three running motors 420 + , current 360 , and a 383 :yes: so if one breaks i can install the other just so i can still race

haha dam sweet!!








or you could give me one :D:D:D:D jk!