1989TransAm

Lighter rotating assembly.

dhirocz

Long story short:

Shorter rods are great for driveable torque.
Longer rods take some of the load off of the cylinder walls (less wear)
Shorter rods allow more suction on the intake port up to 90 degrees ATDC which is great for streetable intakes.
Longer rods suck on the intake more from 90 deg ATDC to BDC.
Shorter rods (under 6.0") dont clear internally balanced small block stroker cranks.
Longer rods allow a piston with a shorter compression height with the potential to be more lightweight.
Shorter rods normally have to be a little stronger because of cylinder pressure (which is different through the cranks range of motion because of piston speed than compared to a longer rod)
Longer rods can be a band aid for a weak exhaust port. They compliment more exhaust duration than a shorter rod so power doesnt drop off so fast after peak TQ.

Pick your poison! For tuned ports I try to go with 5.7" rods to help the engine pull from the intake. With something more like an LT1, I try to go 6" or longer if at all possible. Either a short or a long rod will work in either application really. Some people are more concerned with reliability, wear or have a lower E/I flow ratio so they go with longer rods. Some people want functionality (like me) so I choose depending on it's intended use.

jeffp1167

ZZ383/425 TECH SPECS:
Part Number: 12498772
Engine type: Chevy small-block V-8
Displacement (cu in): 383
Bore x stroke (in): 4.00 x 3.80

see it uses the common 4.00 350 bore but stroke was increased with a stroker crank while retaining production length rods.

so again tell me how stroke doesn't affect displacement?

mseven

I never said it did not, second, a 383 does not use a 3.80 stroke......
you need to start here (beginning on pg.10):
http://books.google.com/books?id=GUC...esult&resnum=9
or:
How to build a small block chevy by D. Vizard

jeffp1167

well this 383 does! and it's a chevy performance crate motor so I am sure others know of it's 3.80 cola crank. Do a search they used a special block for crank clearance and ran production length rods and pistons with a 350 bore.

so what would the displacement be using this 3.80 crank, 6.00 rods, and .030 over 350 block? would it not be around 395 cubic inches?

mseven

First of all, ifl using a 3.80 stroke with a 4.00 bore would be 382 c.i. displacement........maybe GM should call it a zz 382 ??

Second, GM does NOT use a Cola crank, pretty sure it was a Scat crank.

Third, Rod length has nothing to do with c.i./displacement calculations, however, if using a 4.030 bore with a 3.80 stroke (no crank made that I am aware of) would be 387. c.i.

do some reading from the link I posted

c-4 lhozwalte

a 396 sbc typically has a 3.875" stroke and 4.030 bore.and its a 396 with 5.56"rods,5.7",or6"rods. 383 has 3.750"stroke.and no one said that more stroke doesnt increase displacment.only that more rod lenghth does not increase stroke or displacement.

rodj

387.7ci
Would still be same capacity with 5.85" or 6" rod

The GMPP ZZ383/425 uses the same #10105123 4 bolt 1 pce seal block as used on the ZZ4 350.
The ZZ383 uses the same crank as used in the GMPP HT383 truck motor; a GMPP crank not a Cola crank
http://www.superchevyperformance.com...p/12489436.htm
The 3.80 crank uses the # 12497870 5.7" rod
"rod is machined to clear the camshaft in most small-block stroked type engines".

dhirocz

Let me clarify the things I know.

Rod length does NOT in any way affect cubic inches. At all. In any way. In any form. Only STROKE and BORE have an effect. The longer the rod is, the shorter the compression height (centerline of the piston wrist pin) of the piston is or the piston will be pushed out of the block.

The zz383 IS actually 382 cubic inches. They call it a 383 so people can relate IOW it's a sales tactic. It's not worth GM's time to make a stroker shortblock and bore new blocks .030" over just to call it a 383. And if they called it a 377 (std bore 3.75" stroke) people would confuse it with a destroked 400. It's easier to use a slightly longer stoke and make up for the slightly fewer cubes.

The zz383 DOES use a cola crank. To be more specific it is sold as a cola though it is made by another manufacturer...not a widely known one at that. But it is a nice 4340 piece and it is American made I know this because I have built an engine with one, and I have spoken to people prior to having mine internally balanced. It's also an externally balanced crank. It does NOT use a special block, it uses the same block as any other late 1pc 4 bolt main roller engine would. With the rods that come with the motor (capscrews) there is no significant concern for clearance with the stock notches in the block. I replaced all my PM capscrew rods with scat rods and also had no clearance issues other than the factory windage tray.

FWIW, a 3.8" crank is a late model block at a .030" is 388 cubes. If you used a piston for a 408 sbc (1" compression height 4.030" bore) with a 6.125" rod, you keep an acceptable rod length to stroke ratio (1.61, slightly less than a stock 350 at 1.63), minimize rotating interference during assembly, and make good torque (I tore the rear wheels off my camaro with my 382 guts in an LT1 block with ported heads, single plane and duals, on motor, sitting on street tires) This combo would make for a zero deck height with a stock 9.025" deck, the long rods are good for power and help reduce power drop after peak torque (and a decent exh port), and minimize side loading the cylinder walls so the engine lasts longer and oil temps stay decent. The only thing I wish I could get out of it was a longer 6.25" rod, but that isnt happening in a factory cylinder case. This is still a relatively low rod length to stroke ratio but it's street friendly. See my post above.

I have another one I'm building in my garage thats going to be topped off sb2.2 style. The first one was turned into a 382 cube tuned port LT1 because it had 5.7" rods and the GM hypereutectic pistons still in it.

Yeah, I play alot with these

jeffp1167

my friends build is also going to have heavily ported TPI stuff, some afr 220 heads and a ATI pb600 (something like that) supercharger on it. TPIS full lengths and TPIS exhaust. His 89 block I gave him was then setup for splayed four bolt mains. It's all going into his 1990 6 speed vette. I know the TPI will kill it but calif. emmisions need to be kept. So he is having the slp runners and TPIS bigmouth hogged out and a 58MM throttle body. Even so it should be a pretty quik car, stock I think he said it has 3.45:1 gears or something like that.

His builder also O-ringed the block, balanced the whole rotating assembly. He basically bought the crank and carillo rods for I think 1100 shipped and the nodular caps for 150. I think when its all done it will have costed him about 10-15k installed in his car.

dhirocz

The 'heavily ported' portion of the TPI thing kills me. What people dont realize is that the same thing they complain about when it comes to TPI (flow restriction) is what makes it make such awesome low end torque. IMHO porting of a tuned port intake should be aimed more at hitting an ideal cross section for the owners intended goal throughout and minimizing CSA variance in the intake and areas that might create turbulence. This is why extrude honing is so awesome...and is also why it is so expensive. I hope they dont overport it.

The supercharger is a good idea, I always liked them. I never did build a full out supercharged tuned port though because it totally throws off the tuning effect of the intake. Because of this, if I went supercharged I would probably go with a roots style for torque or a different untuned manifold for a centrifugal. Superchargers have a way of forcing air past what would normally be a restriction if run N/A. The only good thing is that overporting a tuned port will lower the restrictions of the air in the manifold under boost. But that manifold will probably be too large to properly work on that motor again if run N/A.

Something I dont think anyone has ever done is factor in a supercharger or turbocharger's effect when calculating CSA for porting a TPI intake. My first thought would be seeing how far up the motor would make power with the blower, port for that figuring the added airflow, then bringing the the boost as early as possible. You just gave me something to think about...

Seth McKown

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I just got ahold of a 1997 5.7 vortec I'm wanting to go carb on it it's my first build. I'm wanting to make it a 383 what all will I I need? It going into a 92 S10. If anyone could get me going would be great. I have it tore down now

confab

Related:

https://www.corvetteforum.com/forums...questions.html

Lots of good info here.