Chevy Decoding Information Camaro Information & Statistics Online Camaro Restoration Guide Site main page Club Merchandise Photo Gallery Event Calendar Cars for Sale/Wanted Camaro Chat

Note: This is an archived topic. It is read-only.
  Second Generation Camaro Owners Group Message Board
  Drivetrain Information
  5.7" rods -vs- 6.0" rods in 383 ... (Page 1)

UBBFriend: Email This Page to Someone!

profile | register | preferences | faq | search


This topic is 3 pages long: 1  2  3 
This topic was originally posted in this forum: Engine Topic
Author Topic:   5.7" rods -vs- 6.0" rods in 383 ...
Mr_Metal
Veteran Member
posted May 14, 2002 09:38 AM     Click Here to See the Profile for Mr_Metal   Click Here to Email Mr_Metal     
Getting ready to purchase rods for my 383 stroker build-up. I've heard good things about both rod lengths, as opposed to the 5.565" ones.
Does anyone have an opinion or experience in 383 stroker build up that could offer some explanation of which rod would be best for a "street" driver build up, with some racing capabilities?
My set-up will be:
Performer RPM dual plane manifold, Holley 650 double pumper, 1.94/1.50 mildly ported heads, roller rockers/lifters, Magnum 260 cam, MSD 6A & HEI "Super Coil", TH700R4 (Corvette servo + shift kit), and 3.08:1 GM "corporate" 8.5" posi unit.
Any and all help is appreciated !!

------------------
M_MtL
Restore 'em ... don't crush 'em !!
'81 Z28 (undergoing resto.)
Z28Camaro@usa.com

[This message has been edited by Mr_Metal (edited May 14, 2002).]

[This message has been edited by Mr_Metal (edited May 14, 2002).]

Strkr383
Veteran Member
posted May 14, 2002 10:20 AM     Click Here to See the Profile for Strkr383   Click Here to Email Strkr383     
I run a 6" in my motor. Less travel in the cylinder and moves the wrist pin up on the piston. I have been running mine for over 6yrs. without a hitch.

Strkr

Mr_Metal
Veteran Member
posted May 14, 2002 12:25 PM     Click Here to See the Profile for Mr_Metal   Click Here to Email Mr_Metal     
Thanks Strkr,
A guy that runs big modified Hemis told me the same thing ... and he's making 2200 HP on alcohol w/ big blower.
Thanks for the input.


Lowend
Administrator
posted May 14, 2002 12:50 PM     Click Here to See the Profile for Lowend   Click Here to Email Lowend     
In theory the engine with a longer rod will always make more power than an engine with shorter rods. This has to do with piston dwell @ TDC, and sideloading pistons on the cylinder bores.
In the real world (espically on a street motor) rod length dosen't make all that much difference in power output. However a long rod motor will generally last longer.
The thing about a 6" rod 383 that makes me nervous is the piston pin location - in the oil ring. This fear is unfounded (in fact I'm building a 6" rod 383 right now), this has been done for years without problems. The piston just looks a little funny at a glance.
The only real advantage a 5.7" rod presents is that you can use your stock rods. After refinishing your stockers the savings isn't that much over buying new rods.

Since the cost of a 5.7" rod and 6" rod 383 are essentally the same I would recomend a 6" rod setup.

I would also suggest having the engine internally balanced. But thats another post.

------------------
1971 Camaro
350 / M21 4spd
12" brakes
16x10" Wheels
Autocross competitive
'83 VW GTI FSP for daily driver
Sales / Tech - The Speed Merchant, San Jose, CA
1-800-994-0930
http://www.speedmerchant.com/


Mr_Metal
Veteran Member
posted May 14, 2002 01:04 PM     Click Here to See the Profile for Mr_Metal   Click Here to Email Mr_Metal     
Thanks Lowend
I'm DEFINITELY w/out a doubt getting the entire rotating assembly internally balanced, checked for cracks, etc.

6" rods seem to be the right choice.
Thx again !!


MR71RS
Veteran Member
posted May 14, 2002 04:11 PM     Click Here to See the Profile for MR71RS   Click Here to Email MR71RS     
I`d keep an eye on your clearance`s.And a longer stroke draws in more fuel and air mix. I`d stay away from a overly high lift cam. I`d invest in some racing pistons,with a short skirt.And balance every thing...


Mr_Metal
Veteran Member
posted May 14, 2002 05:42 PM     Click Here to See the Profile for Mr_Metal   Click Here to Email Mr_Metal     
MR71RS
Thanks for the reply ... a buddy of mine has an IHRA alcohol funny car that I turn wrench on and crew member for ... he's got a bunch of decent suppliers for "racing" applications.
I want to do this right the first time ... I appreciate the advice.
Thx


BluEyes
Veteran Member
posted May 15, 2002 07:52 PM     Click Here to See the Profile for BluEyes   Click Here to Email BluEyes     
Here's all the reason I'd need to run a 6" rod...

Piston for 5.7" rod - 505g
Piston for 6.0" rod - 425g
(these are both KB hyper pistons, 1/16" rings, 10.9:1 w/ 64cc heads)

A 6" rod only weighs 10-20g more than a 5.7" rod.

80g less in the piston means a LOT less stress on the rod bolts at high rpm, and 60-70g less per piston/rod makes for a much lighter assembley - rev faster, easier on the crank, easier to balance, etc...

Also, a 6" rod will be easier on piston skirt/crank counterweight clearance. BUT, it will probably make rod/cam clearance a bit tighter...

Mr_Metal
Veteran Member
posted May 16, 2002 01:20 AM     Click Here to See the Profile for Mr_Metal   Click Here to Email Mr_Metal     
BluEyes
That's a good point on the weight of the rotating assembly.
6" is what I have decided on, after much consideration and help from members here at the SGCOG.
Thx for the input.


Lowend
Administrator
posted May 16, 2002 01:55 AM     Click Here to See the Profile for Lowend   Click Here to Email Lowend     
email me, I have a smokin deal on 383 rotating assys right now


Racer1283
Veteran Member
posted May 16, 2002 09:11 AM     Click Here to See the Profile for Racer1283   Click Here to Email Racer1283     
I agree with Lowend. In my opinion, unless you're looking for the last 3 or 4 horsepower in a serious race engine, six inch rods aren't worth the expense.

------------------
Mike Wozniak
'79 Z28
485HP/482ftlb, 383
11.81@114.88
All Throttle, no bottle.
Life is hard, life is even harder when you're stupid.


Mr_Metal
Veteran Member
posted May 16, 2002 12:02 PM     Click Here to See the Profile for Mr_Metal   Click Here to Email Mr_Metal     
Thanks for all the replies ALL !!!
I'm going with a 6" rod setup.
Anyone have rods/pistons for this set-up for sale??


BluEyes
Veteran Member
posted May 17, 2002 11:28 PM     Click Here to See the Profile for BluEyes   Click Here to Email BluEyes     
quote:
Originally posted by Racer1283:
unless you're looking for the last 3 or 4 horsepower in a serious race engine, six inch rods aren't worth the expense.

if you're looking at just for power, I agree. I'd do it for the weight savings, regardless of power. Lighter weight makes for less stress on the engine, and quicker engine response. You might not be any faster, but it'll be more fun...

Mr_Metal - e-mail Lowend, I think he's got a setup for you.

Marv Davis
Moderator
posted May 18, 2002 12:38 PM     Click Here to See the Profile for Marv Davis   Click Here to Email Marv Davis     
I think your making a good choice Mr_Metal if there are "faster faster faster" aspirations anywhere in all this. BUT... I 100% have to agree with Lowend,, on the street I sincerely doubt you will feel one bit of 'butt-o-meter' difference between the 5.7 or a longer rod.

Big thing being the cost is nearly the same when you are building a motor from the ground up like this. Cost is more a function of the quality of parts you choose,, rather than the size. Point I'm getting at is the short block will cost about the same if your building for the future... SRP pistons for 5.7 rod cost the same as for 6" rods, Eagle H beam rods cost about the same,,, 5.7 or 6". Balancing is going to be the same (within like components,,, internal / external balancing). So WHY NOT if you are looking to step the output up sometime in the future!

I believe it's lost now, but some time ago there was a very good discussion on the effects of the longer rod on intake and exhaust flow. If your looking to make the best of what your building,,, You've got to consider the effects of that dwell at TDC and BDC... the effects of the longer rod on piston acceleration / decelleration, at what point will the long rod motor reach peak vacuum signal vs. intake duration and centerline. One part of that conversation was the 'rate of compression' through the last few crank degrees of the compression stroke. The slower 'rate of compression' as the piston nears TDC can go a long ways in fighting off detonation with a pump gas motor.

One place you do add additional headaches is in clearance between the longer rods and other components. Don't be too surprised to need a small base circle cam (although probably not with the small cam you listed), a little more grinding on the bottom of the bores and inside face of the block depending on who's rods you choose. Piston stability at TDC is also a consideration. With the raised pin location a loose bore will show more leakdown (blowby) than more standard pin configurations. Possibly because pistons intended for a long rod / stroker application generally take a thinner ring than a more standard package. I don't mean to make this all sound more complicated than it really is, but be aware that there are other factors at play here other than just rod length.

Myself, I would more look at the expected output of the motor (and possible future changes) and use that as a guidline more than anything else. With the head / cam package you listed I really would be hard pressed to justify the 6" rod. Once your expectations exceed 400-450 horse then it justifies the high dollar / high quality components. But with mildly ported stock heads and a 260H cam,,, I think I'd recondition a set of stock 5.7 rods and clerarance the shoulders, pick up a set of TRW L2491 flat top pistons, use a nodular iron crank, zero deck the motor and have a good external balance job done. With the cam you listed I just don't see the RPM/power potential that would push me towards much more. With the $'s I saved on the rotating assembly I'd put that towards a decent set of heads. But that's just me. It's your money and you should build it the way YOU want.

I'm running two 383's right now. One in my drag car with 6" rods, the other is on the street and strip with 5.7 rods. The two motors have a similar configurtion. Both are AFR 210 heads (CNC package on the strip, Race ready on the street/strip). Both run a SuperVic intake (4500 flange on the track, 4150 on the street), Both are roller cam motors, with hydraulic roller on the street, solid roller for the track. Both are a flat top piston / zero deck with chambers that make 10.5:1 on the street and 12.6:1 for the strip motor. Both make more torque than the chassis can effectively use. There is night and day diffence between the two motors but it has NOTHING to do with the rod length.

Just some thoughts to consider.

Racer1283
Veteran Member
posted May 18, 2002 12:56 PM     Click Here to See the Profile for Racer1283   Click Here to Email Racer1283     
Blueyes, how the heck are 6 inch rods ever going to be lighter than 5.7 rods if they're made of the same material?


This topic is 3 pages long: 1  2  3 

All times are ET (US)

This is an ARCHIVED topic. You may not reply to it!
Hop to:

Contact Us | Second Generation Camaro Owners Group

Copyright 1997 - 2003 North Georgia Classic Camaro


Ultimate Bulletin Board 5.47e