BBC Connecting Rod Question - Chevelle Tech
Performance Our High Performance area

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
post #1 of 19 (permalink) Old Nov 19th, 09, 3:46 PM Thread Starter
Lifetime Premium Member
Dan
 
Join Date: Aug 2007
Location: orange county
Posts: 8,483
BBC Connecting Rod Question

Chevy produced several Rods for the Big Block. The two in question follow; How do the "thumb" truck rods compare in strength to the dimple rods used on the LS6&7? Realizing the rod bolts are 3/8 and 7/16 respectively. Thanks, Dan
Stokerboats is online now  
Sponsored Links
Advertisement
 
post #2 of 19 (permalink) Old Nov 19th, 09, 5:56 PM
Tech Team
paul
 
Join Date: Jul 2001
Location: LOXAHATCHEE FLA U.S.A.
Posts: 804
Re: BBC Connecting Rod Question

the typical stock chevy rods weak point is the rod bolts that may stretch or caps, held by the rod bolts, the BETTER ARP rod bolts (L19 )are typically at a minimum 50%-100% stronger,than the stock bolts, if the same diam. is used, going from a 3/8" diam. to a 7/16" diam. adds about a 18% additional cross sectional area, significantly adding to the strength, but its rather silly to refurbish the stock 3/8" bolt BBC rods, in my experiences building BBC engines ,when there are far stronger aftermarket rods already built with ARP cap screw rod bolts and made from 4340 forged steel that cost about the same as all the work typically costs to bush,the small ends, refurbish,the rods,add ARP fasteners, polish, balance those rods and still have an inferior, and weaker rod.


http://www.adperformance.com/index.p...78642e07cca44d

" IF YOU CAN,T SMOKE THE TIRES FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"
GRUMPYVETTE is offline  
post #3 of 19 (permalink) Old Nov 19th, 09, 7:48 PM
Tech Team
Bryon
 
Join Date: Apr 2005
Location: Nebraska
Posts: 942
Re: BBC Connecting Rod Question

Dan,

You can go to this "sticky" for more information. I think there is something in there about that.

BBC Info.

Stock rods are OK for normal/stock use. Once you get to higher performance, aftermarket rods are probably needed. Thumb rods probably are not as strong as the dimple rods, and the dimple rods are not as strong as aftermarket rods - in most cases.

But like Paul said, the price on the aftermarket rods is so reasonable now, sometimes it doesn't make sense to recondition old rods.

Red 1967 Chevelle SS 396, 4 speed, 3.31 12 bolt posi, black bench seat interior, Bolero Red - long term restoration project
68 Camaro SS - 468 BBC, 781 heads, RPM Air Gap intake, Lakewood bellhousing, M21, BO coded 12 bolt - but 3.31 posi now. Old drag car, back on the street.

Last edited by bcmiller; Nov 19th, 09 at 10:09 PM.
bcmiller is offline  
post #4 of 19 (permalink) Old Nov 20th, 09, 1:03 AM Thread Starter
Lifetime Premium Member
Dan
 
Join Date: Aug 2007
Location: orange county
Posts: 8,483
Re: BBC Connecting Rod Question

Thanks for the replies. I'm fully aware of the fact that some aftermarket rods are a better choice than the chevy stuff but that being said years went by where chevy was the choice. It is not always the case that aftermarket rods are better and it is not always the case that resizing and upgrading rod bolts is neccessarily a bad thing. I've seen some pretty heavy abuse on factory rods (nitrous runs included) without an issue of reliability. Are high quality aftermarket rods better? YES but cheap chinese stuff isn't always what it is advertised to be.
Stokerboats is online now  
post #5 of 19 (permalink) Old Nov 20th, 09, 1:13 AM
Senior Tech Team
 
Join Date: Mar 2004
Location: Oologah, Ok.
Posts: 6,248
Re: BBC Connecting Rod Question

I've never broken a Chevy "high performance" rod, ever. I've seen lots of aftermarket rods break, mostly rod bolt failures. The lesser Chevy rods aren't nearly as strong, but all the high performance rods are very strong. I knew an old time Chevy racer state that the 3/8" rods were stronger than the 7/16" rods because there was more material in the weakest part of the rod than the bigger bolt ones where the bolt passed through.
Harold Sutton is offline  
post #6 of 19 (permalink) Old Nov 20th, 09, 5:46 AM
Lifetime Premium Member
Darren
 
Join Date: Oct 2000
Location: Indianapolis IN
Posts: 3,018
Re: BBC Connecting Rod Question

What material (4340??) are Chevy rods? Are all OEM rods made from the same material?

Darren
1971 Chevelle
496
CFM Ported Stage 5 Brodix Race-Rites 310cc
10.5 scr
Ultradyne Solid Roller 256/264 .660/.660 108 lsa
CFM Ported Victor Jr / Pro Systems HP1000
T-56 Magnum 6 Speed, DFX
12 Bolt TrueTrac, 4.56 gear 33 spline Mosier axles
30x12.5 ET Street Radial
525++ rwhp
http://www.chevelles.com/showroom/da...0930-00149.jpg
http://www.chevelles.com/showroom/da...m/Vic_Jr_1.JPG
71454Chevelle is offline  
post #7 of 19 (permalink) Old Nov 20th, 09, 6:35 AM
Lifetime Premium Member
Randy
 
Join Date: Sep 2003
Location: Dallas, Mexas
Posts: 1,700
Re: BBC Connecting Rod Question

If I'm redoing stock rods, I use these. http://www.summitracing.com/parts/AR...1/?image=large

These are sooooo much better than rod bolts with a knurled shank, and easier on the rod bolt bore.

That being said, till you add the price of these bolts and the cost of resizing, straightening, and balancing a set of stock rods, the best value out there, IMO, is these. http://www.summitracing.com/parts/SC...6/?image=large

You can buy these from Flatlander Racing for $299.00. Well worth the price, as these are really nice, stout rods. http://www.flatlanderracing.com/


Randy

'66 Chevelle SS396 L-78 M-20 4-speed 4.10 posi Black-on-Black numbers matching (SOLD!)
'67 Cutlass with a 540
'67 Camaro (SOLD)
'65 Biscayne 2-dr post (kind of a BIG Chevelle)
Vega S/G (For Sale with REAL nice 18 degree SB motor parts and a 9.40 350 in it.)
several Olds 442's (funny lookin' Chevelles) (2 sold)
ToyzRMe is offline  
post #8 of 19 (permalink) Old Nov 20th, 09, 7:28 AM
Lifetime Premium Member
 
Join Date: Dec 2004
Location: woodbine, md
Posts: 6,780
Re: BBC Connecting Rod Question

when i built my "budget" 496, i used a cast Scat crank, stock truck rods, and Wiesco pistons designed for the stock rod length-i decided on the truck rods because i had them and fig in the price of rebuild and new bolts comp. to aftermarket
even if i bought cheap aftremarket, i would still need them ck'ed to be safe
the 7/16 BB rods seemed to vary a lot, right at the part line, you could almost see the bolt on some, part of the reason some fav. the truck rods with 3/8" bolts
on the average performance engine, if built right, i dont think you would see a rod problem
i ran truck rods on a blown 454 for 8 years, a few 1/4 passes every year, nothing really high dollar, they were perfect when the engine was pulled apart
In todays world, esp street stuff, there is a lot of over kill on parts, not a bad thing, but
you can get by with less

when your credit cards are maxed, have the limits raised
forcd ind is offline  
post #9 of 19 (permalink) Old Nov 20th, 09, 7:56 AM
Senior Tech Team
 
Join Date: Dec 1998
Location: Lubbock, TX
Posts: 3,811
Re: BBC Connecting Rod Question

Quote:
Originally Posted by Harold Sutton View Post
I knew an old time Chevy racer state that the 3/8" rods were stronger than the 7/16" rods because there was more material in the weakest part of the rod than the bigger bolt ones where the bolt passed through.
I've heard the same thing several times from many racers. In addition, there are a lot of 454's with stock truck rods with stock bolts going thru the traps at 6500rpm's and higher and a lot do it for a few years. Some of 'em are connected to TRW Forged Bricks that weigh a ton! The biggest favor you can do for your rods and bolts is run lighter pistons.

I THINK that Chevy rods are 5140 steel but I'm not sure. I am sure they're not 4340.

Gary Adrian
The correct spelling is
HILLIARY
Busted Knuckles is offline  
post #10 of 19 (permalink) Old Nov 20th, 09, 8:00 AM
Lifetime Premium Member
Dave
 
Join Date: Jan 2006
Location: Maryland
Posts: 1,378
Re: BBC Connecting Rod Question

GM forged rods are 4340.

19170198
Forged Steel Connecting Rod


Magnafluxed 4340 steel with heavy-duty 7/16
" bolts
Machined for pressed piston pins and color-coded white
Used in Gen V 454 and 502 engines
6.135


" c-c length
Use rod bearing P/N 12329715

http://www.summitracing.com/parts/NA...2/?image=large

Attached Thumbnails
Click image for larger version

Name:	10198922.jpg
Views:	485
Size:	19.7 KB
ID:	24741  

TC# 3439
MCC# 742
ACES# 7415
1968 SS396 138 code 408/M20/3.73 Truetrac
Showroom
68chvlss396 is offline  
post #11 of 19 (permalink) Old Nov 20th, 09, 9:29 AM
Tech Team
Bryon
 
Join Date: Apr 2005
Location: Nebraska
Posts: 942
Re: BBC Connecting Rod Question

Dave thanks for that information on the 4340 steel rods. Those are GEN V rods. Do you know if the rods used in the late 60s and through the 70s were the same composition?

Red 1967 Chevelle SS 396, 4 speed, 3.31 12 bolt posi, black bench seat interior, Bolero Red - long term restoration project
68 Camaro SS - 468 BBC, 781 heads, RPM Air Gap intake, Lakewood bellhousing, M21, BO coded 12 bolt - but 3.31 posi now. Old drag car, back on the street.
bcmiller is offline  
post #12 of 19 (permalink) Old Nov 20th, 09, 10:05 AM
Lifetime Premium Member
Dave
 
Join Date: Jan 2006
Location: Maryland
Posts: 1,378
Re: BBC Connecting Rod Question

Bryon, The LS6 and LS7 crate engines built on the MKIV blocks back in the 70's and 80's used the 7/16 dimple rod for pressed fit pins PN/3963552 and they were 4340 forged steel. I would imagine that all HP dimple rods regardless of 3/8's or 7/16's bolts are the same.

TC# 3439
MCC# 742
ACES# 7415
1968 SS396 138 code 408/M20/3.73 Truetrac
Showroom
68chvlss396 is offline  
post #13 of 19 (permalink) Old Nov 20th, 09, 10:13 AM
Tech Team
 
Join Date: Mar 2002
Location: Somerset, KY
Posts: 392
Garage
Re: BBC Connecting Rod Question

I have a buddy who has run 9.90's for years in a bracket car, 468 with 3/8" truck rods and TRW pistons, shifting as high as 7200 rpm. Never had any kind of rotating assembly problems. He simply replaces the bearings every couple of years and that is it.
I have run 3/8" truck rods in every motor I have built. Always use ARP bolts. No problems whatsoever.
SILVERSS454 is offline  
post #14 of 19 (permalink) Old Nov 20th, 09, 11:22 AM
Tech Team
Bryon
 
Join Date: Apr 2005
Location: Nebraska
Posts: 942
Re: BBC Connecting Rod Question

Quote:
Originally Posted by 68chvlss396 View Post
Bryon, The LS6 and LS7 crate engines built on the MKIV blocks back in the 70's and 80's used the 7/16 dimple rod for pressed fit pins PN/3963552 and they were 4340 forged steel. I would imagine that all HP dimple rods regardless of 3/8's or 7/16's bolts are the same.
Thanks Dave. I really appreciate that information.

Red 1967 Chevelle SS 396, 4 speed, 3.31 12 bolt posi, black bench seat interior, Bolero Red - long term restoration project
68 Camaro SS - 468 BBC, 781 heads, RPM Air Gap intake, Lakewood bellhousing, M21, BO coded 12 bolt - but 3.31 posi now. Old drag car, back on the street.
bcmiller is offline  
post #15 of 19 (permalink) Old Nov 20th, 09, 11:46 AM
Tech Team
 
Join Date: Apr 2001
Location: Kansas
Posts: 564
Re: BBC Connecting Rod Question

Quote:
Originally Posted by 68chvlss396 View Post
GM forged rods are 4340.

19170198
Forged Steel Connecting Rod


Magnafluxed 4340 steel with heavy-duty 7/16
" bolts
Machined for pressed piston pins and color-coded white
Used in Gen V 454 and 502 engines
6.135


" c-c length
Use rod bearing P/N 12329715

http://www.summitracing.com/parts/NA...2/?image=large



$118 a piece holly crap
Darracq is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Chevelle Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address. Note, you will be sent a confirmation request to this address.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools Search this Thread
Show Printable Version Show Printable Version
Email this Page Email this Page
Search this Thread:

Advanced Search
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome