We are currently running on the new domain and server: www.Speed-Talk.com

IMPORTANT: Update your bookmarks to https://www.speed-talk.com/forum/
(Right-click the URL and select "Bookmark this link")

Lighten an I - beam rod

General engine tech -- Drag Racing to Circle Track

Moderator: Team

Little Mouse
Expert
Expert
Posts: 591
Joined: Mon Oct 21, 2013 8:48 pm
Location:

Lighten an I - beam rod

Post by Little Mouse » Mon Mar 16, 2020 2:25 pm

If you were to try and lighten an I- beam rod where would you remove the metal. Say the manufacture claims it can handle 1000 hp at high rpm, you still want to do high rpm but make 525 hp with no boost or Nos ever used, the piston, pin, rings all very light. sbc manufacture weight 680 grams. Drill holes down the length of the rod ( naw just kidding ).

rebelrouser
HotPass
HotPass
Posts: 1026
Joined: Tue Sep 15, 2015 2:25 pm
Location:

Re: Lighten an I - beam rod

Post by rebelrouser » Mon Mar 16, 2020 3:13 pm

I have only been brave enough to polish the beams on stock rods. Rods are relatively cheap for the damage they can do. I have been drag racing since 1974 and have only lost two engines, both broke rods.

https://benthamopen.com/contents/pdf/TO ... J-7-14.pdf check out some of the science.

miniv8
Expert
Expert
Posts: 654
Joined: Mon Sep 11, 2006 5:22 pm
Location: ICELAND

Re: Lighten an I - beam rod

Post by miniv8 » Mon Mar 16, 2020 3:16 pm

On a stock I beam rod I grind down the casting flaws on the sides, and sand it smooth.
The weight reduction is not worth all the work, but I feel the rod might be less likely to develop a outward stress outlet from the structure.

I am sure most aftermarket I-beam rods could very well be run in a lower power application with four or five holes in them. Nobody would be able to sell them, but I am sure they would be strong enough.

Adding holes after final production might not be a good idea though, and a computer load stress analysis for hole size and placement would be fun to see.

PackardV8
Guru
Guru
Posts: 6052
Joined: Sun Jul 30, 2006 2:03 pm
Location:

Re: Lighten an I - beam rod

Post by PackardV8 » Mon Mar 16, 2020 5:29 pm

Little Mouse wrote:
Mon Mar 16, 2020 2:25 pm
If you were to try and lighten an I- beam rod where would you remove the metal. Say the manufacture claims it can handle 1000 hp at high rpm, you still want to do high rpm but make 525 hp with no boost or Nos ever used, the piston, pin, rings all very light. sbc manufacture weight 680 grams. Drill holes down the length of the rod ( naw just kidding ).
In your case, I wouldn't. Inertial force generated from RPM is the greater enemy of rods and you'll still have the full meal deal of those. Rods are tremendously strong in compression and can usually handle boost or NOS.
Jack Vines
Studebaker-Packard V8 Limited
Obsolete Engineering

DeezNutz
New Member
New Member
Posts: 7
Joined: Wed Aug 22, 2018 10:48 am
Location:

Re: Lighten an I - beam rod

Post by DeezNutz » Mon Mar 16, 2020 5:59 pm

Start by taking it off the typical balance areas, cap and pin end... beyond that it will get much more interesting.

Charliesauto
Pro
Pro
Posts: 226
Joined: Wed Sep 03, 2014 2:01 am
Location:

Re: Lighten an I - beam rod

Post by Charliesauto » Mon Mar 16, 2020 6:21 pm

Little Mouse wrote:
Mon Mar 16, 2020 2:25 pm
If you were to try and lighten an I- beam rod where would you remove the metal. Say the manufacture claims it can handle 1000 hp at high rpm, you still want to do high rpm but make 525 hp with no boost or Nos ever used, the piston, pin, rings all very light. sbc manufacture weight 680 grams. Drill holes down the length of the rod ( naw just kidding ).
Why do you want to lighten the rods? Unless you are having trouble balancing the crank and need a lighter bobweight, there is little or nothing to be gained by lightening the rods.

Little Mouse
Expert
Expert
Posts: 591
Joined: Mon Oct 21, 2013 8:48 pm
Location:

Re: Lighten an I - beam rod

Post by Little Mouse » Mon Mar 16, 2020 7:27 pm

I have a set of K1 rods I'm almost sure I will end up using there 6.250 long , 507 grams. Scary to look at them when I first got them. Howard's makes a new I- beam rod 6.50 long 680 grams. Have decided will do 3.00 stroke that long of rod could be used with 1.00 CH pistons. I would have to get a gram scale, then something to weigh the big end and small end of the rod, stuff shops have. Then I guess you could take a mic measure as you go. Be a hell of a long hour job to get it all right. I was thinking up above the curve of the big end and a ways below the pin end. Maybe take some off the length of the outside and some down the center. To me there's no such thing as to light of reciprocating weight as long as its strong enough.

bigfoot
Member
Member
Posts: 164
Joined: Thu Mar 22, 2012 9:45 pm
Location:

Re: Lighten an I - beam rod

Post by bigfoot » Mon Mar 16, 2020 8:05 pm

What are those 6.250 K1 rods worth ??

1972ho
Expert
Expert
Posts: 796
Joined: Thu Nov 21, 2013 12:52 am
Location:

Re: Lighten an I - beam rod

Post by 1972ho » Mon Mar 16, 2020 8:28 pm

This is video of a shop lightening a connecting rod

exhaustgases
Guru
Guru
Posts: 6786
Joined: Sun Oct 06, 2013 9:03 pm
Location:

Re: Lighten an I - beam rod

Post by exhaustgases » Mon Mar 16, 2020 9:31 pm

Aren't I beam rods always lighter than H beam?

Little Mouse
Expert
Expert
Posts: 591
Joined: Mon Oct 21, 2013 8:48 pm
Location:

Re: Lighten an I - beam rod

Post by Little Mouse » Mon Mar 16, 2020 10:11 pm

bigfoot wrote:
Mon Mar 16, 2020 8:05 pm
What are those 6.250 K1 rods worth ??
They still sell them I bought mine $100.00 cheaper then the $654 they have been selling them for still today. I'm going to use them I believe they will do what I need to be done. Was more interested in if I were crazy to try to think you could lighten rods or not. If those 6.50 rods were more like 570, 580 grams would want them. I hate heavy stuff but rod strength or the bolts not really best place to cut any corners. But a 3.00 inch stroke is easier on rods along with them being longer to even help a little more on rod angle. If you look at high rpm high stressed motorcycles they tend to have a long rod in them. Just think for endurance not drag racing a longer rod better way to go.

Krooser
HotPass
HotPass
Posts: 1618
Joined: Wed Jul 31, 2013 10:14 pm
Location: Tropical Wisconsin

Re: Lighten an I - beam rod

Post by Krooser » Mon Mar 16, 2020 10:44 pm

I like his videos although I don't think he has made any in the last few years.
Luxemburg Speedway Hall of Fame Member Class of 2019

econo racer
Expert
Expert
Posts: 554
Joined: Mon Nov 26, 2007 11:44 pm
Location:

Re: Lighten an I - beam rod

Post by econo racer » Tue Mar 17, 2020 5:25 am

Sometimes I think me and little mouse outta have a 302 chevy contest. :lol: Those Hi RPM's were addicting weren't they
mouse :D

Jeff Lee
HotPass
HotPass
Posts: 339
Joined: Sun Jun 26, 2011 1:20 am
Location: Anthem / Phoenix Arizona

Re: Lighten an I - beam rod

Post by Jeff Lee » Tue Mar 17, 2020 5:59 am

I like that video. On you SBC rod, the BE is .940” wide. If you went to a NASCAR wrist pin guided rod, I believe they then narrow the BE of the rod to somewhere around .720” wide with the beam centered equal distance from each end of the BE. Then the bearing width is also reduced.
You can buy new pistons manufactured to proper SE width clearance, or, using your old pistons, fab an aluminum spacer w/ thrust bearings so the SE of the rod only has .0015” - .002” clearance (per side). You can still grind and smooth the sides of the beams, caps and outside radius of SE of an aftermarket I-Beam rod. I would bet the end results of bearing and rod weight would be significantly lighter.
NHRA SS/H
1970 AMX
390 4-speed
Advanced Clutches
Red Line Racing Cams

burdickjp
Member
Member
Posts: 162
Joined: Sat Jul 09, 2011 10:22 pm
Location:

Re: Lighten an I - beam rod

Post by burdickjp » Tue Mar 17, 2020 3:47 pm

I'm a bit surprised at how thin he's going in that video, and that there's not a larger fillet between the perpendicular faces.
I've not done this, and he has. I trust that it's sufficient.

Post Reply