Rod Weight For Engine Balance (1 Viewer)

[Pitter Patter]

tech question plus a parts ask (I know this is the wrong forum for the parts ask)

One of the many potentially excessive things I’m doing is balancing the engine. I found my rod+cap+new hardware to weigh in grams:
965
964 X 2
961
956
937

There’s no combo of pistons/wrist-pins offset that comes close to working and the rods IMO don’t have enough material to remove from the heavy ones to come down to range. Questions:

1. Anyone else experience this. If so…
2. What did you do?

The ask is:

1. Any member here in need of a couple of light weight rods in exchange for some of your heavy ones? They are in fantastic condition so I’d like to do a swap or purchase of something also in equally good condition. These are NLA from Toyota. Also open to any recommendations for where to find good quality used rods that someone will weigh before shipping.

Thanks!

 

[brian]

Does balance really matter on a 4k rpm motor?

 

[Mark Jennings]

Are you balancing for total weight or end weight?. I’d put the small end on an inverted ‘V block’ and see how close in weight the big ends are. Balance just the big end of the rod Then match/trim the piston for weight. And @brian is correct, unless you plan on extended hi revs, your balance is almost a nill effort. These engines make max torque at 2000 rpm…..this is where this engine comes alive. You need to make it pull form idle to 2000 rpm with WOT.

 

[Pitter Patter]

Does balance really matter on a 4k rpm motor?

Agreed. Not much, especially in a push-rod, I6 but that’s not the point. It’s disassembled, I’m doing this once I’m my short life, the cost of getting it perfectly balanced should be negligible, why not make it epic? People on this forum and beyond spend countless hours making their FJ40 as perfect as possible, why not make the engine as silky as possible?

 

[Pitter Patter]

Are you balancing for total weight or end weight?. I’d put the small end on an inverted ‘V block’ and see how close in weight the big ends are. Balance just the big end of the rod Then match/trim the piston for weight. And @brian is correct, unless you plan on extended hi revs, your balance is almost a nill effort. These engines make max torque at 2000 rpm…..this is where this engine comes alive. You need to make it pull form idle to 2000 rpm with WOT.

Right now I’m just looking at total weight. Then will adjust for weight on the cap vs the rod shaft. I need a reasonable starting position. One rod being 28 grams low is not a good starting position to match these up.

 

[Mark W]

With a good 260(ish) degree cam, a 2F will pull strong from 1k to 5-6K RPM. Many of us have built 200HP motors (several IH8Mudders have been dyno'd over 200 over the years. Operating a 2F as if 2000 rpm is the top of your range is just silly.

IMHO I can tell the difference in how a static balanced motor feels compared to one that has not been balanced.

Five of your rods look to be well withing parameters for matching. That one light one might make it tough however.

If you have not resolved the situation by the time breakup is over, I can probably lay hands on a couple of milk crates full of 2F rods. Right now the rigs they are in are snowed in more than I care to dig out still.

Mark...

 

[Mark Jennings]

At 5k RPM, that would require like 750 CFM of intake air. If you’re not running a 4 barrel on an Offy manifold, I doubt you’re making those HP numbers. The biggest issue with these stove bolt 6’s isn’t balance, e.g. rev’s to make HP, it’s getting enough air and fuel into the combustion chamber to make it. Unless you do extensive head work and open the intake, and exhaust, including whatever cam you think is effective, it’ll be difficult for the DYIer to make those numbers. The F and 2F are rated max torque at around 2000 RPM, you can shift that around a bit with a compression bump and a slight increase in lift, but until you attack the intake/exhaust flow issue, you’re HP is limited….

Be Good, Be Safe

 

[charliemeyer007]

Its burger king, have it your way. Good luck.

 

[Mark W]

At 5k RPM, that would require like 750 CFM of intake air. If you’re not running a 4 barrel on an Offy manifold, I doubt you’re making those HP numbers. The biggest issue with these stove bolt 6’s isn’t balance, e.g. rev’s to make HP, it’s getting enough air and fuel into the combustion chamber to make it. Unless you do extensive head work and open the intake, and exhaust, including whatever cam you think is effective, it’ll be difficult for the DYIer to make those numbers. The F and 2F are rated max torque at around 2000 RPM, you can shift that around a bit with a compression bump and a slight increase in lift, but until you attack the intake/exhaust flow issue, you’re HP is limited….

Be Good, Be Safe

500 cfm Eldelbrock on a Clifford or Offy (C series or "dual plane") works just fine for 5000-5500 shift points. There are couple of Chevy intake/exhaust valves can easily be fitted to increase airflow a bit (but not much). The head design is the limiting factor, no doubt. So are the rod bolts unless you fit ARPs for chev big blocks (beyond 5 grand on OEM rod bolts is approaching the edge). 9.5 compression is easy to attain via a head mil, or (my favorite) a swap on a late model F head onto the 2F shortblock. I never saw much bottom end power loss from the 260* advertised duration compared to thr 250* sticks, so never use the shorter ones. The longer cam will keep pulling strong long after the rod bolts scream No More!

The 200 hp numbers I mention were all done by "DIYERs". The ones I have personal experience with were all excellent daily drivers and got better fuel economy than before the work was done.

Relatively recent 2FE builds discussed here on Mud have pushed over 200 hp... AT THE REAR WHEELS.

Moving up the scale a bit, one of our older members (a Kiwi who sadly has passed away) and another Aussie "mudder" (who has not passed ) both made north of 400HP from 2Fs a few years back. But they were turboed, intercooled, injected, running on race gas with custom pistons and rods and I do not even remember what else. NOT daily drivers. I saw a vid of the one from NZ running on the course. Sounded like the Devil's own sewing machine as it blasted by.

Mark...

 

[Pitter Patter]

Update: I called SOR, they have rods for sale at $81 each but refused to weigh them for me. The response was I just need to buy them and see what you get. I was about to offer to buy them a scale and ship it to them as a ‘gift with purchase’ in reverse but didn’t want to come off condescending a digital scale is all of $25 so… happy to donate that to SOR

Have a message into Man A Fre and waiting on a call back. Assuming they will have parts and hopefully they can produce a weight measurement.

I’ll also call Mosley tomorrow since they probably throw 2F rods in the bulk metal recycle bin.

 

[Pighead]

Update: I called SOR, they have rods for sale at $81 each but refused to weigh them for me. The response was I just need to buy them and see what you get. I was about to offer to buy them a scale and ship it to them as a ‘gift with purchase’ in reverse but didn’t want to come off condescending a digital scale is all of $25 so… happy to donate that to SOR

Have a message into Man A Fre and waiting on a call back. Assuming they will have parts and hopefully they can produce a weight measurement.

I’ll also call Mosley tomorrow since they probably throw 2F rods in the bulk metal recycle bin.

SOR and MAF are both pretty far down on my list of people to call looking for parts. For a connrod or two I might call Mark A. in Burbank, maybe Georg in Stockton or Mudrak, think he's in Napa or thereabouts.

 

[Pighead]

Agreed. Not much, especially in a push-rod, I6 but that’s not the point. It’s disassembled, I’m doing this once I’m my short life, the cost of getting it perfectly balanced should be negligible, why not make it epic? People on this forum and beyond spend countless hours making their FJ40 as perfect as possible, why not make the engine as silky as possible?

Yup, pretty much why I had mine balanced. That and I've always balanced the engines I've rebuilt. With the help of the best machine shop in town and 'Mud (I think Mark W. even chimed in on my build thread) I put together a pretty good engine. That was 20 years ago, I had it ready for the Surf'nTurf 2004. I have taken it to 5K RPM once or twice (jumping the sand dunes at SnT 2004) not so much anymore. It is still my daily driver, always has been. Once a year I drive the Rubithon. I did put the Late F head on an early 2F block (bored), RV cam, had a little head work done and drove it. It's just like a 2F but better a little tiny bit.
I do have a sneaking suspicion that a balance job helps the internal wear items last longer. I hate to jinx it by saying it, but I still have great oil pressure. Like new.
Funnily enough, just last week I took my head to the best machine shop in town for a valve job, and some more head work. Getting the chevy SS valves and stuff, matching the '69 intake manifold and head. I don't know if the '69 intake is better or worse that other years, I've heard arguments both ways, but it looks cool.

 

[Pitter Patter]

Closing the loop. Found a guy on eBay that had some for sale and was willing to weigh them. $70 each + shipping/tax. Showed up today and he was honest about the weight. Condition seems fine but they will be tweaked as necessary.

Now back to body work

 

[charliemeyer007]

Awesome. I have had really good luck with ebay seller's for the most part. Hope your build goes as planed.