116E rods in Lotus Twin Cam

[garrathj]

Hi All,
I'm rebuilding a TC engine and it currently has 116e rods in it.

I know that 125e rods are preferred but I was wondering if these are ok for a standard build? The engine will see light use, certainly not pushing any limits.

I would look to update the bolts to ARP if this was doable.

I looked at some aftermarket rods as well but they are slightly longer so I'm a little concerned that they may push the standard pistons too high.

Any thoughts would be appreciated.

[h20hamelan]

viewtopic.php?f=39&t=44118

[Billmack]

Looking at the odds, if you build one engine in your garage chances are in favor of you getting away with it. If you are in business building engines and build quite a few you chances of getting bit are much higher and the profit margins are low enough that you will have to stand behind the failed one and build a few more before your bank balance gets back to zero. Hence I don't take too many chances. A set of 125 e rods is not that expensive and magnaflux inspection of them by a reputable firm is needless to say a must.

[benymazz]

My view is that if you drive your Elan mildly and never push it above redline, 116E rods are satisfactory. But you really, really, really, really should use uprated bolts.

Personally, I have only ever built engines with 125E rods.

I am currently working on a final report for my engineering materials science course at college that examines the 116E connecting rod assembly more closely and (hopefully) numerically defines what the weak link is, and to what engine speed they are safe to. I'll hopefully have it finished and publish it here at the end of the term (in about 6 weeks). Stay tuned.

-Ben

[garrathj]

Thanks for the replies all, I don't have a desire to take a risk, just given the planned use I thought they may be a reasonable option with new bolts. Getting 125e rods isn't that easy.

I had seen the topic on the rod lengths, if I have room to do that I may just go after market but depends on how much the block has been skimmed.

Cheers

[benymazz]

Thanks for the replies all, I don't have a desire to take a risk, just given the planned use I thought they may be a reasonable option with new bolts. Getting 125e rods isn't that easy.

I had seen the topic on the rod lengths, if I have room to do that I may just go after market but depends on how much the block has been skimmed.

Cheers

Depends on your use case. If it is for a stock, roadgoing car, I'd say that yes, with ARP bolts (if available, I do not know if they make them, I would think so) the 116E rods will do okay. The stock bolts are definitely the weak link, not the rod itself.

Also a viable option are the Maxspeeding rods on eBay. They are certainly better than a 116E rod and likely stronger than a non treated 125E rod. For the price point they are a very good option. I'm sure some members on here have a set of 125E rods that they could offload. I would be one of them but I still think I may need them one day

Also, while magnafluxing rods is definitely a good idea it will only reveal surface cracks which in a connecting rod will likely spell imminent failure the next time it's pushed near or beyond redline. Most (all?) failures end as a fracture, which is the result of a crack, but start due to fatigue which is a subtle rearrangement of the individual crystal grains in the metal's crystal structure. There is no way that I know of to identify this other than x-ray diffraction analysis of the metal.

-Ben

[garrathj]

Thanks Ben,
Yes, would definitely go with ARP bolts, I think these are the ones.
https://arp-bolts.com/kits/arpkit-detai ... cordID=797

I've been looking at the maxspeeding ones, I think they might be a good option in my case but I'll need to check the piston height.

Thanks

[SENC]

Bean has reconditioned 125E sets and Kelvedon has used 125E sets - or both did last week.

[garrathj]

I'm in Australia do it's not so easy unfortunately!

[Billmack]

The vast majority of cracks in things nucleate at the surface. Its why magnaflux is so popular and effective. Fatigue is certainly an issue especially in engines pushed to high rpm. The similar to twincam formula ford cranks are generally replaced every 3000 miles or so if the engine is run over 6800 often.

[h20hamelan]

Any recollection or idea what one should be paying for used 125e rods.
Looks like $300 for the ebay Chinese MaxSpeedIng. More like $600 for 125E.

Max seems to get very good ratings.

Bean price?
Kel price?

Kind Regards

[vstibbard]

I've purchased Maxspeeding rods in the past for warm rod going TC's and been pleased with them, minimal variation in end for end weight and overall weight, from memory ARP2000 bolts. I had 125E rods but by time I had the tested, balanced, new little ends, closed and honed it would have been twice the cost and they're now ~50+ years old!
I currently have a set of 5.23" long rods for the next build.

In the race engine I have DKE crank and Arrows rods, another DKE crank with Carillo rods.

Cheers

Vaughan

[Panda]

Hi Garrath, I'm in Sydney and have a set of rods which should suit. I'm open to silly offers

ring me at 0409 914455

Alan P

[garrathj]

Ok so I ended up getting a set of the Maxspeeding rods and have another question about the little end diameter.

Little end diameter according to the manuals should be 20.62/3 from what I can see.

Spec given on the Maxspeeding rods is as follows:

//Small end diameter: 20.62mm//

However, when I measured the diameter on the rods I got it is smaller at 20.40mm and the pin will not be able to fit obviously.

The new piston pin fits the old pistons and the old 116E rod small end just fine, just not the new rods.

Am I doing something wrong? I wouldn't have thought I would need to get it reamed to suit?

Cheers

[rgh0]

Am I interpreting correctly and are you saying the current piston wrist pins you have are 20.40mm versus the new rods small end at 20.62mm?

cheers
Rohan