Dave W.

Just a quick thought, I prefer the larger surface area of the original SBC pin diameter. Weight doesn't change much, the smaller pin saves roughly 15 grams. I didn't look into the cost difference. The Eagle rods have plenty of material in the small end, there's no need to worry about weakening it by boring it out to 23.5mm. I compared the amount of material of Eagle rods small end to other aftermarket rods and even after re-working it's still comparable to rods that are considered to be much stronger, and those rods can handle over 9k rpm. Just be aware that Eagle rods tend to reach their limits around 450 to 500 lb-ft of torque on most 4 cylinder platforms depending on the aggressiveness of the tune.



Twice as much fun!
Honestly I'd like to sort out the smaller details before I tackle another one.

Thanks, the suspension is M474 Koni's with 225 pound Ground Controls up front and 27mm rear torsion bars. It came with 25/18mm sways. Wheels are 19x8.5 up front, 19x10.5 out back. Tires are 235/35 front, 275/30 rear.
Here's a pic of my car in the staging lanes last year.

Dutch944

Nice stance! I see i need to lower my front end as well..

Chris White

What's the usual failure mode? The tensile stress on the rods at exhaust TDC 9k rpm is way more than the stress from the power stroke.

blown 944

In regards to the small end strength. In my initial build, I looked closely at other rods too. I found that it really wasn't removing much material (other than the bushing). That's about the only drawback to using the larger pin. However, I've never had any issues without the bushing, and my engine still floated perfectly. If I were starting from scratch for a 16 v, I'd probably just have custom pistons made. Otherwise, I like being able to get them off the shelf. Even going to this bigger bore, they were right off the shelf

Dave W.

The failures I've seen typically occur in the mid section of the rod. The broken rods all have a bend going in the same direction as the bent rods. It was pure luck that I caught that rod before anything bad happened. I just happened to have the head off the car to install O-rings in the block and I noticed one piston was .5mm lower than the others.

Tedro951

I really haven't looked at the material remaining, but I'm liking retaining of the bushing. I understand a bushing isn't mandatory, but I guess I'm too old school to comfortably delete it. DLC pins would make me feel better, but that drives the price up.

The only reason I'm thinking .866 is that at the PRI show, a JE engineer said they haven't announced it yet, but they will now make custom pistons in the SRP line. I like the alloy, but until recently, off the shelf was the only option on SRP.

Chris White

sounds like a compression related issue - what kind of ignition advance do you run on those engines? It may be that the peak combustion chamber pressure is too high for the rods.

blown 944

Check with Wiseco, I bought my current set from them and talkies about doing a custom piston. The turnaround wasn't too bad and price was good too. If hadn't already done the pin machining, I would have went with them.

refresh951

Dave,

I have been researching this and it seems guys are running 600+ rwhp all over the place with these rods without issue. What do you think specifically caused your issue? What kind of boost pressure? Rpm?

Dave W.

I consider it to be a safe limit. As Chris mentioned, a bending failure is related to peak cylinder pressure which is related to torque. As you know, an engine that's built to rev can make high HP with lower torque, but I haven't seen many engines that suffer from rpm related failures.

I'm not exactly sure what caused the issue with the Eagle rod in my DSM. It happened several years ago. That engine had been pushing 600AWHP/ 35psi of boost for a year, then I converted to E85 and began tuning on the new fuel at lower boost. I may have made a few mistakes in the learning process but the rod didn't fail catastrophically. Comp ratio was 9.0.

But my original point was that I believe the weak link in the Eagle rods is not the thinner small end. For example, Manley Turbo Tuff rods are considered to be much stronger than Eagles, despite using the same ARP rod bolts and having a thinner area above the pin hole. Luckily I had a set of each to compare.
My modified Eagle rods with 23.5mm pin bore have 0.156" of material at their thinnest point. Manley rods have 0.144" with a 22mm pin bore (stock EVO size). Both are the same width at the pin bore and have a similar profile, although there may be a difference in the quality of the material.

refresh951

Thanks for the response Dave. I did read that several years ago Eagle had a quality control issue that resulted in some failures and I wonder if maybe your failure was related to this. Definitely looks like a compression failure which would make believe somehow timing was radically off during high load. Have you seen similar failures on other engines in your shop? Still curious about max runnout on your crank. I love your approach, very cool build.

spencang

I'm currently gathering information on rebuilding my 91k engine. Where are you located?

pole position

Most of today's budget rods are made in China and then quality controlled in the US aka forged in the same foundry and farmed out with different brand names.

www.racingpartsmaximum.com is also a good source for rods.

Dave W.

oh dang, I forgot about my notes on runout, and today is Sat.
Yes I heard about that, too. I've seen a few other engines with Eagle rods and similar rods that had problems at similar TQ levels. I also noticed the appearance of Eagle forgings changed around 1.5 years ago.


I work in Hayward.

thanks for the tip!

mr965

Nice build. great info. Thanks for sharing the info.