broken con-rod

[srad750c]

Anyone broken a con-rod in a TRX 3.3 engine? It's been about 20-25 tanks of fuel after break-in. Last 10 tanks were with O'Donnell 30% racing fuel with an os A5 glow. It was about 55-60 degrees outside and I let the truck warm to 190 degrees before I took off. I started running got one good pass then the OS A5 glow died and then I switched to a dynamite platinum hot plug. Then about in about 60-90 seconds stopped running. No weird sounds or actions. Tried to start motor and easy start was jamming. Originally I thought this was the problem but after trouble shooting discovered it was con rod not the easy start. During the first 3-4 tanks of O'Donnell fuel runs there were a couple of times when temp got to the 290 mark when the fuel gets really low so I richened it up some never had any more heat problems. Is this abnormal for a con-rod to fail this soon? Did the new fuel, glow plug combination cause this failure. Or was it just time to fail?

 

[olds97_lss]

I wonder what the top of your piston looks like... to go from a cold plug to a hot plug with that high of nitro would cause detonation and more than like really early timing in general. Which means, the fuel was exploding as the piston was on the upstroke. A few minutes of that could have caused your issue.

The con-rod is split right up the middle which lends itself to way early fuel ignition as well.

Did you have an extra head shim to accommodate the higher than average nitro?

Most RTR engines are shimmed/timed to run 15-25% nitro with minimal adjustments (other than tuning). Going any lower or higher has a high likelihood of requiring a plug change and head shim change.

Higher nitro = more shims and cooler plug
Lower nitro = less shim and hotter plug

Although... after reading the 3.3 manual, it says the engine is fine for 10-33% with minor tune change only... odd that many other manufacturers say otherwise.

 

[srad750c]

piston looks good on top i think, traxxas top fuel is 33% what do you think? will add pic of the top of the piston, just some carbon build up, no dimple from burning still. smooth on top of piston.

 

[panpan]

Did you run in your engine well? Do you highly rev the car with its wheels off the ground?

 

[srad750c]

Did you run in your engine well? Do you highly rev the truck with its wheels off the ground?

Yeah took it easy for about the first 15 tanks, then I turned into a speed freak!!!! I have never ran the truck with wheels off the ground other than at idle for a short period. I always hold the brake even when I flip the truck over and have to run over to flip it back over. Are there any after market rods that are stronger yet light?

 

[bigredz71]

sure did !!

 

[flm_savage]

very nice carnage