Rod knock brand new 2.3

[DankDSM]

Hey everybody i need your help. I recently put together a new motor and i am trying to figure out why i got a rod nock on it on the first dyno pull. So here we go from the start.

Engine build consisted of eagle rods weisco pistons and rings. Used a CUT crank .25 under and topline bearings. Did everything by the book when constructing this thing, everything torqued to specs and done correctly. Oil changed at 9 miles and 200. Everything on this engine was new or replaced.
I broke in the motor for 476 miles when i am pulling onto the dyno and everything is running perfect. No problems whatsoever. I tell the guy tuneing it to stop if it peaked over 20 psi. So on the first pull he hit 22 psi and he lets off at about 4-5 grand. No problem. We notice it looked pig rich and he messes with the afc and i turn the boost down. Next pull it hits 18 psi and then drops down to 16 and he carries it to 7 grand. It is still running pig rich at over 5grand. After this pull the engine drops on itself and stalls. We go to start it back up and we hear the rod nock.

Pull the barings off the crank and they didnt spin but they are trashed.

So here are my thoughts on why it happend. A) The cheaper barrings in conjunction with the abusive nature of a 2.3 and the fact i didnt change the oil befoer the dyno tune caused the barrings to get trashed. B) Running it pig rich and the fact that i didnt change the spark plugs before the dyno tune maybe caused the engine to try and compress fuel and put a lot of stress on the barrings causing them to be trashed.

Any help you can provide would be useful. Also one of the main reasons why i ask is because i think the shop i took it to might of over richened the mixture to try and trash my motor. Me and the WELL KNOWN SHOP that everyone has heard of have been having arguments ever since they tryed to rip me off on my head.
Any help would be apreciated thanks

 

[andymoraitis]

Ouch! Sorry to hear that you have problems already.

You mentioned that the motor was pig rich. Do you have an exact reading of what the AFR's were at the time of failure? What kind of timing were you running? Also what were your oil pressure readings? Did you plastigauge the bearings during the assembly process? Were you on pump or race gas? Are you only tuning 780's with an AFC (hello crazy timing)?

I run an .025 undercut crank, shift at 7200 and run 28 psi on a conservative tune (11:1 A/F with 12 degrees of advance) so I don't think the problem is necessarily tuning unless something was way out whack with your timing. I'd point more towards an assembly/tolerance error.

Sorry about all the questions, but we'll need a more complete picture to get an idea of the cause.

 

[kspharris]

I bet it was the specs on the bearings and crank. Definatly plastigauge everything to make sure that you are in spec. There should be a guide in your manual. You could always have someone mic it but that may cost a little. Hope that you get it fixed and it didn't hurt anything to bad.

 

[DankDSM]

Ouch! Sorry to hear that you have problems already.

You mentioned that the motor was pig rich. Do you have an exact reading of what the AFR's were at the time of failure? What kind of timing were you running? Also what were your oil pressure readings? Did you plastigauge the bearings during the assembly process? Were you on pump or race gas? Are you only tuning 780's with an AFC (hello crazy timing)?

I run an .025 undercut crank, shift at 7200 and run 28 psi on a conservative tune (11:1 A/F with 12 degrees of advance) so I don't think the problem is necessarily tuning unless something was way out whack with your timing. I'd point more towards an assembly/tolerance error.

Sorry about all the questions, but we'll need a more complete picture to get an idea of the cause.

AFR ratios where well below 10:1 and the guy tuning it still went to 7 grand without letting off.
I was running Stock timing but the afc was probably retarding it.
Did not get to see an oil pressure reading and the guy tuning it said he didnt check it out either. Although it has had very good high oil pressure the whole 500ish mile break in.
I Dont think plastiguage was used during the assemly, but i heard that this doesnt have a proven positive effect. I have seen some seriouse race cars use plastiguage and still blow up.
I was on pump gas 93 octane
and yes i am using a 2g mas with an afc, but for my low throttle it is only at like -5% to -10%. My next upgrades are a shep trans and eprom ecu with either a chip for 780's or dsmlink. Do you think that the retarded timing could of cause undo stress and done this?

Also update on what happened and some more info to help figure this thing out. Cylinder number 2 had a spun bearing but the crank still looks good. I am switching over to a stock crank with stock sized bearings.
Also i bought this kit from a ex dsmer that i found in the classifieds add. He was getting out of dsm's and gave me everything he was going to use for his rebuild. This included a lot of extra stuff that was not for a 1g. So he could of supplied the wrong bearings. Could oversized bearings work on a non cut crank? and if so could that have been the problem?

Thanks for the help and your time

 

[keymaster]

So, you are running 780's with just an AFC, correct? Running an AFC will not retard your timing, but advances it quite a lot. Trying to run 780's with an AFC would totally explain your pig-rich condition though. You simply can't run injectors that big with just an AFC. Can't speak to the bearings, never dealt with that.

 

[perley03]

Before you start spending cash on dsmlink and a shep tranny, solve the bad bearing thing first. Get the crank and rods mic'd. Something is definatly wrong here because a bearing just won't spin on its own, some tolerances are definatly out of whack. I would recommend going to a high performance engine builder who builds boosted drag and race engines who knows his shit. You're going to be spending some serious cash here, but it's worth it. Don't go back to the guy who built it in the first place. Anyone who doesn't plastiguage there bearing journals is definatly asking for trouble. Tolerances are something not to be messed with. They need to be right in spec or stuff like this is going to happen. If your crank is bad, trash it and get a new one. Same with the rods. Good luck finding your problems and keep us posted, AND FIND A NEW BUILDER!!!

 

[DankDSM]

So, you are running 780's with just an AFC, correct? Running an AFC will not retard your timing, but advances it quite a lot. Trying to run 780's with an AFC would totally explain your pig-rich condition though. You simply can't run injectors that big with just an AFC. Can't speak to the bearings, never dealt with that.

This was untuned on the first dyno pull. There was plenty of room to lean out the fuel mixture on the afc.

Before you start spending cash on dsmlink and a shep tranny, solve the bad bearing thing first. Get the crank and rods mic'd. Something is definatly wrong here because a bearing just won't spin on its own, some tolerances are definatly out of whack. I would recommend going to a high performance engine builder who builds boosted drag and race engines who knows his shit. You're going to be spending some serious cash here, but it's worth it. Don't go back to the guy who built it in the first place. Anyone who doesn't plastiguage there bearing journals is definatly asking for trouble. Tolerances are something not to be messed with. They need to be right in spec or stuff like this is going to happen. If your crank is bad, trash it and get a new one. Same with the rods. Good luck finding your problems and keep us posted, AND FIND A NEW BUILDER!!!

only one rod was damaged and it was the one that had the spun barring. I have already purchased 1 new rod and a set of new rod and main barrings standard size. I am also going to replace the crank with a stock 2.4 crank instead of the one i am currently using even though it still looks good.
Is there a way to tell if the crank i was using was even cut? Because i was def using .25 oversized barrings.
Also can i possibly get a link to an article or two that deals with plastiguage and clearancing, more specifically how it is done?

Thanks for all the help and i really appreciate the advice so far.

P.S. Also my builder is one of my best friends who has plenty of experience rebuilding motors. He has done it plenty of times and never had any problems unless he was dealing with a cut crank. He has built a car exactly like mine except it had a stock crank and it dynoed at 450 to the wheels. He sold the car to someone on here and they still coresspond with him about how much they love the car. I think his only problem is that he is not to experienced with plastiguage or clearancing, so any advice on this subject would be greatly apreciated.
EDIT: He does know how to plastiguage he just didnt because it was sold as a kit

 

[perley03]

It's easy. Go to your local parts store, ask for a plastiguage kit. It comes with many strips and a "guage" to go by. Start off with the crank main journals. Do one at a time. Place the crank in the block, upside down, then put a stip of plastiguage in the main journal. Take the main cap (with the bearings installed, both on the cap and the journal on the block) and place it over the journal. Tighten the cap bolts to spec. Turn the crank over 1 complete revolution. Take the cap back off, and use the guage to determine the clearance. Its pretty accurate. Do this for all the main journals, then procede with the rods. Same idea as the rods, just don't turn the crank over. Write every journal down, record all clearance numbers. This needs to be very precise.
As far as determining if your crank has been cut, measure all journals in different places with a micrometer. This will tell you if your crank has been cut. Unfortuanatly i don't have my book here with me so i cannot tell you the diameter of the journals.
The 2.4L crank I BELIEVE has a longer stroke than a factory, so i don't think it would work unless you buy new pistons and rods. (Pistons and rods made for a 2.4L stroker because of lenght and clearance issues.) If anyone can help here, chip in and help this guy out. While you have the block all apart i would get it hot tanked and clean every galley out to get the old metal shavings out, including the head. THis will make a very reliable, powerful engine when you are done. Hopefully you will not be back in this situation when you are done. Good luck and keep us posted.

EDIT: Here is a link on how to use plastigage.
http://rpm-mustangs.com/articles/howto-plastigage.html

 

[DankDSM]

It's easy. Go to your local parts store, ask for a plastiguage kit. It comes with many strips and a "guage" to go by. Start off with the crank main journals. Do one at a time. Place the crank in the block, upside down, then put a stip of plastiguage in the main journal. Take the main cap (with the bearings installed, both on the cap and the journal on the block) and place it over the journal. Tighten the cap bolts to spec. Turn the crank over 1 complete revolution. Take the cap back off, and use the guage to determine the clearance. Its pretty accurate. Do this for all the main journals, then procede with the rods. Same idea as the rods, just don't turn the crank over. Write every journal down, record all clearance numbers. This needs to be very precise.
As far as determining if your crank has been cut, measure all journals in different places with a micrometer. This will tell you if your crank has been cut. Unfortuanatly i don't have my book here with me so i cannot tell you the diameter of the journals.
The 2.4L crank I BELIEVE has a longer stroke than a factory, so i don't think it would work unless you buy new pistons and rods. (Pistons and rods made for a 2.4L stroker because of lenght and clearance issues.) If anyone can help here, chip in and help this guy out. While you have the block all apart i would get it hot tanked and clean every galley out to get the old metal shavings out, including the head. THis will make a very reliable, powerful engine when you are done. Hopefully you will not be back in this situation when you are done. Good luck and keep us posted.

EDIT: Here is a link on how to use plastigage.
http://rpm-mustangs.com/articles/howto-plastigage.html

Thanks for the helpful advice about plastiguage. My block was hot tanked and bored 40 over already and i have all the right parts for my setup. 6 bolt rods with stroker pistons. It all came together in a kit with a remand crank. The guy who helped me build the engine told me he didnt plastiguage because it came with a kit and he didnt think the clearances would be off with a kit. We are trashing the crank and going with a nice stock one out of a N/A block with low miles and using plastiguage just to be safe this time.

But on to my origional topic, why do you think this happend with a kit from a well know company?? I dont want to mention names because i am going to be contacting them in regards to this.
Could it be the fact that it was a cut crank that used .25 over bearings and the abusive nature of 2.3's on bearings?

Thanks again for all the help.

 

[andymoraitis]

If bearing tolerances aren't correct on any crank (undercut or not) then it's a given that you'll see failure. I run a cut crank as well and my bearings were matched to the amount of undercut and I've had no issues. I'd say that if your specs are right on and your engine builder is experienced, then this should alleviate future problems.

 

[DankDSM]

So what your saying is that the crank i got probobly wasnt exactly cut to .25 under? I dont even want to mess with this crank anymore so it is no longer an issue but that would make sense as to why the spun bearing happened. And if this was the case why would it not happen in the first 500 miles? during the break in period the most i ever did was a 3rd gear pull at 15psi to 5k rpms. Why would it wait till i ran it on the dyno at 16 psi to 7k to fail?

 

[andymoraitis]

Actually what I'm getting at is this: if the bearing tolerances aren't correctly matched to the cranksomething's going to fail.

As far as why it happened when it did, I can't answer that since I'm not a machinist. On my old 2.0 I had shut the motor down, changed some plug wires, started it up and had rod knock. Why it happened when it did is beyond me. All I know is that it happened and, eventually, why.