So my car was being tuned and the wastegate line blew off. While it was idling on the dyno, it randomly shut off. The shop went over spark, fuel, compression on 1/2, and could not find out the issue. They then pulled the valve cover and saw the exhaust cam was not rotating. However, I was told...

"We can't visually see the crack because the cam has not been removed and it is up front. The cam sprocket is still in place and turning because the timing system is still working, and the cam angle sensor bolts into the exhaust cam and the ecu shows accurate rpm and fires spark correctly. That said, the cam lobes do not turn while cranking."

He also provided a small clip,
http://vid198.photobucket.com/albums/aa ... f28098.mp4

He said he didn't believe anything internal was hurt, but was concerned the cam journals may be worn from whatever stress caused the cam to break. In the video, it dosen't sound bad either...given its a really small sample. Is there any possible way the valves are not bent, pistons not hurt, etx? I'm trying to prepare myself for any possible outcome while I await them to look into it further.


On a more positive note, it made 421 on 93 octane and only 17lbs. Not bad considering it was going to see E85 and more boost. He was assuming it would have seen ~480 on 93, broken the 5xx mark on E85 and more boost.

Did you change the cams? or remove them before and installed them wrong? I would think if it's broken it would hang up some valves but I could be wrong.

no, thats the crazy part. I did have the timing belt off, but I put it back on per the FSM and torqued it to factory spec. He said he heard some sort of noise, said it usually was the tensioner too tight, but after talking with me about it thought it could be something else. It had about 8hrs of tuning under it when it broke. I'm going to go down and scope it myself monday or tuesday and go from there.

It depends on how it broke. If it snapped clean in the middle and the valves were in the closed position and the remainder of the shaft continued to rotate in time, you'll be fine. Otherwise, I'm afraid of what the scope is going to discover.

I received the updated this morning, and while not catastrophic, I believe the destruction warrants the car to come home broken and sit while I decide the next step. Valves did make contact. They also removed the cams and found wear on the bottom of the cam journals. With the cams out, the valves didn't seat, showing they are bent as well.

Damn, that sucks man.

yea, went and picked it up today. I will pull the cylinder head and check everything out later this week. When I get out there i'll take more pictures and post them up. I also plan on pulling the oil pan and a rod cap and main cap to make sure no metal worked it way down there. The cam broke at the very front, at the part that the CAS slips into. Wasn't a clean shear either. The cam journals don't look bad to me, but I'm also not a machinist. There is one small part on the exhaust side that looks a bit worn, but nothing I would be too concerned with myself. The cams themselves look fine, no awkward wear spots etx. May just be a clean up of the head, set of valves and cams, and back at it.

Well, decided to put my saturday to use. I went out to the car, got it back up in the air and started pulling it apart. Both V-Band clamps on the down pipe were stuck, I had to cut the lower one off. The upper one broke free once the downpipe was able to be moved. After that, the hot side was pretty simple. I ended up getting the hot side all apart, ate dinner, and took off the intake side on saturday. I tried to take the head studs off, but did not have a 12pt deep socket to remove them. Today, I met up with a friend and borrowed a set, and removed the head. 13mm 12pt for the ARP RB25 Head Studs if anyone ever needs to know, lol. I couldn't find a 100% answer anywhere, so now if anyone searches, maybe they find it here. Next step is to find a valve spring compressor tool and get the rest of the head apart so I can send it off to get checked. By visual inspection only, the pistons look fine. No marks, nothing on the piston walls, I feel pretty good about that. There are 2 exhaust valves that are obviously bent, not sure about the rest yet. The marks in the quench pads don't seem bad...but I'll let a professional tell me that. I'm not sure what the buildup is on the under side of the head. Looks like maybe burnt coolant, but i'm not sure. It could be common for all I know. Pictures below.

well, kind of an update, and a question or 2.

I ended up taking the head to a machine shop and we built it. HKS 256/262 cams, supertech +1mm valves, springs, retainers, new idler and tensioner pulley, timing belt, head gasket etc etc. Put it all back together on saturday but could not get it to fire. I put a new coolant temp sensor (gauge sensor) in cause I broke the last one, and also pulled out the old E85 and put new in. Still no fire, so decided to start at square one on what could be the issue. Did a compression check. Get back to cyl 6 and there is no compression.

The car was working just fine before the cam broke, replaced all the broken head components. The piston looked just fine. What could be causing the cylinder to have no compression? I triple checked timing and its fine. Could a collapsed lifter cause no compression? I'm going to pull the intake/exhaust back off and get the cams out of the head. Then pull the head back off. Looking for any opinions or ideas on potential issues I could have overlooked?

guides gone thru and replaced on overhaul?

yea, they were replaced with a set of bronze guides.

Damn, this brings back TERRIBLE memories for me. I had an exhaust cam snap on me when the head was sent out for milling. After I replaced the OEM cams with Tomei 256/256s, threw everything back together and fired it up, I also had no compression in one of the cylinders! Long story short, it ended up being a dead lifter. I had soaked the lifters in oil for a couple of days before re-installing them but one of them didn't survive the journey and was stuck. I ended up buying a brand new one, dropped it in, and the problem was fixed.

TL;DR: Check your lifters, you might have a dead one that needs to be replaced.

Good luck!

kouki-gymkhana wrote:Damn, this brings back TERRIBLE memories for me. I had an exhaust cam snap on me when the head was sent out for milling. After I replaced the OEM cams with Tomei 256/256s, threw everything back together and fired it up, I also had no compression in one of the cylinders! Long story short, it ended up being a dead lifter. I had soaked the lifters in oil for a couple of days before re-installing them but one of them didn't survive the journey and was stuck. I ended up buying a brand new one, dropped it in, and the problem was fixed.

TL;DR: Check your lifters, you might have a dead one that needs to be replaced.

Good luck!

This is what I'm hoping. I think it makes the most sense, and is best case scenario for my wallet . I asked the machine shop if he primed them beforehand and he said yes, but could not have. I'm putting the heads back on my V this week, will pull the RB apart end of week/weekend.