RB25det Cam Question

[Rustys14]

My engine developed a knocking noise from the head the other day and after doing some diagnostics the noise was due to the CAS keyway shearing off the exhaust cam. I'm not sure what caused the issue but the cam journals measure out fine, so I'm thinking I can get away with just replacing the camshaft and CAS. The problem I'm having is that I've been unable to source a good used S1 Rb25 exhaust cam which leads to my question:

Are stock RB20 exhaust cams interchangeable with the S1 RB25? There are several used RB20 cams available locally and charts I've seen online show that they are the same lift and duration, but I haven't been able to find anything online about them being interchangeable. I know the intake cams are not due to the NVCS but I'm not sure about the exhaust side.

My other option would be to grab some Poncams or HKS step 1's. Both Tomei and HKS state that their cams are "drop in" and don't require tuning which seems sketchy to me. Is it really safe to run them without getting the car re-tuned? I have a standalone ecu but really don't want to go through the time/hassle/cost of having the car re-tuned if I can avoid it. I'm happy with where the car is now so I'm not chasing any power gains. It would be nice to just get some cams delivered to my door though and most places seem to have them in stock.

The weather is starting to get nice around here so I'm trying to get the car back up and running ASAP. Any input would be appreciated!

[koukizhang]

I know people who've ran rb20 cams in an rb25. both intake and exhaust. they just ran without variable cam timing and used rb20 sensors/loom. not sure if this helps much but just a fyi.

[PoorMans180SX]

You can definitely use an RB20 exhaust cam in place of the RB25 one. Interesting if they are indeed the same lift and duration. Regardless the ramp rates are the same and you won't hurt anything.

You'll definitely want a tune if you put aftermarket cams in.

[Rustys14]

Originally Posted by koukizhang

I know people who've ran rb20 cams in an rb25. both intake and exhaust. they just ran without variable cam timing and used rb20 sensors/loom. not sure if this helps much but just a fyi.

Originally Posted by PoorMans180SX

You can definitely use an RB20 exhaust cam in place of the RB25 one. Interesting if they are indeed the same lift and duration. Regardless the ramp rates are the same and you won't hurt anything.

You'll definitely want a tune if you put aftermarket cams in.

Thanks guys! That's what I needed to know. I'll grab an RB20 cam and call it a day