1jz Valve Interference with Jun Cams?

**gxyboi** · 12-04-2007, 03:38 AM

Hello Everyone

I am currently working on a 1.5jz setup and have decided to install new cams. I was considering the JUN setup below, but I'm a little concerned about the lift and combination. Would a 9.3mm lift interfere should the timing belt break with the 1jz head and would the JUN setup make any considerable difference in power / powerband & driveability? I see some choose to go with a higher duration on the Intake side while others choose to go higher on the exhaust - I've done much reading and have yet to fine a clear-cut explanation of what each combination would do.

JUN Intake Camshaft - 264 degrees duration, 9.3 mm lift
JUN Exhaust Camshaft - 256 degrees duration, 9.3 mm lift

Thank you in all advance for your assistance!

**jeffro ra28** · 12-04-2007, 07:39 AM

less duration on exhaust means the valve is closed for longer resulting in higher cylinder pressure.

However you are only going to gain HP with more lift if the heads are capable of flowing more with higher lift. In alot of cases, the max lift the manufacturer gives the cams is basically where the ports start to platue with their flow and dont actually flow any more with more lift, which obivously means there is no point to more lift.

**chris davey** · 12-04-2007, 08:49 AM

The HKS 272's are 9.3mm lift also IIRC.

Having increased lift will help the low end a bit but the extra duration will help the top end.

What are your power goals? Stock cams are 7.9mm lift IIRC.

ANy reason you aren't going for the HKS 264's with 9.0mm lift? >9.0mm lift wasn't recommended for the 1jz but I can't remember if it was because of going interference or not.

That is right the HKS 272 intake is 9.3mm lift but the exhaust is 9.0mm. I was told that a lot of people go the 264 intake (9.0) and the 272 exhaust (9.0) to stay there rather than go to the 9.3's. I can't remember if it makes it interference or not though.

You would probably know but some US guys were going for 272I/264E. From what I read the reason for this was, closing the exhaust quicker would help prevent revserion where the exhaust gasses are forced back into the cylinder because of back pressure in the exhaust manifold and contaminating the charge. This was first done on 3s-gte's successfully and some 2jz guys followed but AFAIK the regular 272/272 combo worked better.

So what power are you after? Is the car street driven?

For a 3L, I would probably be thinking 264/264 or 264/272 but stick with HKS to stay at 9.0mm lift.