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S1 RB25 intake cam torque issue

slow'n'sideways

By slow'n'sideways,
in Engines & Forced Induction

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slow'n'sideways Newbie

slow'n'sideways

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Gday guys,

Trying too put my intake cam in (Tomei PonCam) and it doesn’t want too torque down without going over the 9-12nms and is damn near impossible too turn once it is tightened down. 

History on the motor: one of the valves on the intake side got damaged (rear valve, cyl 6) by FOD, so I pulled the head and it went too a machine shop I darwin. I just goot the head cleaned up and checked over with new stem seals. Got the head back assembled and put it back on the block With thicker Cometic gasket and ARP studs. Checked the torque on the cams and got the car running again (double, triple and then checked timing belt again!!).

Car would start but would run rough as and once it warmed up didn’t want too start again, I put it down too being untuned and it had a very strange metallic vibrating noise from the motor. While idling to bleed the coolant it made metal snapping bang and stopped. Compression tested it and it read 125-125-40-110-125-110 (semi warm)??

Pulled the rocker covers and found the 7th cam cap cheered off, 6th was tight, 5th-3rd were loose and the rest tight.

Decided too pull the motor too make it easier to investigate, tightened remaining bolts on the cam back down and decompression tested it; 115-113-113-113-117-110 (dead cold). Attributed the low #6 to not having a cam cap on.

Now the issue I am having now is when putting the cams back on with brand new oem bolts, the exhaust side went down evenly and as it should, but the intake would not go down without over torquing the bolts, I put the old bolts back in and ran it all the way down (evenly) and once it was seated it would not turn!!

Comparing the intake, exhaust cam and respective valves, the intake side has far more wear on it across all cylinders (basically brand new cams).

So after writing a bloody novel, my question is;  what can cause excessive wear and make the intake cam so much harder too install? It seems too me that the valves aren’t dressing properly,  which would explain the noise and wear, but whim at a loss as to why that would be the case? 

Cheers for any help!!

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Ben C34 Grand Master

Ben C34

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What cam caps did you use? The same ones or others? Did you swap them around but mistake?

What orientation was the engine when you were doing all of this? Tdc, bc, don't know?

 

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slow'n'sideways Newbie

slow'n'sideways

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Same cam caps, made sure there were in the right order, orientation and weren’t damaged at all. Engine was top dead Center and cams were on the TDC markings, so the pistons aren’t interfering with the the pistons as all, I double checked that.

The head was (meant to be) decked when it sent it off to be machined so the head shouldn’t be warped....I considered the possibility of the cam being bent since the caps did snap while it was running but this wouldn’t have caused the excessive wear across all the cylinders?

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slow'n'sideways Newbie

slow'n'sideways

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10 hours ago, GTSBoy said:

Decked != straight.  Take a bent head.  Machine the bottom surface of it flat.  Sits on the block nicely, BUT THE TOP IS STILL BENT.  It's a common mistake.

Yeh I see what you mean, did think of it that way, wouldn’t that cause the intake and exhaust cam too be hard too install tho? 

Is there a way too test of the top of the head is bent?

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