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So didn't you check the clearances when you installed the cam to make sure it didn't hit? Also, were you running the cam 6 advanced on top of the 4 advanced already ground into the cam, making it 10 advanced total :eek:

Guess thats the reason for the disclaimer then :

"An experienced professional should only do cam timing changes. Serious engine damage could result if done improperly!"

So what all did it destroy? Looks like all 6 pistons, probably all the valves and at least the one head? Ouch
 

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I installed the cam +2 degrees on top of the 4, total of +6 degrees. I spun the engine by hand and nothing was touching, I didn't think that the lifters will pump up and that's where I screwed up. It was just a timing problem, because the exhaust valves were lifting .584 and the intake were .575. All pistons have marks, but they are not scuffed on the skirts, so set of valves, one piston and a head. $350 and it's back together. I cannot believe the forged piston is so strong- the piece of valve that is stuck in the head is so beat up, I had to pry it out with a pry bar :) Well, at least it looked and it sounded good. For those 15 minutes or less, I was free :D Stupid, stupid!!!
 

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I'd be suprised if you didn't need all new pistons, and maybe both heads as well. I mean, I'd be afraid the pistons would be cracked or overly stressed around the places where they got hit- it had to be an extremely high force to be able to leave dents in the pistons.

Also, I'd check the heads carefully too; I'd be afraid that the valves would have bent when they hit the pistons, and that could screw up the valve guides and possibly the seats depending how much they bent. While I had it out, I'd probably also check the whole valvetrain all the way from the valves to the cam because the force would obviously be transmitted through the valves into the rockers into the pushrods, lifters, then to the cam.

One other thing, I'm wondering how you were able to spin the assmbly by hand with all the valvesprings in (and I'm assuming you're running the 130# springs)?
 

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Actually, the rest of the pistons are fine- the dents are not as bad as they look on the picture. No scuff on the sideskirts and the rear head has exactly 200PSI compression on all 3 cilinders-the valves are fine. If you look at the pic of the damaged head you can see how the intake valves(the ones that were touching the pistons) were spinning like thay are supposed to(the clean area around the edge) and they seal nice. I am trully amazed how strong these pistons are. I broke a stock piston before and it was really broken in 2, without any valvetrain damage. This piston beat the crap of the valve head and it's still in one piece- I will reuse the gapless rings from it. At least, now I got more clearance for the valves, with grooves in the pistons :eek: ;) I am running the 105# springs- I spun the engine with a torque wrench and no plugs. That's what I meant "by hand", not by using the starter.
 

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cam and timing

Jonathan_Cain said:
if you know you need to degree a cam, then why dont you understand +4 etc? no cam is made perfect. you need to find TDC, where the valves are opening and closing and match it to the cams birth sheet.
when I had my heads bowl ported and valve grind at the time of buildup... the Perf eng shop doing the work told me that every cam they install... OEM or PERF cam... they wip out the degree wheel... they see all types of cams and they see all types of timing variances.... there policy is just check it to make sure, dosent take but a few minutes to know 0 TDC is 0 TDC
 

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With all the talk about the higher gas prices and that i will soon be installing my S1X cam i have a question about adv or retarding cam timing.

does retarding the cam save fuel for low end driving? If so, this may be a good way to get the around town fuel mileage with the WOT power we all yearn for - :D
 

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Advancing and retarding a camshaft will tell you one thing; you have the wrong camshaft. I can not preach enough from my soap box to match components to build a combination. One of the last things bought should be the camshaft. To often we buy a cam based on hear say and get led down a path of dissapointment.

As Scott said, advancing most of the time will lower the powerband, in some cases I have found it doesn't. Retarding will move the powerband up higher but in some cases it may not. If you have to do either and you get positive results of power where you want it, then you have the wrong camshaft in the engine. Valve events determine how an engine will run, duration is nothing more then a by product of these numbers. Valve lift is based on the port CFM in relation to how fast the valve must be opened to reach 100%+ cylinder fill for maximum power.

When the cam (the brain) is thought out the correct way per combination you should not be able to improve its performance durning dyno testing because it is all ready there.
 

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As Scott said, advancing most of the time will lower the powerband, in some cases I have found it doesn't. Retarding will move the powerband up higher but in some cases it may not. If you have to do either and you get positive results of power where you want it, then you have the wrong camshaft in the engine. Valve events determine how an engine will run, duration is nothing more then a by product of these numbers. Valve lift is based on the port CFM in relation to how fast the valve must be opened to reach 100%+ cylinder fill for maximum power.

When the cam (the brain) is thought out the correct way per combination you should not be able to improve its performance durning dyno testing because it is all ready there.

Apologies for the 3 year old thread dig but....... What are peoples thoughts on an IS4 cam retarded a few degrees with a Gen3 M90 and ported heads etc....?

This is on a rwd l67 with stock bottom end but all bolt ons possible
 

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Advancing and retarding a camshaft will tell you one thing; you have the wrong camshaft. I can not preach enough from my soap box to match components to build a combination. One of the last things bought should be the camshaft. To often we buy a cam based on hear say and get led down a path of dissapointment.

AGREED! some of us consider this the "wal-mart" mentality...if its good enough for this guy or that guy then it must be ok for me. many fail to actually research with thier true end goal in mind and just buy one "off the shelf" (like at wal mart)...
!


As Scott said, advancing most of the time will lower the powerband, in some cases I have found it doesn't. Retarding will move the powerband up higher but in some cases it may not. If you have to do either and you get positive results of power where you want it, then you have the wrong camshaft in the engine. Valve events determine how an engine will run, duration is nothing more then a by product of these numbers. Valve lift is based on the port CFM in relation to how fast the valve must be opened to reach 100%+ cylinder fill for maximum power.

i did the exact same thing. 6 seperate trip to the dyno to gather information and retune..advanced/retarted etc..ended up right back at straight up (+4 ground in already). so the original design/grind was a good match for the package.


When the cam (the brain) is thought out the correct way per combination you should not be able to improve its performance durning dyno testing because it is all ready there.
great post mang
 

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Adding to this very old thread...
We are using a VS cam in a N/A build. I was going to install the intake valve on a 109 center (+6 degrees). It is on a series 3 bottom end. Did anyone ever document the practical limit for piston-valve clearance? This is a fairly low lift cam with short intake duration, so I'm guessing it won't be a problem, but I'll measure anyway.
 
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