Piston to valve contact on overlap.

[Dred]

So I used some puddy on my pistons ad measure the distance the valves go to the piston. They touch. Has anyone incountered this problem before? I have 1mm oversized ferrea's installed on my head, and wondering if anyone ran into this problem before, and what they did to fix it. I had a previous post about "why" my valves would get bent, but now I know so I thought it should be a new topic.

P.S. 6boilt w/ stock internals w/o balance shafts.

 

[sleek98]

do you have the head gasket inplace to space it out a little? maybe use a thicker head gasket

 

[VelocitàPaola]

I think you know this already, but just to make things as clear as possible - the 4G63s are interference engines, so the pistons and valves occupy the same space at different times throughout the combustion cycle. As long as your timing is correct, they won't touch and your valves won't get bent.

 

[megadeth0]

I think you know this already, but just to make things as clear as possible - the 4G63s are interference engines, so the pistons and valves occupy the same space at different times throughout the combustion cycle. As long as your timing is correct, they won't touch and your valves won't get bent.

What he's getting at is there is a good possibility you timing is off.

 

[Dred]

The timing is right on the marks, I haven't cranked the engine, cause I already have bent valves sitting on the bench, I just put the head on and checked the dinstance that the valves travel to the piston. The problem is that it isn't a new head, and it has been resurfaced when I had my headjob done and I'm not th first owner of th engine so I'm not sure whether or not it has been resurfaced before. I'm also running larger diameter valves, so that could also play a role. I was thinking of machining valve groves in the pistons a little bit so that the valves get a little more room on the overlap cycle.


Edit: Yes i do have a headgasket on when I am checking, i'm also thinking of getting an extra thick headgasket, but I'm not sure which to get w/o having my block decked. I just droped the engine and tranny in the car on sunday, and wednesday I already pulled the head, so I dont really want to go through the engine removal/install again unless I absolutely have to. Stupid of me not to check the clearences before I put the engine in, but unfortunately we learn from our mistakes, and hopefully this will help others down the road not to make the same mistakes I made.

 

[95blackGsTurbo]

Did you clean your lifters before you reinstalled them? If the lifters are primed full of oil this will cause you intake valve's to hit the pistons even with the timing dead on. Also I would get the head checked to make sure it hasn't been resurfaced before. Also did you check to make sure you have the right trigger plate or have it installed the right way.

 

[Dred]

Yah I did prime the lifters before I started up the first time (ran for 10mins then 0 compression). I asked about the lifters at the local "performence" machine shop they said that the valves shouldn't hit the pistons even if the lifters are stuck open WTF

If you know for a fact about this, what's the proper way to install the lifters on the 4g63. I've installed lifters on other cars (hydraulic that is) and I primed before I ran them, although most of them have specifics as to whether or not they should be primed, I however used my old lifters, which are also getting replaced before I try runnin again.

 

[blue1]

imposible to do a piston to valve clearence with putty using hyd' lifters, you need a couple of old lifters, gut them out and shim them as if you were degreeing in the cams, this will give you a true reading in the putty. you should have between .060exh and .080 inlet clearence. NO LESS

 

[Dred]

Tks for the numbers blue, I got the machinist coming down to my shop today and we're gonna measure.

 

[pneumo]

Make sure the lifters have been installed along with the cams for about two hours before checking the clearance. The lifters will extend to full length when they're out of the head, and when you put them in they need some time to bleed down to proper height, otherwise they'll lift the valves a few millimeters more.

There are indicators in the head that can show you how much material has been removed during resurfacing. Look for three bullseye shaped features, one below the #1 exhaust port, one below the #4 exhaust port, and one below the #2 intake port. The center of the indicator should be deeper than the outer ring by 0.5 to 1mm. If the center is at the same height as the outer ring, then the head is beyond it's resurface limit.