Pat-Man

iTrader: (3)

Would that mean the push rods are too long? or timing off?

calongo_SS

iTrader: (7)

timing off or cam has too much duration most likely.

rufretic

iTrader: (37)

I'm guessing the cam has too much lift but now I'm going to have to take off the timing cover just to be sure. Can't I adjust the timing with the chain to help the problem as well? It's adjustable to advance up to +4 and retard up to -4. I have no idea how that stuff works though, I always just put it on 0.

Here are some pics. You can see the valve marks on the piston, worst one. The heads are holding the water with no leaking so far which is weird.

calongo_SS

iTrader: (7)

What are the cam specs?

rufretic

iTrader: (37)

cam specs: 246/250 .632/.635 on a 112+4

I also had 7.4 pushrods in it and after measuring with a pushrod checker, I need 7.35 and that's with .075 preload so if I went with less preload like .05, I could even go shorter. I'm wondering if that's my problem right there, the longer pushrods are causing all my problems. It just doesn't seem like .05 would make enought difference but maybe since my cam is already cutting it close, it was enough to cause problems? I thought the lifters eat most of that though, I wonder how much would bottom out the lifter? With 7.4 pushrods, I had .125 preload on the lifters which is too much but enough to bottom them out, I don't know.

2000_SS

iTrader: (24)

lift is important, but your duration is what will usually cause clearance issues. i'm not a cam expert, but even still, i would think your cam is fine. pushrods could DEFINATELY be the culprit here.

...and that little nick on the piston is going to create a hot spot, and possibly a lof trouble i think...

veee8

iTrader: (40)

That LSA is a bit tight. What kind of clearance did you have when you clayed it? You need to check with a solid lifter too. They are easy to make with a hyd. lifter, just pop the snap ring out and take the spring out and replace with something solid so the plunger cant move. If you used regular lifters when you clayed it, the could have bled down. A cam with a 115 lsa or more, would be more desirable for FI, and could give you more PTV clearance.
And...
If the piston hit hard enough to ding them, you need to check all the valves. Pull them out, and check them to see if any are bent.

Rickys S/C Z28

iTrader: (13)

i would take the heads to a machine shop and have them gone through

2000_SS

iTrader: (24)

this is an excellent point, i forgot this was a procharged motor...

dude, if i were you, i'd have the heads checked out by a shop and flowbenched, and have a new cam ground FOR YOUR APPLICATION....but that's just me.

helicoil

iTrader: (104)

Wisest thing to do at this point is pull all the valves and have them checked for runout, with dings like that in the pistons odds are you have bent some.

rufretic

iTrader: (37)

The weird thing is that I never once felt any resistance when turning the engine over with a wrench. I would have thought to put dings in the pistons from contact, I would have been able to feel something.

The other thing I don't get is the heads are holding the water I put in them, not one drip seeped through the valves in the last 7 hours they have had water sitting in them. If the valves were not sealing wouldn't the water find the leak?

As far as the damage done to the pistons, can't I just flycut them to clear the valves? I want to try this cam, I know it's not typical for boost but I'm not going for typical. If it doesn't make power then I'll change to another cam.

calongo_SS

iTrader: (7)

I think the cam will make power just fine, you just need to get it to clear the pistons. I'd get the heads checked out for sure though.
Hopefully someone with more knowledge than me will chime in on what to do about the pistons. I don't see why you couldn't cut some valve reliefs though.

98Z28MASS

iTrader: (6)

Damn been watching this thread for a while and hoping to see it all up and running but keep it up your almost there! As for flycutting the pistons, im not positive but wouldnt that be a no-no on a High HP FI application? Figure with that much pressure on the pistons you wouldnt want anything done to jepordize their structural integrity? Just a thought.

rufretic

iTrader: (37)

I'm not sure about that. These are high boost pistons from the factory and they came with valve reliefs, they are just in the wrong spots as you can see from the picture. Now that I have marks on them already, I'm not sure what option I have other than to fly cut them and then smooth off the edges. I wonder if I can just smooth off what's there now and leave them as is? Then if I have to, I can switch to another cam so I don't have to worry about the ptv clearance.

99SSragtop

Push rods look to be the problem. Good luck take a big breath and hang in there.
PS Hows the girl friend is she still helping you?

DanZ28

iTrader: (5)

I agree, you need to recheck PTV clearance with the right PR. If you don't have the right clearance I would find another cam, I personally wouldn't flycut my high boost pistons. Also, did you check all your other valvetrain clearances? How about open and closed valve spring seat pressures? How about coil bind?

BTW, the factory valve relief in those pistons may have been for a bigger valved head which may explain why it was off like that. IMO, even if you had a .050" shorter PR, you would not have proper PTV clearance anyway judging by the divits made. Here is a good read from Katech on preload https://ls1tech.com/forums/showthrea...ghlight=lifter .

Dan

98Z28MASS

iTrader: (6)

Right but with any high boost application you need to be weary of the structural integrity of the piston, which is why Ive been told that if your pushing a lot of boost you dont want pistons with too much valve relief. Since they are already dished if you are going to flycut them on top of that I dont see anything good coming from it. If you want to give it a try by all means go for it as it may hold, id just be cautious if your going to be pushing 18+ psi with that F2. JMO and good luck man you will def have a badass machine once your done!

rufretic

iTrader: (37)

I see what your saying. If I do cut them, it wouldn't even need to be as deep as the ones they came with, just in a different location so I don't see it hurting the strength. I really don't want to do it at all but I'm not sure what to do with the pistons as they are now. If they will be fine, then I'll find another way to fix the ptv without touching the pistons but I think the way they are now, something needs to be done? If I can just smooth down the spots that got nicked, that's what I will do but I've never worked on pistons before and I have no idea what needs to be done, if anything?

sevanseriesta

iTrader: (34)

are the pistons installed the right way.... I believe that they should have a mark on them saying which way they should be facing. If the piston have valve reliefs and they are not in the right spot then they are installed incorrectly and that may be your issue with the valves touching. However I am not sure that this would stop the car from starting either so you may have another issue also

rufretic

iTrader: (37)

I'm pretty sure they are in right, they have an F marked on the side of each one and it is facing the front. If you reversed them to the other side of the block, the valve reliefs would be on the oposite side of the piston, the reliefs wouldn't be anywhere near the right spot. They are only off alittle bit, I think they are just made for if you use larger valves.