Twin76mmTA

iTrader: (1)

that cam isnt all that big

i was running a .034 gasket with a 268/254 .693/.693 on a 114-1 lsa and it cleared my reliefs without a problem.

are you sure the cam is installed properly?

00pooterSS

iTrader: (40)

No just read this post of his so left it at that

Haans249

iTrader: (24)

Rufretic,
Given all the time and MONEY invested into your setup, I WOULD NOT RUN those pistons. You have no idea of the dimensions of the piston now, it could be warped from the contact, and or microscopic cracks forming. Also, given the looks of those pistons, its also possible your ring clearance in the ringland is too small now and givin heat, BOOST, can pinch the ring. You're talking about a lot of ifs, not to mention the problem with the timing of your cam being off. You need pistons with the proper valve reliefs CUT, not pounded by the valves. Didn't you measure your PtoV clearance?!

Take it with a grain of salt, but man, i'm tellin you, you don't want to f' this up.

KingSS

iTrader: (1)

Something isn't right for that to happen on startup. Are your heads milled? what's the dish on the piston? With a dished piston of any sort you should not have any PtoV issues at all, especially on a blower motor. Even with that cam, which looks horrible for boost IMO, you should have LOTS of clearance. You need to check everything on that setup because PtoV issues should not be happening at all.

rufretic

iTrader: (37)

Yeah, I clayed the pistons so I thought I was good but I guess my lifters were not pumped up? Then I spun it over by hand and never felt or heard anything wrong. Then when I couldn't get it to start, I started trouble shooting and got to the point of taking the heads off and to my surprize, I found the pistons like this. It's good it never started because the damage would have been worse. Now I'm just trying to get ideas on where to get started with fixing them. I know I can't just fix them and then put the heads back on and start it up. I'll figure out why it was not clearing and fix that problem but the first step is getting my pistons ready to run. I'm going to be taking the timing chain off and going over everything before putting it back together including new heads and possibly new cam. But I want to make sure my pistons are ready to run first. I don't see how any damage like your talking is even possible, the car never fired so it was only the starter turning it over that caused the nicks and they barely hit. I has able to turn it over by hand before I ever tried starting it and it never had any resistance or like I had to force it, it spun over freely. It's not like the piston was wacking the valves at high rpm.

rufretic

iTrader: (37)

Yeah, I'm thinking the cam should be ok too. It's starting to look like it may be timing chain related.

427

iTrader: (3)

The pistons will be fine if you just de-burr them to relieve all the sharp edges. You may want to have them fly cut to match the cylinder heads you are running even if your valvetiming was off.

Kurt

00pooterSS

iTrader: (40)

flycutting is the best idea for this situation, great idea. Equal cutting no worry about the valve not being in the relief etc..

rufretic

iTrader: (37)

Yeah, that's what my first thread was about and I got a lot of negative responses like, "you can't run boost on fly-cut pistons" which I think is a bunch of bull ****. As long as I don't go deep enough to weeken the pistons I think this is my best option as well.

crashinaz

iTrader: (35)

Relieved custom Wisecos... 20psi + a 100-150 shot... Brian Nutter and Dave Diluca (RIP) both said NO PROBLEM... You're only relieving a small area on the top land and the button... Mine are relieved into the DISH. If you've got a nice thick top ring land, taking a little out of it isn't going to be a problem. I'd have concerns about reliefs on a piston that wasn't BUILT for boost (ie: stock or off the shelf for a NA application), but not on what we're talking about... BTW - I'm running slightly less duration and very similar lift on a 114+4... No PTV issues on a 67cc AFR225, .054 Cometic, (9.4:1).



If you follow the radius on the refliefs in your pistons, you can see how much higher they are...

rufretic

iTrader: (37)

Nice man!
I'm going to start looking into how I can do it now. I'm not planning on going deep, just enough for some extra clearance and to clean up what I did with the valves.
Do you mind sharing some details on your set-up and how it worked out for you power/track. You can pm me if it's I'm just interested because it sounds like it's one of the closest set-ups I've seen to mine.

crashinaz

iTrader: (35)

This combo isn't in the car yet, but if there's any specifics you'd like to know... Feel free to IM me.

00pooterSS

iTrader: (40)

rufretic.... why such a thin gasket with boost? why not just use stock thickness so you can keep a decent quench but allow yourself more room for **** like this.

I am assuming its something compressionr related that made you decide that but that just seems backwards to use a thin gasket and boost.

rufretic

iTrader: (37)

To be honest, I'm not sure. My engine builder got it for my and said to use that size. Why is that backwards with boost? I didn't know thicker was better with boost, I actually thought the opposite.

00pooterSS

iTrader: (40)

thicker the gasket the lower the compression, same reason you bought dished pistons, lower compression. The thicker gasket will give you that much more room on p/v clearence too.

But you dont want to go to thick because it will kill your quench area and increase the chances of detonation. I would suggest stock gaskets, thats my opinion though and thats what I will be using on mine, I dont really like messing around with gasket thickness it changes more things than just compression.


also with boost the less compression the more room for error such as bad gas, bad tune, glich in fuel control etc...

rufretic

iTrader: (37)

Yeah, I understand the compression part. I actually wanted higher compression than what I would have with the -28 pistons, 72cc heads and stock gaskets. That put me at 8.4:1 and with these .04 gaskets I'm at 8.6:1, I wanted to be closer to 9:1 but that's tough with -28 pistons.

00pooterSS

iTrader: (40)

ahh I see, damn thats alot of dish and alot of cc's in the head nice and low on the compression. around 8.5 is not bad though at all, when I was boosting imports the general rule was 9.0 was the highest the high end tuners wanted you to go they actually preffered the 8.5 range, so I wouldnt be to concerned about that small amount of compression, besides like I said it gives you that little extra bump in your safety cushion.

rufretic

iTrader: (37)

True, but these are 6 bolt design $200 cometic gaskets that are reusable for when I have the 6 bolt heads. Plus my engine builder wanted me to use this thickness because of the way it's set-up I think to get more quench. I should be able to get these gaskets to work, I'm just going to have to clearance the pistons a little and possibly retard the cam -2 degrees with my timing chain. I really should have clearance with this set-up, it seems like I had too long of pushrods also so once I get the shorter pushrods that will help my clearance as well.