I posted this on ls1tech also but only got 1 reply so far. So here it goes.

First off, I wanna start off by saying that I'm not completely new to all of this. I have been reading these message boards for a long time. But anyway here is my situation. I have a 95 Z28 that I bought a couple years ago for $900. The engine in it was just rebuilt before I bought it but the previous owner could not get the engine to fire. So I pulled the engine out and took off the heads and intake only to find a couple pushrods shoved through a couple stamped rocker pockets and a couple more broken pushrods in the lifter valley. Turns out he installed the biggest xfi LT1 cam (xfi292 ?) And put the stock rockers with Crane dual valve springs in it. After pulling the heads off I noticed a few of the pistons had some marks on them that indicated that the intake valves were hitting the pistons. On 2 of the pistons, it looks as if the valve got hung up in the relief and "pulled" some of the metal up. I have since started collecting parts for a rebuild and now I have run into a few questions.
I know that I will have to replace the pistons but I am not sure which ones to use. I will be keeping the stock rods and crank but will I need to buy pistons that require a pressed wrist pin or does that matter? Anyone have a recommendation?
Also, before someone asks, this is not a daily driver but rather a weekend cruising-street/strip car. I already have a very nice set of heads, with a ported and corrected intake, 58mm BBK throttle body, CC503 cam (it was free so don't say to get a different custom cam), I have an A/C delete pulley and have removed the A/C box from the firewall, and a set of pacesetter mid length headers & y-pipe (came with the car). I also have 2 more blocks, 3 sets of heads (2 aluminum, 1 cast), 2 more intakes with stock throttle bodies. My only problem is, I don't have any extra rotating assembly parts. My main goal right now is to just get this thing running. I am tired of seeing it sit. I want to keep the compression up a bit, but not crazy either.
Thanks.
I know ill have more questions later.

I'm on a family man with 2 kids budget too.

 

I'd say there's no reason you shouldn't just find some stock pistons/rods to replace the damaged ones. That way you don't have to bore the clyinders or spend cash on new pistons. You shouldn't have to balance anything since the stock parts should all weight about the same. You may want to look into new rings, however you may want to talk to a engine builder/machinist and see what they think. Maybe hone/re-ring the motor and depending on miles do the bearings.

The XE503 is a good cam, especially with stockish heads. Dump that XFI292 on ebay and use the cash to finish the motor. Also lose those stamped rockers and make sure the rest of your valvertrain is up to the task.

-Dustin-

 

Thanks for the reply, and I responded to your pm too.

This shortblock was just rebuilt by a local machine shop that is known for good work. Its just that the previous owner installed the cam and top end. So all in all there shouldn't be any miles on the rebuild yet. The heads I picked up are the AI 200cc heads and intake. My end goal is to have a 383 built very close to Joe's (RamAir95TA). Its just that I'm tired of just seeing it sit and I really wanna drive it this year.

 

In that case you should be able to just place the rings from the rebuild motor onto some stock pistons [as long as that's what they are] and go with it.

Joe's got a damn nice car and I think for a while he was thinking about selling it. Running 10's with a HR cam ain't easy but Joe and a few others have proven it can be done.

I hear you on getting cars on the road, mines been down for 1.5 years now, I'm just itching to get it back on the street. Almost there..

-Dustin-

 

Thank for the kind words fellas. It's only easy if you do your homework and get the right parts. I am still considering selling it to be honest, if the price is right.

 

Oh no, I'm in trouble now. I am having a hard time finding money to just get my car running. Now I gotta buy a whole car.... Lol. Believe me, if I had any extra savings, I would be knocking on your door!

 

Do you actually know what pistons are in the engine? You indicate its been rebuilt, before you bought it? Did they bore it?

 

How about some pictures of the piston crowns, cylinder walls, etc - piston to valve contact doesn't always mean the pistons need to be replaced.

 

First things first. You said the push rods were through the rockers. And valves hit the pistons. So likely the cam contacted the cam bearings.

Have you even pulled any piston and rods to see what condition they are in? Do you know if any are bent?

Decide which of the blocks you have is best. Have it checked for everything. Then decide where to go. Stock bore, over bore etc.....

You then need to have the heads you are going to use CC'd if you don't already know, so you can decide which pistons to give you the correct CR.

Next up is the cam. It requires the correct converter and rear end gears. Given any thought to those? Not to mention springs, rockers and push rods for at a minimum, the correct clearances. As you are painfully aware.

If I were you, I would pull everything apart and catalog it. Know what it is. Then with a little research, you can decide which best fits together.

Saying you merely have a cam and heads that you intend to use is the wrong approach. Do you even know if the heads can tolerate the cam you have?

 

Sorry guys, I have been busy the past couple days and haven't had a chance to get on here. I will answer all questions and take some pictures as soon as I get home. Thanks !!

 

Fred, yes the engine was rebuilt but the previous owner told me that the machine shop reused the stock rods and pistons. He said there was an oiling issue and had to replace the crank, oil pump and bearings, but that was it. He also said the machine shop did the short block and he did the top end and cam.

The cylinder walls all seem to be fine, no scratches, gouges or anything serious. Also, l looked at the pistons in some better light and there are more than 2 that look damaged. Here are a few pics of the piston crowns. Let me know what you think.







Speedy, yes the pushrods went through the rockers lol. I have a couple pics but we all know what that looks like. I have pulled the cam out and got rid of it already too. I didn't think too much about the cam bearings to be honest. He said the engine never ran other than cranking it over trying to get it to run.
I have not pulled the engine any further apart, mostly because my garage is not insulated and has no heat. To be honest, unless it is obvious, I have no way of checking the rods to see if they are bent.
My main interest right now is to just get my car running because I am tired of seeing it just sit, so stock is just fine for me right now. I have a running lt1 in a caprice right now but it has over 250,000 miles on it and I have a feeling it will need rebuilt as well. I'm just trying to figure out the cheapest way possible to get my car running and then I will focus more on the performance aspect. Eventually I am wanting to build a 383 similar to Joe's.
The cam I have now is the cc503, and I'm planing on running it with the stock heads for now. As far as the other parts go, I have considered and studied quite a bit on what I am going to use, but that will have to come with time and I'm not going to discuss it right now. I just can't afford to do it all at once.
I have been tearing apart stock and performance engines for quite some time, and done several H/C/I swaps so I know all the parts and what they do. The majority of the time though, the machine shop has assembled the bottoom end for me.
Oh, and the heads I have are the AI 200cc heads. I am confident they will tolerate anything I am willing to throw at them. But once again, I probably won't be putting them on right now.

Thanks for all help and replies!

 

Those pistons will be fine - you just need to detail the damage and knock down the sharp edges. Use a deck bridge or dial indicator to check piston to deck height just to make sure they're all the same(straight edge and feeler gauges will also work), but I don't see any reason to suspect a bent rod - that's pretty minor damage on those pistons, the valve didn't hit far enough out to risk pinching a ring.

Use a light and a mirror to inspect those cam bearings.

 

Thank you very much for looking and the advice! I have a couple mitutoyo (sp?) dail indicators so ill check the clearances and cam bearings tomorrow.

Adam