Okay i'm attempting my first engine build i'm planning to use this bottom end set up.

http://cgi.ebay.com/ebaymotors/NEW-S...Q5fAccessories

Eagle crank and rods, speed pro pistons and arp bolts, as well as the rings and bearings.

It comes with either flat tops or dished. I was under the impression that the stock pistons are dished, but the compression listed for 54cc heads is stock 10.4:1. I am guessing I am wrong lol but i just wanted to be sure. Also has anyone used this combo? Is it any stronger than stock. Turn higher rpm's? Thanks in advance.

 

The rotating assembly you choose will depend on what your goals for the car are going to be. What valvetrain are you planning on using?

DEFINITELY stay away from the Eagle cast parts, especially their crankshafts. Too many failures have been popping up recently, myself included. A simple search will bring up tons on them.

10.4:1 compression is similar to stock, FYI. You really need to lay out your goals to give us something to go on.

 

If that kit was stronger than what you already have, I'd be surprised.

 

while i am not an expert by any means on gen1 and gen2 compatibility you did read that the kit was intended for motors 1970-1985 right? sorry if i am assume you are building an LT1 because this is LT1/LT4 section. the sbc is one more down. LT1 pistons are flat tops with valve reliefs from my understanding.

 

Like stated I's stay far away from a cast Eagle crank. Many people have had major issues with them including my buddy who recently broke one in half. He wasn't even pushing too much power through it either, sad.

 

Sounds like i won't be buying eagle lol. What are some other options. I don't need anything extremely strong it's just a cam only build. If i was going to just get a replacement bottom end what are my options. The stock one has been in there for 150k and has been through atleast one rebuild. I just wanna go ahead and do it while it's all apart.

 

I'd stay away from that seller, because they obviously don't know what they are selling. The description totally contradicts itself throughout. It states 350 lt1 and that it is for internal balanced 1 piece rear main seal. Thats all good, until it says for 1970 to 1985 engines which are 2 piece rear mains. Nope, I'd look to summit or jegs or a reputable machine shop before going to ebay. That is unless you know exactly which parts you want and can confirm you're getting them from a reputable ebayer.

 

Your compression is partially going to determine the size of your cam. If you want a large cam your going to need need a higher scr or the cam will bring the cyl pressure too and you will lose power from it. For example if my scr for my 383 build is 12.5:1 I'll be going with a 242/248 cam but if it's only a 12:1 I'll be going with somethng along the lines of a 238/244. I would give Lloyd a call and talk to him about specing a cam before you order pistons, he saved me a lot of disappointment recently

 

Ok it's a comp 503 cam. I don't want to change the compression. I am just looking for a stock replacement bottom end.

 

I didnt look but it sounds like the kit is for a LT-1 Not our LT1's

 

You could go with a build like listed in this thread.

https://ls1tech.com/forums/lt1-lt4-m...ottem-end.html

I myself had 158k on my old motor. I just turned the stock crank,new piston rings, new arp and main bolts, and all new bearings..had a machine shop put the bottom end all together for me, was around 600 bucks if I recall correctly. (for rings,arp bolts,bearings & balancing/machine work)

I'd check with your local machine shops and see what kind of pricing they can give you before you start ordering parts

 

Seeing as how STOCK pistons are flat top, thats prob what I'd use...

Buying a rotating assembly for a "cam only" build is kinda retarded. The stock crank and rods are good for solidly DOUBLE the power you'll be making, and then some.

 

Ok. the stock crank and rods don't look good. I was simply looking for a STOCK replacement. Luckily my machine shop is helping me out.

 

whats wrong with the crank ? if its that bad get another stock one and read the thread in the link posted above. Thats a pretty good set up, Its what im using

 

The machine shop said the crank would be fine. I thought the journals were beyond repair but they said after the polish they will be fine. I'm keeping everything but the pistons. Three were broken. I'm going with forged speed pro's just cause they are only like a $100 more than the hypers

 

What happened to your last engine exactly? Three broke pistons?

 

all the breaks were in between rings and about 1 in long. Don't have any idea what caused it. Just one compression and it seemed to run ok til the opti went bad

 

I can't tell without pics, but that sounds like chipped pistons from detonation caused by too little fuel or too much spark advance. Could have been the bad opti that caused it?

Did they break just above the top ring groove where the ring end gap is? The rings could have had too small of a gap from the last rebuild and the ends touched when they got hot, causing a chip out of the piston.

Things like this happen all the time with poorly tuned Grand Prix GTP's.

 

to answer the OP's original question......Flat tops will be perfect for you.