I disagree. From the pictures posted the engine needs a complete rebuild.

What do you think to save them $$$.
It ran.
Leave the bottom end as is?
Throw some +.001 bearings in it, a new set of KB hypers and call it good?

The thing is you seem to post a lot of info that is incorrect and are very confrontational when others bring attention to these obvious errors. You state in your first post on this thread that a 270 duration cam does not require anything better than Hyper pistons but the OP states in his initial post he is looking to increase compression and DCR to where it should be. DCR and peak cylinder pressures will determine the need for forged pistons weather it is N/A, foced induction or nitrous. Camshaft duration is incidental. He has iron heads and a 69 350/350 is running 11 to 1 compression stock and you are recomending a KB hyper piston to him!
I don't think this is a good idea and neither does anyone else but you. This is brought up and you post sarcastic remarks about spending his $$$. Then in the same post you tell him his original block will go .080 or .090 over. My thought is bore as little as possible. If a hone will clean it up leave it at .030 over. If not go for .040 over even if it takes custom pistons. This is a #'s matching 1969 350/350. Best to save all the wall thickness you can in my opinion. I think decreasing compression to around 10 to 1 with flat tops, getting the quench right at .040, running 93 octane and making sure the cooling system is as good as it can be is critical to getting similar to stock performance in this package. This will be pushing the limits on DCR with this cam and iron heads requiring a forged piston.

Defend your ideas with facts. Not personal attacks.

BTW. This motor was originally equiped with forged pistons. And there was 100 octane leaded fuel available.

It is true that some GM crate engines use hyper pistons. The SB ones use PM rods also. When you are mass producing crate engines profit margins are the determining factor. But they are not using KB hyper pistons. And PM rods are not better than forged. They are adequate for the HP produced. Same with the GM hyper pistons. They are running under 10 to 1 compression with aluminum heads with fast burn chambers allowing retarded timing keeping them clear of any detonation issues. They are adequate for the HP produced and this is a totally different build than an Iron head, 11 to 1, 1969 original engine.
The thing is there are a lot of guys that want to build a High reving engine, more than 1.2 HP per CI. Or high compression ratios. For their applications they may need different components than an engine producing 1 HP per CI or less. KB hyper pistons won't cut it for these builds.
Look at the GMPP 572 engines They are GM crate engines. They have forged pistons, forged rods, forged cranks. This is because they are subjected to more stress requiring heavier build specs. Some want to build their bottom end to a heavier spec than required because they only want to do it once. They may want future upgrades, They may be running high DCR and cylinder pressures trying to get maximum power out of their build as in the case of an 11 to 1 1969 350/350. They also would probably be willing to spend a little more on better quality parts to assure their 1969 numbers matching block doesn't grenade like the pictures American Psyco posted.

Defend your ideas with facts. Not personal attacks.

 

One might wish otherwise, but IMCO you just can't get around the fact that there is a huge difference between blueprinting and simply putting parts together, and that a quality build up cost quality time and money spent both on components and at the machine shop (not to mention time spent at the "drawing board").

 

I was cruising at 2300rpms in 4th gear when the piston shattered. I had about 3000+ miles on the engine, broke in properly and was not afraid to run the motor. I never dumped the clutch, but I was shifting at 6200 rpms with no problems.

 

There are any number of things that could contribute to an almost imperceptable detonation that could not be heard at cruise but was enough to shatter that Hyper piston where a forged one would have held up.
You saved a few hundred dollars putting in the hypers on the initial build. How much was the repair and was the block even able to be saved? What piston did you use on the next build? Sorry to see your destroyed motor but maybe your post will help save someone from a similar fate.

 

Those KB pistons were pretty popular a few years back until motors started to blow up real good. Almost went with a set in my old 406ci, glad I didn't

 

The block could not be saved, and I ended up spending $1800 in upgraded parts bought by my engine builder (and he did not charge me for labor or new block since his name was on the motor). I managed to save 7 rods, the crank, and re-used heads, rockers, intake, and such. I went with SRP forged pistons and a billet cam this time around.

KBs are very cheap and their clearance issues are very touchy. I personally would never run hyper pistons on any future engine builds; however if you are going to for a mild setup, it is wise to invest in some quality, which KB is not. I learned this the hard way.

 

The block and crank are at the machine shop now. I will let you guys know what they find so we can go from there.

 

My forged Diamond pistons are quiet.... read too many horror stories on fragile Hypers.

 

 

okay, so I talked to the machine shop today. They said the cylinder walls were 5 to 6 thousands over the piston and that the crack will need to be ground to 10/10 under. They said the crank looked like someone ran it with dirty oil, the bearings had metal embedded into them and were scored pretty bad. I changed the oil before oil primming and running so I don't know where it came from. It looks like I will need a new set of pistons. I got a price quote of $459 on the Mahle SBC550040F4V which seems like a good deal. I'm not sure about the rods, I know they are not stock and can not find any part numbers on them.

 

fm21:
So you're gonna keep heads & block. Gonna bore block. Maybe use your rods, maybe not. Gonna buy new pistons & cam. Gonna rebalance everything too, right?

Suggest you can probably get a decent cast 383 crank for about what it's likely to cost to grind & polish yours. If you're not going racing, a cast sbc crank will be OK. (btw, did those folks use a steel or cast crank when they threw your 355" together?)

In this particular matter, me thinks you can assemble a decent 383" / 385" stroker for about same $ as rebuilding your 355" / 357"

 

When a Waco like this continuously distorts my statements who can you truly believe?

"i disagree. From the pictures posted the engine needs a complete rebuild." The OP hadn't even posted his pix (post #35) when i suggested he use the bottom end again (post #33). Of course anyone can see the damage now. It don't take no expert to see that.

Next accusation: "The thing is you seem to post a lot of info that is incorrect and are very confrontational when others bring attention to these obvious errors. You state in your first post on this thread that a 270 duration cam does not require anything better than Hyper pistons but the OP states in his initial post he is looking to increase compression and DCR to where it should be."
My very first post was "Need more info" ( post #7). I didn't know what the c.r. was and was trying to help him measure it accurately for himself. Again something else that no one tried to do. BTW none of the proclaimed experts posted anything to get a good c.r. to help choose the right piston dish.

Next accusation: "This is brought up and you post sarcastic remarks about spending his $$$".
That's not sarcastic its true. He doesn't need expensive forged pistons. For a 350hp engine sb Hypers will do. And they are less $$$. I have read no objective proof that KB fail more than others. Nothing but hearsay. Even forged pistons fail occasionally. Regardless KB has been doing good business regardless of all the internet hearsay. If the bottom end Hypers for claimer motors didn't hold up to the continuous beating they get in circle track they would not sell. The fact is the continue to sell in volume in by both Jeg's and Summit. Somehow the accuser was choosing hes own piston experts in post #30 then edited that statement out. Well why does my accuser have to edit everyone of his posts if he can post the facts? And what is a piston expert? A pistonologist maybe? where do they get training for that? Internet hearsay? The more gossip they read the better the pistonologist?

Next accusation: "Then in the same post you tell him his original block will go .080 or .090 over."
I believe that block well could go that far given a good core verified by sonic testing of course. And with the boring done by a skilled machinist that can optimize the bore location rather than by a common machine equipment operator.

Next accusation: "It is true that some GM crate engines use hyper pistons."
All Chevy GEN I performance crate engines use Hypers. ALL! Not some. ALL!


The list of accusations goes on and on. But the accuser really can't deal with my "Defend your ideas with facts. Not personal attacks." demand. He really s it and has write it in large letters in red. Well anyone can see by size of his cries he has to distort every thing i say - not just stretch but distort it to justify his bad ideas. How does this guy hold a job? Who has time to post fabrication like that? Does he eat with that mouth?

Moving on. flyingman i am sorry to read the bad news. U have a lot of work a head of u and what ever pistons u chose is up to u. If u feel u need better pistons then do so. I just hope u take the time to get the correct c.r. nailed for the cam u choose.
Good luck,
cardo0

 

Waco?

As I said before, your technical knowledge continues to amaze me!
Don't know what the rest of us would do without your valuable input!
Pistonologist, Good one dude!

 

I would spring for the internally balanced 3.750 crank. This will require a 16 CC dish piston instead of a flat top then. This will put you around 9.8 to 1 compression with your 64 CC iron heads and good quench.

 

I'm a little confused as usual, we have a Waco TX. 100 miles south of Dallas, because of what happened a few yrs back in Waco TX. we like to call it Wacko TX. So now i'm really confused 63mako are you from Waco TX.

Wacko - of WACKY,one who is wacko.
Wacky - erratic,eccentric,or irrational.

Pistonologist, very good to use for personal insults no chance of misspelling something thats not a real word.

 

Please no personal attacks in this thread. Please post what you personally have found to work and I will sift through the information and do some home work to find the best solution. I appreciated everyones input.

For now, I thinking about getting the crank ground 10 under, and using the original heads.

I am working on choosing a piston and deciding if I should keep the connecting rods. For the connecting rods I don't know what brand they are and what they can handle.

Right now I am leaning towards forged pistons because of the peace of mind. I think the Mahle set for $430 is a good deal.

Also, I am going to recheck the springs to make sure they are set up right for the cam.

 

The Mahle's are a great deal at that price. I did use them on my latest 383 build and they are excellent.

 

My apologies.

I don't want to harm your thread at all flyningman. This accuser that's on top of my ignore list continues to call me out by misquotes and exaggerations. I even refuse to address him in the first person but the personal slander goes on from one post to the next. Really want nothing to do with this individual but only the Mods have the authority to make him STFU. Until then the wines go on and on from one post to the next, from one year to the next. Be my guest and contact the mods if u feel it will help as i don't have a solution.

cardo0:o

 

Okay, now on to the connecting rod. I think that I have these. http://www.summitracing.com/parts/SME-3-48-05-100/

I just don't feel right using them. I was thinking about these. http://www.summitracing.com/parts/SME-3-48-05-200/

Does anyone know about Summit brand connecting rods? I would like to stay in that price range if anyone has any recommendations. Thanks

 

Those are the same rods I believe just looked them over quickly.

Only difference is ARP 2000 bolts, which are a good thing. These are also pressed fit does your machinist and you want pressed fit.

What HP level was the motor going to be at again ?