I think I'm going to miss the upcoming boating season.....

Better to be aware of an issue now rather than when it is an obvious and costly problem. If it does cost some time for this season hopefully the pain won't be as bad as it could have been. Now is the time to get the engines right.

Apologies, thought they were 509's. Still, I would have went forged.

The dyno sheets say 4.280" which is .030" standard bore.
Obviously that could be anything typed in.

What pistons do you actually have?
Did you buy 4.250" or 4.280" pistons?

Might as well go all the way in.
what were the engines originally?
what cranks and rods are in them now?
454 mags had forged pistons in them stock so they downgraded them.

The bore is still stock. I read 4.25. These were NOT the magnum engines so all cast stuff inside.

I would have a hard time believing that you could take a standard bore block with some hours on it, hone it to clean up the cylinder walls and only have .002 clearance on new std bore pistons. It could happen, but I bet you have more piston to wall clearance than that.

I agree that forged pistons would be better, but I personally have a favorable opinion on KB pistons. I built many claimer engines back in the day for dirt track cars and used KB pistons in them. I never saw a piston failure that wasn't caused by something else, usually by a dropped valve or severe overheating. We ran these things hard, 7200+ rpm, lap after lap, night after night and sometimes got them very hot. I do know from experience that detonation or too small of a top ring gap will destroy them in very short order. I personally think that if you have enough piston to wall clearance, the top ring has a large enough gap and you don't have detonation, that the KB pistons will be just fine at 500hp. We made way more hp than that with them in small blocks.

KB pistons are junk for marine use,maybe will last totally stock 330 HP engine ,cast I think are better in that case. Ask me why I know this ,fell for the argument over cast pistons once ,never again,also look at casting shift in KB pistons ,one skirt is almost twice as thick as other side,good old Mexican quality control.

Me to, that's why I asked what pistons he actually got.

so you have cast cranks and cast rods with 3/8 bolts?

PQ,
I hope you don't think we're all ganging up on you or coming down on you hard. Just looking out for a fellow boater. But think of it this way. When Merc upgraded your engine to 365hp, it got all forged internals (among other things). They didn't do it because they thought someone might mod it some day. They did it because it needed it. At my shop, we won't upgrade a non-mag engine. It just isn't worth it. IF if its a 4 bolt block we can use it. Its usually beneficial to the client to sell and start fresh. Even the upgraded GM Performance rods (502MAG and some HP 500s) are un happy over 5400. You're already there.

You've got a good group of people here. The one thing we all have in common is the opinion that whoever built your engine isn't in tune with the demands of marine big blocks.

I'm just looking at his sheet and it says piston clearance .002 - .0025 the other engine was all .002. I am however starting to think that some of this paperwork is bogus....

I missed that somewhere.
Ruh roh shaggy.
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https://media.giphy.com/media/3otPoF...3R72/giphy.gif

So they are 4-bolt mains. I used the stock cast crank. My limited knowledge is most engines don't break the crank first. I upgraded the connecting rods. They are from Eagle 6135P but they have the 7/16" bolts. The pistons look to be KB 203 STD.

Your story just keeps getting worse. It’s like watching a sh!ttt movie and thinking “no he’s not going to….. yep he did”

I can't begin to tell you how I wish I was on the other side of this. This too shall pass. Maybe not till next year, but it will pass.

I'm not sure if I brought this up or not but I really thought I was doing everything right. I didn't try to build these myself in the garage. I thought I was doing a pretty decent build based on the money I had to spend and the guidance I was given by a "professional engine builder of racing engines". Sounded like exactly what I was looking for. You guys that do build know that I have a ton of cash (I suppose that's relative) tied up these and now probably another 5 - 7k to get them corrected. Marine spec's versus hot rod spec's aren't exactly on a billboard somewhere so I didn't know to ask. Maybe he should have known? The guy had a nice shop, plenty of tools, machinery and engines around. Same stuff happens in my profession. Hire the wrong guy to remodel your kitchen and it can take years to finish if you can find him.
Some of your memes and comments are hilarious. However, again, I would find them funnier if I was on the other side of this.
Anyway, I do appreciate the help. This really could have gone bad. 5-7k is way better than what could have been.
Missing one more season isn't the end of the world....I hope.
My wife and I still have the pontoon.......

Sorry for all your troubles. Most of us have probably been in your shoes one way or another. At least the ones that will admit it!!. Prosonally I would start off with disassembling the engines. Check to see what the bearing clearances really are. Check to see what the piston to cylinder clearance really is. Same with valve to guide clearances. Check valve spring installed height and measure actual spring pressure at closed and open height. Maybe some will be better then you were told. 🤞

So I made an offer / request to the original engine builder. He was out of the office so I hope to hear back tomorrow. I offered / asked for the amount of money it would take to tear both engines down complete, hone or bore the cylinders correctly to the piston manufacturers clearance spec's and put them back together again. I would assume as part of the cost he would have to buy new rings because the end gap will probably be too large? I don't know if there are other items that should be included. Maybe some gaskets? To be clear, I'm NOT actually going back to his shop nor will I have this work as described above done. There should be a "Dollar Amount" attached to this amount of work as ridiculous as it sounds and that dollar amount is all I'm after. I am holding him "harmless" for the rest of the things. I don't know if anyone has a number or range in mind for this, maybe just engine builders? I realize we all don't live in the same area so pricing will vary (maybe a lot) but I am wondering what this procedure might cost? Any thoughts? I just want to make an educated decision IF he decides to go with it and makes an offer. My first thought is that he will want to actually do the work and control the cost which I can understand however, that's not happening. There is a trust factor that has been broken. I also feel after all of these comments that most or all of the other numbers might be bogus. Thanks for your comments.

The rings will be fine. A couple thousandths ring gap won’t matter.

Not saying do not evaluate and fix what is necessary, but devils advocate.
When I first joined OSO in 2003 every other thread was "330 On Roids". (those who know, know...) It seemed everyone was building 475-500HP cast crank 454's and many were using hypereutectic pistons. I believe Blue Thunder was pushing 5-7lbs boost to his with 177's for years without issue. I just did a search in the Tech section and I did not find any threads that were related to a broken cast crank or an engine destroyed by hyper pistons failing compared to valve trains taking engines out? I could be totally wrong but I was always of the understanding that cast cranks were good to build to 500 and hyper pistons were good to 600HP on a NA BBC. Also, hyper pistons don't expand that much, so on a honed used marine block I don't believe he'd have that tight of piston to wall clearance. Still do your due diligence.
My $0.02

Do you mind me asking how much you paid to get these done by this shop?

yup, lots back then. I don’t think all went unscathed.

For anyone:
Google better search for oso stuff then search in oso.

copy/paste this and put in google

330 on roids : offshoreonly.com

Thanks Rookie, That is good info and it does make me feel better about my builds and the piston choice.
My problem is that the other guy wants to put forged pistons in or I don't think he will do the work. It is his name on the line and forged pistons are not wrong so....The other thing is I saw earlier that it was mentioned too that the piston clearance can't possibly be what they stated because the bore still shown as stock size and stock size pistons installed and the hours on the engines etc. So the only thing left is that he must have "Forged the info" that he gave to me. That is worse than being ignorant in your profession. At least that's my opinion. In the end a man only has his word....
Wildman, I am reluctant to tell you the dollar amount because it is sure to open another rabbit hole and I'm not sure I can take another trip.:cartman:
I'm sure I will forget some stuff but you guys know more than me so here goes.
For the money, he disassembled the short blocks. I had already torn them down including cam removal because in the beginning I was only installing a "top end kit". Hot tank clean etc. Should have new cam bearings bronze or brass (not sure which) freeze plugs normal drill I suppose. Balance the reciprocating parts he supplied the main and rod bearings new connecting rods pistons then installed all of my supplied parts from the cam up. He ended up not using my roller rockers so he supplied those along with figuring out the pushrod lengths and suppling those. Complete assembly of course. Painted the blocks black again. Dyno tuned the best he could. At least I heard them run. He did have to jet the carbs up I think 2 numbers. As far as suppling stuff, he was in charge of the short block stuff basically. Just under 9k. Lets not have this discussion please.
Still looking for a number range from someone to do the work I asked about.

you have your engines in a good place at P.E. nick and the guys have built hundreds of marine engine including mine.

follow their advice and trust their workmanship. i'm not rich, i work everyday and it took years for my to be in a position to afford to build my engines and i chose the builder carefully.

your problem now is you have about 15 chef's all giving you their recipes, just tell P.E. what you are looking for and your budget and go from there. i have never seen these guys run up the bill on anyone.

the engines the guy down the road said i'd regret not having him build and rig....
https://cimg0.ibsrv.net/gimg/www.off...0dd545745c.jpg

Very Nice! I like the red. I couldn't find the matching red flame arrestor where I bought my valve covers so just stainless. Looking at your photo and others gives me more ideas for rigging my boat. I am waiting for Kyle @ PE to get back to me on the specifics for my engines and the cost. I'm really hoping the other guy comes up with some money but I don't really see that happening. Blood from a turnip and all.

Holy crap this thread blew up!! Hahaha sorry been away for a couple days

Saber....I heard countless stories like yours about PE and that's why I went there however my experience was NOT as described. I don't like bashing people on the internet but being this thread is to educate and help PQ I will disclose some of my experience.

I will include pics to show the outcome. I paid them to assemble, machine, dyno my motor...the works they had it from day one. Ultimately I ended up with a stuck valve, ruined piston, 2 seasons of boating, ruined rocker arms, ruined head castings, and an enormous RAN UP BILL since it was brought up. I know everyone can have a bad day and sh!t happens but what ruined my experience was their lack of ownership for their work and the professionalism to make it right.

Valve clearances were set at less than .001 which is obviously a no go
Push rod length was too short on exhausts if I remember right causing the rockers to bind and get ruined
The head guy that Dan(ICDEDPPL) recommended got my heads after the stuck valve and found all this...
PE did take the heads back and go through them again after the stuck valve and not being confident I went to Dan's guy with them untouched and he found that it broke the guide casting in the head and PE jb welded it back on never telling me what happened...the clearance he found was set to .001 which would have seized a valve again if used.
I don't remember numbers but the springs that PE sourced, sold me, and installed were so light that I was floating the valves at 4900 and the motor would not run over that rpm...remember they "dynoed" this motor to 5600 and 5 lbs of boost according to their sheet they gave me.
In the end, the bottom end was done pretty well but I ended up starting over with all new parts, went to a 540, bigger blower, heads built by Mike(Dan's guy), machine work done by another shop, all assembled by yours truly, cam spec'd by Mild Thunder, push rod length determined by me, and all put together then installed in the boat. So far 15 hours in all is well. Full disclosure I do have an oil leak that is my fault and I'm upgrading my EFI/ignition this off season but the nuts and bolts of the engine are still kicking strong.

Now...this is my experience with them and I get it every shop has bad days but what turned me away was the second time they "went through" the heads to make them right and almost 2 years in PE basically told me this is it and you're on your own good luck. NEVER ONCE did they tell me that there was any issue with the heads or that the seized valve broke the casting. Got them back and they were "good to go" good luck..obviously as stated above that was not the case...the bill was 1300 bucks higher than quoted with no explanation as to why...was just told that more parts were needed yet was never called and told..I asked what parts and the owner of the company told me he doesn't know and "didn't want to bug his builder to find out and it is what it is"

Just a bad experience all the way around and I will personally not go back...now as I said right at the beginning....I heard numerous great stories like Saber's but this was mine so take it for what it's worth.

Here's some pics....this motor had dyno time and a half mile of idleing with 200 yards of 4800 rpm when these pics were taken....
https://cimg9.ibsrv.net/gimg/www.off...d901aa5639.jpg
https://cimg1.ibsrv.net/gimg/www.off...f0078ae4da.jpg
https://cimg2.ibsrv.net/gimg/www.off...a38c8df22b.jpg
https://cimg4.ibsrv.net/gimg/www.off...875e8d9040.jpg
https://cimg7.ibsrv.net/gimg/www.off...ebf3c68716.jpg
https://cimg8.ibsrv.net/gimg/www.off...dad23b2990.jpg
https://cimg0.ibsrv.net/gimg/www.off...b452865eaa.jpg

My personal suggestion as to your motors specifically....

I would absolutely have the heads gone through and at least checked and/or corrected before running them. Remember a 5 second sweep on the dyno is A LOT different than pushing the weight of a boat at 5 grand for an hour. I would also keep a close eye on carb jetting as like I said a dyno pull is way different than real world.

I personally think your bottom ends will be fine if you NEVER plan on boosting it and you are conservative on your timing/carb jetting. If you try to ring every HP out of them and get close to or start detonating those pistons are not going to be happy. MY OPINION and take it for what it's worth..I don't find the pistons to be anymore of a weak link than the cast crank which to me for what you're doing I also believe will be just fine.

I am no professional engine builder by any means but those are my opinions...if you search my threads I have asked a lot of questions and learned a TON on this site and don't feel like you're getting attacked...most of us are just trying to help and save you time, money, and grief on the front end before you end up like me with piles of junk broken parts and 2 years of boating gone.

Good luck brotha and keep your head up!! You'll get there...this boating thing has a really harsh learning curve as you are finding out hahaha

Top ring gap on KB pistons is critical. Bigger is better. When they run out of gap, it pops the top ring land right off.

I am just going to leave this here in case anyone needs it

Machine shop services in the Midwest - Offshoreonly.com

So I'm thinking the answer is no however, If I tear down to the short block, is there any way to verify piston to wall without piston removal?
snapmorgan, I may have posted this already but the top ring gap is listed @ .020 on one engine and .021 on the other. I suppose this could be "actual"? Is that too close? I think that the jury is out whether the engines with almost 800 hrs on them retained the stock bore dimension as noted on the paperwork so the stated "standard piston" to bore is in question @ .002.
BBYSTWY, that is a bummer. I'm not sure but did they use the wrong poly locks? Am I mistaken that they rubbed the rockers? I did buy an afr system that will monitor both engines. The dyno showed upper 12's and low 13's so I feel comfortable at least starting the engines in the boat environment. Never going to be boosted in any way. I think this package is all and more than my boat needs or wants.

Correct on the poly locks...those were also too short however the geometry caused by the wrong push rods didn't help the situation lol

According to the KB chart that you posted, end gap should be .02975. We will just call it .030. If yours are truly .021, no bueno.

Of course it is. Still waiting for the original builder to contact me. More ammo for my case I suppose.....

So I looked over the invoice and getting back to my question about how much I should ask the original builder for as far as him installing the pistons with the incorrect clearance for the pistons to wall based on the manufacturer, I come up with $2,120.00. Disassemble, hone to specs, and reassemble. That's assuming the rings will still work and seeing how the end gap is tight as is maybe just perfect after. I don't have money it this for gaskets or shop materials. He will not be doing the work so I need to be fair however I do have to pay another shop. Any thoughts on this?

As some one who has gone through this...I wish you luck my friend! I think you made the blood from a turnip reference...shops don't like to give money back for services rendered regardless of the situation..I sought legal console in my case and was told that it would cost more in legal fees than what I would get back...sucks but that's the world we live in unfortunately

As for tuning, I refuse to run engines in a boat without a wideband, gives you very good idea what's happening in boat...

On post #74 (geez should I start another one? 2nd dyno complete?) I have the piston sheet listed. I want to make sure I'm reading these extremely small dimensions correctly. I was thinking that the end gap on my rings was really tight however the KB Piston sheet shows "Ring End Gap Factor" of .0070 for a n/a marine engine with a bore of 4.1" and up. I don't know if the word "Factor" means that there's a formula that you use or is it straight up that dimension. From my actual build sheet, my ring gap on the top ring is .021. That's a lot wider than what is required correct? I just noticed the extra "zero" on the piston sheet. Now I'm wondering first, am I correct. 2nd, is the gap too large?

Full Force, I did by this unit.

Innovate DLG-1 Dual Lambda Air/Fuel Ratio Gauges 3891

It will monitor one bank of each engine. I'm hoping that is enough. FYI I'm using a QFT M-800 double pumper with the RPM Air Gap.

You multiply that .007 factor X your bore diameter. It says it in the top paragraph just to the right of the chart