cig1988

They sure do. Dont get me wrong...I'm not bad mouthing them at all. I personally spoke with Vinny (electrical1) and he's doing the right thing. All he wants to do is splash the boat with our short lived season. I almost had a stock 330 for him to use for the season but was sitting for a while. Started it and had demons in it...Unusable.
It could be possible its a bad batch of engines from GM. Who knows.

electrical1

Some one asked what the machine shop said. they said they feel it was a clearance problem, piston to tight, not enough clearance. but i'm not a mechanic so what do I know. Thats why I paid someone who supposenly knew what he was doing. I really don't know if it was just bad luck getting bad motors or if it was the mechanics wrong doing. ALL I KNOW IS I'M THE ONE OUT OF THE WATER AND EVERYONE IS TAKING THERE SWEET TIME DECIDING WHAT THEY WANT TO DO. NO ONE IS HONEST ENOUGH TO STEP UP AND FIX THE PROBLEM. I'VE DONE EVERYTHING I POSSIBLY CAN TO HELP, THEY SAID I NEEDED NEW CARB.'S HAD THEM FLOWN IN OVER NIGHT, EVEN KNOWING THEY WORKED FINE ON THE ORGINAL MOTORS. SOMEONE MENTIONED BAD OIL COOLERS, HAD NEW ONES FLOWN IN OVER NIGHT, BRAND NEW FRESH WATER COOLING SYSTEMS AND SO ON. TOOK NO SHORT CUTS. SOMEONE ASKED IF THESE WHERE RECONDITIONED OR NEW. THEY WHERE SUPPOSENLY BRAND NEW GM LONG BLOCKS. THEY LOOK BRAND NEW AND THERE IS A GM PLATE ON THEM AND THEY CAME IN WOODEN CRATES. WITH SERIAL NUMBER AND MANUFACTURE DATE.

HeavyChevSS

Vinny,
Sorrry this just plain sucks, I have been there (just lucky my pos has a single not twins). OK maybe a clearance problem- now the way my (little) mind sees it- either manufacture defect, or if because of differences in marine use why have so many other crate motors been OK. My next step would be to ask the dealer who sold you the engines to ask GM warranty department to inspect the pieces and see what they say. Hell these guy should be looking for someone to help you out, especially since it may get them off the hook. If that fails you will need to be ready for the next step- finding new mechanic and letting both of the others know how many different boards like this one they will shortly be on. After all we have all heard of 800 RunsNew...(why does it run new, is it used) but at this point no one knows what happened so isn't their fault but they should be helping you find the problem! pm me and will give you someone's address that may be help with questions...

articfriends

Electrical one,i realize your not a mechanic and i can hear your frustration(and i imagine your bank accounts empty or your credit cards are just a' smokin),but when the machine shop said they felt it was a clearence issue did they give you specifics? I posted on this thread a few wks ago and my suggestion then was to measure the bad cylinder. Iv'e melted down various engines for various reasons and it doesn't usually destroy a cylinder so completely that there wouldn't be any spot left in the cylinder that could be measured,i would ask the shop if they still have your motor to measure the best part of damaged cyl (probably towards the very bottom where the piston runs but the rings don't) and measure one of your good pistons and calculate the difference. Even the cheapest pistons out there (gm uses good pistons) will be within a few ten thousandths of each other. Example,If the cylinder measured 4.253 and a good piston measured 4.250 ,you would have .003 thousandths clearence. If it measured 4.251 and the piston measured 4.250 it only had .001 clearence. I would also have them measure a good cylinder vs. piston,these cylinder bores were new not high hrs so they wouldn't have taper either. If the results show the cylinders all had same amount of clearence then those cylinders ran hot for whatever reason(localized over heating due to a air pocket in cooling system would be a guess).If i was closer , i would drive over w my dial bore gauge and measure it myself just to see,i feel for you and your at all these mechanics mercy!Smitty

Big Boys Toys

Electrical1, You did mention early on that you are fresh water cooled!
Another consideration may be the size of your heat exchanger.
Is is large enought to handle the 502 cu in motor?
Just throwing things at you.
You are going to be a mechanic by the time you are through this project.
What temp were you running at when you fired up the motors?
Did you touch the manifolds ?
could you keep your hands on them for a few seconds?
Good Luck
Brian

electrical1

The Fresh Water Cooling Systems Where Sold To Us By The Same Company That Sold Us The Motors. Don't Get Me Wrong By Talking To This Board I'm Not Close To 100 Percent Sure That This Is A Motor Problem. It Sounds Like There Are Many Reasons For This To Happen, Leading Me Back To The Mechanic. I Just Think The Company That Sold Us The Motors Would At Least Look Into It. He Can't Be Bothered. He Won't Even Tell Us Where He Buys The Motors, So We Can See If There Is Anyone From Gm To Help Us.
After Talking To This Board There Are Many Reasons For These Motors To Let Go After About 20 Minutes, But How Can You Say Your Selling Something With A Warranty And Then When There Is A Problem Just Say Its Your Fault You Did Something Wrong Without Looking At The Motors. If I Can Get Someone To Warranty These Motors I'm Not Taking Them Back To That Maechanic. I Know He's A Full Marine Service Shop Not A Back Yard Mechanic But Somethings Up.

Big Boys Toys

Electrical keep hunting until you find out what caused the failure.
Could the fresh water system been the problem and caused an overheat???
You need to pinpoint the problem before you move in any direction.
If you have no warranty, recondition the motors by boring, new pistons, etc, and toss them back in with the same hook up HISTORY WILL REPEAT ITSELF!!!
Keep us posted.
Good Luck
Brian

cig1988

Vinny, I totally agree with the above (Brian). Get to the root of the problem, it will save you alot of money and headache's in the long run.

blue thunder

Ahh, I see some of you are coming around to my way of thinking... I run closed cooling and can say if the system is not primed properly. things can get ugly quickly...

BT

mopower

Just reread this thread twice and for what it's worth my bet is it's the mechanic . For what it's worth it sound like either a timing (too advanced) or lean(perhaps a vacuum leak) condition(carb size will have nothing to do with it). The mechanics answer of a bigger carb was the tipoff. I've seen and done both and the results are almost the same...just like yours and the piston picture a ways back.
I know one guy who went though 5 engines and the entire season with his Fountain. Kept dropping exhaust seats. Got to the point it was like clockwork. Run it hard for a bit..leave it idle or high idle a short time and accerate....boom. His turned out to be reversion and while idling it would suck some water in , cool one or more exhaust seats and on acceleration they would come out. Believe me this guy was one HOT SOB. I saw him beating on his boat with a fender , then finally punched it. I know its frustrating as hell . In his case everbody had a different idea (that didn't work) until he finally went to dry pipes.
Try to find someone who will work with you rebuilding these and dyno them(at least one)and check then double check EVERYTHING.
Better luck next season