Performance Boats Forum banner

1 - 20 of 34 Posts

·
just a ski boat with bark
Joined
·
2,811 Posts
Discussion Starter #1
Well I knew I was pushing the cast crank too hard but it kept passing magnaflux during inspections so I was trying to get one more season out of it before I changed it out. As you can see that was a big mistake on my part. IMO with care they live well at 7200rpm but they don't like 7500rpm. I will say that whirlaways make for very nice shut downs and recommend them for everybody.







Here's the link to my photobucket if you're interested in all the carnage pictures

Carnage 7_2_2011 pictures by carnivalride - Photobucket
 

·
Highaboosta
Joined
·
3,431 Posts
Wow what a mess.
It looks like pretty much a total loss on the short block.

Did the cyl head survive ?
 

·
Village Idiot
Joined
·
3,455 Posts
Loren, sorry to see the old warrior finally let go. That had been a great engine. I am very glad to hear that you and the boat are safe and sound. Let us know what your future plans are.

Paul
 

·
just a ski boat with bark
Joined
·
2,811 Posts
Discussion Starter #5
Rhu-roh. No bueno. Glad you weren't hurt.
Thanks Scott

Wow what a mess.
It looks like pretty much a total loss on the short block.

Did the cyl head survive ?
Surprisingly yes they did, however an int and exh valve on each head kissed a piston so they'll need to be disassembled and inspected. I guess since 7 & 8 were able to freewheel and they got out of time and mashed the valves. I think that's how the cam might have broke. None of the pistons ever touched the head castings and the 2 that touched valves don't have dents.

I have 4 good rods and pistons and 2 additional pistons that need to be checked for cracks before I consider them good. But ya pretty much a total loss.
 

·
just a ski boat with bark
Joined
·
2,811 Posts
Discussion Starter #6
Loren, sorry to see the old warrior finally let go. That had been a great engine. I am very glad to hear that you and the boat are safe and sound. Let us know what your future plans are.
Paul
Thanks Paul, I really hated to see that combination grenade but it's my own fault I knew I was pushing it with that crank and was actually going to up the gears when I got back home and was planning on changing the crank this winter when I added the new heads. Shoulda, coulda, woulda oh well it's too late now. :)sphss

Future plans:
same tunnel ram with the 2 x750 dps
AFR 305 heads with cnc chambers and back cut intake valves
Basset twisty headers
Neovane water pump
454 production block
91 octane fuel compatible this time

from there it's up in the air.......

I have an old Velasco 4.25" stroke crank and a nice set of SRP pistons for it but they only use the 6.385" long rod

I can get a nice set of SRP pistons from a friend that changed directions that use the 6.385" long rod and 4" stroke and will give me about 10:1 compression

If I can't find a 4-bolt block reasonable I have a nice standard bore 2-bolt I could add splayed caps to.

So honestly at this point I have no clue what I'm doing.
 

·
AKA Blownjet 468
Joined
·
1,205 Posts
Been there, it sucks for sure, I wouldn't trust the stock crank above 6500rpm, but wouldn't have a problem running the studded 2-bolt block
at all.......:D:D
 

·
Premium Member
Joined
·
25,975 Posts
Loren, I wouldn't even post this, but I don't want to see you build a bigger badder bullet without thinking about something.

The observed torque across the front arm of a crank in a v-drive running off the flywheel is almost nil. The torque transmitted thru the front pin arm of the crank is zilch. The number 8 crank arm sees 100%.
The number one reason a crank breaks at the front arm is a damper with a moving enertia ring(fluidamper), or the damper/front pulley was out of balance.

After looking at the pic on photobucket, as well as the ones posted here, I see something you may care to address on the next build.
The piston pin and bore look like they been to hell and back. A slight dicolorization, but a strange wear pattern at the outboard area of the pin where it rides in the piston, matched by a scored piston pin bore.
If the pin flexes, it goes oval and cannot rotate in the rod or piston bore, not counting the fact that it is now wider across the oval, and stressing the piston bore. I know, I've done it. So has Hass 828. The pin doesn't HAVE to flex to make those marks. Oil and oil supply can do it as well. That is a tough job for an oil. Its what I look for when evaluating an oil. The pins, bores, lifter bodies, and pushrod tips and rocker cups. You can lube a main and rod bearing with wesson oil and pressure. But when it is pure splash and hope, the oil better be up to it.
It could be oil, but my gut says flex. Its much harder on the piston, and doesn't take much of it, or too often to bust the piston bore.
When the piston bore fails, the rod swings around wildly, can take out the camshaft, and eventually, in my case, the pin nails the main cap bulkhead with the pin hanging out there. In my case the crank was a 4340, and it snapped the rod, not the bolts, but the rod in 2, and broke the piston pin. But a cast crank, spinning 7500 may be the first thing to fail. It could very well have broken the crank if the top of the rod stabbed the camshaft while it was flailing around.

Not saying that is what had to happen. But I don't like the looks of the pin and piston pin bore. You have a better view than I do, but you owe it to yourselve to check it out closer. JMHO



100% free webcam site! | Awesome chicks and it is absolutely free! | Watch free live sex cam - easy as 1-2-3
 

·
just a ski boat with bark
Joined
·
2,811 Posts
Discussion Starter #9 (Edited)
Loren, I wouldn't even post this, but I don't want to see you build a bigger badder bullet without thinking about something.

The observed torque across the front arm of a crank in a v-drive running off the flywheel is almost nil. The torque transmitted thru the front pin arm of the crank is zilch. The number 8 crank arm sees 100%.
The number one reason a crank breaks at the front arm is a damper with a moving enertia ring(fluidamper), or the damper/front pulley was out of balance.

After looking at the pic on photobucket, as well as the ones posted here, I see something you may care to address on the next build.
The piston pin and bore look like they been to hell and back. A slight dicolorization, but a strange wear pattern at the outboard area of the pin where it rides in the piston, matched by a scored piston pin bore.
If the pin flexes, it goes oval and cannot rotate in the rod or piston bore, not counting the fact that it is now wider across the oval, and stressing the piston bore. I know, I've done it. So has Hass 828. The pin doesn't HAVE to flex to make those marks. Oil and oil supply can do it as well. That is a tough job for an oil. Its what I look for when evaluating an oil. The pins, bores, lifter bodies, and pushrod tips and rocker cups. You can lube a main and rod bearing with wesson oil and pressure. But when it is pure splash and hope, the oil better be up to it.
It could be oil, but my gut says flex. Its much harder on the piston, and doesn't take much of it, or too often to bust the piston bore.
When the piston bore fails, the rod swings around wildly, can take out the camshaft, and eventually, in my case, the pin nails the main cap bulkhead with the pin hanging out there. In my case the crank was a 4340, and it snapped the rod, not the bolts, but the rod in 2, and broke the piston pin. But a cast crank, spinning 7500 may be the first thing to fail. It could very well have broken the crank if the top of the rod stabbed the camshaft while it was flailing around.

Not saying that is what had to happen. But I don't like the looks of the pin and piston pin bore. You have a better view than I do, but you owe it to yourselve to check it out closer. JMHO
Bob can you call me? (316) 209-9444

I think I understand what you're saying and I noticed the pin area in the broken piston but the pins all rotated fine in the other pistons so I assumed it was caused when it came apart. However I couldn't find anything suspicious about the crank and it would seem like it would need something to cause it to just break. If the piston broke first that would explain it better to me. The bearings are fine and the big end of the rods are not discolored. I suspected a spun bearing but there weren't any. I use the Brad Penn 50w racing oil and it was fresh so I doubt that was it. My cam is broken as well just behind the main of the broken crank journal. I take it you feel the 5 & 6 journal is a strange place to break, dampners cause breaks up by #1 and loads cause the breaks by #8 so this is unusual then I take it and that's why you suspect pin flex started this mess?

Thanks for your input
Loren
 

·
just a ski boat with bark
Joined
·
2,811 Posts
Discussion Starter #11
Sure, but I will have to make it tomorrow about 8-9 pacfic time if thats ok. I tried to sent you a PM but the web page shows an error each time.
That's fine, I tried to PM the phone number as well.
 

·
Already miss the 310/562
Joined
·
13,551 Posts
Well I knew I was pushing the cast crank too hard but it kept passing magnaflux during inspections so I was trying to get one more season out of it before I changed it out. As you can see that was a big mistake on my part. IMO with care they live well at 7200rpm but they don't like 7500rpm. I will say that whirlaways make for very nice shut downs and recommend them for everybody.







Here's the link to my photobucket if you're interested in all the carnage pictures

Carnage 7_2_2011 pictures by carnivalride - Photobucket
WOW!!!!!!!!!!!! You musta been ROCKIN!!!!!!!!!!!!!!!!!! :)devil
 

·
steelcomp was here
Joined
·
26,512 Posts
Ditto to what GN siad except I don't think it was from pin flex, I think that pin had a clearance issue to start with. Although not my favorite piston, the Probes are decent stuff and should hold up to 7500rpm. That looks like one side of that piston was tight. I'll also mention IMO you need to get rid of that bolt on windge tray.
 

·
Premium Member
Joined
·
25,975 Posts
Your right again:)hand I did notice that the other side in the piston appears fine. A possible tight bore along with no forced oiler, and the bore dependent upon the milled slots in the bore ala TRW didn't help it along.
Once the bore scores like that it is pretty much a down hill deal. It never gets better. The pin starts sticking in the piston, leaving the rod bushing to handle all the rotation. Its not oiled all that well either, so its starts getting hot. And well...
The rod small ends is never really considered a rotational bearing point. Its only floating for ease of disassembly. There is no real advantage to them realiablity wise.

With the right clearance, and forced pin oilers, this probably would have never happened. Again, JMO



100% free webcam site! | Awesome chicks and it is absolutely free! | Watch free live sex cam - easy as 1-2-3
 

·
Premium Member
Joined
·
25,975 Posts
I have an old Velasco 4.25" stroke crank and a nice set of SRP pistons for it but they only use the 6.385" long rod

I can get a nice set of SRP pistons from a friend that changed directions that use the 6.385" long rod and 4" stroke and will give me about 10:1 compression

If I can't find a 4-bolt block reasonable I have a nice standard bore 2-bolt I could add splayed caps to.

So honestly at this point I have no clue what I'm doing.
If you don't find a 4 bolt for a good price, throw the studs from you old motors in the 2 bolt. It will be fine.



100% free webcam site! | Awesome chicks and it is absolutely free! | Watch free live sex cam - easy as 1-2-3
 

·
just a ski boat with bark
Joined
·
2,811 Posts
Discussion Starter #17
If you don't find a 4 bolt for a good price, throw the studs from you old motors in the 2 bolt. It will be fine.
I have no evidence of cap walk on the mains so in your opinion how much power is a studed 2-bolt block good for? I guess if I mad an honest 700hp I'd be pretty happy with pump gas and realatively mild cam.
 

·
just a ski boat with bark
Joined
·
2,811 Posts
Discussion Starter #19
Isnt it always that way? LOL Funny you say this I was just talking about this the other day. They haul ass right before they break
Ya I was so hoping to put it on the trailer, change gears and run it again......... :)st
 
1 - 20 of 34 Posts
Top