Bridgeport locator pin carnage :(

**STV_Keith** · 09-30-2014, 11:14 AM

That sucks. I'm in the same boat (pun intended). My 260 lost a locating pin in March 2009 towing a friend in who broke a crank. I didn't even know it until I just happened to decide to check the leakdown before the next event. 1-3% on 1-5, 90% on #6. Side pinned stock 2.5/260 with about 190 hours on it.

The STV has been parked ever since.

**speedinstream** · 09-30-2014, 07:32 PM

Originally Posted by STV_Keith

That sucks. I'm in the same boat (pun intended). My 260 lost a locating pin in March 2009 towing a friend in who broke a crank. I didn't even know it until I just happened to decide to check the leakdown before the next event. 1-3% on 1-5, 90% on #6. Side pinned stock 2.5/260 with about 190 hours on it.

The STV has been parked ever since.

what ya want for the whole rig

**texasvector** · 09-30-2014, 07:38 PM

Originally Posted by tux974

Great choice of new power for that clean Vegas!!
BTW, If you find one with the Vertex pistons do not be too concerned, they have been good for keeping the locator pins.

GL either way.....

i thought wired247 had his fresh promax with vertex pistons FS.???

if so ......you could also save some moola using your brucato box

**Hydro-Peep** · 09-30-2014, 10:30 PM

No unfortunately no motors hiding, he's running out of boating stuff. I think you're on the right track with the promax motor, interested to see what you get

**pyro** · 10-01-2014, 04:52 AM

I definitely want to run the Brucato box on whatever I end up getting. I have the hardware and software to switch the fuel curve over. I also still have the analog ECU and vacuum TPI to go with my motor.

**STV_Keith** · 10-01-2014, 01:45 PM

Originally Posted by speedinstream

what ya want for the whole rig

Oh, it's not going anywhere. I have a bad habit of keeping everything, even if it doesn't run. This is the first year that the Scarab doesn't need some winter fixes, so I'm hoping to get back to the STV.

**JohnR** · 10-01-2014, 03:46 PM

That sucks Chad. I hope you can get it sorted out and keep the boat.

**Sonik** · 10-01-2014, 04:21 PM

I've been talked out of selling mine 3 times this year Chad...and they're all right. You may not think much about it now, but you'll regret letting it go next year, or the year after that......

**CNC_Guy** · 10-01-2014, 05:11 PM

I can only speak from my own experience, but I never want to be boatless again. Always seems to be something coming up to get in the way of getting another one. jmho
Dave

**madtunnel** · 10-01-2014, 05:37 PM

Is there any thing some one can do to prevent this. Or is it just one of those chances you take every time you fire your engine off. Sorry about your bad luck. Sounds like you have a lot of good guys to help you get back on the water. That new baby is gonna want to go for a boat ride

**dumbnfun2** · 10-01-2014, 07:46 PM

If I'm not mistaken u should rebuild any aluminum block race motor around 75 hours

**pyro** · 10-01-2014, 07:50 PM

Upgrade to top-pin pistons.

If nothing else, don't turn side-pin cast pistons 8000+ rpm. Spanking 2.5's is fun, but breaking motors is not.

I was going to freshen this motor in the fall. It was tired. I could feel it. #6 was down about 2-3 psi from the others when I checked it about an hour of runtime ago a while back. That was probably the loose pin beginning to score the cylinder. By then it was probably already too late. I ran a half-dozen 8100 rpm passes at Hardy Party a couple of weeks ago. It was still running good when I put it in the trailer. On Sunday, when I went to start it, I could hear something in the motor when it cranked over, even before it fired. The pin came out as soon as I turned the key. When it started, I heard the knock. I knew it was done. I cursed out loud, and mumbled to myself "probably tossed a pin." I was right.

**David - WI** · 10-01-2014, 09:21 PM

The pins come out because the ports (mainly the exhaust port) are not symmetrical.

Every time the piston ring goes past the port, it bulges out a little bit into the port opening and then gets shoved back into the ring land as it reaches to the top or bottom of the port, If the port opening is not perfectly symmetrical it will shove the ring to one side and the end of the ring taps the side of the pin. The higher the rpm, the harder and more often in taps the pin back & forth... until it finally comes loose. At 8,000+ rpm the pin is getting rapped at least 133 times per second... but probably on the way up and on the way down, so 266 times per second.

If you hit that pin, (even lightly) one million times an hour... it's gonna come loose. Under full power when the top of the aluminum piston is almost ready to melt, banging the steel pin from side to side 16,000 times a minute is a bad thing!

Top-pinning (unless you can do it yourself) is a lot more expensive than just straightening out the port openings and really not needed on an 8k motor. A lot of snowmobile & motorcycle engines turn way over 8K with side-pinned pistons and the pins never come out unless some stooge screws up the port openings trying to make more power. (Outboards have bigger ports so the ring probably hits the pin a little harder when the porting is bad.)

**baja200merk** · 10-01-2014, 10:11 PM

A little schooling goes a long way for pin life

Originally Posted by DaveBushracing.com

A new DBR piston will stand up to 700 plus hp nitrous passes.

Top guided, side pinned, 1 ring, 2 rings are all areas we have tested. Currently we are sticking with Wiseco’s side pin, as it has proven perfect as they claim. We lose ring seal and have more significant leak down when top pinned. We also have deduced that properly shaped sleeves with symmetric ports built on the CNC eliminate side loading of the locating pin.

I built a box stock carb 225 ocean pro with 6 new pistons and fresh bores. 22hrs later on a fishing boat 3 out of 6 promarine pistons had pins that fell out. They sent me 6 new pistons and 2 new sleeves. I know of another looper the same thing happened, parts were ordered a couple weeks apart.. Same "run" of pistons.

I hate locator pin issues. I woudlnt even wish them on Pyro

**Da Bull** · 10-02-2014, 07:19 AM

A few notes: When will someone develop screw in locator pins?
A small amount of leak down dew to top pinning ain`t a bad thing unless on a race course when every little bit counts. Lake boat, No problem. It`s way better than what occured to pyro`s motor.
I`ve always heard that another thing that promotes pin failure is super heated gas behind the pin pushes it out on a lean motor. Where do these gas`s come from? maybe while being installed they compress the air in the hole (much like a piston does in a cylinder) and mix`s with gas expelled by the piston when heated. A very small grove or flat spot on the pin would prevent this. These are just my opinion`s.

DB

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