SoCal Jet Boats

Tech Talk => Engine Mechanical / Electrical => Topic started by: Horizonjet on August 30, 2010, 02:35:42 PM

Title: Stiff Pistons
Post by: Horizonjet on August 30, 2010, 02:35:42 PM
I am rebuilding the 454 in my jet boat and its bored out 30 over and does not have too many hours on  the engine.  I noticed when I took the pistons out on 3 of them when you move the rod on the bushing in the piston it feels a little stiff.  Is this normal cause the others seem too move freely.  Anyone have any thoughts or experiance with this?
Title: Re: Stiff Pistons
Post by: lbhsbz on August 30, 2010, 03:39:02 PM
Are these pressed in pins or floating pins?  Are there little lock clips in the piston to hold the pin in place or not? 

Most likely, the thing was either assembled that way or there is some burned oil coked up causing the stiffness.  If it gets worse, its a good way to bend/break a rod.  At the very least, disassemble, clean and reassemble.
Title: Re: Stiff Pistons
Post by: ROMPERSTOMPER on August 30, 2010, 04:22:16 PM
Are these pressed in pins or floating pins?  Are there little lock clips in the piston to hold the pin in place or not? 

Most likely, the thing was either assembled that way or there is some burned oil coked up causing the stiffness.  If it gets worse, its a good way to bend/break a rod.  At the very least, disassemble, clean and reassemble.


What he said, lol x2.
Title: Re: Stiff Pistons
Post by: Horizonjet on August 30, 2010, 10:08:05 PM
They are pressed pins.  The 2 that are a little stiff had rust in the cylinder and were hard to get out and causr the engine to lock up after sitting it would not crank.  So I should replace the pins just to play it safe. 
Title: Re: Stiff Pistons
Post by: lbhsbz on August 30, 2010, 10:43:19 PM
Lol.  If the engine locked up there's not much that can be saved unless it doesn't move.....like the block....and maybe the crank pulley and flywheel.  Give me a call...I don't feel like typing all night.  310-947-7014.  I've got more questiuons and I'll tell you what you need to do.

-Pat
Title: Re: Stiff Pistons
Post by: Horizonjet on August 31, 2010, 11:04:37 PM
Sorry lbhsbz, Got the message late and thought it might be too late to call but thank you though :)  I am just getting new oins for all 8.
Title: Re: Stiff Pistons
Post by: STWD Cruiser on September 03, 2010, 12:08:18 PM
I got this same issue with 1 piston.....press fit...

i looked around on the net, seems like there's no 'redneck home remedy' for this. ....looking for something i can do to get this bastard out, cleaned up and put back in without fighting with a machine shop

any suggestions?
Title: Re: Stiff Pistons
Post by: IRRebel on September 03, 2010, 02:06:46 PM
I got this same issue with 1 piston.....press fit...

i looked around on the net, seems like there's no 'redneck home remedy' for this. ....looking for something i can do to get this bastard out, cleaned up and put back in without fighting with a machine shop

any suggestions?

OK, there's really not a redneck way to "fix" this. I am a victim, as are about 12 other people on this site right now, of bad assembly and cutting some corners. Mine, I blame myself totally. I mandated improper tolerances for the application, and assembled myself accordingly, taking "close enough" as "good enough". Learned a $4k lesson on Moo. Never Again.

Do it right ONCE and the first time. Might cost up front, but take the time to measure, measure, measure while assembling and if sumpin ain't right, get it to a shop. You'll thank me later when next year, or the following year, or 5 years down the road, your boats still running and a lot aren't.  ;)

Ray
Title: Re: Stiff Pistons
Post by: STWD Cruiser on September 03, 2010, 02:38:07 PM
OK, there's really not a redneck way to "fix" this. I am a victim, as are about 12 other people on this site right now, of bad assembly and cutting some corners. Mine, I blame myself totally. I mandated improper tolerances for the application, and assembled myself accordingly, taking "close enough" as "good enough". Learned a $4k lesson on Moo. Never Again.

Do it right ONCE and the first time. Might cost up front, but take the time to measure, measure, measure while assembling and if sumpin ain't right, get it to a shop. You'll thank me later when next year, or the following year, or 5 years down the road, your boats still running and a lot aren't.  ;)

Ray

yeah, i am usually the one preaching the same thing, but never practice it.
Title: Re: Stiff Pistons
Post by: Horizonjet on September 03, 2010, 02:58:10 PM
Yea, The machine shop said mine were assembles that way so whoever had the boat before did it and it ran fine. they are not locked up stiff but if you push the rod to one die or the other it stiffens up but while its in the cylinder it dont move that far.  But then you have others saying to fix it so I guess the best thing to do is just do it right the first time and NO short cuts. :beer:
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