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Pulled the crank today, going to replace the rod bearings, figured might as well since it looked like junk ran through them and i still had things apart.

I noticed that some rods move very easy, the pins will slide back and forth and let the rod move around easy. Then i have 3 pistons/rods that are hard to move. They are tight enough to where i can position the rod at any angle and it will stay. The others gravity would do it's job and the rod would come down. Is this normal?
 

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Pins and pistons have contamination in them, IMHO the pistons need to be removed, cleaned up and rehung, had the same thing happen to me..

The wrist pins should move very free...otherwise could "tear up a skirt",( a piston skirt :D )

GT :)hand
 

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Talked to dave at dne today about it too, he said the same i need to take them out and see whats going on. Guess this things comming apart... Shit cranks out, pistons are comming out, heads off.... might as well stroke it to a 496 :D if only i had the extra $$
Better now than the alternative!
 

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Shaun, Pfaff just did a freshen up on a set of pistons/pins we had lying around. Take your stuff down there, they can dial-in what youve got, if needed they can set it up for a new slightly (.001) oversized pin.
 

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496??

Talked to dave at dne today about it too, he said the same i need to take them out and see whats going on. Guess this things comming apart... Shit cranks out, pistons are comming out, heads off.... might as well stroke it to a 496 :D if only i had the extra $$
Why? Increasing the stroke MAY slow your boat down considerably. Throwing money at a problem is never a good idea. AS mentioned the rod/pin/piston must come apart. Are these floaters? Or pressed pins? If pressed you MAY destroy a piston or two when pressing them apart. I would suggest bushed rods and floating pins. Also, with the pin in the piston, and the pieces in your hand, it should shake back and forth through the piston dry. If they won't shake side to side chances are the pins are bent... If pressed, the pins will not move in the rods, so the "tightness" you're seeing has to be in the pin to piston boss, which usually means throwing the pistons/pins away. Stroking to 4.25 will only add to the problems you're already experiencing...Ray
 

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Stroking to 4.25 will only add to the problems you're already experiencing...Ray
I dont think that was his solution, only that he didn't think the motor would be coming apart so soon, and that if he had it to do all over again, he would have stroked it to begin with. With his setup, a stroker would only add power & increase performance assuming everything is "right"
 

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...Increasing the stroke MAY slow your boat down considerably. ...Ray
Don't keep us hanging Ray...inquiring minds what to know why?

(Hammer thinking to himself) >Hmmm, should I re-think my 496 rotating assembly w/ aluminum head upgrade, if it's not going to do squat?
 

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Jet? Prop?

I dont think that was his solution, only that he didn't think the motor would be coming apart so soon, and that if he had it to do all over again, he would have stroked it to begin with. With his setup, a stroker would only add power & increase performance assuming everything is "right"
OK, if you say so.



Don't keep us hanging Ray...inquiring minds what to know why?

Power curve, plain and simple. Rate of engine acceleration. Maximum RPM, short stroke vs long stroke....Maximum horsepower is not always maximum performance. Bore to stroke ratio, rod ratio, compression ratio.....There is no free lunch. What you gain in one area you MAY loose in another area....

(Hammer thinking to himself) >Hmmm, should I re-think my 496 rotating assembly w/ aluminum head upgrade, if it's not going to do squat?
Depends on the entire package. Simply adding stroke to gain cubic inches doesn't always result in improvements in boat performance......Engine RPM has a great deal to do with boat speed. Extra power may not be in the "useable" RPM range. Lower Rs, slower speed........

Based on his questions and level of experience I don't think the 4.25 crank is his answer. A good running 3.76 stroke will run just fine and RPM into the power curve a lot quicker. Quicker than a 4.0 and a lot quicker than a 4.25. Maintaining RPM with a short stroke is a lot easier on parts that are changing direction................

Ray
 

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Depends on the entire package. Simply adding stroke to gain cubic inches doesn't always result in improvements in boat performance......Engine RPM has a great deal to do with boat speed. Extra power may not be in the "useable" RPM range. Lower Rs, slower speed........

Based on his questions and level of experience I don't think the 4.25 crank is his answer. A good running 3.76 stroke will run just fine and RPM into the power curve a lot quicker. Quicker than a 4.0 and a lot quicker than a 4.25. Maintaining RPM with a short stroke is a lot easier on parts that are changing direction................

Ray
I fully understand your reasoning Ray...and was one of my main concerns months back and why I started a thread about bore vs stroke and if a square combo was the best all around option...for (me)

Real quick...I would also think a larger piston/bore even on a shorter stroke could be stressed when it's time for that heavy piston to stop dead and change direction. Especially at a faster RPM...no?
 

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Rod throw

I fully understand your reasoning Ray...and was one of my main concerns months back and why I started a thread about bore vs stroke and if a square combo was the best all around option...for (me)

Real quick...I would also think a larger piston/bore even on a shorter stroke could be stressed when it's time for that heavy piston to stop dead and change direction. Especially at a faster RPM...no?
Think about the rod throw. How much further out is it? A lighter tighter circle has less cylindrical force. Also the counterweights must be heavier to equal the longer rod throws.....All around more wear at tear at high RPMs. My main concern is about how quickly an engine gets in to it's "happy" spot. If you look at early Caddy engines with long strokes and large bores equaling big cubes, and compare to a SBC......Where is the performance advantage when it comes to rapid acceleration?......There are places where brute torque is a good thing. Like moving heavy objects slowly down the road or across the water. Going from a 396 to a 496 is a huge step and MAY not get the desired results........Ray
 

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I'm No Expert
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Discussion Starter #13
Are these floaters? Or pressed pins? If pressed you MAY destroy a piston or two when pressing them apart. I would suggest bushed rods and floating pins.
No they are pressed, dave recommended possibly converting them to floaters, said it's relitivly inexpensive.. unless of course my pistons are damaged.

When i was talking about a 496 i was talking a complete rebuild including a new cam from chris with my desired turning RPM.
 

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shaun just clean them up and put it back together:)grnit will save you alot of money:)handlol!!!!okay buy the 496 kit youll love it:p
 

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No they are pressed, dave recommended possibly converting them to floaters, said it's relitivly inexpensive.. unless of course my pistons are damaged.

When i was talking about a 496 i was talking a complete rebuild including a new cam from chris with my desired turning RPM.
Shaun, I think you have already found the problem by stating rod bearings showed junk in the oil:)bulb If the rod and piston floated easy at assembly and then after running they don't!!!! BINGO!!!!! I will also add that I have seen pressed pins sieze after fire up due to lack of lubrication. But usually with-in the first few hours. M
 

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First f-up was the pressed pins. Second was puttin' the engine together when you thought something was wrong. Third was not building the biggest engine you could afford. At the RPM we are in, bigger ALWAYS wins. Dont change anything, build the 496 or better, and watch the tach climb, PERIOD.
 

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The cheapest option is to convert your press fit to full floating pins if theres material left to do it. A nice blueprint and reassembly will get you back on the lake with the most $$$ in left in your pocket.
However, in terms of HP, the phrase "there's no replacement for displacement" rings true in most instances. Someone would have to screw up pretty good to not make more useable and reliable power with a 496 than a 396 in a similar quality build. Shorter strokes need more RPM to make the same power and RPM is what makes motors expensive.
The only good reason to go with a shorter stroke is if you are cubic inch limited by rules. Then a shorter stroke allows a bigger bore which accomodates larger valves in the heads and will usually make more HP than the same combo with a longer stroke.
Best of luck whichever way you go....
 

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Discussion Starter #19
First f-up was the pressed pins. Second was puttin' the engine together when you thought something was wrong. Third was not building the biggest engine you could afford. At the RPM we are in, bigger ALWAYS wins. Dont change anything, build the 496 or better, and watch the tach climb, PERIOD.
First build, i made alot of mistakes... They were not this tight then i put them in, figured it was normal. I agree i should have just done a 496 to begin with but again, first egnine was thinking stroking may make my first build more complex and that may be better for the next build.
 

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The cheapest option is to convert your press fit to full floating pins if theres material left to do it. A nice blueprint and reassembly will get you back on the lake with the most $$$ in left in your pocket.
However, in terms of HP, the phrase "there's no replacement for displacement" rings true in most instances. Someone would have to screw up pretty good to not make more useable and reliable power with a 496 than a 396 in a similar quality build. Shorter strokes need more RPM to make the same power and RPM is what makes motors expensive.
The only good reason to go with a shorter stroke is if you are cubic inch limited by rules. Then a shorter stroke allows a bigger bore which accomodates larger valves in the heads and will usually make more HP than the same combo with a longer stroke.
Best of luck whichever way you go....

;)
 
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