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Old 12-05-2007, 08:19 AM   #1
AWilson
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Default Pressed vs. bushed connecting rod ends

RELATIVE TO MY LESS THAN 400 HP 383 BUILD. Is there any preference or REAL advantage of either pressed and bushed connecting rods.
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Old 12-05-2007, 08:37 AM   #2
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The bushed rods are a full floating design which lets the piston wrist pin turn in the rods end. The floating design is really for high revs which cuts down on the G forces on the wrist pin. If you aren't going to be turning high RPMs there wouldn't be much difference between the pressed rod and the full floating one IMHO, houstonvett
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Old 12-05-2007, 08:40 AM   #3
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Unless you will use Forged or Hypereutectics pistons...... no way to go with floating pins!

Anyway, for my opinion, due to the very good price of today's Hyp. Pistons there is no reason to stay with the cast ones...... so go with floating !

A very few horses..... but much more reliables.... keep in mind that a stroker SBC will have higher side loads at the pistons !
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Old 12-05-2007, 09:50 AM   #4
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Ok, so far the score is even!
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Old 12-05-2007, 09:59 AM   #5
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I vote for forged pistons and floating wrist pins...you may add a power adder later (NOS). Floating pins also make for an easier rebuild. Hypers are a bit brittle IMO, better than cast, not as safe as forged.
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Old 12-05-2007, 10:37 AM   #6
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Every engine I build for myself has forged pistons and full-floating piston pins. You'll get folks saying it is not needed for a mild street engine and they are right, plus it is expensive to go that way, but every little bit helps and I go for bulletproof every time on my stuff.

I'm partial to Venolia or Keith Black, depending on the application

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Old 12-05-2007, 11:25 AM   #7
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Quote:
Originally Posted by AWilson View Post
Ok, so far the score is even!

One part depends on the piston you decide to use cause they will have to have snap right grooves in them to retain the pin. (though there are teflon buttons also but only should be used in all out raceing) If your useing stock type rods it probaly will not be worth modifiying the rod for floating pins and if you do anyway don't go metal to metal have them bushed. There is "0" horse power in floating pins but they will spread the load wear out over a bigger surface.
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Old 12-05-2007, 11:33 AM   #8
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Unless you take your engine apart a lot, there will be no advantage to floating pins.
It is just one more "wear item" in the engine. I vote pressed.
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Old 12-05-2007, 12:01 PM   #9
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Ok, pressed pins it is. Do my pistons have to accept pressed pins or do they all? My pistons are off the shelf Weisco.
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Old 12-05-2007, 12:48 PM   #10
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Most if not all pistons can be used with pressed rods. For a street car I vote the conservative pressed pin for dead on reliability. Yeah you can do double spiro locks etc, but if it's not being torn down on a regular basis why take the chance.
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Old 12-05-2007, 12:50 PM   #11
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Quote:
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Unless you take your engine apart a lot, there will be no advantage to floating pins.
It is just one more "wear item" in the engine. I vote pressed.
There is no hp gains. The only advantage is disassembly.
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Old 12-05-2007, 01:14 PM   #12
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I have had several failures of floating pins used in street applications: The single bearing point at the pin bushing location will fail in a floating setup if the engine is exposed to any amount of detonation (not uncommon to occasionally occur with pump gas). For trouble-free and reliable street service, I only use pressed pins.
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Old 12-05-2007, 02:04 PM   #13
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My rods required me to use floating pins.
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Old 12-05-2007, 02:12 PM   #14
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My pistons can be pressed or bushed. So I will go pressed for reasons stated by others above.

Thanks everyone.
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Old 12-05-2007, 05:56 PM   #15
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Every engine I build for myself has forged pistons and full-floating piston pins.
I should qualify this a little. All the previous post are correct. The main reason I do it is the RPM ranges my engines see. The BOSS is safe to 7900, the vair to 7200 and the 409 should handle 6800, which is a bunch with those heavy pistons. When I do the 427, I'll build it with the same intentions. A that point, floating pins are the way to go for me.

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Old 12-05-2007, 11:50 PM   #16
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Quote:
Originally Posted by AWilson View Post
RELATIVE TO MY LESS THAN 400 HP 383 BUILD. Is there any preference or REAL advantage of either pressed and bushed connecting rods.
For a motor like that ... there's no performance advantage to float ... the only other TWO advantages to float are ease of assembly & no press-stress on pistons. However ... wrangling 4 CONVENTIONAL spirolocs per piston can get a bit tedious ... wirelocs much easier ... floaters will have some sort of pin loc that must be installed.

Many pistons are dual-use ... But I've never seen a dual-use rod.
AFAIK ... you must float pins if rods are bushed.
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Old 12-06-2007, 12:20 AM   #17
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Whether you know this or not, both the L88`s and Z`s 302`s have full floating pins. Do you still object to there use now?..

I better add the ZL1`s too before someone complains.,

You use Nylon buttons as pin locks, thats what I use on the race engines

Last edited by Ironcross; 12-06-2007 at 12:24 AM.
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Old 12-06-2007, 07:06 AM   #18
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Quote:
Originally Posted by Wrencher View Post
I should qualify this a little. All the previous post are correct. The main reason I do it is the RPM ranges my engines see. The BOSS is safe to 7900, the vair to 7200 and the 409 should handle 6800, which is a bunch with those heavy pistons. When I do the 427, I'll build it with the same intentions. A that point, floating pins are the way to go for me.

Hans
I'm missing your point. What advantage do floating pins have at a higher rpm? My 350 will turn 8200 all day with pressed pins.
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Old 12-06-2007, 07:12 AM   #19
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Quote:
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For a motor like that ... there's no performance advantage to float ... the only other TWO advantages to float are ease of assembly & no press-stress on pistons.
The only time there is "press stress" on the pistons is when the pins are pressed out to remove them. At this point, the pistons will be replaced.

To install the pins, the small end of the rod is heated until the pins will slide in with no resistance, then allowed to cool to return the press fit. No stress at all.
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Old 12-06-2007, 07:16 AM   #20
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Quote:
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Whether you know this or not, both the L88`s and Z`s 302`s have full floating pins. Do you still object to there use now?..
I don't think anyone is objecting to their use, well, maybe Lars is, but why add the expense when there is nothing to gain?
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Old 12-06-2007, 07:16 AM
 
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