2001 Z06

Is there one better than other performance wise? And how about installation of them on pistons, is one easier to install vs. the other?

Thanks.

cshuman

Pressed pin is where the wrist pins (which are the pins that connect the pistons to the connecting rods) are pressed into there positon. A bushed pin is when the wrist pin moves feely inside the piston but has a bushing located on either end of the wristpin which holds the pin in place. These buttons as they are called are usually made out of a polomer material.
If you are talking about the small end of the rod?
Bushed would be easier to install, performance I don't think there is any difference.


[Modified by cshuman, 8:39 PM 7/27/2002]

Sharky Guam

Bushed pins tend to have less friction and are preferred by most engine builders. Pressed pins are easier for auto manufacturers and require less costs during the assembly process.

MSR

actually, the majority of floating pins are held into the piston with spiral locks made of spring steel. the buttons are rare.

2001 Z06

Thanks cshuman, Guam Shark, and MSR. So neither requres any special tools to install the piston onto the rod? I thinking the pressed pin will require a vise to push the pin into the piston and rod...is that correct? And the bushed pin requires no special tool for installation? Reason I ask because I want to order the easier style for me to install.

Thanks.

ukchevybuilder

One warning on spiralocks

I am not an engine builder but I understand that getting the spiralocks out again can be a really tough job. So if you order pistons with sliding bushes either go for circlip rings which are removable with circlip pliers or do any trest assembly without the spiralocks installed then put them in last.

I beleive the experts ( like JE pistons) prefer spiralocks but hey have the abilty to get them out again!

MSR

no, pressed pins definitely require a special cradle and press. i don't know how much machine shops charge to do it for you, but it's very little.

you can assemble floating pin setups without any special tools. spiralocks are tricky, though, and as ukchevybuilder said, they're very difficult to remove without damaging them (or the piston).

2001 Z06

Thanks guys. I will order the bushed pin due to the easier installation. I will keep in mind about the spiral locks.

2001 Z06

Also, when I get the bushed pin style connecting rods, any pistons will work with them...right? Another word, pistons are not specify for bushed or pressed pins?

MSR

correct, the pistons/pins will be standard sbc: .927"

2001 Z06

Thanks alot for your help Michael. :cheers:

AquaMetallic94LT1

Pistons have to be machined for the spirolocks so I don't think you can use any piston with floating pins. Be sure you put the pistons on the rods correctly. The rods are usually machined differently on each side and only go on the crank one way. Pistons usually have to be put in only one way as well.

Spiro locks can be removed but they are a biatch to get out and should be considered trash once they have been removed. Each piston takes 4 of them.


[Modified by AquaMetallic94LT1, 6:33 PM 7/29/2002]

2001 Z06

Now I am confused....so only certain pistons will work with bushed pin rods and not all?
You say 4 spiral locks for each piston...I thinking 1 spiral lock on each end of the wrist pin..where does the other 2 go on? Please explain. :confused:

MSR

aftermarket performance pistons, like JE/SRP, KB, etc, are made for floating pins, and include the pins and locks. (not that you would want to, but) you could use those in a pressed pin configuration, just by not installing the locks. KBs are often used in pressed pin configuration, for instance, mostly since they're cheap enough that they're used in a lot of stock rod rebuilds.

the point is that the pin and piston are matched for retention method, even though the pin dimensions are the same in any case. whereas with the rod, the small end inner diameter changes between pressed and floating. however, aqua brings up a good point i had not considered, not all pistons have provisions for retaining floating pins. stock ones don't, for instance.

don't worry, it won't be a problem for you, if you just tell the piston manufacturer your intentions. maybe if you give us more info about what type/size of engine you're building, we could help steer you into getting parts that will work together.

2 locks per piston, ya, although i vaguely recall some piston manufacturers use 2 locks per side, one after the other. so some might indeed use 4 locks per piston, unless my CRS (can't remember s#!t) syndrome is fooling with me...

2001 Z06

Thanks Michael for clearing things up. My situation is my crankshaft, the rod journal scored and rounded off some by a spun rod bearing (#5 cylinder). The block is stock (not stroke) and I just want to overhaul it with a new crankshaft, new rods, and pistons along with all the bearings and rings.I know the crankshaft can be reground at a machine shop, but I just don't want to take a risk of human error and end up redoing it again. I rather spend a little more for new parts since parts for the 350 is relatively cheap compare to other model car. The reason I am getting rods and pistons because the #5 rod suffered some wear when the bearing spun. Again I do not want to get the rod machine for same reason.
I have been asking alot of questions on this forum for help on this overhaul. I sometime feel guilty for absorbing so much info. from your guys. I want to say THANK YOU VERY MUCH for the much needed help. I will someday return the knowledge to someone who needs help in this forum.
OK, I just thought of another ?, will my engine be balance base on what I am going to do. The reason I ask because I read in this forum about internal and external balance of our engine. Not very clear about this.

2001 Z06

Hi Michael,
I notice you lived in Houston also. What year vette do you have and what mods. have you done to your vette?
You been great help with my questioning...Thank! :cheers:

MSR

since you're replacing the whole rotating assembly, you really should consider doing a stroker. the cost will be the same, as now there are very inexpensive stroker kits.

the assembly will need to be balanced by the machine shop, to the flywheel you will use (balancer too, if it's an L98 instead of an LT1/4).

have you contacted any shops and/or builders about this?

i have a '96 LT4. very few mods, so i'm still enjoying it. ;)

2001 Z06

Yea, I know what you mean about leaving it stock and just enjoying it. Once I started modifying my vette is like a never ending process. If it's not this broken is that. I spent more time working on the damn thing than actually driving it. Now that's a shame.
So you saying when I put a new crank, rods, and pistons, I will need to take it to a machineshop for balancing? So I can't just buy a balanced crankshaft?
Wow a 96lt4, that's the year model I really wanted. I not a big fan of the 87 digital gauges or the interior and hates the new bodystyle of the 97 vettes (my brother owns a 2001 Z06, therefore of the name, we post using the same name). Someday I would like to own a 95 or a 96 like yours. What color is your car? Is it a 6speed or auto? Just curious, how many miles so far? I am begining to sound like you are selling your car...hehe. :seeya


[Modified by 2001 Z06, 9:00 AM 8/1/2002]

MSR

correct, the assembly will need to be balanced, period. even cranks that come "balanced" from the manufacturer, aren't. (well, maybe they are, but only to whatever bob weight the manufacturer felt was correct.)

re: other questions: what is this, identity theft? ;)

my car has only 27k miles on it, right now. it's red. all LT4s are 6-speeds. i keep it parked in undisclosed areas, randomly chosen through an encrypted computer program, protected by killer dogs trained as experts in firearms and explosives, and disguised as a '74 vega.

edit: the car is disguised as a vega, not the dogs!



[Modified by MSR, 9:03 AM 8/1/2002]

2001 Z06

Michael,
Sounds like your car is in mint condition. If you ever want to sell it, please...me..me..me. I would like to check out your car, maybe we can meet up sometime.
So do you know any machine shop around Houston you can recommend? Somewhere that does very good quality work? :cheers: