Need History on Chevy V8;Full Floating C/R Pins

[Larry E.]

Just Curious on the following:

I own Corvettes/Camaros. One of my Camaros is a 69 original Z28. I believe I am correct that the DZ Engine had Full Floating Connecting Rod
Pins. Correct me if I am wrong. My Question: Did Chevrolet ever use this
in any other V8 Engine? Any big advantage by doing this vs. pressed in
pins. I'm no Engine expert like some of you guys. Just curious. Thanks in
advance.--Larry

[Warren F.]

Re: Need History on Chevy V8;Full Floating C/R Pins

The L-88 and ZL-1 RPO engines used a floating piston pin set-up, as well as the original design LS-7 engine of 1970.

[Duke W.]

Re: Need History on Chevy V8;Full Floating C/R Pins

Just Curious on the following:

Any big advantage by doing this vs. pressed in
pins. I'm no Engine expert like some of you guys. Just curious. Thanks in
advance.--Larry

The primary advantage of floating pins is ease of assembly and disassembly - no need to heat the rod and have a press and proper fixture to remove the pistons from the rods, so it's the way to go on racing engines that are frequently torn down for inspection.

Also, if you look at the GM Power Manual, the specs for pin clearance in the rod is very narrow in a tight range. Floating pins may also required a small end bushing and must have a provision for adequate oiling. With pressed pins, one doesn't need to be concerned about any of the above issues.

For OE engines with pressed pins that are being rebuilt for the long run, I always recommend retaining the pressed pin design. A machine shop will have to do the disassembly/assembly, but it should only need to be done once.

Duke

[Clem Z.]

Re: Need History on Chevy V8;Full Floating C/R Pins

GM went to full floating pins in newer LS series engine to get rid of the piston noise they were having with the older LS series engines with pressed pins. i was at the canadian engine factory when they were doing the dyno test on the full floating pins

[Terry M.]

Re: Need History on Chevy V8;Full Floating C/R Pins

GM went to full floating pins in newer LS series engine to get rid of the piston noise they were having with the older LS series engines with pressed pins. i was at the canadian engine factory when they were doing the dyno test on the full floating pins

Clem, do you remember when that change for the LS engines was made?

[Clem Z.]

Re: Need History on Chevy V8;Full Floating C/R Pins

Clem, do you remember when that change for the LS engines was made?

it was the year of the 405 HP ZO-6 because i remember looking at the dyno sheets with 405 HP showing

[Larry E.]

Re: Need History on Chevy V8;Full Floating C/R Pins

GM went to full floating pins in newer LS series engine to get rid of the piston noise they were having with the older LS series engines with pressed pins. i was at the canadian engine factory when they were doing the dyno test on the full floating pins

Follow Up Question:

On the full floating design we know the pin "floats" in the piston. Does
it float in the connecting rod or is it pressed in? Maybe Duke or Clem
can chime in on this. Learning all the time with you guys. Thanks;Larry

[Clem Z.]

Re: Need History on Chevy V8;Full Floating C/R Pins

Follow Up Question:

On the full floating design we know the pin "floats" in the piston. Does
it float in the connecting rod or is it pressed in? Maybe Duke or Clem
can chime in on this. Learning all the time with you guys. Thanks;Larry

full floating pins means the pin is a slip fit in both the rod and the piston. press fit pins means the pin is slip fit in the piston but a press fit in the rod

[Joe C.]

Re: Need History on Chevy V8;Full Floating C/R Pins

full floating pins means the pin is a slip fit in both the rod and the piston. press fit pins means the pin is slip fit in the piston but a press fit in the rod

.................and because of that, the wrist pins must be held by means of a retainer. "Spirolocks" are used as well as snap rings.

[Joe L.]

Re: Need History on Chevy V8;Full Floating C/R Pins

full floating pins means the pin is a slip fit in both the rod and the piston. press fit pins means the pin is slip fit in the piston but a press fit in the rod

clem------


Heaven forbid the applications that use a pin press fit in both the piston and the rod!

[Joe L.]

Re: Need History on Chevy V8;Full Floating C/R Pins

.................and because of that, the wrist pins must be held by means of a retainer. "Spirolocks" are used as well as snap rings.

Joe, et al------

...and the major downside to "floating pin" rods is the potential for one or more of the Spirolocks or snap rings coming loose!

[Clem Z.]

Re: Need History on Chevy V8;Full Floating C/R Pins

Joe, et al------

...and the major downside to "floating pin" rods is the potential for one or more of the Spirolocks or snap rings coming loose!

GM production full floating pins use a pin with a bevel on the end and a wire retainer. the bevel on the end of the pin forces the wire retainer into the groove for a tighter fit. snap rings have a "sharp" side and a "rounded" side and you always put the sharp side outward so it would "bite" into the piston pin lock groove. spirolocks came along after the use of double snap rings with the "rounded" sides facing each other and the "sharp" sides would face the pin and face the outside edge of the retainer groove. never saw a spirolock come out when installed with the proper pin end play. i made my own gauge to check the groove spacing and ground the ends of the pins to get the correct end play when using spirolocks.

[Clem Z.]

Re: Need History on Chevy V8;Full Floating C/R Pins

here is the gauge i made to check the the pin length i needed. the 2 large diameters on each end would fit into the piston pin retainer grooves in the piston and then i would tighten the set screw,remove the gauge from the piston pin retainer grooves and use a pair of vernier calipers to read the inside distance between the 2 large diameters and grind the pin to length to get the proper end play. the large diameters on each end are the same width as the retainer grooves so they are a snug fit into the grooves

[John H.]

Re: Need History on Chevy V8;Full Floating C/R Pins

here is the gauge i made to check the the pin length i needed. the 2 large diameters on each end would fit into the piston pin retainer grooves in the piston and then i would tighten the set screw,remove the gauge from the piston pin retainer grooves and use a pair of vernier calipers to read the inside distance between the 2 large diameters and grind the pin to length to get the proper end play. the large diameters on each end are the same width as the retainer grooves so they are a snug fit into the grooves

Jeez, Clem - nice gage! Looks like a toolmaker's handiwork .

[Clem Z.]

Re: Need History on Chevy V8;Full Floating C/R Pins

Jeez, Clem - nice gage! Looks like a toolmaker's handiwork .

when my dad found out i was a tool maker/die makers apprentice you would have though i was going to be a doctor. he died the second year of my 4 year apprenticeship so he never got to see my papers.