AMA passenger car specificatins - 1969 z28 "Locked in rod" piston pins

[69er]

I was looking through the AMA passenger car specifications that someone posted in General Discussion and the GM Archives link. Page 94 indicates that the piston pins in the 302 v8 (z28 engine) were "Locked in rod". According to this GM document the piston pins were pressed into the rod, i.e. not "Full Floating" as the legendary rumor has been touted since the start of time.

If you look at this document it clearly shows that this line and column has the option to be "Locked in Rod", "in piston", "floating etc". 

Over the years I have contacted several CRG members that according to them were the original owners of a 1969 z28 and were in the process of having the engine rebuilt. I asked them to post or send me a picture of the connecting rod, especially the small end. I never heard from them again.

Maybe I'm misreading this document, but if anyone can comment on this I would appreciate it.

Saying that it's a misprint is not enough.

69er

[z28z11]

I pulled my '69 apart in 1974 and rebuilt it - standard bore, floating pins. I had the rods rebuilt before I reinstalled them with bronze bushings by Howard Douglas Machine in Nashville; when I got them back the shop manager told me that they were the toughest rods they had ever seen, apparently because they drilled the pin oiling holes out in the small end, and broke 2 dozen drills drilling them ("pink" rods were shot peened). When I ground the forging flash off the sides, the pink paint was still visible on the sides of the beams. I used TruArc retaining rings to reassemble, not Spiralocs.

My '68 rods are pinks, but pressed pins. They are polished as well - wish they weren't (and I wish I hadn't polished my originals), but that was a step back in the time when you couldn't trust materials and engine construction as much as you can today. Elimination of stress risers is still important, but more modern manufacturing techniques minimizes the risk to a great degree.

Regards,
Steve

[69er]

z28z11,

Great comments.

The General Motors "AMA Passenger car specifications" has printed detailed engine information on the 69z28 302cid engine. Its clear it states that the piston pins were the "Locked in Rod" type. The Chevrolet chassis service manual (Page - specifications 7) also indicates that the 69 302  - Piston Pin: Fit in Rod had an interference fit of .0008" - .0016".

I have pointed out the General Motors documentation that reflects that the 1969 z29 302 had "Pressed Pin" connecting rods. I have read many comments from members indicating that the connecting rods in their 69 z28 were full floating. But, NEVER ONCE, has a member posted a picture of the connecting rod showing the small end with "Babbit" on it. A picture would even show the type of machining on the small end of the connecting rod.

I realize the GM parts books shows piston pin retainers to secure the piston pin in the piston boss, and thus float in the connecting rod. But, this could be no more that GM showing the parts availability so that full floating piston pins could be used for the racing circuit.

Just looking for proof of facts. A picture is worth a thousand words. Just want to see pictures of  "full floating"  connecting rods before they are modified.

As I mentioned previously, I had contacted CRG members whom claimed they were the original owners and were about to have their engines rebuilt. I requested that they post or send me pictures of the small end of the connecting rods during the rebuilding process. After that request, I never heard from them again.

In the past I contacted the person whom did the machining work for "Dean's 1969 Z28" the website address is, "http://69camaro.20m.com/index.html". The machine shop told me during the tear down, the connecting rods were pressed pin type and not full floating"

And as I said before, saying its a "Misprint" is not enough proof.

Can some one post pictures of these connecting rods. Please have a close up also of the small end.

69er

[jdv69z]

Original 69 302 pistons are full floating. I've got my originals. In fact, when I had the engine redone in 1993, the machine shop broke the boss out of the side of one of the pistons. How? Trying to "press out" the pins on full floating pistons with the retainers in place. The rebuild then used press pin pistons. The rebuilder specifically indicated to me that he had to "bush" the rods in order to make the piston pins "pressed".

[1968RSZ28]

Jerry MacNeish states in his '69 Camaro Z/28 Fact Book,

"Full floating, forged-aluminum pistons were used in the '69 302 engine. 1969 pistons were actually introduced in late-production '68 Z/28s."

Jerry has probably seen the insides of original '69 302 engines more than most people.

Paul

[69er]

jdv69z,

Great comments as well. First I would like to say any competent engine re-builder should know the
difference between a pressed pin connecting rod and a full floating rod. Not acceptable that the re-builder did not know how to remove the piston pin. Makes me wonder how the rest of the rebuild went. I'm not sure if GM made a "pressed piston pin" and a "floating piston pin" design. Just to clarify, full floating piston pins move freely in the piston pin boss and in the small end of the connecting rod.

Since, you have your originals, if their not installed in your engine could you please post a picture of the connecting rod small end.

Picture worth a thousand words.

Hi 1968RSZ28,

Thanks for commenting. Yes, I'm aware of the "69 Camaro z/28 fact book". But, I supplied quotes from the manufacturer, "General Motors",  "The holy bible of z28 302 cid facts", their is no higher source. Book writers, bloggers etc. can write what they want, but I would like picture proof.

Let Jerry then post pictures of the connecting rods including close ups of the small end, untouched.

Again, picture worth a thousand words.

69er

[jdv69z]

Never said the engine builder didn't know how to remove the pins. Probably was done by a youngster who happened to work there. Engine builder must do something right. He's still there building racing engines, 23 years later.

Not really sure what the point of this anyway. Sounds like you mind is made uo.

[z28z11]

If GM is the "ultimate authority" on the cars, would someone please look up the proper part number from a '69 dated parts book and confirm this ? I can't trust my '74 printing to be close enough to the build date of '69 Z's to be unimpeachable. Everything I have ever read, seen or suspected points to full floating rods as being Flint correct in 1969 built 302's, including the ones in my car.

Regards,
Steve

[69er]

jdv69z,

I have no axes to grind with anyone, and my mind is always open to what ever the truth is. But, with truth comes evidence and not here say.  I was just looking through the "AMA passenger car specifications" that another member had posted and I was surprised to find the information regarding the 302's piston pins.
I remember seeing other posts before regarding this topic, so I thought it was fair to bring it up.

It's also not fair to a owner of a 1969 z28, who is passionate about the vehicle that he owns, and during a possible engine rebuild finds that the piston pins are pressed into the connecting rod. And then he wonders, maybe my car is not an original z28, its supposed to have full floating piston pins. We'll that's where evidence and truth comes in.

Its like the early 69 z28 had 1968 Camaro spoilers installed due to the 69 spoilers where not yet available. I remember reading some where on the CRG that members where replacing the short spoilers for long spoilers so that their z28 would be more authentic to to others, maybe even judges. And of course we now know that early 1969 z28's did come with the shorter spoiler.

So, let the truth out and be free and false facts.

z28z11,

Could you post any pictures you have of them, with the original machining. I so want to believe that the 69 z28 came with full floating piston pins. But, I have to see any evidence, here or trade shows.

69er

[KurtS]

The AMA doc has several errors. It's a form the manufacturers still submit.
GM issued listings of the Z28 features and the floating rods are listed there, IIRC.

[Stingr69]

3946841 is the original GM part number.  You can Google it, search it on ebay, or find it in Chevrolet parts manuals from back in the day for more detail.

[jdv69z]

OK, here's a pic of the underside of my original 302 pistons. If you zoom in, you can see hopefully the pin retainer grooves. Required to hold the pin in on full floating pistons. Pressed pistons have no such grooves, as the rod holds the pin in place.

[69er]

jdv69z,

Thanks for you contribution. But, most/many pistons are manufactured with the grooves
in the piston boss to accommodate retainers. What really differentiates between full floating
piston pins and pressed piston pins is the connecting rod. If you have your connecting rods available please post pictures of the complete connecting rod and then a couple of close ups of the small end of the connecting rod.

69er

[69Z28-RS]

When I disassembled my original 302 in 1976 for rebuilding, all parts were factory original and included 'fully floated pins'.  I bored the engine and installed Forgedtru pistons (0.030" overbore) also with fully floated pins (using the original rods).  My understanding has always been that the '69 302 included factory fully floated pins, so a better question for you might be....  Someone who has factory parts which are NOT fully floated should post data/photos of those... 

[jdv69z]

jdv69z,

Thanks for you contribution. But, most/many pistons are manufactured with the grooves
in the piston boss to accommodate retainers.

69er

Huh? OK, it's your turn. Show me evidence of a factory pressed pin piston with machined retainers grooves that were machined and then not used. So Chevrolet would only punch the holes necessary for a specific Camaro firewall, but they machined unnecessary grooves in pistons?  Stick a fork in me, I'm done.

[69er]

69Z28-RS, jdv69z,

I agree post pictures of connecting rods that used full floating piston pins and pressed piston pins that came from the factory.

I believe TRW made the pistons for Chevrolet at that time. And yes, pistons are made to support both types of use, ie - full floating piston pin and pressed piston pin design.

I think that we all benefit to get the facts out as best as we can.

69er

[1968 Z28]

Jerry MacNeish states in his '69 Camaro Z/28 Fact Book,

"Full floating, forged-aluminum pistons were used in the '69 302 engine. 1969 pistons were actually introduced in late-production '68 Z/28s."

Jerry has probably seen the insides of original '69 302 engines more than most people.

Paul

jdv69z,

Thanks for you contribution. But, most/many pistons are manufactured with the grooves
in the piston boss to accommodate retainers.

69er

Huh? OK, it's your turn. Show me evidence of a factory pressed pin piston with machined retainers grooves that were machined and then not used. So Chevrolet would only punch the holes necessary for a specific Camaro firewall, but they machined unnecessary grooves in pistons?  Stick a fork in me, I'm done.

Actually this was done at the factory.....not for 1969 302ci but for the 1968 302ci.  Upon tearing down my original 1968 Z engine (06-19-68 build date) I discovered that my engine had the 1969 version pistons (the ones with the pin lock grooves and straight across valve relief) and the 1968 version pressed pin "PINK" rods. Of course, there were no pin retainers used in the pistons.  Apparently they had already used up all the original design pistons but still had some of the pressed pin "PINK" rods left to use. 

[jdv69z]

Yes, it's the same piston intended for.............., drum roll, floating pins

[BillOhio]

See if this works

[asm69]

BillOhio,

Thanks for you input. Your picture shows the retainer for the piston pin. What really is needed is a nice close up photograph of the small end of the connecting rod, and the whole rod as well. Both
pieces are needed in order to have a full floating piston pin. You have posted a picture that
represents the piston side of the pin being retained. A picture is now needed that shows the connecting rod end. Hopefully showing the machining, and at this point should show wear pattern.

If you can please post the picture of the connecting rod.

69er

[BillOhio]

I didn't find any of the piston off of the rod.

[asm69]

BillOhio,

Are you saying you cannot disassemble the piston from the connecting rod. If this is a full floating piston pin,
all you have to do is remove one retainer. The pin should push out of that side of the piston boss. Sliding right through the connecting rod.

69er

[BillOhio]

I meant I don't have any pictures with the piston off the rod. The engine is back together now.

[jdv69z]

Bill, lots-a-luck! 

[69er]

Bill,
Good picture. But, it doesn't show that the connecting rod is a full floating rod.

[69Z28-RS]

Bill,
Good picture. But, it doesn't show that the connecting rod is a full floating rod.

So what exactly are you looking for in a photo to SHOW that the connecting rod IS manufactured for fully floated pins???   I can probably get such a photo for you if you can state what you are looking for...

[cook_dw]

Problem solved.

[1968RSZ28]

LOL!

Paul

[bertfam]

Sorry Darrell, but that's a reproduction letter. Easy to spot compared to an original, but I won't discuss the differences on a public forum since it would give the fakers too much information.

Ed

[69Z28-RS]

that's a good and very important note there Ed! 

[69er]

Thanks for that valuable document. I have forwarded that document to General Motors to be included in the next revision of the "AMA passenger car specifications".

[69er]

This is a great discussion, passionate topic. I respect your written and signed affidavit.
Since my last post I decided to call several machine shops from California to New York. I chose
machine shops that have been in business 25 to 35 years or more and machine shops that had
senior engine builders/owners.

I have listed six machine shops below that I called and asked if they have ever rebuilt 1969 Z28's 302 engines. And then asked if they could tell me how the piston pin was attached to the connecting rod from the "FACTORY". The key word here is from the "FACTORY".

All of the engine re-builders responded that the piston pin was of "PRESSED PIN" design.

From what they said,  the L88 was the only engine that came with full floating piston pins from the
"FACTORY".

I find it hard to believe that all these machine shops would be conspiring in some way. They as well are enthusiast and love what they do and are equally as passionate.

I started this thread due to another member posting the AMA passenger car specifications. I have no axe to grind or want to discredit anyone in any way or manner. Now after speaking with at least six machine shops and engine re-builders from West coast to East coast. I feel even stronger now that the connecting rods from the "FACTORY" on the 1969 Z28 302 were of "PRESSED PIN" design.

I urge any member to call machine shops in their own area and ask the same questions I did and draw their own conclusions. I think the moderator of the CRG should do research as well and see where the facts point. And when enough information has been gathered, post it for all to read.

Below is the list of machine shops I contacted. Company name , telephone number, name of engine re-builder and their comments are listed.

------------------------------------------------------------------------------------------------------
McQuillen Inc.
8171 East Main Road
Le Roy, NY 14482
1(585) 768-2322

Rebuilt bunch of 1969 z28 302 engines all were pressed pin design.
L88 was only engine factory made with full floating piston pins

Mr. Carl McQuillen - Engine builder
carl@mcquilleninc.com
------------------------------------------------------------------------------------------------------
Performance Engine
1-310-679-3604

Tony - Engine builder
Rebuild hand full 1969 DZ - all were pressed pin design
---------------------------------------------------------------------------------------------------
Al Hubbard Machine Shop (Been around since 1960's or before)
21030 Meekland Ave
Hayward, CA 94541
1 (510) 537-1885

Wade - Engine builder
rebuilt 2 to 3 1969 DZ - all were pressed pin

Never seen a "FACTORY" 69 z28 with full floating pins for the connecting rods
and has never seen any small block from the factory with full floating piston pins.

Big Blocks, yes, but not small blocks.

Maybe specialty builds had full floating piston pins not service engines.
-------------------------------------------------------------------------------------------------------------
Champion Performance LLC
24290 Sherwood Ave
Center Line, MI 48015
1(586) 755-7400

Mr. Ed. MIchaels - Engine builder
Rebuilt half a dozen dz engines - all were pressed pin
-------------------------------------------------------------------------------------------------------------
Coast Motor supply
1-818-703-9049

Omar - Engine builder
Rebuilt half a dozen 1969 DZ - all were pressed pin design
-------------------------------------------------------------------------------------------------------------
Pro Formance Specialties
1115 East Main Street
Rochester, New York
1-585-288-1499

Spoke to engine builder with many years of experience
Rebuilt several 1969 z28 302 engines - all were pressed pin design.
-------------------------------------------------------------------------------------------------------------

[69Z28-RS]

Everyone, including 69er, is free to *believe* what they want ....

After reading all you've written here, and also finding a thread from 2006 (started by ASM69 - and you both sound a LOT alike - new user name for you??)..  It seems to me to be so..
Here's the old thread with all the evidence you were presented then:
http://www.camaros.org/forum/index.php?topic=1015.0

Additionally, here is my own 'evidence'...

1) I rebuilt my original (never have been disassembled before) 302 from my '69 Z28 in 1976.  It had, and has, fully floated piston pins.  I have the original rods and original pistons that I could provide photographs for you if you'd like to make a wager?? 

2)  I do recall, when I rebuilt my engine in 1976 it was not uncommon for machinists to *recommend* doing 'fixed' pins in the pistons, but my friend (Robert a Christiansen) who had purchased his own 69 Z28 new in Dec '68, and who was assisting me in rebuilding my 302, told me that there was nothing wrong with the floating pins and I should so that, so I did (with new 30 over pistons).  He had raced his '69 Z28 in SCCA/TransAm, and also in IMSA GT from '69 thru the early 70's.

Bob (Robert) is still alive, and I have another friend who bought another '69 z28 and raced it in SCCA and TransAM/IMSA Gt also.  Both of these fellas are engineers and have excellent memories.  I will inquire with them both.

You said these guys you checked with were 'in business for 25 to 35 yrs; Do you realize that '69 Z28's were built 47-48 yrs ago??  and that most were *already rebuilt* within the first 10 yrs of their lives!  Maybe none of them EVER disassembled a factory original 302.

I'm curious... WHY are you so determined to try to convince people who know better, that the '69 302 piston pins were *pressed*

[bcmiller]

They were full floating pins starting about July of 68 (very late 68 model year) and for the entire 69 model year. The AMA document is not correct. End of story.

I have seen the inside of enough 302s to know, and have talked to numerous machinists over the years - most who have now been retired 5-10 years.

But believe what you want.

[z28z11]

I've got your proof if I can figure out how to post it - pdf @ 225kb, I can't determine out how to downsize it.

Piston/rod assembly removed yesterday from a February standard bore DZ, factory Spiralocs intact. They are pretty difficult to remove, so you'll have to wait a bit for pics of the small end until we can pull the Spiralocs and get a good pic of the pin bores.

Anyone have a tip on downsizing a pdf ?

Regards,
Steve

[z28z11]

Thanks to Darrell for massaging the two pics. One is less distinct than the other, but you can see the Spiraloc in place in the piston pin bore.

No doubts from me as to the originality of floaters in '69 302's -

Regards,
Steve

[KurtS]

And I thank you all for having a civil discussion on the topic.
On some other forums, the thread would have gone up in flames long ago....