69 z28 rods

[1968RSZ28]

For years, I've had stock 3/8' rods in my 302 race car.  The onboard Racepac data logger computer does not lie about rpms.  Two of my engines are abused to as high as 8600 rpm.  No other engines take this asbuse unless it's a pro stock or modified eliminator engine.  They rev highrer but remember they have light-weight aluminum rods.

Jerry

8600 RPM!  Nothing beats a 302!        

Paul

[AFONEFE]

A few years ago I was lucky enough to observe one of Jerry's engines on the Dyno.  It was amazing to see the horsepower (458) and the high RPM's (8100) the 302 was putting out.  I think they did over 18 runs that day I was there.  I have the data sheet of one of the pulls.  I only wish I had brought my video camera.      

[sam]

Bring that video camaro to a (NHRA) DIV-1  points meet. Then you will see what the 02 is noted for!!

[KurtS]

Jerry,
I'm agreeing with you.

I wasn't clear enough. I've heard of some PM rods from other OEM's that reputedly hold together. Obviously that isn't true of the Chevy PM rods.

[asm69]

I dont want to continue to stir the pot regarding wheter or not 1969 z28's
came with full floating piston pins or not. But, I have a comment then a question
for Jerry or someone else with connecting rod knowledge.

The first comment I have is that this morning I met with the owner of Watson Racing
and Engineering in Concord California. He has been in the racing business for over 30
years. His comment regarding whether the 1969 z28 came with full floating rods were
interesting. According to Mike Watson, he seems to recall that some 69 z28's came with
full floating pins that were shipped to certain dealerships and ordered differently. Other
69 z28 came with the pressed pin version. In his own experience having ordered a brand
new1969 z28 along with his friend and upon tearing down the engine one had full floating pins
and the other did not. It was his opinion that GM quality control of components was very loose.
When 302 engines were being built to meet demand and the rods available were pressed pins,
they would use those rods,  production would not stop. According to Watson Chevrolet may
have said one thing, printed it on paper, but in production it may have been something else. He
provide me with an example, how two people that he knew (racers) both had bought new 1969 z28's.
One was very fast and the other was okay, he did'nt understand why that would be the case.
So, they tore apart both engines and sent both camshafts out to be measured for lift, duration and
overlap. What they found was that one camshaft had a different overlap than the other by about
2 degrees. His point was that Chevrolet did not have tight quality control over production. Machining
quality was very poor, hence a major cause of many 302's blowing up. He also commented that
Chysler was the worse for quality control and not doing what they said on paper. I dont know if
this makes sense, maybe some one can comment on that. In my  own research I'm just not sure what
to believe anymore.

Watson Racing and Engineering also informed me that if he was restoring someones 1969 z28
instead of spending alot of money on checking the rods and balancing. He instead would purchase
a brand new set of Manley connecting rods, keep the old rods in a box. His feelings were that
using Manley connecting rods provided the stability and quality needed.

So my question is if your rebuilding your 30 year old 302. Is it smarter to use a brand new connecting
rods like the Manley and keep you original rods in a box. I would like to know what Jerry does.
If the rods you get in someone's engine are pressed pins do you have them floated? If they are the floating type
due you reuse them or do you use another quality supplier of connecting rods like the Manley?

asm69

[GaryL]

It is common knowedge and a fact that the 302 was built with full floating piston pins.

The 30-30 has such long seat to seat duration that 2 degrees of overlap is not much I would think.

[Jerry@CHP]

Everyone is entitled to their opinion, and I always try to share my experiences and knowledge with anyone who asks. 

Would I use the Manley rods in my stock 302 engine........no, absolutely not.  The Chev 3/8 rods are excellent if they are shot peened and magged.  My NHRA Stock Eliminator car is a test bed for these engines and in the 14 years that I've been running this 302 combination............up to 8600rpm, I have never broken a connecting rod in any of my engines.  Now, does an enthusiast who is restoring his car need to install Manley rods..........no.  That's a waste of money.  Save this $$ for something that you really need in your resto project.  You can buy a set of good GM 3/8" rods ready to go for about $250.  The Manleys are much more $$.

Don't believe me, talk to Bub Whitiker of Burtonsville Machine or Gary McGlasson of McGlasson Racing engines.  These are two of the best engine builders in the country with impeccable reputations for building race engines and stock eliminator engines.  They will tell you the same thing about GM connecting rods and the applications.

Read the Chevrolet AMA specs and NHRA stock eliminator manuals.  All of the 1969 302s got the full floating pins.  We have rebuilt more 302s than just about all of the shops in the country.  We have never found pressed pins in a 1969 302 engine.  Over the past four or five years, we've rebuilt and restored at least 70-80 302s.  I have four 1969 302 engines in my shop right now!  All have full floating pins.

I have no reason to make any of this up.  I am just stating what is published and written............and what our experiences have been.

Jerry

[Jerry@CHP]

I should also point out that there are no noticable performance gains in ET at the strip or on the street with full floating pistons.  Both work and run well and we build them both ways. 

Regarding what was said about some 302s running better than others.  That was the case with many performance cars built during the late 1960s.  This depended on engine break in and engine tolerancing more related to deck heights and piston to cylinder wall clearance, core shift, etc.  Maybe John Z can shed more light on this. 

Many seem to think that becuse these cars were built during the late 1960s, it was the "Stone Age" with cavemen working on the cars........and anything went on the assembly line.  Not the case.  There were strict qualtiy control procedures that had to be followed.  I know this from interviewing many of the Norwood workers who were transferred to the Baltimore plant in the late 1980s.  This was at the time when I began writing the first 1967-68 Z28 Camaro fact book. 

Having lived the era as teenager during that time, my perspective is that the cars were for the most part, very nice and consistant.  And to think that GM gave a five year 50,000 mile warrantee makes a statement about how confident GM was about its product.   

Jerry
   

[fireZ]

When you say 3\8 inch is that the bolt size used?

[Jerry@CHP]

Yes, 3/8" bolt size, started in '68.  Before that 11/32" was the rod bolt size and there were plenty of connecting rod failures with the smaller rods.

Jerry

[JohnZ]

Here's a photo that compares the "early" and "late" small-block rods - note the "bump" adjacent to the rod bolt seats on the "late" rods on the right; the "early" rods without the added material at the bolt seats are a time-bomb in a performance engine. NOTE: These are small-journal 327 rods with 11/32" bolts, not large-journal 350/302 rods.

Note: These engines weren't built by neanderthals with bastard files and sledgehammers; considering the technology available at the time, they were amazingly consistent, even though each engine plant built 5500 engines of 35-40 different suffix configurations per day, every day. Some were a little better than others as a result of more favorable (and random) tolerance stacks, but nowhere near what some people would have you believe. I was there, and the people spouting "internet legends" were not.

[fireZ]

Thanks for the info. That clears up some questions I had. I sometimes hate to ask fearing they are stupid questions,but if they are not asked people are unsure.

[asm69]

Thank you Jerry and John. I believe your comments are accurate and correct.

So, Jerry when restoring a 1969 z28 and using the GM 3/8 rods, would you
float them by using a bushing or float them by honing the correct clearances
in the connecting rod?

Thanks again for your comments. I'm just trying to build the engine correct
to the era and have it be reliable. (non-racing, street use, Occasional burn outs).

asm69

[fireZ]

So if they are 3/8 bnolts does that mean they have the extra bump by the rod bolt seat as john Z showed us?

[Jerry@CHP]

John,

You could not have made a better statement about GM's engine program.  I get these questions everyday at the shop with many who own the cars saying, "well this car has this item on it and I know it's original to the car because that's the way it was the '60s."  Most of my customer base didn't even have a driver's license when the cars were new.  Most are in their late 30s to mid 40s, which is good for the hobby because it means these cars made an impression on younger generations.

Regarding the connecting rods, you can build your engine in many ways.  Bush the rods or use originals with the factory babbot material and fit the pins to the rods.  In many cases, we go back together with a pressed pin.  Why, because many of the 69 302s had sprial lock failure with pins coming out and digging into the cylinder walls.  Not a good thing........and it's one less thing to worry about when you're building an engine.  It's a little added insurance building them with pressed pins.  

Jerry