[brokenscrewdriver]

Rebuilding a 1967 Pontiac 400 for street use (Grocery getter for my wife), has 95,000 miles. Did the connecting rods last or were they prone to break occasionally? If so, any recommendations what make to replace with? Thanks.

[Tim Corcoran]

Your factory rods would need to be re-sized and new fasteners installed before they were safe to use. I also recommend having them magnafluxed and shot peened. Sometimes rather then putting money into 47 year old rods most people will just pick up a new set of rods.

[steve25]

They do not always need to be re-sized and reloaded with new bolts.
When you break them open and remove the bearing incerts take note of the impressions in the bore left from the stampings in the back of the bearings.
If they are clearly impressed in the bore than the size is good as are the bolts in so far as holding the rod cap to the big end.
At that point make a close inspection of the shank of the bolts after the threads end for nicks, if that checks then you can get them maged for cracks and checked for size and I would then have no fears of using them in a G getter that would never see anything higher than the 4500 rpm shift point of the auto trans with your wife behind the wheel!

[hurryinhoosier62]

HUH? Steve, I don't often disagree with you, but IMPO it's folly to NOT resize ANY connecting rod and at the very least magnaflux the rod/nuts and check the stretch length.

[steve25]

Like I posted, if the number and letter impressions left by the back side of the bearings are clear then the bearing crush was right, and that needed amount of bearing crush was provided by good bolts that torqued up to the needed spec range.
If the crank side of the bearings show normal ware the the rods are good if they pass the Mag test.
The stock rod bolts do not have the needed dimples to check for stretch, so that check is out the window, and if you replace the bolts your then tied in to a resizing job, which at that cost point new 400 buck rods would be the way to go!
Like I said, in a motor with the stroke loading of a 3.750 like in a 400 motor,and will never see over 5k rpm I would sleep quite easy at night when reusing rods that pass the check outs posted.

[hurryinhoosier62]

Steve,

With all due respect, I've seen thousands of set of connecting rods. Few, if any, remain concentric once disassembled then reassembled using the same bolts. That's the main reason WHY I always replace the connecting rod bolts and resize the connecting rods in EVERY engine I build. It's CHEAP insurance.

[Tom Vaught]

I am a fan of newer parts (or new never used older parts).

Every part has a given life cycle. Then the part just gives up.

I have destroyed two engines (designed for "test to failure" long term durability testing). In both cases a rod gave up after about 1600 HOURS on the dyno.

(300 hrs works out to about 100,000 street miles.)

So the rods JUST GOT TIRED AND GAVE UP.

The point of this is, with a connecting rod 50 years old, who knows how many hours were on the cast iron rods that were installed. They could fail tomorrow from fatigue with brand new bolts and being resized.

Just saying.

Tom Vaught

[PONTIAC DUDE]

Originally Posted by brokenscrewdriver

Rebuilding a 1967 Pontiac 400 for street use (Grocery getter for my wife), has 95,000 miles. Did the connecting rods last or were they prone to break occasionally? If so, any recommendations what make to replace with? Thanks.

Before recommending.............. street use as in ???

Upgrades?

However, If close to stock. ARP rods bolts and resized will work fine.
Other option.............For the buck. Steel rods, bigger bolts, etc, 10 times stronger and cheap.
http://store02.prostores.com/servlet...0-Stock/Detail

[hurryinhoosier62]

Originally Posted by Tom Vaught

I am a fan of newer parts (or new never used older parts).

Every part has a given life cycle. Then the part just gives up.

I have destroyed two engines (designed for "test to failure" long term durability testing). In both cases a rod gave up after about 1600 HOURS on the dyno.

(300 hrs works out to about 100,000 street miles.)

So the rods JUST GOT TIRED AND GAVE UP.

The point of this is, with a connecting rod 50 years old, who knows how many hours were on the cast iron rods that were installed. They could fail tomorrow from fatigue with brand new bolts and being resized.

Just saying.

Tom Vaught

I had a friend killed when the Lycoming engine in his Piper Comanche failed due to a broken connecting rod bolt. The bolts passed magnaflux inspection during overhaul. Under inspection after the crash, the bolt that failed was found to have intergranular corrosion due to an extended period of work cycles. In layman's terms, the bolt failed because of fatigue that did not show up under NDT.

[77 TRASHCAN]

Butler has new "I" beam rods for $288.~~, for a set, and a set of "H" beams for slightly over $400.00

Ken, I like the looks of your stuff!!!

Tim, You have a website for your stuff yet??? Contact info???

FWIW.
My engine builder friend would through sets of rods for the characteristics the Steve described above. This was way before the days of the incredibly affordable engine parts we have access to these days. They were used in moderate builds, nothing radical. He also like to stay away from having rods resized, prefered the factory work, if possible, and if still in spec. He often used resized rods, when needed. I never asked why....on any of this reasoning, possibly experiences...

[Big Injun]

It may be the wife's grocery getter but all it takes is one blast by you (or even the misses) and....

[Nicks67GTO]

A set of those 5140 I beams are like $250 bucks, theyre about the same weight as a stock cast rod if im not mistaken and they're much stronger than a cast rod could ever dream of being. Its a no brainer IMO.

[steve25]

I agree that for 250 bucks you just can not go wrong, that being said I have been wondering around a engine shop once and observed a worker installing SPS rod bolts right out of the skin pack that where rusty and I said to myself two things.
1) I was glad I did not ever have any work done here and 2) that the rods where for a SB chevy!
The rust issue is a thing that not alot of first or second time builders know about until the rod(s) exits the block.
From what I have seen with most Women, I would be more concerned that she would run the motor low on oil than do in the stock rods!
Maybe a Accusump set up and a low oil pressure Ing kill switch should be in the plans also! LOL.

[geeteeohguy]

A friend's '67 GTO with the stock engine threw a rod at about 1100 rpm while idling out of a driveway back in the day. The engine had been overhauled by the Pontiac dealer in 1977 at 80,000 miles 'just because' and the car at this time (1980) had 98k on the clock. Granted, we used to race that car a LOT, and float the valves. But it blew up without any warning, on another day at just over idle speed. That said, my '67 GTO has 245,000 miles on the original rods, and has been revved to the moon and had its valves floated, and is still going strong (for now). I think luck has a lot to do with it. I baby this car now, but if I were to rebuild another Pontiac any time soon, it would get aftermarket rods for sure. Cheap insurance.

[rohrt]

Originally Posted by geeteeohguy

A friend's '67 GTO with the stock engine threw a rod at about 1100 rpm while idling out of a driveway back in the day. The engine had been overhauled by the Pontiac dealer in 1977 at 80,000 miles 'just because' and the car at this time (1980) had 98k on the clock. Granted, we used to race that car a LOT, and float the valves. But it blew up without any warning, on another day at just over idle speed. That said, my '67 GTO has 245,000 miles on the original rods, and has been revved to the moon and had its valves floated, and is still going strong (for now). I think luck has a lot to do with it. I baby this car now, but if I were to rebuild another Pontiac any time soon, it would get aftermarket rods for sure. Cheap insurance.

I find that fascinating. No knocking before hand?

[geeteeohguy]

None. We had just tuned it up the day before, and it ran fine. Fresh oil, too. He had been really racing the heck out of it and abusing it, though. Had just filled it up and was pulling out of the gas station and boom...#2 rod came up and broke the cam, and busted the block. We had purchased the car for $1350 about 8 months before from the original owner, a lady who got it as a high school graduation present. '67 GTO hardtop, Cameo Ivory, (cherry original paint) gold interior, rally gauges, deluxe wheel covers, A/C, TH400, and 2.93 posi. That car was cherry and an absolute terror on the highway....got beat once by a '69 GT500 Shelby, and that was it. He ended up selling it for $500 with the blown motor. We figured it should have blown up during one of its many races, not loafing out of a gas station!

[Tom Vaught]

Most of the engine issues I had with Pontiac Engines were totally random.

1)Broke a pushrod 20 miles from home after driving 6 hrs each way to Niagara Falls and back.

2) Jumped a tooth on the timing chain pulling into a driveway.

3) Had a fuel pump leak (Mechanical) driving home from church and noticed smoke was coming up from under the car. Gas was spraying on the exhaust pipe and catching on fire.

Sometimes the stuff just happens like those rod failures I posted about earlier.

Tom V.

[Tim Corcoran]

Tomahawk Performance Products
No website
Tomahawkperformance@gmail.com
623-428-7125

[steve25]

I dont know about that failures just happing thing there, as in his second post he finally brought to light the fact that they had been racing the HECK OUT OF IT.
I would like to know if the the big end of the rod came apart, or if the beam section busted?

[rohrt]

Has me wondering a few of things.

I have only had rods come flying out when at high RPM and usually accompanied with rod knock. What Tom V has posted about a given life cycle scares the hell out of me. I still have a 455 that I built back in the 90s and recently put the stump puller in. At the time it had ARP rods put in and were shot peened. It was the best most of us could do at the time. Its hit 6K RPM before but mostly kept under 5200.

Can a person just swap the rods without a re-balance. $250 is one thing but removing the whole bottom end is another.

The other thing I was wondering, after watching a few videos on 'at home piston and rod swaps' I see they would heat up the small end to 400 deg and just slid the piston pin in. How perfectly should the rod be centered in the piston?