[torqhead]

Originally Posted by JLMounce

I believe Dave acquired the shortblock pre-assembled. If it's otherwise in good condition without the need for a full tear-down, I'd say run it unless it's a full race build.

I agree if you're doing the whole thing from the ground up, worth it to go with aftermarket rods, pistons, bolts etc.

Exactly where I'm at Jason!

[jamaca85]

i did 6000 with a 400 i USED to have..... i think broke a rod , oil pan and block.. track prep guys hated me that night....

[70 bird]

I had a 400 that I spun to 6200 once....... spun a rod bearing. at least I saved a few hundred bucks on buying decent rods! lol.

[Cliff R]

Stock cast rods are stronger than they get credit for and will work fine for high performance work. Problem with them is that most have pretty heavy pistons/pins hung on them and at high rpm's the big ends go out of round and the bearings grab the crank. When this happens the rods end up breaking and more often than not the block gets "windowed'. I really can't ever remember just seeing one snapped in half and still free on the cranks w/o bearing damage. Still difficult to figure out what came first, the chicken or the egg, but I still avoid stock rods here as we simply have so many other options out there these days that are superior in every respect.

WAY back before we had good options we did a 455 drag engine for a customer who spun it to 6200rpms for many hundreds of runs w/o issue. The rods were completely stock with ARP bolts and correctly sized on the big ends. We eventually upped the power level of that engine and good rods became available so it got one of the very first sets of Crower rods. I slept better at night after that upgrade!.......Cliff

[Sirrotica]

I raced a 428 with stock, resized rods, good bolts, heavy TRW forged pistons, and balanced, in a dirt track car. It ran 6000 RPM twice each lap, for 3 years with no failures. That was in the 69 GP in my signature pictures.

I also ran a 400 with stock rods (5500 RPM), stock pistons for 2 years and pulled it out and put it in a street car. The body rusted out on the street car and the engine was still running fine. This engine was in the 67 GTO/Lemans in my signature pics.

I ran prepped stock rods because there was nothing factory or aftermarket I could afford at the time. Crower, Oliver, and factory SD 455 rods were about all that was available at the time, and for my situation, cost prohibitive. The SD rods were also really tough to procure as there was a factory parts bulletin that prevented anyone without an actual SD car limited to buying more than 4 rods at a time without a SD car VIN.

Running on a closed course, and running the engine near redline lap after lap is a bunch harder on the rods than drag racing, or an occasional light to light on the street. When I raced, we ran an 8 lap heat, 12 lap semi final, and a 20 lap feature, 40 laps a night under green, plus any hot laps you ran before the races started.

From previous experience, if you take a stock engine and run it hard on a dirt track, you might get one race out of it before you spin a rod bearing. Preparing the bottom end is a must if your going to run it hard lap after lap, season to season.

As has been said previously, the cast rods are stronger than people give them credit for. Improper bearing clearance (too tight) weak bolts, and compromised oil systems take out more Pontiac rods than them just flat out breaking due to being overstressed from design parameters. People trying to rev a stock Pontiac bottom end like a SBC is exactly how Pontiac got the rod chucker title in the hot rod world.

If anyone wants to find out what breaks any engine, running it on a closed circuit such as a dirt track will show it's flaws quickly..............

[Cliff R]

Good info.

Reminds me of my High School days. The Pontiac GTO and Firebird owners were constantly scouring the local junk yards looking for engines. It was difficult if not near impossible to find a decent 400 in a 68-70 GP or Bonneville in this area. This was mostly due to the quick destruction of their Pontiac engines after trying to keep up with the SBC's and Mopar's that could EASILY do a full throttle burn-out and "donuts" I the High School parking lot and survive the ordeal.

Anyone I ever knew who ran a Pontiac engine to those rpm's in a similar fashion very quickly found out the limitations of the stock cast iron connecting rods.

One of my very best friends had a perfect green 1969 GTO Ram Air car, and his dad was a big deal at GM at the time, so he had nearly unlimited funds. I think he went thru more engines that I changed my underwear my Senior year! The kid ran that car like he stole it everywhere he went, and his engines didn't last much longer than it took me to type this.....mostly if not solely due to the "weak" cast iron rods......IMHO........Cliff

[Sirrotica]

Just thinking about a few other things that helped Pontiacs live, was the adoption of the baffled pans in 1973, not a cure all by any means, but a bandaid for running all the oil away from the pickup on long turns. Since the T/As were becoming more common than GTOs the handling of the T/A chassis would aggravate the problems of non baffled pans in stock engines.

Running an extra quart in the pan was something the factory tried for a year in 1967 (7 quarts) but I'm guessing there was limited success because the factory dialed it back in 1968 to 6 quarts, and never increased the factory capacity until the Stratostreak engines ceased to exist in 1981. In any Pontiac being used in corner speed racing, running it a quart over full, will help keep the oil pump pickup covered under most adverse conditions.

There is more to take in consideration than just saying that cast rods were the weak link in Stratosteak engines. Windage, baffled pans, only having mains 1/2 grooved in standard duty engines, as opposed to fully grooved in the HP applications, all this factors into engine longevity. Especially if you plucked a 2 bbl engines from a Catalina and dropped it into your GTO with a low performance oil pump and bearing package, chances of you building the top end of the engine with better heads and camshaft with standard duty bearings and oil pump was a recipe for destruction. It happened often during the 70s.

Racing Pontiacs on an oval track, plus making a living every day turning wrenches. I saw plenty of destroyed Pontiac engines due to lack of knowledge about the engines peculiarities, as well as lack of common sense about what parts and assembly procedures can be used to make these engines live under racing conditions.

Just a few of the mistakes that compound the cast rod being blamed for all the engine destruction when there were other factors that contributed to early engine demise in the 60s, 70s, and into the 80s, when Pontiac engines were plentiful, and running the roads daily.

[Cliff R]

I'm not the first bit afraid of the factory cast iron rods and have never once lost an engine due to one failing. I also know how to set up the bearing clearances, oil system, and can keep the oil in the pan and pick-up covered in any application.

Even with that said we belly-ached for years for better parts, especially connecting rods. The aftermarket stepped up with excellent and affordable options that aren't much more money that taking a set of stock rods, putting good bolts in them and having them completely rebuilt. They gave us modern forged pistons as well with full-floating capabilities, better alloys for tight fit, modern ring packs and for sure a LOT lighter than Speed Pro and TRW offerings.

Pretty much a no-brainer far as I'm concerned, so every engine I've done here dating back at least 20 years has had aftermarket forged rods in it, and it's been nearly that long since I've used a Speed Pro or TRW forged piston in one...........Cliff

[meangene]

I dirt race stock Pontiac rods and turn them 7800 at the end of the straight away and didn't have any problem for a whole year. Now that said, I would not waist my time rebuilding them when you can buy new for less than 300 and their better forge steel http://www.competitionproducts.com/5.../#.Wo3GWUDwa1s

[dataway]

Since weight matters a lot .. I've always wondered what you could turn a 326 with some modern lightweight slugs and pins in it using stock rods. Wonder about forged rods, roller cam, roller rockers, Ti retainers (Ti valves and stellite seats?). Would be fun to have a reliable street Pontiac that would turn 8,000 rpm

[Tom Vaught]

Except for the bore diameter and piston weight, (not pin weight). the 3.75" stroke would be the same for the 326, 350, 389, or the 400 engines.

The stroke and the Inertia Load Factor is what sets the rpm limit.

This is based on the same rod weight, same pin weight, same ring weight, with only piston weight changing due to the diameter change.

So you put modern light weight pistons and rods in a 326 to 400 cid engine with the same stroke they all will be happy and will be able to run higher rpm.

Tom V.

[meangene]

Cross drilling the crank plays a big role in rod and rod bearing life, most people don't do this and I don't know why they don't, I've never had a failed rod or crank issue after doing this

[mgarblik]

When the decision is made to scrap the cast factory rods and go with Chinese aftermarket offerings, just a common sense warning. The new replacement rods need careful inspection, housing bore verification and pin end checks before installing. Given the choice between reusing cast factory rods with no bearing damage or out of the box Chinese new rods that have not been verified, I would reuse the Pontiac cast rods every time. Once the Chinese rods have been verified and generally corrected, there is no doubt, they are a better choice. They are lighter and made of better material. When they first came to market, every one had to be rebuilt before use. Didn't matter who made them. The last 3 or 4 sets we have checked, Eagle and the others, 1 or 2 still need a little "tune-up", before they can be considered excellent. Every now and then an entire set will be right on spec. and just require washing and installation. IMO, buying new aftermarket rods from China and "assuming" they are out of the box great, is a dangerous assumption.

[slowbird]

Originally Posted by meangene

Cross drilling the crank plays a big role in rod and rod bearing life, most people don't do this and I don't know why they don't, I've never had a failed rod or crank issue after doing this

Crossed drilled cranks are an issue at higher rpm, that is why no cranks are crossed drilled anymore.

[GRX]

Are the stock rods used? If so I would be highly surprised if they were not stretched somewhat. Many over look this.

[meangene]

Originally Posted by slowbird

Crossed drilled cranks are an issue at higher rpm, that is why no cranks are crossed drilled anymore.

cross drill crank issue at higher rpm, i don't think, every 421, 428, and 455 is cross drill and when i ran a 69 ram air IV in my stock car, with stock rods and crank that was cross drill turning 7800 at the end of the straight away with no issue for a whole season, don't believe ya

[pastry_chef]

Originally Posted by meangene

cross drill crank issue at higher rpm, i don't think, every 421, 428, and 455 is cross drill and when i ran a 69 ram air IV in my stock car, with stock rods and crank that was cross drill turning 7800 at the end of the straight away with no issue for a whole season, don't believe ya

Slowbird is correct.
While a cross drilled crank is not a guaranteed failure it is less efficient.
Bryant, Winberg and Callies all agree.

[PunchT37]

I believe, at lower rpm`s, the cross drill has a benefit as it lets the rod bearing get oil "2 times" instead of having to get that big a$$ 3.25 bearing go 180 more degrees to get oil to the rod. A full groove main? Yeah but, the load capacity of the half groove is better, especially on that heavy crank with a long stroke.

I believe that`s why the engineers cross drilled the 3.25 mains and not the 3`s.