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  #31 (permalink)  
Old 11-07-2012, 07:46 AM
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The trend is to go to the "stroker". The 455 block isn't as physically strong as the 400 block. 400 blocks are much more "plentiful". The best place for 455s today is the collector crowd.

You were "lucky" with the 455 and cast rods "living". That's the weakest point in the Pontiac. Change the rods and it's every bit as tough as any other engine, maybe tougher than most.

Jim

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  #32 (permalink)  
Old 11-07-2012, 09:14 AM
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The 1963-1979 cast nodular iron Pontiac rods are strong enough for 7,000 RPM in a 400 and 6,000 RPM in a 455, if prepared correctly. The 1973-1979 cast rods are better than the 1963-1972 rods because GM eliminated the cam oiling spit hole in the rod cap parting line starting in 1973. The lack of the spit-hole forces more oil and increases pressure on the rod bearing where it is needed most. Rod twist must be checked for all rods and the side clearances should be opened up .010" for the 1973-1979 rods to maintain flow across the rod bearing. The old regular production 1961-1962 389 forged "rubber" rods and the 1963 421 H.O. forged "rubber" rods were low carbon forgings for low RPM. Many many people think they are the rods to use and they are cheap. I am sure not many people don't buy that myth anymore after finding bent rods.

The problem with all stock rods is the stock rod bolts. The stock rod bolts must be replaced with ARP bolts, and the rods resized if the engine is going to be anything but a grocery-getter. The scenario is that the stock rod bolt stretches at high RPM on the piston return stroke, the rod pin bore goes out of round, the rod bearing spins out, the rod seizes on the crank for an instant, the rod snaps just below the pin-eye and takes the engine with it. Then the cast iron rod gets the blame for the weak rod bolts.

Another problem with stock rods is improper torquing and over-torquing the stock rod bolts by amateur engine builders. Being curious, I put a stock Pontiac rod in a vise and turned the rod bolt with a torque wrench. The stock rod bolt stretched and broke at 65 lb. torque.

Last edited by MouseFink; 11-07-2012 at 09:21 AM.
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  #33 (permalink)  
Old 11-07-2012, 12:00 PM
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Mousefink,

While this is a popular "arguement" among those that would try to reuse the rods, it's simply not true. A cast part (regardless of where it's used) is much more rigid than a forged part. As a result, they will hold their dimensional stability very well right up to the point of failure. It will then fail "without notice". The factory bolts were SPS, like the Chevys.

It simply makes no sense to pay $150 to resize a set of rods, add $65 for new bolts, when you can buy 5140 forgings with BETTER bolts for $250. MANY a Pontiac found its way to the scrap yard with rods hanging out of the pan.

The spurt hole was eliminated to reduce emmissions. It has no effect on oiling the crank. And contrary to popular belief, the oiling system in the Pontiac is quite good.

Jim
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Old 11-07-2012, 12:59 PM
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No argument about the old Pontiac forged rods. They are worthless even if you can find one that is not bent.

However, I must take issue about the rod cap spit-hole. The oil spit-hole was mandated by the EPA in an attempt to reduce emissions by reducing oil spray on the cylinder walls and it certainly DOES help rod bearing oiling. It helps rod bearing oiling by re-directing the oil from the spit-hole and across the rod bearings. The re-directed oil flow is more effective if the side clearance of each pair of rods is opened at least .010" (.005" each rod) so the re-directed oil will have a path for escape.

Aftermarket forged steel Pontiac rods are available from $480 to $1,250 for the all-out competition engines and for competition, those rods are the best choice. It is becoming difficult to find a good stock rods. Pontiac engine have not been built since 1978. "Pontiac" engine vital parts are now being built by aftermarket suppliers, blocks, cranks, rods, and heads etc., and they are far from being "Pontiac" engines.

Pontiac powered cars have gone the way of the "Do-Do Bird" and those that remain should be in Barrett -Jackson Auctions.
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  #35 (permalink)  
Old 11-08-2012, 11:15 AM
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I feel totally gypped. I never got to rebuild an engine in physics class!
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Old 11-08-2012, 11:37 AM
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Quote:
Originally Posted by Silver Surfer View Post
I feel totally gypped. I never got to rebuild an engine in physics class!
Don't feel to bad, Neither did I, I got to balance the rods and pistons though and spend my 2 week expulsion rebuilding the 326. It was still a topic of discussion at our last reunion in 2003.

Ray
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Old 11-08-2012, 11:47 AM
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My school wouldnt let me take Automotive.....still sore about that to this day....
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  #38 (permalink)  
Old 11-08-2012, 12:20 PM
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Why not? You should be able to take whatever you want...I know when I went to school (many years ago), some people in the facility considered taking a shop or trade course was for the less academically gifted...I thought it was ridiculous then and I think it's ridiculous now.
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Old 11-08-2012, 12:30 PM
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It is stupid, Long Story Short I was in "Gifted" classes....talked my parents out of it....vowed to never do that to my kids. I just talked to my machine guy and he says go for the Pontiac 350. Bring it down to him so he can check out the block and heads and he wont charge me to teach!
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  #40 (permalink)  
Old 11-08-2012, 12:59 PM
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Yes it's amazing how some people pigeon hole other people into what they think is right. I know the "jocks" in my high school used to call them "shop dummy's" until several of the guys taking automotive became extremely successful. One owned a GM dealership and the other a large construction company...I loved it and these guys didn't throw it in popular crowds face...they just went on with their business.

Glad to hear your machinist is willing to help you out...That's going to be a major expense avoided.

Good luck and any questions, don't be afraid to ask....You can see there are a lot of opinions.

Ray
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  #41 (permalink)  
Old 11-08-2012, 03:03 PM
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Wouldn't say useless...only thing useless is something that doesn't make sense.

I know what you mean by working hard to get what you want...I started working for my father at a young age and believe me, he made sure I worked...I never got a break or got off easy because the boss was my father. I worked before and after school and weekends. When I was 16 I bought a 67 Firebird...cash. Work ethic is one of the things that I tried to instill in my kids...(I did buy each of them their first car, but never gas, insurance and repairs both my son and daughter worked beside me when I put the parts on the car that they paid for from the job that they had)...Funny you should mention...my kids never ended up in jail either...maybe there's something to this working for what you want and appreciating it more when you get it.

Ray
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