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Hi folks, I'm new, great place!!! I recently got into a 1964 GTO project, looking to build a pretty stock GTO, but with a 421... I picked up a date code correct 64 421HO block, with tripower, crank and forged rods. Im new to pontiac, so I need some help with the rods... I understand the early forged were ok, but except for the SD 421, the heat treatment was suspect, and aftermarket rods are better.. Problem is, these rod are unmarked, except for a GM on the beam. They reportedly came out of the 64 421 I have. Can anyone give me an idea of what they are, when made, and if they are ok for a stock rebuild, 5000 RPM motor?
Thank you in advance!!!
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The rods don't have a part number. The 1958-'62 are low rockwell. The SD rods were better and had 7/16" bolts. No mention of the '63-65 forged rods with regards to Rockwell.

Would I use them? No. Spend the money and get new aftermarket rods with the better tensile strength and 7/16" rod bolts. You can sleep at night knowing they are not old and could fail. You will also want forged pistons. Should be no problem spinning the engine to near 6,000 RPM's with the right cam, 5,600 RPM's is a better number if you want to be really safe. 5,000 RPM's is for old lady's and 2 Bbl carbs with single exhaust - not 421HO engines. (y)

The most important thing with the larger main journal cranks/engines is the oiling system and bearing clearances. I suggest the Butler Pro 60PSI oil pump that will flow more oil, a good quality aftermarket oil pump pushrod (I am using the one from Nitemare Performance - but Butler has them as well and cheaper), and the 3/4 groove main bearings - which I am using in my 455 build, and the Best brand graphite rear main rope seal. Use a quality filter like Wix or the Napa Gold - which I am told is made by Wix.

So just some tips that you can think about and discuss with your engine builder.
 

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Thank you sir! I'm going to stay pretty stock, small tires, but put the ram air exhaust manifolds, and a 2.5 exhaust. Might include a 66 center carb, I understand they flow 25-30 cfm more then the 64... Yes on the pistons, might do a roller cam, and rockers, but stay with the stock lift. At 9.5 comp, I think 375 hp would be the goal... With that light body, and small tire/4 speed, I dont think it will see over 5000-5300rpm? Its gonna be too expensive to wring out? LOLOL
 

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Any value in the rods? Worth it to have them hardness tested? They came from a collector who has some pretty over the top stuff... Like X400 parts...
 

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The 421 HO had the same rods as the standard 389 - cast. I used the '58-'62 forged rods for a long time when there was no other option. I did lot of work to them and they survived fine to 6000 RPM. Then I used they '73-'74 SD rods. In this day and age I would never use either one again. You can get very inexpensive forged rods and sleep well after revving the engine a little more than you intended.
 

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Yea, can lighten the recip mass quite a bit between rods and pistons... thank you!
 

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Carburetor - If you have a '64 tri-power, don't try to use a '66 carburetor. It would require an adapter that causes clearance problems and effects performance. Plus the small carburetor flows about the same as the larger one anyway. Even though the throttle body holes are smaller on the '64, the internal throat of the carburetor is actually larger.

Rods - There's no value in those rods. Don't bother having them tested.
 

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Any value in the rods? Worth it to have them hardness tested? They came from a collector who has some pretty over the top stuff... Like X400 parts...
Very cool, X400 stuff. There may be value for someone, but with the options on new replacement rods at reasonable prices, it is wiser to go with new to ensure an engine that doesn't have a rod let go and take out the engine - you don't know how many cycles the rod has on it or if it was pushed/abused beyond its limits.

The '64 tri-power should have the smaller center cab, which means you cannot just slap the larger 1966 center carb on it. You may be limited to the factory small center carb.

Not a fan of a roller cam, but they have their positive aspects. My biggest problem is the side loading they put on the lifter bores. I have seen pics of the lifter bores busted due to the side loading put on them by the steep ramps some have. So you want to make sure you use a cam lobe profile that is not too aggressive and somewhat gentle in its lift. You can also add a "lifter brace" which can be had as an aftermarket piece - this will strengthen the lifter bores and reduce any chances of the roller cam busting the lifter bores. You will also need the correct length pushrods AND if using the stock iron heads, they are press-in studs and can pull out with higher lift cams or heavier rate springs. They are also "bottle neck" rocker arm studs which can snap off with excessive lift/spring rates. You can have 7/16" screw-in studs added if you have a machine shop that knows what they are doing.

And, without looking this up, I don't know what year Pontiac stopped using tge "oiling through the block" for the rocker arms. You may be fine with the '64 421 as the GTO 389 went to pushrod oiling versus through the block. Not a big deal to change over to oiling through the pushrods if your machinist has done this, or if it is even needed.
 
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