[Nacs Fab]

I bought a new old stock set of 6.625” Aluminum Rods for my Street Car. I’m going to go with an Ohio Forged 3.75” Crank and some custom pistons. When I order pistons how far down the hole do I need my Compression Height? I read .060” clearance and I was planning on an .043” gasket. I’ll measure the rods when they arrive to see if they are short. I’ve never owned aluminum rods so I have an extremely newb question, the pins are press fit, is that correct?

Plan is to build a lightweight rotating assembly and spin it to 7,000 max, keep cubes around 406” for a single TorqStorm Supercharger. I have 330cfm High Port heads, Northwind Intake port matched, hydraulic Roller Camshaft, 1000hp E85 Pro Systems blow through carb.



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[Nacs Fab]

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[25stevem]

The pistons you run with those will need pin locks.

[Nacs Fab]

I actually thought about this, I can get an Ohio 4130 3" main 4.21" stroke crankshaft with Pontiac 2.25" Rod Journals, then go with an off the shelf DSSDSS-2-6120-400 piston. Piston is lighter than the 400 piston and has a 1.480 CH putting it .030" down the hole (maybe less if i deck the block), run a .043" gasket for a CR of 10.05:1 which is right where I want to be. Any reason not to go more Cubes?

[Skip Fix]

Might check the rod length BME Pontiac rods came 0.010 or 0.020 shorter already.

[68WarDog]

[QUOTE=Nacs Fab;6332096]I bought a new old stock set of 6.625” Aluminum Rods for my Street Car. I’m going to go with an Ohio Forged 3.75” Crank and some custom pistons. When I order pistons how far down the hole do I need my Compression Height? I read .060” clearance and I was planning on an .043” gasket. I’ll measure the rods when they arrive to see if they are short. I’ve never owned aluminum rods so I have an extremely newb question, the pins are press fit, is that correct?

Plan is to build a lightweight rotating assembly and spin it to 7,000 max, keep cubes around 406” for a single TorqStorm Supercharger. I have 330cfm High Port heads, Northwind Intake port matched, hydraulic Roller Camshaft, 1000hp E85 Pro Systems blow through carb.



Over at John Betts today and we were discussing aluminum rods for street applications, he mentioned something about my 428 block would have to be clearance for aluminum rods and street life would be diminished from using a good forge steel rods

[Gary H]

MANY years ago I ran a set of SuperRods in a 428 block with a 421 SD 990 crank, Ross pistons, and RA IV heads, Warrior intake. Probably put 200 runs on them shifting at 7500 RPM. No issues.

[krisr]

What sort of valve train are you going to run to spin it that high? I tried with a hydraulic roller and struggled to get stable valve train. I could have probably got it to get there with more stiffer components, but ended up going solid roller, with said stiffer components anyway, 1-2 shift is 7100 now LOL

[mgarblik]

You did not state what size the big ends of the rods were? Typically, they would be 2.200 which is BBC size and would match the Ohio crankshaft. If you verify it's BBC size, I have dozens of sets of correct rod bearings for aluminum rods with the hole drilled for the pin. I can fix you up. Just PM me. Also verify the small end size as well. Most aluminum rods will be .990 which is BBC as well rather than .980, the Pontiac size. Only running caution on the street is to bring them up to temperature under light load before putting any boost on them. Hard to tell from the pics, but I don't see any provision for pin oiling on those rods. I may just not be seeing it. If no pin oiling hole, I would have that added, especially for street driving.

[Half-Inch Stud]

my BMEs are 6.615" for the 6.625 application, 2.20 big end 0.927" little end. Weight 723 grams.

If you ever need Woody Oconnel @ GRP will sell single rods to your dimensions, and fair price.

[Nacs Fab]

I received the rods and measured them with a cheap pair of dial calipers and I found mine to have .927” pins too. Is this common with aluminum rods of that era, using a SBC pin? Do you think they can be bored on the small end to .980/.990? Is that big a wrist pin needed for a blower? I also think they are measuring out to be 6.800” but I’ll get them professionally checked. They are indeed 2.250” big end. Kauffman found me a forged 455 crank with 3” mains. I guess it would be down to a custom set of pistons which is not an issue. Thoughts?


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[Nacs Fab]

Originally Posted by krisr

What sort of valve train are you going to run to spin it that high? I tried with a hydraulic roller and struggled to get stable valve train. I could have probably got it to get there with more stiffer components, but ended up going solid roller, with said stiffer components anyway, 1-2 shift is 7100 now LOL

I’ve got a Hydraulic Roller and 930-16 springs, 7/16” studs in the heads and I’ll use a girdle.


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[Dragncar]

Originally Posted by Nacs Fab

I received the rods and measured them with a cheap pair of dial calipers and I found mine to have .927” pins too. Is this common with aluminum rods of that era, using a SBC pin? Do you think they can be bored on the small end to .980/.990? Is that big a wrist pin needed for a blower? I also think they are measuring out to be 6.800” but I’ll get them professionally checked. They are indeed 2.250” big end. Kauffman found me a forged 455 crank with 3” mains. I guess it would be down to a custom set of pistons which is not an issue. Thoughts?


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.927 pins with aluminum rods used to be the thing to have back in the day. If you are going to go with the .927 pin get the best .300 wall pin you can afford.
Blowers could care less about the extra weight. A lightweight .927 pin flexes under great load. That starts working your pin bosses in the pistons. That work hardens the aluminum.
Pin rips out no fault to the rod and folks blame the rod many times.
I just had a conversation the other day with Ed at Molnar about just this very thing.
Take it for what it is worth. How much do you like your engine ?

[Nacs Fab]

Most definitely going heavier Pins. Kauffman said same thing.


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