427 BB rod length? - Chevelle Tech
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post #1 of 34 (permalink) Old Jan 27th, 20, 12:50 PM Thread Starter
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427 BB rod length?

Im building a 427 BBC. Its going to be a pump has alu headed hyd roller engine around 500hp.
I have a forged #7115 crank Im going to use but no bushed connecting rods just oem 3/8 with pressfit.
Im going with bushed so I can mount the pistons my self. So question is 6.135 or 6.385 or even 6.535 long?
Dont think I will notice much difference in power but guess it will balance easier with 6.385 and Icon makes several different cc pistons fot that combo. 6.535 needs custom pistons I guess?
Will the 6.385 piston and rod have much less weight vs 6.135 combo?

Is there any decent priced(under 1000$) usa made rods? Or just use scat pro stock or Eagles sir I beam? Are they same quality or is one of them better as far as size etc?

Last edited by LevonH; Jan 27th, 20 at 1:30 PM.
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post #2 of 34 (permalink) Old Jan 27th, 20, 1:23 PM
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Re: 427 BB rod length?

Tall deck or short deck 427 block?
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post #3 of 34 (permalink) Old Jan 27th, 20, 1:39 PM Thread Starter
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Re: 427 BB rod length?

Short deck.
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post #4 of 34 (permalink) Old Jan 27th, 20, 2:08 PM
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Re: 427 BB rod length?

I would just use the 6.135 rods. If its not a race engine, its not a big deal for weight. The longer rods will help with balancing a longer stroke crank, but yours being internally balanced anyway doesn't matter. As far as rods, for a street engine, I would use Scat Pro Comp rods.
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post #5 of 34 (permalink) Old Jan 27th, 20, 2:43 PM
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Quote:
Originally Posted by bracketchev1221 View Post
I would just use the 6.135 rods. If its not a race engine, its not a big deal for weight. The longer rods will help with balancing a longer stroke crank, but yours being internally balanced anyway doesn't matter. As far as rods, for a street engine, I would use Scat Pro Comp rods.

What Ray said
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post #6 of 34 (permalink) Old Jan 27th, 20, 2:59 PM Thread Starter
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Re: 427 BB rod length?

Theres no difference in cost, rods is same money and same with pistons I was thinking of Icon. Only way to get away cheaper is if I go with speed pro with 6.135 rods but they are so heavy I guess I need to add mallory since the crank last was used in a 396. With the speed pro pistons I need to have the shop press them on the rods so maybe not much of difference in price in the end?

So wouldnt it be wiser with the longer rod?

Eagle SIR i beam or scat pro stock? Or If I can find a used or new set of Us made rods for a resonable price.
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post #7 of 34 (permalink) Old Jan 27th, 20, 3:06 PM
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Re: 427 BB rod length?

6.700" rod with a hockey puck piston will rev to the moon! Custom pistons about $850
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post #8 of 34 (permalink) Old Jan 27th, 20, 3:44 PM
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Re: 427 BB rod length?

Quote:
Originally Posted by Busted Knuckles View Post
6.700" rod with a hockey puck piston will rev to the moon! Custom pistons about $850

It will only rev to the moon if the valve train allows it which a hydraulic roller will not. There is no need to reinvent the wheel. A 6.135 rod is your best choice and will be faster in a 427, especially if you have a auto trans.

Eagle or Scat will be fine. A good set of GM 3/8 with new bolts and resized will be trouble free in your application.
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post #9 of 34 (permalink) Old Jan 27th, 20, 5:11 PM
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Re: 427 BB rod length?

You dont need no 6.35" rod for a short stroke.

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post #10 of 34 (permalink) Old Jan 27th, 20, 9:17 PM
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I used stock length scat pro comp rods and SRP pistons.

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post #11 of 34 (permalink) Old Jan 27th, 20, 10:34 PM
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Re: 427 BB rod length?

Some folks dont like their slugs, but I also used SRPs hung on my old L88 rods, and it made surprising power with the cam/head combo Mr Brookshire dialed in for me. 10.5:1 alums. The slugs looked great upon re-fresh. coming up on 28K miles, but now its doing an 1/8 mi at a time!

The 7115 was originally an L88 crank I was told. That is what my crate L88 had. So, from the factory , it was likely balanced with the 11:1 TRW medium dome slugs. Pretty heavy. Maybe it was also used in 375hp 396 apps tho, IDK? Always thought it was 427 only.

Hey 66, you're only shooting for 500, so the whole rod length thing is pretty academic. Now, its your call, but 427 make GREAT POWER to 700 rpm, like a small block. But as the pro has indicated, using a hyd roller may limit that somewhat. CERTAINLY dont do the stock Comp cams /350 lb spring thing. It wont rev and give teh short stroke rat it natural advantage.

Who ever said hockey puck and long rod rev to the moon never owned solid cammed , well sprung 427... they rev to the moon just like the General built them. 8000 rpm mine saw, no issue. ( clutch overcentered on powershift- no pill in )

So I may suggest forget the rod length debate and focus on valvetrain stability that lets that 427 eat. For the record, Straub told me he'd set me up with a HR stable to 6800 rpms, so my 427 could enjoy stretching its legs. Or, I'd just run lighter solid rollers on the hyd cam. ( you could make near 600 with the right heads/cam btw as he will tell you! )
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post #12 of 34 (permalink) Old Jan 27th, 20, 10:37 PM
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Re: 427 BB rod length?

Heaviest stock pistons of any GM big block are 427's due to the location of the pin (not including the 4-ring bricks in tall decks). Your bearings will appreciate a lighter piston. Scat ProComp rods are great value for the money.
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post #13 of 34 (permalink) Old Jan 27th, 20, 10:47 PM
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Re: 427 BB rod length?

Ya, even the medium grade SRP were ALOT lighter than the TRW ( 100gr maybe?) . I didnt know 427 was heaviest.

and no "hokey pucks" busted, decent light slugs, heavy springs, Ti retainers, these bay rats like to SCREAM!

Yet I expect 66 wants SOME manners and idle quality.

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post #14 of 34 (permalink) Old Jan 28th, 20, 12:28 PM Thread Starter
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Re: 427 BB rod length?

Quote:
Originally Posted by sleeper View Post
It will only rev to the moon if the valve train allows it which a hydraulic roller will not. There is no need to reinvent the wheel. A 6.135 rod is your best choice and will be faster in a 427, especially if you have a auto trans.

Eagle or Scat will be fine. A good set of GM 3/8 with new bolts and resized will be trouble free in your application.
Quote:
Originally Posted by 427L88 View Post
Some folks dont like their slugs, but I also used SRPs hung on my old L88 rods, and it made surprising power with the cam/head combo Mr Brookshire dialed in for me. 10.5:1 alums. The slugs looked great upon re-fresh. coming up on 28K miles, but now its doing an 1/8 mi at a time!

The 7115 was originally an L88 crank I was told. That is what my crate L88 had. So, from the factory , it was likely balanced with the 11:1 TRW medium dome slugs. Pretty heavy. Maybe it was also used in 375hp 396 apps tho, IDK? Always thought it was 427 only.

Hey 66, you're only shooting for 500, so the whole rod length thing is pretty academic. Now, its your call, but 427 make GREAT POWER to 700 rpm, like a small block. But as the pro has indicated, using a hyd roller may limit that somewhat. CERTAINLY dont do the stock Comp cams /350 lb spring thing. It wont rev and give teh short stroke rat it natural advantage.

Who ever said hockey puck and long rod rev to the moon never owned solid cammed , well sprung 427... they rev to the moon just like the General built them. 8000 rpm mine saw, no issue. ( clutch overcentered on powershift- no pill in )

So I may suggest forget the rod length debate and focus on valvetrain stability that lets that 427 eat. For the record, Straub told me he'd set me up with a HR stable to 6800 rpms, so my 427 could enjoy stretching its legs. Or, I'd just run lighter solid rollers on the hyd cam. ( you could make near 600 with the right heads/cam btw as he will tell you! )
Quote:
Originally Posted by Busted Knuckles View Post
Heaviest stock pistons of any GM big block are 427's due to the location of the pin (not including the 4-ring bricks in tall decks). Your bearings will appreciate a lighter piston. Scat ProComp rods are great value for the money.
Quote:
Originally Posted by 427L88 View Post
Ya, even the medium grade SRP were ALOT lighter than the TRW ( 100gr maybe?) . I didnt know 427 was heaviest.

and no "hokey pucks" busted, decent light slugs, heavy springs, Ti retainers, these bay rats like to SCREAM!

Yet I expect 66 wants SOME manners and idle quality.
Crank was new nos and balanced and put in a 396 that my uncle used in the 80s. He parted the engine several years later and I got the crank. So thats why Im thinking of longer rods and lighter parts so it will balance easier and hoppfully without mallory. I Dont have any rods to start with. So see no reason why not use the longer lighter piston setup?

Think Icon are alot lighter speedpro list their piston 931 gr with pin icon 768 gr with pin.

Going with Comp cams custom billet hyd roller cam.
Comp cam hyd roller short travel lifters.
Comp 929-16 springs.
Comp cam tool steel retainer.
Comp cams hi tech pushrods.
Comp cam stainless hi tech roller rockers.
So Only parts with very good quality even the Comp haters cant say they are bad?
Think it easy will rev 6500-7000
Even my 496 with similar parts will rev 6500 easy.
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post #15 of 34 (permalink) Old Jan 28th, 20, 12:56 PM
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Re: 427 BB rod length?

Well then you will need to find out the bobweight of what was in it. I had a JE piston stock, rod 427 and it was nowhere near a forged speed pro 396 piston with a stock rod for weight. It would have needed a big adjustment to make the crank work in the 396. Without knowing what the weight was, its a crapshoot of what you buy and having to adjust the crank weight for it.

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