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Discussion Starter #1
Hi all,

Relatively new poster here about my 489 BBC build. I've had plenty of issues along the way but my 489 streeter is on it's way to being built. It's got:
- GEN V block decked+honed (all 4 bolt mains replaced with ARP studs)
- Wiseco forged pistons +0.030" (21cc dome)
- 10:1 measured static compression (pump gas for streetability)
- Eagle forged steel 4.25" crank
- Eagle forged connecting rods (ARP bolts)
- 320cc aluminum heads 121cc chamber 2.25" intake 1.88" exhaust (flow chart below)
- Crane gold 1.7 roller rockers
- Crane hydraulic roller (.621/.632 lift - 240/248 duration @.050" - 112LSA) 2600-6200rpm
- Victor jnr 454-R intake
- 950 Prosystems carby

I think this should put a smile on my face, especially with the 4 speed manual behind it.

What are your predictions for HP and TQ?
 

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Ummm, with a 4 speed....I predict 1st and 2nd pretty much useless, lol

All kidding aside, it looks like a pretty solid combo. Should make for a really nice street/strip ride
 

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Discussion Starter #3
Ummm, with a 4 speed....I predict 1st and 2nd pretty much useless, lol

All kidding aside, it looks like a pretty solid combo. Should make for a really nice street/strip ride
Should be fun :grin2:

Anyone else for HP and TQ predictions?
 

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Discussion Starter #5
Assuming on pump gas, I’m wildly guessing
570tq
600hp
It's being built for 93 pump. I closely followed Mark Jones' (Vortecpro) 496 builds as he's a great engine builder, so hoping around 630hp for mine with slightly smaller cam
 

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you have the parts to be north of 600. Something that isn't clear is what bore the heads were flowed on.
Performance wise I expect the car to be lazy in the first 60' compared to a smaller intake runner head given the compression ratio.

I did a head swap last year.https://www.chevelles.com/forums/13-performance/1043025-2018-496-phase-3-plan-afr315-heads.html
The shop flowed them at a bore of 4.280". I know the big AFRs Brodix etc are flowed at 4.60" so this puts my heads in approx the same region as the AFR265s which have proven to get good results
 

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I have a very similar build with a smidge more lift and duration and it made the numbers in my signature.

Oh, and by the way, massive torque can and will break parts!!! :grin2:
 

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The shop flowed them at a bore of 4.280". I know the big AFRs Brodix etc are flowed at 4.60" so this puts my heads in approx the same region as the AFR265s which have proven to get good results
I'm not sure how you think your 320cc heads are equivalent to 265cc heads.....but best of luck to you regardless.

I agree with the poster a few above this that these heads are too big and could be a little lazy down low.

Fortunately, with 489 cubes, you've got some built in forgiveness.
 

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Not sure what brand of heads you have. If they are some of the China 320's, like off ebay for cheap, then I'd have your local shop go over them with a fine tooth comb. Check valve jobs, guides, ect. The cheap China made heads have been known to be troublesome and not of very good quality. And even if they are not China made, any head bought assembled, should have a valve job done, unless you get them from some of our board member engine shop owners like VortecPro, Wolfplace, Foxwell, ect.
 

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If this motor only makes in the 600 horsepower range you might want to double check that all the spark plug wires are on. My smaller 427 motor with smaller cam less flow heads smaller intake and smaller carb made 580 horsepower even with a bit more compression. Figure this should be an honest 120 horsepower more a the minimum.

RH
 

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x2 dont fall for those big chinese heads esp if you have any kind of decent cam. Simply not worth it

If you ran a mild hft cam under an old shortblock you didnt care about that woul dbe a big maybe.
 

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If this motor only makes in the 600 horsepower range you might want to double check that all the spark plug wires are on. My smaller 427 motor with smaller cam less flow heads smaller intake and smaller carb made 580 horsepower even with a bit more compression. Figure this should be an honest 120 horsepower more a the minimum.

RH
489 - 427 = 62 cubic inches. I really don't think a 10:1 engine is going to make 2 hp per cubic inch. I'm not a fan of the head choice. I ran a 489 for 5 years. it ran well with race rites and a flat tappet cam with lower compression than the engine in this thread. with AFR265s it was later dynoed with a .612 lift 250 @ .050 hyd roller and made a modest 585/590.

Something not mentioned is header primary tube size. for my current 496 a 2 1/8" primary was up an avg of 20-25 hp for 800 RPM from 5700-6400 and was better from 5k-6500.
 
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Discussion Starter #16 (Edited)
Not sure what brand of heads you have. If they are some of the China 320's, like off ebay for cheap, then I'd have your local shop go over them with a fine tooth comb. Check valve jobs, guides, ect. The cheap China made heads have been known to be troublesome and not of very good quality. And even if they are not China made, any head bought assembled, should have a valve job done, unless you get them from some of our board member engine shop owners like VortecPro, Wolfplace, Foxwell, ect.
Bought a bare set of 'Bravo' heads from Skip White for cheap. My local shop cut back intake valves, blend machine work and blend seats valve job, CNC bowls + intake runners and chamers, and faced them. We put components were XVT race valves, comp dual valve springs, 7 degree retainers and locks. I did my homework and cost less than a comparable set of branded heads
 

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Discussion Starter #17
489 - 427 = 62 cubic inches. I really don't think a 10:1 engine is going to make 2 hp per cubic inch. I'm not a fan of the head choice. I ran a 489 for 5 years. it ran well with race rites and a flat tappet cam with lower compression than the engine in this thread. with AFR265s it was later dynoed with a .612 lift 250 @ .050 hyd roller and made a modest 585/590.

Something not mentioned is header primary tube size. for my current 496 a 2 1/8" primary was up an avg of 20-25 hp for 800 RPM from 5700-6400 and was better from 5k-6500.
My headers are 2 1/8" into a 3 1/2" collector
 

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I did my homework and cost less than a comparable set of branded heads
So....you skimped on possibly the most important, power producing part of your motor.....and they're still too big?

Not sure how that is doing your homework.......
 
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So....you skimped on possibly the most important, power producing part of your motor.....and they're still too big?

Not sure how that is doing your homework.......
The heads flow better than Skip White's bravo's and they make 674hp on his 496-505 build. If you have never owned a high performance bbc, I'm happy to give you advice on anything you might not know.
 

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Supernova sir. No disrespect and never thought this motor would do 2 horsepower per cubic inch. But I do think these bigger motors should soundly beat the factory 427 l88 motor by quite a bit. Dont you. My l88 short block with ported oval 215 heads that have been ported stock gm 30 over pistons and stock zl1 cam made 580 horsepower. So yes with 60 inches more and way better heads and piston design or ring package. Most get 30 horsepower going to a roller cam over the flat solid cams. So rings piston and roller could be 50 horsepower alone. Now add bigger and better cam and heads and intake. So 1 horsepower for 60 inch bigger plus just roller and better piston and rings could easily be 90 horsepower. Thats how i see it. Nothing wrong with the china heads bare either.

RH
 
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