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Discussion Starter #1
I am about to begin a build for a customer and would like some input of the members here. What I want to do is a big block Chevy, 540-632 cid, with conventional heads, probably AFR 357's to 385's, low compression in the 9.5:1 area, and twin turbo it. Looking to make big power, say 12-1400hp, on pump gas, limited valvesprings, fairly small cam, as low maintenance as reasonably possible. I would like to turn it 6500 to 7000 rpm, it will have shaft rockers, just trying to keep a light valvespring in it. I am hoping with what has been done at higher boost levels on much smaller motors, this should be doable at 8 to 10 lbs. Planning on doing a 5 or 6 stage dry sump, billet fab. pan, BS3 controller, good parts throughout....

What I would like to discuss is turbo selection, cam supplier, injector sizing, and overall combo thoughts. This will be going in a 62 Chevy Biscayne, all tube chassis, struts, 4 link, probably a th400, Dana 60....

I have read recently that the new GT5533's are more responsive (better spool times) than the 4718's and move more air, sounds good, thoughts?

Want to build it big and not "lean on it" very hard, make less power than it could, but make it survive a long time, too...I should also mention that this will be a show quality build, and may never make it to the track, he just likes crazy, over the top stuff, and having it functional, driveable, enjoyable.

Hoping for input from a couple specific members, thoughts?
 

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The problem with big cubic inches is that you need large enough turbos to match. If your limiting yourself between 540-632 BBC I would stick with a 540 (4.25 stroke). Especially if your going with afr 357's. GT4788's or similar turbos. It will be a good combination but really too much for the street. I run a close combination to that and at 7-10#'s of boost it is pretty much rediculous on the street. I run a 33x14.5 ET street rear tire. I hope you plan on putting a big tire under it?
A single set of 160's should be fine if you don't go too high with the boost. I design my own cams but use Comp to grind them. A converter matched for 1200-1400 hp will allow those big turbos to spool up pretty quickly. Good luck!
 

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Typo on my rear tires- they are 33x18.5x15

If you go with a neil Chance Promod bolt together a 25 pump with a 4 stator would work well at that boost level. I have mine for sale if your interested.
 

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Discussion Starter #4
I do plan to use that particular tire, as I have in the past with good results. A "street" tire is downright dangerous in my opinion above 800 hp, like driving on wet roads. After these are warm, they stick pretty good.

Thinking about the displacement some more, I was assuming a big engine with big turbos should be as easy to spool as a small engine with proportionately smaller turbos. I am aware that the power level desired is easily achieved with a smaller motor, I was just thinking build it big and run it easy. I know it will need some big 60 mm wastegates, to keep boost down, and I was hoping to make as little heat on the cold side as possible to not need an intercooler. I would run it at 6 psi if the power is there, and keep the hot side happy, less back pressure, less potential for cracks....

Injectors....do you think a regular set of 160's will feed this okay? Doing the math at a bsfc of .65 still shows a 120 would barely be enough, do I need to be that far over? Or is it just safe? I am confident I can get it to idle with the BS3.

Any estimates of power on, say, a 540 with 4788's at around 8-10 lbs? If that will easily make the power, no need to go crazy, keep it as simple as possible....
 

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Typo on my rear tires- they are 33x18.5x15

If you go with a neil Chance Promod bolt together a 25 pump with a 4 stator would work well at that boost level. I have mine for sale if your interested.

How much you looking to get??

ScottRod
 

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I have $2900 into it including a extra stage 2 stator that goes with it. $1400
I need to go tighter again, so I have to buy another $2500 converter.
 

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damn, all these builds and I could not give my 509 away........that sucks.........oh its a 515 now...... ooooppsss...... good luck with the build......
 

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Are you talking solid roller or solid lifter? You mentioned limited valvespring, but 6500-7000 rpm.
 

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Discussion Starter #10
I have no issue with spinning it higher, just don't see why it would be necessary...fully intend to run a solid roller, but to keep potential spring and lifter failures down, I am trying to keep the spring pressure lower. Planning on bronze lifter bores and at least a 904 lifter, very interested in the Isky easy roll bearings, just for peace of mind. I have discussed with the owner a range of maybe 200 miles round trip to and from a show or event, so I need to be able to fill it up with premium and keep driving, lol....

Thinking more about turbos, and not sure if I should only try to put on 1500 hp worth of turbos and run them harder, not so much as higher boost, but lbs. per min., or run a properly sized set and only run them at maybe 40%....wonder if I will be able to get big enough turbines in a smallish turbo, too...

Will I be able to buy a reasonably capable convertor for this without going to a bolt together unit? Or is that coming regardless....? Didn't expect that, but we will do what makes sense before cutting corners....
 

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I have already given my opinion on ci., turbos and injectors so I wont comment again on that but as far as converters go... You don't need a bolt together but you should buy a good converter now or youll buy one later. I like to be able to make stall chages myself and be able to clean and inspect my converters that is why I like the bolt togethers.
 

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Discussion Starter #12
tt69camaro, thanks for your input, we have discussed the combo in more detail and have come very close to your suggestions as far as displacement and turbos go. I had less boost in mind, and wasn't concidering compressor surge being a problem....also considering a clutchless standard trans, before anything is purchased, looking at how we could make a clutch halfway streetable and hold the power as well. I will update, stay tuned....
 
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