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Old 02-24-2014, 12:40 AM   #1
joshtried
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Default little help nailing down the internals

Hey guys, its been a while but i am man enough to admit when i need a bit of help.. I have decided on a 454 build and am wanting to get to about 800 hp at the crank. problem is, i have never put together an engine with this much; ergo, i need a bit of help on parts selection to get me there...

Having said (or wrote) that, there are a few stipulations.. I want compression to stay low, first because i want to stay on pump gas (we have 93 here) and second because i intend on using a 8-71 supercharger (or similar model). havent exactly had a chance to look around and am familiar with the 6-71 as it was included w/ my last engine. Forged internals, of course... dont want this to grenade on me any time soon.. The other thing to keep in mind is that this WILL have side pipes.

For heads, the ones that came with the motor are the 781's, so if they will be adequate, then thats cool... what would need to be done to make them adequate if they are at least in the same ball park? If i do have to dump them, recommendations?

Cost wise i am wanting to stay around 7k for the build.. this may not be realistic (especially pending head decision), but i dont have 20k to throw into this motor either (well, not if she is to get done by this year), ya know? I do know for just supercharger kit, carb, and side pipe kit to fit, i am already at 5000-5400, so i am not exactly leaving a ton on the table for the entire rest of the motor... If it can be done to build a reliable engine within that price, cool beans. if not, a cost break down would be great. I am not including machine shop fees in the build cost. This is more of a parts cost "limit".

Finally, i assume a stroker kit would be one of the better routes to go, and take her on up to a 496... how much would that affect overall reliability?

And for those that love pictures... her she is waitin for her new heart!
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Old 02-24-2014, 01:15 AM   #2
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With a good block, taking it .060 over to get the 4.310 bore and then a 4.25 stroke crank for the 496, won't be all bad. Use studs for the mains, and get it line honed and make sure it's all square and straight. As far as reliability, With the right parts, I'd bet it won't be too far off any other blown BB- depending on how far you're willing to kick the boost.
The rotating assembly is pretty easy- There are several different companies that can do the bottom end. Tell them what you're planning and where you want to be and they can spec the best for your application.
I've been playing with a Desktop Dyno- With a 496, AFR heads and 10.5 compression, 750HP is no trick. Jump the carb and intake up to a 1150 Dominator, and it's kissing 800. I suspect the program is a little dodgy but the numbers DO look good on paper.
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Old 02-24-2014, 10:06 PM   #3
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im willing to kick the boost to whatever i need for 800 hp :P

what about cam for a supercharger?? kind of unfamiliar waters..
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Old 02-24-2014, 10:26 PM   #4
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That would be the one place I'd get on the phone or email-- But you're going to need some specific specs first. CID, trans, rear gear, car weight, tire size, compression and how much boost you plan on running. All that will play into the cam selection. And along with the cam, what lifters and springs and what heads you have. Straub is on here a bit, and then all the others are around too.
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Old 02-25-2014, 11:17 PM   #5
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Why 800hp? That car can get dangerous at 500hp.

Use forged stroker crank and lower the compression with large open chamber aluminum heads rather than larger piston dish. I would start with the largest chamber aluminum head I could find/buy. Stroke it to 496" is best band for the buck. Always match your cam to your compression so measure your piston/block and head volumes accurately. Every cam company has their blower cam section and contact them when your finally ready for a cam - maybe several years if u have never rebuilt an engine before.
Yes like Tim said u will need to build the engine to match your drive line equipment - Lower gears (hi ratio), more rpm, more compression, more cam duration or higher (freeway) gears (lo ratio), less rpm, lower compression, less cam duration.

Good luck and have fun,
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Old 02-26-2014, 12:42 AM   #6
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cardo0, The why for 800hp is it is what the wife will let me build, and shes not exactly thrilled at that. The "really long term" goal is 1200hp, but that is for another build years from now. The last motor i had (which was stolen), had ~525 hp. It was fun, but it was not quite enough... I know there isnt really ever "enough" horsepower, but i feel confident that 800 will tide me over. Also, i do plan on getting to the track every once in a while (maybe 3+ times a year).
And i know all to well that some people cannot handle high horse cars... My father in law managed to wreck my '79 vette into a cow with that 525hp motor... it was WAY to much for him. he was babysitting it while i was in hawaii. as soon as it was out of the shop my uncle took it up on a curb and crunched the front end. that car went through hell....... then it was stolen and parted out.

As to have i ever done this, i have rebuilt several motors, just never one to this extent. It was your basic stock parts replacements generally. the highest horse rebuild i did was ~400 on a 351 modified for my '80 f150. The only thing slowing down this build will be money... I make just enough that the wife likes to think its endless :P

"lower the compression with large open chamber aluminum heads rather than larger piston dish. I would start with the largest chamber aluminum head I could find/buy."
In saying this, is that a que that i should not use the 781 heads i already have? If so why should i not use them?

Also, since the general consensus thus far is 496, lets assume that is the route i am going. compression staying 8-8.5:1, how would i figure out how much boost i need to get to 800hp?

Last edited by joshtried; 02-26-2014 at 12:45 AM.
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Old 02-26-2014, 12:49 AM   #7
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I would have gone LS motor .. It is almost a no brainier when looking to develop so much hp. If you said 550 to 600 ok old school.. But 800 which may be 1200 in the future , well stop using old school motors for new school power.
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Old 02-26-2014, 01:19 AM   #8
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this motor will never see 1200. that will be a different engine entirely
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Old 02-26-2014, 07:42 AM   #9
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Quote:
Originally Posted by joshtried View Post
I make just enough that the wife likes to think its endless :P
Don't they all?!
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Old 02-26-2014, 09:02 AM   #10
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Quote:
Originally Posted by diehrd View Post
I would have gone LS motor .. It is almost a no brainier when looking to develop so much hp. If you said 550 to 600 ok old school.. But 800 which may be 1200 in the future , well stop using old school motors for new school power.
I like the ls motors also. 5.3 and 4.8 engines are plentiful and cheap in the junkyards. Guys are making big horsepower numbers with these engines with turbos, intercoolers, and methanol injection.
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Old 02-26-2014, 10:45 AM   #11
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Quote:
Originally Posted by joshtried View Post

Forged internals, of course... dont want this to grenade on me any time soon.. The other thing to keep in mind is that this WILL have side pipes.

Cost wise i am wanting to stay around 7k for the build.. this may not be realistic (especially pending head decision), but i dont have 20k to throw into this motor either (well, not if she is to get done by this year), ya know? I do know for just supercharger kit, carb, and side pipe kit to fit, i am already at 5000-5400, so i am not exactly leaving a ton on the table for the entire rest of the motor... If it can be done to build a reliable engine within that price, cool beans. if not, a cost break down would be great. I am not including machine shop fees in the build cost. This is more of a parts cost "limit".

Finally, i assume a stroker kit would be one of the better routes to go, and take her on up to a 496... how much would that affect overall reliability?
So Im gathering you want to spend $7000 total. $5000-$5400 on a supercharger. That leaves $1600 to $2000 for the total build. Sorry, that won't buy a rotating assembly that will support 800 HP. Stock heads won't do it. You need at least another $10,000.
Fast, Dependable, Cheap. Pick 2
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Old 02-26-2014, 11:15 AM   #12
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The issues with 800 hp are going to be immense. What trans are you running ? What have you done to the rear suspension ? Why not turbos ?

800hp no matter where you use the car is gonna break a lot of parts even after you spend money trying to make sure it wont
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Old 02-26-2014, 11:56 AM   #13
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Quote:
Originally Posted by diehrd View Post
The issues with 800 hp are going to be immense. What trans are you running ? What have you done to the rear suspension ? Why not turbos ?

800hp no matter where you use the car is gonna break a lot of parts even after you spend money trying to make sure it wont
IRS to handle 800 HP $6-8000, Trans to handle 800 HP $3-7000, Rotating assembly to handle 800 HP. $2000+, Heads that will support 800HP. $2500-3500. then you have valvetrain, machining, and numerous other expenses. What about brakes? What about suspension? What about tires and rims to get the power to the ground? flairs or offset trailing arms? Built offset trailing arms set up with Tom's outers are about $2500. It cost me over $25,000 for a 500+ HP 383 with a 150 shot and the driveline to get it to the ground dependably.
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Old 02-26-2014, 02:10 PM   #14
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Quote:
Originally Posted by joshtried View Post
cardo0, The why for 800hp is it is what the wife will let me build, and shes not exactly thrilled at that. The "really long term" goal is 1200hp, but that is for another build years from now.
Do you have any idea what 800 hp is going to do this car?

Quote:
The last motor i had (which was stolen), had ~525 hp. It was fun, but it was not quite enough...
I'm going to guess that this motor was over rated at 525 hp.
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Old 02-27-2014, 12:25 AM   #15
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cardo0,..."lower the compression with large open chamber aluminum heads rather than larger piston dish. I would start with the largest chamber aluminum head I could find/buy."
In saying this, is that a que that i should not use the 781 heads i already have? If so why should i not use them?


Josh, im really not familiar with BB parts but the supercharging fills the area above the piston better with a larger head chamber volume and smaller piston dish than the other situation using smaller head chamber and larger piston dish for the same compression ratio. So if your replacing both then the larger chamber head is the choice for supercharging. Biasing with higher exhaust flow will aid the higher exhaust flow from greater cyl filling of supercharging. But u will have to do your own parts shopping here.
Now the block should be O-ringed for a stronger cyl head seal.
Also the stock oil system may be marginal for that kind of hp - u should research that also - again im not familiar with big blocks.

Well Smokey Yunick said many hot rodders earned their way to the fast lane over their own broken parts. Or maybe it was they went broke while breaking parts. I see in your profile a manual trans in your '68. U would need a very stout manual trans to handle that much power - maybe a race only trans like a Lenco. The stock rear would not live long behind a manual trans unless babied and a straight axle rear for our C3s are not cheap. Its just that a supercharged BB will make so much power at low rpm its more likely to tear things up.

As for "how much boost with a 496?" all i can use is thumb rules. 10psi boost should increase hp by 50% and starting with 1hp/ci that would be like 744hp for a 496. Close enough? Add more boost then.

My suggestion is that if u want to get near to 800hp with a BB on a $8k budget i would look at using high rpm on a natural aspirated engine and skip the blower. A 496" BB with great heads, hi compression, and big cam would be in that price range and the rest of the drive line may live with it. I would expect no less than 600hp. U still need strong rotating assembly either way just change the compression and cam.

But hey if a supercharger really pushes your piston then build as you can afford to, muncies are cheap (please use a scatter shield) and so are C3 rear ends (again use safety loops) compared to the upgrades.



Hope this helps ya,
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Old 02-28-2014, 12:43 PM   #16
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Do you have any idea what 800 hp is going to do this car?
Yes. Yes I do. for the purposes of this thread, i am only worried about the motor.
I'm going to guess that this motor was over rated at 525 hp.
No. It was not. having seen the dyno sheet on the engine, and then the dyno in car, the numbers line up. Seat of the pants feel was also a **** ton better, and was comparable to the 2SS camaro (rated somewhere around 500... i forget exactly)
I like the ls motors also
Thank you, but i am not going to use an LS motor. I have this one and am going to build this.
Stock heads won't do it.
Thank you for answering if the 781s will work.
But hey if a supercharger really pushes your piston
Yes, yes it does :P
So Im gathering you want to spend $7000 total. $5000-$5400 on a supercharger. That leaves $1600 to $2000 for the total build. Sorry, that won't buy a rotating assembly that will support 800 HP
Thank you. At least this way i can be honest with the wife. i dont see 10k more needed... but obviously i havent done this before. i guess then that this will not really have a budget :P I will find what i need and buy it as i can, though admittedly, that will take longer.
all i can use is thumb rules. 10psi boost should increase hp by 50%
so, 5 is 25% and 15 75%? or what would be the increments? generally speaking though, 10 psi would be close enough.. i just dont want a lot of "close enough" parts and then end up @ 650hp...
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Old 02-28-2014, 12:48 PM   #17
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Why not turbos ?
forgot this one.. so, turbos are not out of the question, but seemed like they would be just as much as a supercharger.. from what i have seen and read, turbos are better in the top end. granted, a 496 wouldnt exactly have "turbo lag", but MOST of my driving will not be higher in the rpms.
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Old 02-28-2014, 02:00 PM   #18
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i dont see 10k more needed... but obviously i havent done this before.
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Old 02-28-2014, 02:22 PM   #19
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http://ls1tech.com/forums/forced-ind...i-pumpgas.html

This guy on LS1 tech is making 741 REAR WHEEL HORSEPOWER @ 17 psi with a junkyard 5.3 ls motor and ebay turbo and his Fairmont runs 9's.

He probably has less than $6k in his whole setup, including the price of the car.
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Old 02-28-2014, 02:26 PM   #20
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IRS to handle 800 HP $6-8000
Good guess. The diff alone is $4800. For everything wheel to wheel figure $8400. And this setup is going to need everything. For brakes to stop it figure $2000-$4800.
Mike
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