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SBC S-10 10-13-2005 09:42 PM

Twin Turbo SBC build, need help
Ok, I did a search, and found some help, but I'm still in need of some answers.

Looking to build a motor top put down ~850-1000rwhp in a 78' Vette.

Anyone know of a manufacturer of turbo manifolds or headers for Vettes?

What kind of turbos would I be looking at for the numbers I am looking for?

It's going to be a 350ci motor, need some help on the rotating assembly, going forged everything, probably ~9:1, sound good?

As far as heads go would like to use a set of GM Fast Burns with some serious work done to them, will these work well?

I'm nearly lost on blow-through set up carbs and what not, some schooling in that department would be great.

I'm familiar with all turbo components, wastegates, bov's intercoolers, all plumbing, and can work all of that out, just need some help on what works well on small blocks.

Does anyone sell a kit for this type of thing?

Any help would be greatly appreciated.


DoubleVision 10-14-2005 07:09 AM

I`m not much on Turbo`s but I`m sure there are others here that can help, but I will say if you plan on making that kind of power you`ll need a aftermarket block.

StevenC 10-14-2005 07:47 AM

Compression ratio seems a bit high to me

ap72 10-14-2005 08:07 AM

I would go with dual T3/T4 hybrids, and your compression is way high if you want 1,000 horse- more like 7.5:1 is ideal. It is possible to run blow through carbs, but I wouldn't do it on this setup, not in a million years. I would go with a MegaSquirt II system. They offer great tuneablitiy, are fairly simple to use and are the cheapest, even if you buy it fully assembled instead of doing it yourself. You'll probably also need to get a custom cam ground, I don't know what RPM ranger you're looking at, but remember to include atleast another 10 degrees duration on your exhaust and a pretty wide LSA (115ish). I guess that should get you started.

1BAD80 10-14-2005 08:29 AM

This has been discussed many times before, plus all the info is in the Knowledge Base on this site.

firestone 10-14-2005 10:24 AM

It is probably possible with the setup you are looking at, but you will have to run race fuel. I was looking into putting a 101mm turbo on a 358 that I have with an air to water intercooler, 9:1 compression and 25-30psi boost. The company that was helping me with it said that it would produce around 1500hp at the crank. That is with 118 octane fuel though. In the end it looked like it was going to be too expensive (around $11,000 for turbo fuel injection intercooler and all the other parts), so I just stuck with the setup that I already had.


SBC S-10 10-14-2005 11:40 AM

The block is a GM Performance ZZ4. Is that going to hold up? Wanting this motor to run on C12 if possible, but obviously not if running fuel injection like some have suggested. Any input on carbs vs. FI on a setup like this?

7.5:1, really?

Thanks everyone and keep it coming


ap72 10-14-2005 01:18 PM

I would go for a Dart block, the one you have may hold...but that's a big risk. If you're racing it though I'd go for a 327 with a light rotating assembly and spin it to the moon- its a lot easier to get hp with high revs rather than down low- especailly with forced induction.

TurboS10 10-14-2005 04:22 PM

Your goals are not undoable, but I hope you have planned to spend some money. As mentioned you will need aftermarket everything in the bottome end. The fastburn heads are not bad, but I would look at a big port race head like a Dart, AFR or something like that. They dont cost much more and will flow alot more air. When you are talking about making that kind of power you have to have good heads even with the turbos.

As for the turbos a pair of T3/T4 hybreds will not do **** for your goals. You need a set of large T4's and that is still pretty small for 1000HP. I would be looking into going with a large single turbo in the high 70's to low 90's on the compressor inducer. You will want a large frame turbo like a big garret from a diesel application. They will move alot of air and are very comfortable making high boost. If you are not going to do a BUNCH of research, you would be better going to a turbo shop and getting something they have put together that will work for your power goals. There are a couple that sell on ebay that have some nice turbos for decent prices from time to time. If you go to somone like turbonetics you can plan to spend close to 3k for a turbo like that, but there others putting together turbos from rebuilt oe parts that are just as good and 1/3 the cost.

You will want to fuel inject an engine like that. Blow through turbo at that level is just asking for a big boom. It will take high boost to make that power on a small cube small block and EFI is the ONLY way to control an engine like that.

You will not find a company that makes a manifold or headers for that application. You will need heavy gauge steel or stainless steel headers. Stainless is the best, but on a budget mild steel will work at low boost. But, with your power level stainless is almost a must. While velocity is important, it is relative. Typically you keep tubes smaller on a turbo engine, but at that power level 1.75" is probably what you want to plan for. For stainless it will probably cost you 2k to get someone to build them, so consider doing it yourself.

And the lower the CR the better. 7.5 is fine. Lower would be better, but it would be hard to maintain quench and get the engine to run off boost.

SBC S-10 10-15-2005 02:35 AM

Money isn't much of a factor here, well it is but doing a budget 1000hp car is not a good idea in my opinion. T4's were one of my ideas, I just didn't know if they were too big or not.

Don't worry, will be doing tons of research before I even think about buying parts or swinging a wrench.

Help me out with a cost analysis guys, how far off am I here?

Rotating assembly: ~3000
Headers: ~2000
Intercooler and Plumbing~1800
EFI setup~2300

It is 3:30 am right now so Im probably missing a lot, and then of course misc. stuff that will add up, but I'm just trying to get a close number to work with.


NXS 10-15-2005 04:46 AM

Some $'s look off like the cam {look more like $600-$800 for the setup, ie cam, lifters, push rods, rockers, stud girdle} and $2k for headers seems high? But when you have your total multiply it by 1.50 {150%} to get the amount it will take to accomplish your goals.

I would look at building a 7.5-8:1 450 hp combo then use a turbo setup that will yeild about 25psi max boost {but you may only need 20}.
I would plan on using something besides a zz4 unless you plan to mud it and run little or no coolant.

revvin kevin 10-15-2005 09:15 AM

If you're serious about doing research go to you can learn tons about turbos there, even chevys! Blow through carbs aren't all bad, if you can tune efi you can surely tune a carb. Will not be as expensive as stated if done correctly.

coldknock 10-15-2005 09:25 AM

Since cost is no object, these fine folks will sell you one ready to rock-n-roll.

If you insist on building a stock block grenade, they'll sell you a twin turbo kit that will positively create enough boost to do it.


TurboS10 10-15-2005 01:00 PM

That banks kit will not even touch 1000HP. Turbos are too small to start and they have those crappy manifolds. I am sure kevin has built a few turbo cars so might as well listen to him on the carb and price thing. My experience and research has been that EFI is BY FAR THE BEST at high power levels. No one said that carb would not work, but for almost 3HP/cid you cant just slap a carb shop holley on it and expect all to go well. You will need a good wideband and datalog equipment just to tune it. Since you can get all that stuff with an EFI setup the price is about the same for EFI as it is for a good carb and all the needed equipment. Not to mention you can tune it from the drivers seat going down the road or in between runs in a drive way. I do all my tuning at the kitchen table from datalog information. All it takes is the data and a little math to correct problems.

You are way low on the rotating assembly if you get an aftermarket block. I would up that 1k at least. You also forgot heads which will run you around 1k at a minimum if you get a good deal. The turbo you could spend alot less if you do some research and look around. I spent $175 on mine on ebay. It is good for close to 1kHP. I also got my wastegate and bov from ebay for pretty cheap. Matter of fact, crank, pistons, rods, heads, efi, injectors, radiator, and other stuff I am forgetting came from ebay. I did my engine on a budget and probably have $7500 in a stock block engine, but it has good EFI equipment and good heads. However, I am looking to upgrade soon after a recent screw up that hurt a couple cylinder walls. I am going to run the stock one till it gives up or till I have the $ for the aftermarket setup.

coldknock 10-15-2005 02:22 PM

Not that I disagree with you but the company website disagrees. They state "in excess of 1000HP" concerning the 366" engine they sell. They even have a graph showing over 1100hp. It is worth noting that that state 100 octane fuel and an intercooler was needed to make that much power. With their reputation at stake I don't think they'd make false claims and place false ads.

With that said, I agree that it's easier with larger turbos, more boost, less compression and a big intercooler. However, I don't care how easy a turbo is on the rotating assembly, a stock 1st generation block will not handle that much pressure long enough to enjoy it. I doubt it'd last long enough to tune it for that much power.

We're talking about rear wheel horsepower right?

1200-1400hp at the flywheel would get you over 1000 at the wheels. It's a very different ball game when it's in the car. Yes, I agree the Banks kit won't touch that.


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