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I would like to discuss a few options of how to build a turbo sbo. I have watched the series on the engine BTR built for project S71 and the one the Andrade’s built and are racing. They both used a DX block but different crank and rods. Let’s start the discussion with a early 70’s block and a 330 crank. Let’s call this a semi budget build, factory block and crank but aftermarket rods and pistons. What piston and rod combo would you use and what compression ratio would you shoot for? We will use a roller cam but what specs? This will be a blow thru carb on a single plane intake. For the turbo I’m thinking the billet 78/75 from VS racing unless someone has a better idea. How much power could you make and not worry about surpassing the limits of the stock block and crank?
Option 2 would be a larger budget, DX block, stroker crank, aluminum heads, the works. Looking for a reliable 800ish hp, how would you build it? List the details on compression, cam, turbo size, fuel injection set up, etc.
Gas block will hold about 650 or so. After that you’re looking at a pan rail girdle and most likely some block fill etc.
DX block wouldn’t need any of that. Good main studs, a properly prepped crank or my billet DX crank and you're there.
Gas block will hold about 650 or so. After that you’re looking at a pan rail girdle and most likely some block fill etc.
DX block wouldn’t need any of that. Good main studs, a properly prepped crank or my billet DX crank and you're there.
What happens at 655hp? I've seen pics (never personally witnessed) 455s split at the cam valley and 403s spit the crank out the bottom, but have never even heard of a "good"/68-72 gas block failure. I can see a later block failing similarly to a 403, though.
DX Block for strength, don’t waste time or money on girdles and ladders for the stock gas blocks.
Main bearing spacers to get to the smaller diameter main bearings is best if you will rev over 6,000rpm.
You would actually want stock stroke with a forged or billet crank, if at all possible, vs. a stroker crank.
Turbos make torque, lots of it even if you have a bad setup.
More than 650-700 ft-lbs of torque will likely be wasted on tire-spin. A long stroke crank will only narrow the powerband and add to tire-spin, and be very difficult to hook on the street and strip unless your chassis/tires are dialed in and conditions are perfect.
Depending on what gear ratio and trans/converter/tires you plan to run, you could build a real steamer out of a mild DX block that revs to 6500 +/-.
What heads are you thinking? Aluminum will allow more compression without detonation. You could run 9:1 or 9.5:1 most likely and get to your 800hp goal on pump gas if your combustion chambers are correctly shaped and polished. Heck, you could run 10:1 all day on E85 with iron heads and boost. If Iron heads, probably 8-8.5:1 on pump gas, but you may need a splash of race fuel mix, real octane booster, or a methanol injection system.
For twins, I like the Borg Warner S366-S369 family of turbos for a wide Compressor efficiency island (low boost ~600hp to 1300hp+ at high boost). They spook quick, are reliable journal bearing designs, and the housings aren’t too crazy heavy. I really dig the V band inlet and outlet turbine housing clones from VSRacing. You could also easily go to a single 78-85mm turbo from VSRacing.
2618 alloy pistons will take the most HP and detonation before damage occurs, but won’t last a lot of miles on the street, 4032 is less forgiving of detonation without breaking ring lands, but will last many more miles before the ring lands get loose and you get flutter and lose compression. If 800hp is your max target, you can get away with 4032 if no detonation. If you think you will do more in the future, go 2618. Rods are limited more by RPM than turbo Hp, it is just that they are rated for HP because more RPM = more HP in a Naturally aspirated combo. Rods typically break on the extension (exhaust stroke) at high RPM, or under hydraulic tension (head gasket leaks water into the cylinder). They don’t usually fold under cylinder pressure, even at very high HP.
A Molnar or Eagle rod that has been properly resized on the big and pin ends will work, but I really like the Howard’s Billet I beams (made in USA) and of course brands like Oliver, etc are great as well.
A good hydraulic/solid roller cam in the 225-235@.050 range with .550 Lift and 110 lobe sep will work great and not be a spring killer. You can use an austempered core so you don’t have to run a bronze gear. I will run BAM solid bushing roller lifters in the next build I do. RPM goals and budget limitations would dictate setup.
Your HP goals and responsiveness with your drivetrain setup are what will set the table for which turbo combo is best.
A blow through carb and good hat will run you $1400+…. And will be sensitive and slower to tune or convert for different fuels (a gas carb can only run gas, E85 carb can only run E85, etc). I have read of several people spending thousands on blow-through carbs and then wishing they would have just started with EFI to begin with.
As for electronic fuel squirts….
Go with a Motec M84, M800, M880, M8 or even one of the newer GPA-M-130 units.
The upper end Holley stuff works well overall, but don’t think that you will get the best or most knowledgeable tech support people…. And some of their best stuff does have issues.
With Motec, you can buy used, older systems, and they still support you like you just bought one of their newest pieces (other companies do not support their older EFI products worth a crap). They are not cheap, but you never hear of people moving away from a Motec, people go to Motec when they are fed up with other brands.
Injector Dynamics makes good injectors. Dependent on how much HP you want to make, and if you want to run E-85 or just gasoline, will determine your injector sizing/type.
Last edited by Battenrunner; Oct 3, 2022 at 09:17 AM.
You’ve run all these components?
Your cam choice is wrong for a turbo, an lsa of at least 114 will work better.
2618 pistons will last just fine if the tune is good. 4032’s have minimal boost tolerance. NO piston likes detonation.
You forgot ring choice, just as important as piston choice, maybe more so. Steel/Nitrided top ring would be my first choice.
Personally I wouldn’t use an Eagle rod in anything that makes 800hp.
And increased displacement, whether by stroke or bore, just makes everything peak sooner, all else being equal.
Last edited by cutlassefi; Oct 3, 2022 at 10:00 AM.
You’ve run all these components?
Your cam choice is wrong for a turbo, an lsa of at least 114 will work better.
2618 pistons will last just fine if the tune is good. 4032’s have minimal boost tolerance. NO piston likes detonation.
You forgot ring choice, just as important as piston choice, maybe more so. Steel/Nitrided top ring would be my first choice.
And increased displacement, whether by stroke or bore, just makes everything leak sooner, all else being equal. But it’s a good way to still hit a target if you have limited boost potential.
My cam choice was generic, I know that wider separations can do a little better for turbos, but they also cause more detonation on the street with pump gas. As Richard Holdener says, any cam can be a turbo cam….
2618’s are softer, and therefore the ring lands are softer, and won’t hold a ring as long. Stock Supra 2JzGTE’s used 4032 alloy, last for 200,000 miles + and can make 1,000 whp for a long time before they break. Good steel rings are a bonus, at least ductile iron… more power has been made with less, but not as reliably.
I wasn’t trying to compete on doing a build for him, just adding my $.02.
More stroke chokes potential powerband with the limited airflow available through Olds factory-shaped ports and affordable head options.
A single good turbo that the OP lists will get him there on stock stroke, iron heads, and likely 15-18psi of cool boost.
Thanks for the replies so far, I wanted to start a discussion on possible combinations to see what options there are. I am hoping for a few different build ideas to put as much information in one thread as possible. I have 2 projects ahead of this one so this is for research purpose’s.
This will be for my 72 Cutlass, it has th400, gearvendors unit, 9” rear, and and a proper fuel system for forced induction. I do have a Holley HP EFI set up on another car so I am somewhat familiar with the software.This will remain a street car and will be set up for drag and drive type events.
I did not think of bearing spacers for the DX block. Does anyone know the approximate cost to get a 425 crank to fit the DX block?
Does anyone know the approximate cost to get a 425 crank to fit the DX block?
Normally about $1200-1400 by the time you cut the rod journals, counterweights and balance it. For another $600-800 you could just get one of my DX billet drop in cranks. They’re stronger, about 9 lbs lighter and not 55 years old. Just sayin.
Ahhhhh, the old boost reference..... what do you mean by 8lbs? Is it just a function of its design? I've never heard that.
My point is that "boost" is backpressure. 8lbs isn't a bad thing if the intake tract flows well. 8lbs on stock intake and heads isn't as good.
Trimble has DX 434 on a stand, ready for a power adder. I mighta, shoulda grabbed it before rebuilding the 468 last time. It would put you over the 425 BB/SB cut for Drag Week, but I heard them mention small blocks running in the big block class.
Steve Morris did a dyno test with this twin setup. At 23psi he made 1800 hp on E100. I think if I was looking for that much power, I would just do a F2 Procharger...less garbage hanging off the front of the engine.
Steve Morris did a dyno test with this twin setup. At 23psi he made 1800 hp on E100. I think if I was looking for that much power, I would just do a F2 Procharger...less garbage hanging off the front of the engine.
Agreed! As well as the belt slippage/management for two superchargers, let alone one..
Ahhhhh, the old boost reference..... what do you mean by 8lbs? Is it just a function of its design? I've never heard that.
My point is that "boost" is backpressure. 8lbs isn't a bad thing if the intake tract flows well. 8lbs on stock intake and heads isn't as good.
Trimble has DX 434 on a stand, ready for a power adder. I mighta, shoulda grabbed it before rebuilding the 468 last time. It would put you over the 425 BB/SB cut for Drag Week, but I heard them mention small blocks running in the big block class.
Yes Sir, you are correct, we should speak in terms of lbs/min of airflow or CFM requirements, not in boost numbers.
Agreed! As well as the belt slippage/management for two superchargers, let alone one..
turbos look better every time I consider boost…
Watch the Outlaw guys. They started with a decent mix of power adders, then mostly turbo, now more are going supercharged. Why? Turbos are finicky to tune; supercharger boost is more linear and instant, no spooling required.
A race car that needs to stage and leave reliably with a linear power curve is definitely a better place for a Procharger vs. a turbo.
Those race units from Procharger have to run a cogged drive and or chain drive as well as having to be rebuilt pretty often.
Even race turbos rarely get rebuilt unless they have trash go through the oil or the unfiltered compressor inlet, or spit parts out the exhaust into the turbine wheel.
For a street/strip car, turbos last a long time and really work great if properly installed, and don’t have to be rebuilt every year.
Turbo engines also tend to break less connecting rods even at high rpm because even on the exhaust stroke, the backpressure from the turbine wheel keeps a load on the rod.
Last edited by Battenrunner; Oct 5, 2022 at 01:17 PM.
We are going turbo, Flemming knows the the car I am going against. A great friend of mine has a Comet that can run 8’s. I have to at least put up a good fight. I have thought about a supercharger but I dont think that is the way to go. I understand boost is a measure of restriction. I need to be able to adjust boost according to track conditions and not what the supercharger is limited to.
We are going turbo, Flemming knows the the car I am going against. A great friend of mine has a Comet that can run 8’s. I have to at least put up a good fight. I have thought about a supercharger but I dont think that is the way to go. I understand boost is a measure of restriction. I need to be able to adjust boost according to track conditions and not what the supercharger is limited to.
With you being in the middle of corn country, you can probably get away with filling to the water inlets and run it on e85. I would definitely use aluminum heads, just for heat dissipation if nothing else.. O-ring and stud the block and heads with good head gaskets.
See this is why don't come here any more lol. Non sense. Oldsmoboogie there is a guy in your area running a very fast boosted olds ( pro charger ) nice guy but he ain't much on the Internet. I remember when guys told me my engine would blow up. Here I am running 11.50's 200 + 1/4 mile passes and 3k street miles with parts no one would ever use because " why risk it "
See this is why don't come here any more lol. Non sense. Oldsmoboogie there is a guy in your area running a very fast boosted olds ( pro charger ) nice guy but he ain't much on the Internet. I remember when guys told me my engine would blow up. Here I am running 11.50's 200 + 1/4 mile passes and 3k street miles with parts no one would ever use because " why risk it "
What are you referring to as nonsense?
I purchased one of the 4" billet dx cranks to have on hand for a future project. My cutlass has a filled block, e85, solid roller 440 BBO and am highly interested in building something milder with far more capability.
Non sense in some of the comments. Just some of the back and forth is redundant. I wouldn't hesitate to do a 550 HP boosted SBO. But I would rather do smaller cubes higher RPM the head would be more efficient imo. With the small block you have less rotating mass. The stroker crank and rods will add strength of still available and would require les work than a dx or Diesel block. If not than I think the 403 rods are the strongest sbo rods and a 330 crank and if not then a 330 crank and some rods mark offers. My 350 is proof you can beat the living **** out an sbo and it will live with nothing super fancy.
Last edited by coppercutlass; Oct 14, 2022 at 05:58 AM.
Non sense in some of the comments. Just some of the back and forth is redundant. I wouldn't hesitate to do a 550 HP boosted SBO. But I would rather do smaller cubes higher RPM the head would be more efficient imo. With the small block you have less rotating mass. The stroker crank and rods will add strength of still available and would require les work than a dx or Diesel block. If not than I think the 403 rods are the strongest sbo rods and a 330 crank and if not then a 330 crank and some rods mark offers. My 350 is proof you can beat the living **** out an sbo and it will live with nothing super fancy.
If youre fine making 550 hp (crank or wheel?) with a boosted small block. I'm sure the gas block and aftermarket rod's/330 crank will hold no problem. It all depends on budget and goals.
I'm interested in taming my current car, but making considerably more power. A 430 inch dx stroker with a ported set of edelbrock, or rocket heads would twist to 7k with a properly sized T6 turbo before running into backpressure issues easily. At this cubic inch it would be a big borg warner, or garret gt55 based unit.
A gas block or any stock rod would not withstand the cylinder pressure the above combo would produce. In the LS world people spin 4" stroke china forged cranks to 7k+ making 1000+whp constantly.
I stopped and talked to the machinist at our local shop. He and his brother raced olds back in the 80’s. He has a Moldex crank and thinks he has a diesel block in the back of the shop. We will see if I can make a deal on this. I have a line on another diesel block local so we will see how that shakes out. Now I have to figure out what heads to run? This might come together sooner than I had planned.
So I was able to make a deal on the diesel block and moldex crank today. But I need to find a set of spacers as the crank has 2.5” mains. Does anyone know where i might find the required spacers?
So I was able to make a deal on the diesel block and moldex crank today. But I need to find a set of spacers as the crank has 2.5” mains. Does anyone know where i might find the required spacers?
Bill Trovato BTR Performance Is making a set for me. With a new process. Give him a call.
See this is why don't come here any more lol. Non sense. Oldsmoboogie there is a guy in your area running a very fast boosted olds ( pro charger ) nice guy but he ain't much on the Internet. I remember when guys told me my engine would blow up. Here I am running 11.50's 200 + 1/4 mile passes and 3k street miles with parts no one would ever use because " why risk it "
i believe that is mark and his black cutlass
he was running a screw blower then went to procharger if i remember correctly
ran high 8's with that screw blown DX
