Most basic turbo combo...
 

Let's assume well built bottom end. 400ci - 463.



Iron heads and have longevity.


Flat tappet or roller?
What cam specs?



How much power / boost?

400 ci 3.75 stroke is better
flat or roller will work 230-240 .050

8 psi hp somewhere around 700-750

70 Bird and myself have had good luck with a summit 2802 cam in a 455, I did have the first one get a flat lobe, but once I upgraded my valve springs, seems ok now, but dont have many miles on it, and on the second one I used the Comp cams lifters with the tiny oil feed hole on the bottom of the lifter.

What about with 265 cfm Iron d-ports @ 8.5-1 on a 406?

If you do some searches on PY you would find that Marty Palbykin's 406 engine had a very conservative 260 cfm type cast iron head and he was able to make 1600 hp and run 6.96 and 206 mph. Your projected 8.5 compression ratio will be fine.
Marty was running on alcohol so his compression ratio was closer to 10 to 1. Easy 1000 hp with the right turbo(s) for you at lower boost levels.

Tom V.

Im thinking what Charlie said sounds pretty close. I would limit the boost because of the factory block.....GO Boom, Boom! :)
Its easy to make power BUT its harder to keep it together!!

GTO George

Are you building something?

Charlie made over 700 HP with 4 cylinders and 200 cubic inches of displacement. This was factory cast iron block parts upgraded to be stronger. Lower boost and proper machining and a street/strip pontiac block around 3.75 stroke
should be fine. Charlie also ran factory 4 cylinder cranks but at much higher boost levels vs what we are talking about here.

Tom V.

I recommend that he not use a factory block with a power adder that’s making 750 or more HP. The cost of a broken engine out ways the price of an aftermarket block and good rods. It’s like Mr. Goodwrench use to say......”Pay me now or Pay me later”!


GTO George

Luhn Performance made 863 HP HP at 5300 rpm driving a belt driven supercharger at 13.5 psi of boost. The main caps were moving on the block, Fretting, and was apparent on teardown.
With a Turbo that combination could have been over 900 HP easily at 13 psi of boost.

Very easy to make the power. Much harder to keep the boost down so that the block will survive. But it has been done by different people on the street.

If you can afford it buy a good block and good crank, rods, and pistons.

Tom V.

When Marty ran his 406 cid engine, the only block out there was a original Dick Duclow block and Dick only had 50 made.
Marty stayed with a stock 67 400 block with mods. It lasted 3 years at 40+ psi of boost. All factory blocks will fail under boost at some point. Just like stock Ford and Chevy blocks do.

Tom V.

^^^^^^ what I said.....its your money not someone elses!


GTO George

Then why did you have to say it in multiple posts except to get your post count up.

The people are going to do what THEY want to do, not what George wants them to do.

Tom V.

Trying to stir up the chit in the boost forum too George?

Just giving my opinion. I've run stock blocks and different aftermarket blocks with different power adders combinations. I've also shelled out the money to fix the breakage, so when i give an opinion I understand the money cost........been there done that. Its always cheaper to do it right the first time!!
NOW............if you're only going to run 4,5,6,7 lbs of boost and play with it on the street once in a while............then a stock block with GOOD rods will work!

GTO George

As somebody that's not a racer, but is interested in turbocharging, it's helpful to see the side that says, do it right the first time with an aftermarket block, high end rotating assembly etc. However we also need to look at the basics too, which is what was being asked about here.

I also need to know what the limitations are of different types of configurations.

stock block/stock rotating assemblies
stock block/aftermarket rotating assemblies

etc.

What a lot of people forget is not everyone that wants to try hotroding something like this, has 15-20K to spend on just an engine.

My setup is a 455 with an N crank, prepped factory rods, Speed Pro pistons and a set of as cast KRE D ports at around 10.2:1 compression. I "think" this setup could work well with e85 and mild boost in the 8psi range. But if I ask that, instead of talking about the technical aspects of that plausibility, the default for most is just to say don't do it, go spend a lot of money on an aftermarket block, rotating assembly, heads etc.

I would say stock block is fine . As for a stock prepped factory rods and none forged pistons, I would say no way . Stock cast crank , yes its ok . 10 to 1 fine with e8 but not optimal but will work.. The stock rods in my mind would scare me. Thats why i say no. But try it if you feel different . Id like to know if im wrong for sure...

The only thing I will say about the 455 combo, is get a set of better rods. Eagles are cheap and will handle a lot of power.
I have had a stock block for a long time. The stuff I broke had nothing to do with the block. I add the 3 billet center caps, forged eagle crank and good rods. 8 psi gets me about 700-750 h.p. Plenty for the street and with the proper tune will run a very very long time. 12 PSI on the street and hang on, you go for a ride with the car trying to peel the tires off the rims.
Turbos are easier on parts than high compression and nitrous.
No reason to be worried about a stock block if you know it's limits.

I would not be afraid of putting 1000 hp to a stock V8 block with a turbo. My 4cyl block has been living with 800hp which is 200 hp per cylinder . Now think of it this way. theres alot more force going though and and against the cylinder wall with 200 hp per cylinder then 100 per cylinder right? So 800hp being produced from a 8 cylinder is nothing compared to whats going on with 800hp on a 4 cylinder.. So why wouldnt it live with 1000hp ?

i agree 100% but boost can be addictive that 5-8 lbs of boost can turn into 10-15! :)
With only 5-8 lbs of boost stock block would work with good rods and forged pistons.

GTO George

Absolutely agree on the slippery slope. I've had boosted (actually have currently, but that's just a modern daily) cars in the past and the want for more more more is always there.

Hey Ponjohn are you building something ??

An inline 4 cylinder engine is much easier on the block with high cylinder pressures (boost) than a V8 engine. Look at how the V8 pistons downward force transfers to the block- the left bank of cylinders try to push the right pan rail apart, and the right bank of cylinders try to push the left pan rail apart. This 'spreading' of the pan rails is what cracks V8 blocks up through the mains oil holes, and it's only the mains caps that stop this. Hence why splayed main caps work well,they pull the pan rails in towards the main saddles, and cross bolted blocks work even better. A 4 pot has a straight downward push on the main caps ,and stronger caps or cap straps and better bolts/studs will do the job. Yes I know the Pontiac half a V8 doesn't push straight down on the mains,but it pushes in one direction on the mains, so in theory it would be less likely to crack up through the mains.
This means Charlie, that you can shoot for a 1000hp with out a care in the world!

The engine that's in my car is a stock 2 bolt block with the stock caps and bolts. It has a cast Eagle crank, forged Scat rods, Ross pistons, and a flat tappet cam. On 7.5-8psi I went 9.45@145mph weighing 3,770lbs. Calculator says that's between 850-930hp. Now I'm running around on 14psi. It's pretty rowdy. I'm not saying that it's not gonna blow up tomorrow, but I've been beating on it for a few years now. I'm guessing with open exhaust it's around 850whp now. The last time that I dynoed it put 744whp down through the full exhaust on 12psi and low air in the drag radials. Anyway, that's my stock block experience.

I forgot to add that I have E heads that flow 308 cfm at my cam's lift.

I know the whole theory about the 4 cylinder . I agree with you 100%. But i still think 100 - 125 hp per cylinder with a turbo is safe to have . especially being a street driven car... Im building a 400 4 bolt main 9.5 to 1 steel headed motor with twin 6870's . So ill be finding out how right or wrong im am. I believe ill be fine....

I would love to have a reason to build a turbo 400". I like 400's a lot anyway, just haven't had one in fourteen years. Sounds like a long time!

Why you need a reason? Just do it .. Would make a better street motor for traction.....

Deciding on N/A 463 or turbo 400.


I have 93cc 265 cfm d-ports - good for either combo.
I would use twins just because of appearance.

What cam?

ONLY a few years, at 14 psi of boost and a cast Eagle crank. The engine owes you nothing.
You sure put that "it will blow up tomorrow after you use those non racing parts" bs to rest with your engine. Plus you are about 800 lbs heavier vs the expert with the supercharger. Nice work.

Tom V.

Im workinng on that with Tim at Bullet cams..

Will be on a 114 around 580 lift and 230-240 duration..

Nothing in stone right now though...

Thankyou! No, that old engine has treated me well! I'm planning to go the track in two weeks. If I do I'll post in here.

With a 30" tall rear tire - what do you think would be ideal 3.73 or 3.50 gear?

I run a 3.50 with my 4cyl. It works good...

3.5 gear has worked well (with a bunch of turbo cars) as the Engines make so much torque at fairly low engine rpm. Higher load on the engine and the turbos work that much better.

Tom V.

Ignore the idiot in the Race Forum Charlie.

I have a 3.25 gear with 28" tires. The next set of tires I buy will be 30". There is so much torque available that there is no need for any higher. Plus, all that boosted Pontiac torque likes to loosen converters up so you'll have to watch the rpm on the big end if you want to keep the rpms under control.

You beat me to it. Lol

In either combo N/A or turbos I am running a 4l80E with lockup.

Don’t start name calling! I haven’t called anyone names just stating my opinion!


GTO George

Yes i remember you telling me that .Thats why i tried the gear change from 3.90's . It was a good choice ....

Everyone has an OPINION.
All I will say on that deal.

Tom V.

Here are a few facts:
1) Supercharged engines use a belt system to drive them or they are driven by a drive mechanism off the crankshaft. They take horsepower away from the crankshaft power to drive the supercharger. So the bigger the load from the supercharger the more power you need to make from the engine to reach a given power level.

2) Turbocharged engines use some of the energy the engine produces to drive the Turbocharger Turbine. Rough rul of thumb: 1/3 of the engines heat pushes down on the piston, 1/3 of the engines heat is transferred thru the cooling system to protect the engine from engine damage. 1/3 of the engines heat goes out the exhaust and is lost forever with a supercharged engine. 1/3 of the engines heat goes out the exhaust and is USED BY THE TURBINE to drive the compressor wheel on a turbocharged engine.
Turbo engines like load so a turbocharged engine will make more power the higher load it sees and it will drive a larger turbocharger unit and make more overall hp.

Supercharged engines hate load so a supercharged engine will make less power as the parasitic loss, (LOAD) gets higher and higher.
Bigger engines offset some of that higher load and so the engine makes more overall power.
A High HP supercharged engine might take 1.5 HP for every 10 hp it makes. 1000 hp at the crank needs 1150 hp from the combustion process. Turbocharged engine uses energy normally wasted out the exhaust pipe to do work. More load, more work, more exhaust, more power to drive the turbo, more power.
Very simple really.

A 281 cid engine with Turbos has run 5.7s in the quarter mile. A 670 cid turbo engine might run 6.00s because the same sized turbos are not seeing the same load as the 281 cid Turbo engine.

So the comment made in a forum that a given racer needs a Larger Engine is inaccurate.
One of the racers actually went the other direction and went to a smaller engine with turbos as it is easier to make more power and the traction capability on the street is more predictable.

So not surprising in the turbo forum that members changed their gear ratios to a smaller number and the engines made more actual power.
Higher Load, more efficient HP from the turbos.

Simple really if you actually understand how turbos work vs superchargers.

Tom V.

Keep after it Charlie.

Another reason for staying a little smaller on the cid is that it is harder to get the exhaust out of a big inch high horsepower engine. If you reduce the engine's size some and use two medium sized turbines that still spool but allow the engine to breathe you can rev it a little higher to make the same horsepower while not having to deal with extra torque on the bottom end. Accurate Tom Vaught?

I should have said turbo selection is easier for the smaller cid. You don't have to run twins. On a big inch engine you probably will need twins to make a lot of power.

When you get into the larger frame turbos and start spooling them at higher rpm you can run into a thrust bearing issue inside the turbo.

Journal Bearing turbos need a thrust bearing, much like a crankshaft needs one to keep the shaft in the correct location under load.
The more power you make the harder the forces are on the thrust bearing inside the journal bearing turbos.
At some High compressor flow the thrust bearing wears quickly and the turbo needs repair.
It is a combination of shaft rpm of the turbo and the diameter of the compressor wheel trying to move the air thru the compressor housing.

You can fix that issue with a Ball-Bearing style turbo whose design does not need a thrust bearing. More $$$ but can handle higher compressor flow rates with large turbos and higher compressor shaft rpm.

You might run for years with a larger single turbo with a journal bearing and thrust surface if you keep the load on the compressor wheel and shaft by running less boost pressure. Dual Turbos share the load and reduce the loads by splitting the airflow demand across two boosting devices. 30 psi is very common on engines and diesels can see very high boost pressures but for very short times in each gear.

Again engine size is not as critical as the turbos are helping with multiplying the mass flow thru the engine.
Mass flow is what makes power, as long as you add the proper amount of fuel with the mass flow of air.

Typically 1 POUND of AIR will make on average 10 HP. (Some make 9.7 HP, some make 10.2 hp).
If you move 100 pounds of air thru the engine the engine will make 1000 HP.
Does not matter if it is 1 turbo that moves 100 pounds of air mass or 2 smaller turbos that each move 50 pounds of air mass.
But, like you said, the plumbing can be easier at times with packaging 2 smaller turbos and the related systems vs one massive turbo and a 5" down pipe. Drag cars are a different story as the cars are many times built around the turbo configuration. Superchargers package very easily vs most turbo installations.

So you are correct on all of your thoughts.

Tom V.

and you get more sealing space for the head gaskets.

Everything being equal a larger 480-540 CI turbo engine will out perform a 281 cubed Turbo engine easily!
A turbo car will never out 60’ or 330’ a supercharged car!
I only have a 3:73 gear in my car....I probably could go to a 3.50 if I wanted to and it wouldn’t miss a beat!

GTO George

OK George, You have a Pontiac so lets compare Pontiacs.

You have a 520+ cid engine with a supercharger on it. Marty Palbykin had a 406 cid Turbocharged engine.

You have a Ported High Port Head I believe you have posted about What is the head flow on that head? Must be more than 340 cfm as E-Heads can go 340 cfm all day long and you say E-Heads are chit.

Marty had a 240-260 CFM Cast Iron Pontiac Head. So you have a 100 cid bigger engine and 100 cfm better flowing head

You say you make over 1200 hp.

How come George, the expert on turbos and superchargers, that you run low 8 second times and Marty ran 6 second times with less head flow, (cast iron Pontiac Head) less cubic inches, both of you on methanol, and you say the supercharger will beat the Turbo car.

BS George. You do not have a clue. Just like to argue just like Charlie said. The topic is about Turbos, you have never run a Turbocharged vehicle, so stay out of the thread with your comments. As they are just BS anyway, Just like your knowledge of Street Racing. Never saw you down on 12th Street in Detroit.

Tom V.

Only 11 lbs of boost and my car is heavier!


GTO George

Actually I’m running 11 lbs of boost for around 1,200hp and Marty’s car had 1,600 hp and what around 40 lbs of boost...he should have had around 2,000 hp plus with his twin turbo engine! Just saying!


GTO George

But george , You have better flowing heads . It make a differnce ...

And whats the difference in your cam sizes ??? Means alot buddy!

Charlie.....boost is boost and I have a small cam in my engine....ie Bracket engine!


GTO George