Hi,
So I have this 72 Skylark with a 471 inch Big Block Buick and a T56 with a stage 2 upgrade in it. It is my first car and I have had it for 17 years. It dynoed 609 hp at the crank, limited by carb size. Probably had 20 or 30 more in it.
On the Buick forum, I'm one of the big boys, and really, over 600hp on the street, all motor, is nothing to laugh at no matter what the brand.
Well I just moved to Colorado, and I lost about 100 hp to thin air. I have been thinking for some time about a turbo 6.0 or 5.3 for more power, better street manners, and better mpg so I can enjoy my car (it gets 4 mpg currently)
I would like about 650-700 rwhp on pump gas with no meth, at 6000' elevation. I understand this is not a difficult number with these engines. I love the idea that as long as my turbo is not maxxed out, if I go a little higher elevation into the mountains, the turbo will compensate.
I have built many engines and am not afraid of internal mods.

Should I go 6.0 or 5.3? Does it matter?
At what hp level should I upgrade the rods?
Would some 317 heads do the job? Port work needed?
Single turbo or twin? How big? (keep elevation in mind)
What should I use for an intake and throttle body?
I hear about guys having good results with cheap (CXRacing) turbos. Experiences?
One other thing, and i know it's petty, but... it's a musclecar, and it has to lope. What's the point if it doesnt? is there a decent turbo grind cam that will lope at idle?

I just moved into my new house and will be building a nice big garage in the spring. Nothing will happen till then, so i have plenty of planning time.
Thanks!

 

I'm doing the same except I'm ditching the 496 out of my 69 chevelle.. I'll be following your thread.

 

1. No real difference in 5.3/6.0. For the most part its preference. There are some variations in the years for each of them so you'll have to do your research. Some have stronger rods than others, and can get you over 600whp without doing any internal mods.

2. The stronger rods are good up to your power goals. Anything above 650whp or so is probably putting them on the edge of reliability. There are guys that have pushed close to a grand on the stock rods, but eventually they fail.

3. 317 heads would work fine. No port work needed, but it won't hurt.

4. Single or twins is still preference. Single means less parts and easier packaging. Power goals can be hit with either. An S475 is a fairly cheap turbo (less than $700) and can reach your power goals by itself. Lots of people are making your power goals on a 76mm turbo, and they are very common an inexpensive unless you opt for a billet turbo.

5. Stock intake and throttle body will work fine, even if you get the engine from a truck. There may be a little power gained in swapping to an LS6 style intake, but its definitely not necessary.

6. A few of the guys here who have built multiple turbo engines usually do so with CXRacing turbos. On3 turbos seem to be another option. These can be had for less than $350 and will get you close to your power goals.

7. Lope means overlap. Overlap is bad on a turbo car. You can get a mild turbo cam with a slightly aggressive idle, its up to you. Lope also plays a part in your big block getting 4 mpg.

 

Do a 5.3 they are cheap and tough. The stock bottomend is good to 750whp on good tune. Heads dont matter since for forcing air thru them. Put a cam and intake and valve springs in it and let it rip. S475 turbo flipped truck manifolds a comp turbo cam and edelbrock proflow is what im running. With a stock 5.3 bottomend thru a th400 its making 633whp at 13lbs and ive been beating on it for the last year.

 

OK, thank you for the answers.

So what I got so far is, either engine will do, I should probably play it safe and do some rods, 317's are good, stock intake/TB is good, and for turbos, whatever I can fit. A little bit of lope is ok, but don't overdo it.
I'm thinking twins, because anything over 3" exhaust will be tough to fit over my rear axle, but I do have 2 sides.
The more I read about CX turbos, the more I wonder why so many people hate these things so much.
If I do twins, should I go for the GT35 or 45?
Safe to assume the 6.0 would make a little more torque down low and spool the turbos faster?
What about pistons? Stockers OK, or should I upgrade those too?

Yeah, my current cam is huge, with lots of overlap. .636" lift, 268 dur @.050", 108 LSA. It rattles the house windows. Love it. Nothing beats that sound. But, I think it's time I saw the light and embraced boost and modern EFI.

 

I had a 1972 Skylark 350 when I was in high school. Loved it!

Some ideas for you... to get you going...

https://ls1tech.com/forums/forced-in...on3-70mms.html


http://www.hotrod.com/techarticles/h...g_bang_theory/

http://www.truckinweb.com/tech/engin...g/viewall.html


Yes... the cam would be way too big for what you're thinking of doing. Maybe something along the lines of 224/230 .588/.598 @114 LSA would do you better. There are a few good turbo cams out there. Consider a custom cam like that or have something spec'd for you. Two big names on here are Martin from Tick Performance and LilJohn. They've both had good results for people.

Good Luck!

 

No no no, the cam that I gave the specs on is in my 471 Buick motor. That is an all motor setup. I would not dream of running that much duration or overlap in a turbo setup. I would blow all my boost out the exhaust!

So I gather the GT45s would be too big for a street setup unless I was going for over 1000 rwhp, which I am not (yet... we all know how that goes)

Would a pair of GT35s support my hp goals, bearing in mind that I am at 6000 ft elevation?

 

I have the twin On3 70's thread that was posted as an example. My car is a 3720lb daily driven chevelle. I easily put 300 miles a week on it. I drive it to every track I race at, never trailored. It had a 496 in it and I pulled it and now I run 6.00 @ 116 mph in the 1/8th and average around 18-20mpg's. The On3's are a very nice piece and are $324 shipped to my door. I have had them for over a year now with no issues. I previously had the 62's from precision that were a grand a piece and had nothing but problems and was $500 a rebuild.

If it was me and since you are not afraid to do internal mods, I would change the pistons in your current engine and do a set of twin 76's from ON3. Now that would be bad *** and save you a ton of money.

 

X2. Turbo the BBB.

 

That would be pretty badass.

At the same time I bet I could sell the BBB for more than this swap would cost.

 

I was was wondering the same line of questioning for 5.3, guess Hexenlord summed it up.

 

5.3 Engines have extremely thick cylinder walls. Even the aluminum ones are very durable. The 6.0 engines use the same crank/rods (for the most part) as they both have the same stroke, the 6.0 just has a larger bore.

There are benefits to the 6.0, but they are the same benefits that apply to any build. Bigger means more off-boost torque and slightly faster spool. You also have the L92 heads as an option. And at the same time it also means more cost. 6.0s are usually two to three times the cost of a 5.3 and far less common. You have to decide if the 700cc displacement difference is going to be worth the cost difference. As far as peak power goes, probably not.

My 69 Nova has an aluminum 5.3 with a single On3 76mm turbo. Shooting for ~20 mpg on E85 and 600 whp.

Its replacing the 468 big block that I pulled out earlier this year. The big block was loud, rough idle, 4 mpg, unreliable for everyday use, and weighed 700 lbs with iron Brodix heads. It overheated if driven in traffic, and had catastrophic cold start issues (thanks to the fire hydrant of a carb on it).

The 5.3 that I bought weighs about 340 lbs fully dressed (half the weight of the big block), idles smooth, will get substantially better gas mileage, be far more reliable (sticking with OEM computer /w HP Tuners), and I can take it on long trips.

Btw, GrampasBuick, there are lots of exhaust possibilities you should consider before making the final decision on twins because of packaging. I can't run a large 4" Exhaust all of the way to the rear, either. So I plan on a large 4" downpipe that comes out on the passenger side behind the front tire. The open dump will actually be behind a cutout valve, so I can run a single 3" with mufflers to the rear. Mild 3" tone at the rear while driving/cruising (I plan on taking the car on LONG cruises, but exhaust drone can be annoying on the highway), and I can flip the cutout open and have a straight 4" dump for max power/muscle flexing.

 

This is great info, guys. I appreciate it.

I gotta say though, this almost seems too good to be true. I am into my Buick motor for about 12 grand after all is said and done. Roughly half of that is for power, half is for durability because the 455 block goes kaboom after 600 hp/ 6000 rpm if you don't do a full block girdle and a really expensive set of rods. Everything is more expensive for these motors.

So for a small fraction of that, I can have a stout bottom end motor that makes a ton of power reliably and acts like a normal engine when I'm not being stupid. Is it just that people were scared of turbos and tuning until just a few years ago?

 

Most people just refuse to believe that technology has actually went somewhere since the 60s and 70s.

I know guys that think the only way to build a car is an 11 second small block in a stripped out car with too much cam and carb for the street that has to be tuned up constantly.

Then I make them feel bad taking a 600 HP car with near stock idle and 20 mpg on road trips after driving to the track and spanking their trailered car by more than a full second.

Most production cars are going turbo for this very reason. production reliability and economy with no sacrifice in torque or power.

 

Need something in the mid to high 210's intake duration and low to mid 220's exhaust duration for a turbo 5.3 unless it's an all out race car in a light weight chassis that will never see below 5000rpm.

 

Id put an S480 on the big block and convert to Holley EFI.

 

What part of Colorado do you live in? The air really sucks up here, takes about 3-4lbs just to make up for the elevation difference.

 

I'm in the Springs too. Love it here, but the car doesn't. We get used to it in a few months. Cars don't, unless they have turbos.

 

I'm in Colorado springs as well. My Stock Ls1 with magnum 80mm just laid down 560 uncorrected spinning tires on the dyno dynamics on 14 psi. This was the first pull 12 psi 500hp.