455 Twin turbo STREET motor

[stoneshrink]

Okay - 1st Thank you Paul - you've been an amazing help, even though this build is far more complex because of your input (it's really a good thing).

I'm build a 455 for my Skylark (I'll do a picture post later). The car itself is a long story, but the end is I'm going to build a 455 for it that will be streetable and not necessary for competition... just a dang cool motor that runs hard.

The specs
1976 Block
.030 over bore
forged, speed pro pistons
full girdle
Edelbrock heads
fuel injection
twin GT 2870 turbos

- in short, something simple, easy and reliable
I'm still not convinced on what cam to use.... probably will be hydraulic roller, but could be solid roller/ custom grind (imagine that, no off-the-shelf twin turbo 455 cams available)

[tyoneal]

Be careful choosing a cam, because that will dictate the total personality of the engine. If this is a fun street motor use a Hydraulic Cam only! (KISS, Keep it simple .....)

Be sure the LSA has very little over lap 112* or higher otherwise you will bleed off your boost.

Make a call to 3 or 4 of the Big Cam Manufacturers and see what they offer. Be sure and have all the specs of your engine handy when you speak with them, and you don't need to go over board on the cam. A TT 455 when make tons of power so you don't need to go Crazy. Buy something Modest, If it doesn't make enough power you will want to re-asses your goals.

Be sure and stick to a street friendly engine, you will have a lot more fun and a lot less headache.

Google Turbo Buicks. There are a ton of sites that you can glean some information from.

If you can afford a intercooler, and can do the pluming correctly, do it. everything on the engine will work more efficiently, and you can run more boost without detonation. For the street try and stay away from alcohol injection. More Complicated=More Headache=More Expense.

Good luck,

Ty O'Neal

[stoneshrink]

thanks for the input - problem with googling "Turbo Buick" is all you get are black cars.... not that there's anything wrong with that, however, for some reason (which I'm sure I'll find out) people don't turbo 455s... ah well, someone's got to be the hero (or the goat)

Cam specs

218/218 .525 lift, 114 LSA hydraulic roller. Should idle just like grandma's car.

[tyoneal]

thanks for the input - problem with googling "Turbo Buick" is all you get are black cars.... not that there's anything wrong with that, however, for some reason (which I'm sure I'll find out) people don't turbo 455s... ah well, someone's got to be the hero (or the goat)

Cam specs

218/218 .525 lift, 114 LSA hydraulic roller. Should idle just like grandma's car.

======================================
What is your Compression Ratio?

The reason I mentioned the Turbo Buick is that the "Black Car" People are some of the most knowledgeable people with regards to Buick's and Turbo Chargers, Plus they will know all the best places to buy things for Turbo Charged Engines.

I know they can at least point you in the right direction. I would imagine that the main reason you don't see more of them is that the 455 can make a ton of power pretty easily without Turbo Chargers.

Make sure your block and heads are up to the task. 2 Bolt Main vs. 4 Bolt Mains, Forged bottom end, etc.

Can you describe what type and quality your parts are?

Ty

[stoneshrink]

When I get done with this car, I'll have to post a book with acknowledgments in the back to all the people who have provided excellent input in this motor, the Skylark's suspension, and on this one - http://www.bangshift.com/forum/showt...229-CTS-Spider - which is my other "current" project. Before that my resume includes several blown Chevs, and about every combination you can have with 231s - including that terrible draw-through design turbo (fun when it ran). Cadillac motors in my Studebaker truck....

I appreciate the kind words about the guys (and gals) at TurboBuick.com. It is true there is a wealth of knowledge there.

I agree that the 455 is a pretty stout motor all by itself, however, when my dad was racing in the late 50s and early 60s, they used some parts that were amazingly weak - yet ran some pretty quick times - the trick they used was easing into the power.... the turbos on this 455 follows that same principle. It'd be breathtakingly easy to break this motor into small bits by abusing it so I won't. And still be very quick for a DD Buick. In my experience, there's no such thing as easy power...

Parts... to the above, of course everything is ARP studs. Intake and exhaust are things I enjoy building myself (I'm kind of sick in the head, but it keeps me happy).

CR will be 9.66:1
no 4 bolt main - wouldn't really help because of the weak web design of the 455 block, but there's a full girdle tying the mains to the side rails. No need for a forged crank, I'm going to live dangerously with shot peened, arp bolted rods. If anything breaks, it'll probably be the rods.



So enough about me - you have a current project or two?

[bobc455]

A couple of thoughts here.

First of all, since this will be a true street motor and the turbocharging is done mostly for the "coolness", you'll probably only want to run 6# of boost - 8# at most. Plus you won't want to exceed about 5500 RPM. That will eliminate you from needing a girdle and an intercooler, etc.

The nice thing about the black cars is that they are exactly 1/2 of what you are doing - they run a 231CID motor with one turbo. 231*2=462, so with two turbos are doing about double what they do. You have essentially two of their engines.

However, the black cars tend to run a helluva lot more boost. I know guys that run the black cars at 25 to 27 PSI, and run alcohol and intercoolers. Your stock block would be blown to smithereens WAY before you ever hit 27PSI!!! So the knowledge that the black guys have won't really apply to you. Even stock, the GNs ran 12 PSI, so in theory the stock GN turbo is already much more than you need.

I don't know if this has been mentioned previously, but you'll need a lot more oil volume (not pressure) to handle your turbos. You might want to consider a new front cover from TA performance in your build.

For camshaft, i run a motor that relies on a lot of nitrous (which in most ways is similar to a boosted motor). My cam has 116 degrees of lobe separation. TA did a custom design for me. They will do a custom design for anyone, at no extra charge - the only downside is that you have to wait longer while the cam is ground. But to me, that time is totally worth it.

I run about 9.6 compression in my car, but I think that's too high. If I was building the motor again, I would run around 9.0 or maybe even slightly less. 9.6 is fine for a normally aspirated street car, but once you add nitrous or turbos (especially non-intercooled ones) I would rather see you drop the CR a bit. My pistons are custom-made by JE (through TA performance who created the specifications and worked with JE), however I think the forged Speed-Pros are designed as a nominal 10:1 piston. Also, they are designed for NA motors, and for a boosted engine you might want to consider a piston designed to work with boost (slightly larger top land, etc.).

-Bob Cunningham

[stoneshrink]

I always cringe when someone says I'm building something for the "coolness" factor. It's not, turbos allow you to get incredible hp while being able to drive it on the street. This motor will be 700 hp, I challenge you to build a 700 hp motor NA motor that you can drive on the street that operates vacuum brakes, idles smoothly, and doesn't load up at lights.

I'm intercooling the turbos, and it will be port-efi. the only coolness is it will be the Buick equivalent of the Kurt Urbain (former) Nova. Look like grandma's car.... probably be grey when it's done.

It also has a girdle - just because I'm building it where it could survive, I also recognize that I could upgrade turbos and injectors and be in the hero world.... all without hood scoops and idling like a kitten.

[bobc455]

How much boost pressure do you plan to run?

-BC

p.s. I LOVE the "grandma's car" thing. I bought my car from my grandmother - so it is a true grandma's car. Sleepers rock!

[stoneshrink]

6-8# all in before 5200 rpm. The goal of the turbos is to cure the lazy hp curve in a manner that doesn't break parts with sudden pressure (such as happens with nitrous)

I actually have (and use) the afghan that was in my 1st skylark....

[bobc455]

Then do you really think you need an intercooler?

If it were me, on 8# I would not intercool. Intercooling adds a lot of extra underhood hardware, and I like to work a lot under the hood. Right now, I can completely pull my motor by myself, working at a casual pace, in about two hours. I feel like if you add an intercooler to the mix, things will be very complicated under the hood. It's not a bad thing to intercool from a performance perspective, but it's not like you are running 22# and your air temps are astronomical.

I've looked into supercharging quite a bit, and I was going to go down that road for a while. (In fact I have a procharger sitting in the garage that I haven't installed, but that's a different story for another day.) And even up to 10# of boost, I would probably not intercool, but I realize that would be running on the edge.

And don't go nitrous bashing - as long as you use good hardware, and use it intelligently, it is an amazing power adder. But I won't preach...

-BC