Let me first say I read through the entire post from BBS as well as the sticky at the top, but I just figured out compressor maps and stuff this weekend as I havent had a chance to pick up any books.

Anyway, my ultimate goal is a single turbo 427 small block. I want to go single turbo for a number of reasons:

1. LT1 style accessory brackets leave the entire driver's side of the engine bay wide open.
2. Less of a plumbing nightmare with single turbo
3. Cheaper
4. Keep A/C

My initial thoughts for the engine are as follows:

-World Products Motown block
-Eagle H-beam 6" rods
-Undecided 4" stroke crank
-JE 4.125" pistons
-AFR 227cc heads w/64cc chambers if possible
-LT4 intake or carb manifold converted to EFI
-Custom headers
-Custom COMP cam, same as Monty is running in his vette

I made up an MSExcel spreadsheet to look at different engine sizes, rpm ranges, boost ranges, and the resulting flow requirements. So far, the only compressor map that I've found that is anywhere near what I would need or want is the T88. After reading through some of the other posts, I assumed an 85% VE at 6000 and 7000 rpm to simplify things a little. As you can see on the map, I plotted both sets of numbers. Obviously, as calculated, 15 and 20 psi at 7000 rpm gets into uncharted territory, but I really doubt I would turn it that high anyway. Also, I'd probably only run 10# for the most part, maybe 15 or 20 at the track, obviously with race gas.

For 83 Crossfire TA, here is the T88 compressor map I found.

Here is the drawing I made.


Also, by my calculations, I could have 10# of boost at 3000 rpm.

Now here is my main concern. Does any of this sound even remotely feasible? I'd probably also run an intercooler similar to Monty's setup to keep the intake temps down. I've got a year to plan this out as I'll be getting a substantial loan Junior year, I just want to have a good plan before I get to that point.

Any and all suggestions will be appreciated.

*Edit* One more thing, I'm going to do a 427 no matter if I turbo it or not. I may even build it up first, even with the low compression pistons and just run a nice n/a cam until I do the turbo system. Just depends on how much the entire project would cost. I'm definitely not doing this on a "high school" budget, but its not going to be unlimited either.


-Tristan

 

Using the compressor map and your numbers as reference, definately stay below the 6000 rpm's with that turbo. Building the engine first for turbo without the turbo is a very good idea. You give the engine time to get good break in without wearing your turbo, but please dont wear the engine without the turbo on, resist the temptation
Talk to "erictheviking", he is also building a 427 for turbo. There was also another guy building a turbo 427, but I forgot the name... They might help and interchange ideas.

 

TPIS makes a miniram that is sized to the "different" AFR ports both large and special "tall" ports.

 

Sweet, didn't know that.

 

I guess the main thing I was wondering was is a T88 sized turbo suitable for what I'm thinking? This is going to be a street car with a T-56, but I'm still looking for 700-800 horsepower, if not more.

Also, can anyone recommend a crank? I plan on keeping the engine below 6500 rpm at the highest, if not even 6000.

I'm also thinking of using the World Products Motown 220 Lite heads now instead of the AFRs. They still have a 220cc intake port, but have the 64 cc chambers I'm looking for. Only thing is they require .150" offset intake rockers...

 

the AFR 227 heads require different rockers too.
I almost bought them, till AFR told me that.
from my own personal experience, I would never buy a complete head package from AFR only the bare ported heads. My heads had metaL shavings under the spring shims and in the springs. the valve guides were not straight and the valve job is very poor.

I think that turbo would work great for you, not too much lag and tons of power!
For a street car that would be awesome!

 

get this kit and tell them you want blower pistons

http://cgi.ebay.com/ebaymotors/ws/eB...tem=2478736507

 

That surprises me. For the price of AFR heads and the period of time it takes to get them, I would expect more from them. I'm pretty sure I'm going to go with the Motown heads anyway, they flow about the same out of the box and are cheaper fully assembled.


B4Ctom, I just called about the pistons for the rotating assembly you showed and they said, with 64cc heads, the lowest they could get was around 10:1 because there isn't enough piston to dish it enough to get lower compression. You could with custom pistons, he said, but that its not really worth the cost for what little more you get? I was looking at Monty's setup and he's running custom JE pistons at $84 apiece. I just looked through Jeg's and a set of JE forged pistons is about $600-700. So I don't really see a price difference. However, if I can, I would rather not get custom pistons. Any ideas? I'm not set on it being a 427, so I can drop the stroke down and run a short rod.


On another note, do you have any experience with or know of anyone that has used the Edelbrock Victor-E intake? I found that the other day and it seems like a nice piece. If I went with that I'd used the Wilson Manifolds 100* intake elbow and one of their 90mm throttle bodies.

 

consider a 5.7 rod 406 then? you aready said you arent set on high RPM, if that is so then you can get:

performance 400 block <---check for correct part #

4340 crank

5.7" H-Beams

Forged reverse dome Federal Mogul .030 406 pistons
LW2606-30
_64___68___ 72____74__ <---cc's
9.78__9.43__9.10__8.80__<--compression

This rotating assembly by no means would be for a extremely high reving engine but surely would be about as tough and resilient to abuse as you could build without custom parts. Some shopping might reveal some cheaper prices.

Note: aftermarket blocks with 4.125" (400) bores are available main journals for 350 or 400, make sure you purchase your crank with the according journal.

 

I definitely like the block and crank. But I'm not sure about the rods. I mean, I have the possibility of producing near 1000hp at high boost with the T-88. Do you think those rods would be up to the task? I've already priced out some Eagle H-Beam rods, which seem to be the rod of choice for boosted apps.

And upon further investigation, I think I will go with the AFR heads after all. They have the 76cc chambers, which will help with finding a piston, and they are in fact cheaper than the Motowns, I finally found some prices for them. $1800 for the Motown's versus $1495 for the AFR's.


Oh, and one other thing, if I got an internally balanced 400 crank, would I be able to use an LT1 balancer to use my LT1 accessories?

 

probably but LT-1's arent internally balanced on the flywheel end, just the balancer end. None of the 1 pc rear main seal chevys are. they have a flywheel with the special latemodel counterweight on them to make up for the absence of the extra material removed from the back end of the crank for the 1 pc rear seal design.

 

To choose your turbo, plot the whole rpm curve on the turbo map.

your engine might make the most power at 6000rpm, but its not going to spend much time at 6000rpm.

plot points at 5500, 5000, 4500, 4000, 3500, 3000, all the way down.

A. make sure that you are on the right side of the surge line, and

B. choose a turbo where you engine spends the most time where the compressor is the most efficent.

 

Are there any downsides besides more heat to operating the turbo outside its most efficient areas? To do that, with a T-88, I would have to keep the boost below 15 psi and the RPM below 5000, that stays withing the 80% island on the T-88 map. However, if I go down to 74%, I could turn it up to 20 psi and 6000 rpm, or 25 psi and about 5800 rpm; i.e. much more power.

 

know where to get one of these flywheels?

 

for a T-56?

unless you want to run a stocker, you might as well get the aftermarket T-56 flywheel. If that is the case then you don't have to get a LT1 crank (no 1 pc, you can get 2 pc) from centerforce. They make and sell special T-56 internal or external balanced flywheels for late or early applications. I had one in the JYD with neutral balance for 2pc rear main seal on my 355.

 

Awesome. I was thinking a Spec clutch anyway, and I know they have flywheels for the T-56. I'll check into that and see if they have one like what you're talking about. If not, I will definitely find one. Thanks.

 

who spec?

they sell fidanza aluminum flywheels I think. I believe fidanza has a "adapter" flywheel as well

 

Well more heat=less power. also, cooler air=less knock, which allows you to run more boost on the same octane.


But anyway, the rule of thumb is choose a turbo where your powerband is in the 65% efficently island or more. clearly, more efficent=better.

Figure out how much power you want to make, then figure out how much boost it is going to take to make that much power, then choose a turbo that matches your setup, don't look for your 6000rpm point on the graph to be in the compressor's peak efficency range, just look for it be above 65%. because if this car is going to be driven on the street, you have to figure its going to spend most of its time under 4500rpm. So you need to plot those points as well, and make sure you are clear of the surge line.
Depending on how much boost you are planning to run, you might want to look into a slightly smaller turbo, or one with a wider compressor map. Innovative's GT80R has a very wide compressor map, and would probably be a bit more street friendly.

 

Got a link to the map for the GT80R? I've only been able to find one for a GT60R (I think). Anyway, after doing as you suggested and plotting the various points you suggested, the lowest island I am in up to 6500 rpm is 72% efficiency, so I'm not too concerned about that. For street use I plan on keeping boost at about 10 psi. But for track use I plan to use methanol injection and race gas to allow for more boost (up to 25 psi).

As far as power goes, I'm thinking 6-700 on the street, 900+ at the track on higher boost. I want to go all out on this sucker and eek as much power out of it as possible. Basically, I want to completely skip the 11's. I'll never cut the car up to tub it and run fatter slicks, so I'll never get the full ET potential out of the car, but it'll be interesting to see what kind of mph I'll get out of it. I guess I would ultimately love to hit 1000, but that's probably going to be pushing it.

*Actually, I just found a map for the GT80, don't know if the 80R is something different. Anyway, initially the 80 does look like it might be better. However, after comparing airflow numbers and the maps between the 80 and the 88, it looks like the 80 might spool up 1-200 rpm sooner, but will not flow enough air at higher rpm and boost levels to support what I'm looking for unless I reconsider my goals.


*Also, is there anyway to control the boost so that once I pass a certain RPM point I can up the boost? It looks like I can get 10 psi at about 2800 rpm, but if I want to run 20 psi I need close to 4000. Is there a way to control the boost so that once I hit say 4000 rpm it goes from 10 to 20 psi? Or do I completely misunderstand the way it would work?

 

There are several methods of controling boost. And there are electronic boost controllers that can limit boost based most anything. They can limit boost to "XX" in first gear, and "YY" in second gear, and so on.

as far as how fast the turbo spools, that is dependant mainly on the size of the turbo, and the A/R ratio.

A built 427 pushing 25psi boost is going to make lie 1,300 hp. A GT80 or even GT76 would easily be good for 1,000 hp.

I hope you have about 30 grand to spend on all this.

 

I guess thats the next thing I'll do is start checking into boost controllers then and see just how I'll be able to do what I want to do, if I can.

And you're the second person that has guessed pretty close to what its going to cost to do this. I've already got a pretty comprehensive list together of parts and prices, and I think I just might be able to pull it off.

 

Due to the fact that I don't understand turbo maps and how to plot your rpm to the turbo's whatever, most of the stuff is over my head for now, but anyway. I was curious. Texas couldn't you just turbo your lt1? And if you can't what are you gonna do with it?

Ray D.

 

I could, but without completely rebuilding it to handle more boost, I wouldn't be able to get anywhere near the power levels that building an engine built for high boost would produce.

 

Now that I think about it though, with the budget I'm going to have, this may be the better way to go. I can get my LT4 heads ported instead of getting brand new ones. I can get a new rotating assembly and keep the stock block instead of getting a new one, and I can keep the intake. And, I will still be able to achieve somewhere in the neighborhood of 700 hp. Not too bad. I'll update once I look over the compressor maps again and airflow for a 350.

 

After looking over everything, I definitely like the idea of doing a 350 better if I decide to do a turbo engine. I think if I stay N/A I'll go for the 427, but its going to fit in my budget better to do a single turbo 350.

After looking over some maps I've got, I still think I'm going to go with a T-88 turbo. I'm going to keep the revs below 6000 rpm, and since this is a street car, the T-88 will spool a little later (just a couple hundred RPM) than a T-76 so I would think it would have a little better manners around town. Also, if I decide to go bigger with the engine, I won't need to upgrade any of the turbo equipment as the T-88 will support quite a bit more airflow than what I'll be producing with the 350.

 

So a single turbo 350 would have more power potenial then a lt1 or lt4 and, would be better budget wise also. I plain on upgrading my 305 to something but, I haven't decided yet. I like the Lt1 engine, but I love turbo's also. Hard decision.

 

Oh I'll keep it LT1/4, just build a bulletproof bottom-end for it and hog out the heads as much as possible. Probably still switch to an aftermarket ECM, still researching that.