gt45+lt1355?

[jizzlezworld]

finally came to the conclusion that my project will be.

97 camaro lt1 355 fully forgded internals 10.5:01 compression/
stock aluminum heads mild ported/
efi vic jr intake/6061 intake elbow
E85 system capable of supporting 1000hp/
th400 3.42 gears need help with convertor choice!

COMP CAMS 12-253-4
specs:
XTREME TURBO CS XT262H-14 Hydraulic Flat Tappet Camshaft
Lift .462"/.455"
Duration 262/269
RPM Range 2200-6400

gt45 y2004k single/FMIC
spec:

Compressor Size: Inlet = 4 3/16", Inducer = 68.7MM, Exducer = 97.8 MM, Trim = 69,A/R = 0.66, Intake (ID / OD) = 2.25" / 3.25"



turbine: Outlet = 4", Turbo flange = T4, Downpipe flange = 3.5" V-band, Inducer = 87.4 MM, Exducer = 77 MM,Trim = 92, A/R = 1.05

looking for info on street/strip manor,and hp/rpm boost range?

thanks in advance

[popo8]

Changed the color of the font for you.. Black on our dark back ground disappears...

[Tyler Wheat]

I'm a nitrous fan, myself. I'm not real knowledgeable with FI, but isn't the comp ratio a little high?

[zmm95]

Thats a lot of compression for boost!

Sent from my SCH-I535 using Tapatalk 2

[Z28pr0jekt]

Couple things...
1. that is a big turbo for a 355
2. That is a lot of compression
3. That is an extremely odd cam with extremely low lift.

[Fastbird]

And to piggyback Ryan....

1. That is a BIG turbo for a 355, or rather, a motor with a not so high VE like an LTx with ported stock heads. It's going to take a LONG time to spool.
2. That's a lot of compression for any significant amount of boost. Think more along the lines of 9.25-9.5:1 if you're going to be running 10+lbs.
3. The cam, not only being flat tappet which isn't for the LTx generation, is a very very odd choice. I would bet that's not even an LT1 cam. Scratch that one.
4. Have you thought about hot parts for the turbo? A turbo of that size isn't going to be easy to package in the engine bay. You're talking about moving the radiator, losing parts, the downpipe is going to have to be huge, etc.
5. Have you budgeted out what this is going to cost? If do, add at least 50% if not more. Little things add up quick on a build like this.

[jizzlezworld]

hoping to get info from knowlegeable people please...compression is perfect.10.5:1
1.quick spool
2.e85
turbo being to big...DON'T THINK SO!

[jizzlezworld]

thanks popo

[Tyler Wheat]

hoping to get info from knowlegeable people please...compression is perfect.10.5:1
1.quick spool
2.e85
turbo being to big...DON'T THINK SO!

What are you needing help with?

[sick70malibu]

And to piggyback Ryan....

1. That is a BIG turbo for a 355, or rather, a motor with a not so high VE like an LTx with ported stock heads. It's going to take a LONG time to spool.
2. That's a lot of compression for any significant amount of boost. Think more along the lines of 9.25-9.5:1 if you're going to be running 10+lbs.
3. The cam, not only being flat tappet which isn't for the LTx generation, is a very very odd choice. I would bet that's not even an LT1 cam. Scratch that one.
4. Have you thought about hot parts for the turbo? A turbo of that size isn't going to be easy to package in the engine bay. You're talking about moving the radiator, losing parts, the downpipe is going to have to be huge, etc.
5. Have you budgeted out what this is going to cost? If do, add at least 50% if not more. Little things add up quick on a build like this.

I think Fastbird lays it out pretty good here. The CR is a bit to high to build an engine with any good amount of boost. The cam is for a Gen I Small block Chevy, plus the lift is a little to small.

[Badbird_96]

hoping to get info from knowlegeable people please...compression is perfect.10.5:1<br />
1.quick spool<br />
2.e85 <br />
turbo being to big...DON'T THINK SO!
I agree with above post. The bottom end won't handle that much compression long. For a 355 a T67 is plenty of turbo.

[Fastbird]

hoping to get info from knowlegeable people please...compression is perfect.10.5:1
1.quick spool
2.e85
turbo being to big...DON'T THINK SO!

That attitude isn't going to get you far here. I guess people already building a turbo setup or actually running turbo cars aren't knowledgable, not to mentioned the two of us who listed the same stuff have been around these motors for at least a decade each. You can go your own route man, we're just trying to help.

[Z28pr0jekt]

hoping to get info from knowlegeable people please...compression is perfect.10.5:1
1.quick spool
2.e85
turbo being to big...DON'T THINK SO!
Yea I'm extremely confused by your response, and in all honesty you are the one who is not knowledgeable on this topic.

E85 is not going to magically make a 10.5CR motor run high boost. There will be absolutely no quick spool on a turbo of that size with such a small motor.

I'm keeping my eye on this as a possible troll

[Fixxer99TA]

That attitude isn't going to get you far here. I guess people already building a turbo setup or actually running turbo cars aren't knowledgable, not to mentioned the two of us who listed the same stuff have been around these motors for at least a decade each. You can go your own route man, we're just trying to help.

This is what I was thinking..

Along with what everyone else said..

Way too much comp, turbo a bit too big.... not going to spool "quick" as you said... second that on the cam, thats lower lift than a hotcam on 1.6s (which is a VERY small cam to begin with even on a NON FI car) and ALSO dont think its even a cam for an LT1.. I havent even built an FI car yet (coming very soon, though) and even I know that stuff wont work.

Seans built two of these things successfully, and Z28projekt has one of his own also... These are the guys to listen to, not bash as "unknowledgeable"

[94Blackbird]

Yea I'm extremely confused by your response, and in all honesty you are the one who is not knowledgeable on this topic.

E85 is not going to magically make a 10.5CR motor run high boost. There will be absolutely no quick spool on a turbo of that size with such a small motor.

I'm keeping my eye on this as a possible troll

Dude's asking the same thing on yellow bullet. Got radically different responses there than here. If he's not a troll, he's probably upset that someone said his carefully researched and hand picked parts aren't going to work well together.

[Z28pr0jekt]

Dude's asking the same thing on yellow bullet. Got radically different responses there than here. If he's not a troll, he's probably upset that someone said his carefully researched and hand picked parts aren't going to work well together.

So he's posting about advice building a turbo lt1 on a mustang board?

[jizzlezworld]

looking for info on street/strip manor,and hp/rpm boost range?
yeah i may need a better cam choice,also is the compression to high for a lt1 you think or with any forced induction,because i've done reasearch from the other forums im in theturboforums.com yellowbullet.com ls1tech.com and been told E85 or a high octane will work for that compression.

[Z28pr0jekt]

E85 helps with eliminating detonation but it's still an enormous risk with high compression like that. However it's not going to just make a motor run right at high boost without the serious best in forged internals and a very good tune.

It's not just a better cam choice you need, it is an entirely different cam that is actually meant for this motor.

Fact is, a 355 is not going to spool a GT45 to optimum levels until 5000+ rpms. It is completely unnecessary to run a turbo that large on such a small motor. A 76mm turbo is all that is needed and will make more than enough power.

A GT45 is more suited to a 383 (preferably a 396) with around a $15,000 motor (i.e. dragonslayer crank, diamond pistons, etc etc) looking to run low 9s high 8s. So if you have let's say to be kind $30,000 laying around to actually setup a turbo/motor/fuel system for that then be my guest but that's not even remotely counting the drivetrain and suspension needed to handle that.

[jizzlezworld]

and no im not a troll,I figured I would get help from every avenue.Deside what i fill is right and go from there,attitude don't have one.And yes I am somewhat of a noob to the turbo side of forced induction my first project was this same motor with a small p600b cc305 cam,snow water meth kit,bigger injector etc... I understand i have a bad choice in cam selection what would you guys recommend loking for something off the shelf?

[jizzlezworld]

got you,thanks greatly appreciated.

[jizzlezworld]

This is what I was thinking..

Along with what everyone else said..

Way too much comp, turbo a bit too big.... not going to spool "quick" as you said... second that on the cam, thats lower lift than a hotcam on 1.6s (which is a VERY small cam to begin with even on a NON FI car) and ALSO dont think its even a cam for an LT1.. I havent even built an FI car yet (coming very soon, though) and even I know that stuff wont work.

Seans built two of these things successfully, and Z28projekt has one of his own also... These are the guys to listen to, not bash as "unknowledgeable"
I actually never said anyone was unknowledgeable,and yes you guys are right in the cam choice thats a no go.

[jizzlezworld]

E85 helps with eliminating detonation but it's still an enormous risk with high compression like that. However it's not going to just make a motor run right at high boost without the serious best in forged internals and a very good tune.

It's not just a better cam choice you need, it is an entirely different cam that is actually meant for this motor.

Fact is, a 355 is not going to spool a GT45 to optimum levels until 5000+ rpms. It is completely unnecessary to run a turbo that large on such a small motor. A 76mm turbo is all that is needed and will make more than enough power.

A GT45 is more suited to a 383 (preferably a 396) with around a $15,000 motor (i.e. dragonslayer crank, diamond pistons, etc etc) looking to run low 9s high 8s. So if you have let's say to be kind $30,000 laying around to actually setup a turbo/motor/fuel system for that then be my guest but that's not even remotely counting the drivetrain and suspension needed to handle that.

got you z28 projekt,thanks greatly appreciated.

[Fastbird]

Really, compression ratio is going to depend on how much boost you plan to run, components used, computer system being used. The higher the static compression ratio (I'm not even going to bring dynamic into the conversation) the more cylinder pressure obviously. Pressure = heat generation. Add boost, and you get that much more heat generation. Too much heat, you get detonation, I.E. bad juju. So starting with a stockish 10.5 compression ratio, even with quality heads with better designed combustion chambers, forged rotating assembly, tuning, it's just asking for detonation. You can also go too low. My motor is 8.8:1 static, and at the absolute low end of the spectrum IMO for our motors. It's almost a little sluggish down low. Almost I said. :D From my personal experience, a very happy medium for a car running in the 7 to around 16-18 PSI range is going to be about 9.25:1, maybe 9.5:1. Granted it was an LS motor, but I specced my 99 Vette's build out at 9.25:1 and is responded remarkably well making 760 RWHP @ 14 PSI. If you're running an aftermarket computer that's got complete tuning control (BS3, XFI, DFI, etc) then you can probably get away with a little more compression, but not a lot. You can overcome too low compression, but you have to build it all over again if you go too high.

I LIKE the fact that you'd doing a 355. Shorter stroke, larger bore. It's more efficient than stroking the motor to a 383 or 396. But that GT45 is really gonna take a little while to spool. I'm running what I consider to be a pretty dang healthy 383, and my turbo is a PT76GTS with a .96 A/R, and even it doesn't fully spool until about 3000-3500 RPM. BUT.......what are you building the motor for? Track car? If so, then if you're launching off a brake or footbrake on an auto and can build boost on the line, then it might work for you. But street car? Let's just say that it would be an interesting race between your setup and a big turbo Supra. Sure, the power is there, and it'll scream on the top end, but it's gonna take a while to get there and in that timeframe you'll end up playing catchup.

As for a camshaft.........man, this can go so many ways. You'll see a lot of talk about having a reverse duration split where the intake is open longer than the exhaust. I for one simply don't understand that thinking, because exhaust is what drives the turbo. I personally like to see a long split between the intake and exhaust with a wide LSA for a dedicated turbo cam. Think 12-14* positive split with a LSA in the 114-117 range. You want to minimize overlap with a turbo, because any overlap is exhaust pressure being bled away from the turbo. You also do NOT need a huge cam for a turbo (or any FI setup for that fact) motor. LE specs a pretty decen 224/236 cam that does very well. I'm pretty sure AI has a grind he likes too that's similar. Cam selection is really going to depend on what you are using the car for though, and how broad you want the powerband to be.

Keep the questions coming man, we're all here to help.

[jizzlezworld]

Really, compression ratio is going to depend on how much boost you plan to run, components used, computer system being used. The higher the static compression ratio (I'm not even going to bring dynamic into the conversation) the more cylinder pressure obviously. Pressure = heat generation. Add boost, and you get that much more heat generation. Too much heat, you get detonation, I.E. bad juju. So starting with a stockish 10.5 compression ratio, even with quality heads with better designed combustion chambers, forged rotating assembly, tuning, it's just asking for detonation. You can also go too low. My motor is 8.8:1 static, and at the absolute low end of the spectrum IMO for our motors. It's almost a little sluggish down low. Almost I said. :D From my personal experience, a very happy medium for a car running in the 7 to around 16-18 PSI range is going to be about 9.25:1, maybe 9.5:1. Granted it was an LS motor, but I specced my 99 Vette's build out at 9.25:1 and is responded remarkably well making 760 RWHP @ 14 PSI. If you're running an aftermarket computer that's got complete tuning control (BS3, XFI, DFI, etc) then you can probably get away with a little more compression, but not a lot. You can overcome too low compression, but you have to build it all over again if you go too high.

I LIKE the fact that you'd doing a 355. Shorter stroke, larger bore. It's more efficient than stroking the motor to a 383 or 396. But that GT45 is really gonna take a little while to spool. I'm running what I consider to be a pretty dang healthy 383, and my turbo is a PT76GTS with a .96 A/R, and even it doesn't fully spool until about 3000-3500 RPM. BUT.......what are you building the motor for? Track car? If so, then if you're launching off a brake or footbrake on an auto and can build boost on the line, then it might work for you. But street car? Let's just say that it would be an interesting race between your setup and a big turbo Supra. Sure, the power is there, and it'll scream on the top end, but it's gonna take a while to get there and in that timeframe you'll end up playing catchup.

As for a camshaft.........man, this can go so many ways. You'll see a lot of talk about having a reverse duration split where the intake is open longer than the exhaust. I for one simply don't understand that thinking, because exhaust is what drives the turbo. I personally like to see a long split between the intake and exhaust with a wide LSA for a dedicated turbo cam. Think 12-14* positive split with a LSA in the 114-117 range. You want to minimize overlap with a turbo, because any overlap is exhaust pressure being bled away from the turbo. You also do NOT need a huge cam for a turbo (or any FI setup for that fact) motor. LE specs a pretty decen 224/236 cam that does very well. I'm pretty sure AI has a grind he likes too that's similar. Cam selection is really going to depend on what you are using the car for though, and how broad you want the powerband to be.

Keep the questions coming man, we're all here to help.
for sure a mental note/sticky...wow i have some serious learnig to do thanks

[Badbird_96]

For cam you should get le or equivalent to make a custom grind cam for your setup but that's my 0.02

[Fixxer99TA]

I actually never said anyone was unknowledgeable,and yes you guys are right in the cam choice thats a no go.

If you didnt mean that, sorry, my bad and I apologize... But it seemed like it from when you replied "Need help from knowledgeable people on this please" after Sean (Fastbird) and Ryan (Z28projekt) already replied... Almost like you were saying they werent knowledgeable... I think thats how they took it too.

But no worries, I doubt you meant it that way. Everyone here is here to help... These guys know what they are talking about, they wont steer you wrong with anything FI related. Chances are I will be asking a few things in the coming months if I go the route I think Im going to go with my car.

[bigtoyz]

for what it sounds like what you want to do I'd do a 210/220 boost cam. 9.5 cr will make it snapper for on the street. And as for turbo and for the street more than anything....question is how much you want to make?

300-550 I would say turbonetics hp62 it would be a pretty fast boost maker for a single turbo setup but if you push it to its limit past 600 hp it will be out of its effienency fast anything past 550 and 20 psi roughly it drops from 75% down to 65% and will start to surge it past 600 hp. If more than 600hp then I would say a hp66 for 700 hp max at roughly 29 psi to hp70 that would be about 400-800, with 800 in low to mid 20's psi. But exact hp levels depend on engine variables also. cam, heads, rpms, and all that good stuff. Just remember bigger the turbo the slower it will be to boost up.

If you want to learn how to read the compressor maps just drop me a pm....I'd be glad to teach yeah what I know. I learned from an ole navy boy that worked with turbines in the navy, and when he got out of the service he was a book worm on those things. And he got into it back when the grand nationals were big. And he was a whiz at building them and setting them things up. But any whoooo that is where I have picked my knowledge up and from reading myself.

by the way sorry for being so wordy. Its just hard to have a simple answer when it comes to turbos. Supercharging now that is easy:D

[Z28pr0jekt]

for what it sounds like what you want to do I'd do a 210/220 boost cam. 9.5 cr will make it snapper for on the street. And as for turbo and for the street more than anything....question is how much you want to make?

300-550 I would say turbonetics hp62 it would be a pretty fast boost maker for a single turbo setup but if you push it to its limit past 600 hp it will be out of its effienency fast anything past 550 and 20 psi roughly it drops from 75% down to 65% and will start to surge it past 600 hp. If more than 600hp then I would say a hp66 for 700 hp max at roughly 29 psi to hp70 that would be about 400-800, with 800 in low to mid 20's psi. But exact hp levels depend on engine variables also. cam, heads, rpms, and all that good stuff. Just remember bigger the turbo the slower it will be to boost up.

If you want to learn how to read the compressor maps just drop me a pm....I'd be glad to teach yeah what I know. I learned from an ole navy boy that worked with turbines in the navy, and when he got out of the service he was a book worm on those things. And he got into it back when the grand nationals were big. And he was a whiz at building them and setting them things up. But any whoooo that is where I have picked my knowledge up and from reading myself.

by the way sorry for being so wordy. Its just hard to have a simple answer when it comes to turbos. Supercharging now that is easy:D

Do you understand what it takes for one of these motors to handle 29psi like you're talking about?

It also takes nowhere near those boost pressures with a properly sized turbo to make power like you're stating

[Badbird_96]

I'm not 100% convinced a lt1 can handle 29psi period. If it can that would be a ridiculous build lol

[bigtoyz]

I was mainly saying that the hp60 would do 550 hp at around 20 psi, but said it could do 600 but at 29 psi and that would really be pushing it with a hp60 I agree. If you wanted 600 and over I would say a hp66 upto 700hp and then the hp70........ and a 355 with forged could hold together if the turbo's weren't pushed to the max which he was going with. This is where I would probably do AFR heads cause of the 3/4 deck and APR studs. But some brag that they are in the 10's with stock heads doing Nitrious of 300+ shot............ not that I would do that. Probably have to firewire the block and use copper gaskets. With that boost level you could lower the cr to 9:1 and the psi and acceleration would more than make up for the lower compression ratio.

I plan on boosting that much for the track (mid to upper 20's) with my system and up to 20 psi for the street.

I built a 88 tbird turbo couple 2.3 to take 23 psi (Stock was 18 psi) with ford head gasket......and stock top and bottom end. And it has held together since 95 with no issues. With no firewire and no special head gaskets. I know that they are difference in blocks. But what I was getting at is that at 20 psi give or take you could do 550hp and be snappy as hell and probably no lag. BUT all he was asking was some input......if your gonna build a good 355 forged it can be done without going with a huge turbo and deal with lag. Im use to turbos the min you push on the gas there is the boost, that is a true turbo street car.

[Z28pr0jekt]

Yes I do........ and a 355 with forged could do it also, which he was going with. This is where I would probably do AFR heads cause of the 3/4 deck and APR studs. But some brag that they are in the 10's with stock heads doing Nitrious of 300+ shot............ not that I would do that. Probably have to firewire the block and use copper gaskets. With that boost level you could lower the cr to 9:1 and the psi and acceleration would more than make up for the lower compression ratio.

I plan on boosting that much for the track with my system and up to 20 psi for the street.

I built a 88 tbird turbo couple 2.3 to take 23 psi (Stock was 18 psi) with ford head gasket......and stock top and bottom end. And it has held together since 95 with no issues. With no firewire and no special head gaskets. I know that they are difference in blocks. But what I was getting at is that at 20 psi give or take you could do 550hp and be snappy as hell and probably no lag. BUT all he was asking was some input......if your gonna build a good 355 forged it can be done without going with a huge turbo and deal with lag. Im use to turbos the min you push on the gas there is the boost, that is a true turbo street car.

I want to respond but you're comparing apples to oranges and it's just not worth it.


355 76mm turbo 15psi. Over 550whp or you did it wrong. Plain and simple.

[bigtoyz]

He can take what info he wants.......... but I would call the company and see what they think before doing anything just to be assured.

[Fastbird]

It takes a LOT of work (or expense rather) for a V8 to be able to run 20+ PSI of boost (boost being a relative term at that). My car can do it, was build by a shop that does a lot of FI motors. We decided the safest route was low compression and o-ring the block. No half fill or anything, but you've GOT to have top notch components. Reason being is that's a LOT of cylinder pressure across 8 cylinders. Cheap components are asking for a catastrophic failure. Not to mention the possibility of lifting a head at those kinds of pressures. It's not as common in the LTx world as it is the LSx mind you, but it can and does happen. Aftermarket heads with a thicker deck surface are almost a given if you're going to run a substantial amount of boost.

A 67mm turbo is the absolute smallest I'd put on an LTx motor. There's a LOT of airflow through these motors, and you'll choke it off up high in the power band, and anything smaller would be a simple waste of time IMO.

[popo8]

Wow... i read this...tge Op def came off wrong at first but i think he came thru and straightened that out.

Thanku OP for doing that... I promise...FastBird and projekt wont steer u wrong..THEY KNOW what they are talking about..

Ps...im at 10-12 lbs of boost (i cant remember what i was told on the phone) and my p1sc procharger is pushin my stroker to 590....

I know...apples to oranges as far as a turbo....but its a small parasitic blower at way less than 29 lbs of boost.... :banghead:


Larry (Popo8) Co-owner
LTXtech.com

[bigtoyz]

That is why I kind of asked what hp he was wanting.......If he is only wanting in the 450-550 hp range and wanted for the street I stand by the hp62 (may have said hp60 in the past but ment hp62) turbo that will be a very fun streetable turbo for under 5800-6000 rpm. It will do more hp but at the cost of high psi which will require a good block,firewire and 3/4 deck heads and no 0.60 over bore to keep the threads for the studs meater. Anything bigger in hp I agree nothing smaller than a hp67 I agree with you on that.

However with the LT1 block not being able to take more than 20 psi I disagree with you on that. For instance look at the LT1's doing the F1 supercharger or equivlant are doing 20+ with alot in the 25-30 psi with 1500-2000 cfm depending on the model of F1 supercharger......and reason I am bring up superchargers is because it is basically a turbo but gear driven and mutiplied so their is no lag. But psi can be lower than advertised also. All depends on cubic inches, head flow, cam, and compression ratio, and exhaust flow.

And for the quality of the engine depends on how maticulous he is when he puts the engine together. Plastic gauging isnt doing it right either. Dig out the micrometers and gauges and do it right and feeler gauge the throws for the crank and cam. That way you know if something is off before it comes a problem at all. And you will then tell how good the machinist did when he did the machining also. I don't care how good of a racing machine shop is...they can mess up...chances are probably not, but you always check it no matter what.

But with that its all good and I am finished....just my 2 cents

[bottledbird68]

I'm looking at doing almost the exact same build.
Only forged rods/pistons, stock crank, stud the mains, stud the stock heads.
Currenty have a hot cam but thinking custom grind.
Planning on exactly the same turbo as the op. There's a 31 page thread on it over on theturboforums with a lot of people saying its almost too small for a 355. Plenty of people building good boost by the low 3k rpm range on 302's.
Seeing all that I'm lost on how you guys say it's way too big? If 302's are spooling it fine and that whole turbo forum is saying its small for a 355 what are we missing?
From what they've said since its an eBay Chinese unit the housings make it behave like a smaller unit. But, for $260 plus shipping and a 4 year long thread with zero failures I'm planning to give it a shot.
Figuring 10-14 psi on meth injection on a primarily street car with some drag/open road course use any idea what I'm looking at power wise? I'm thinking 500ish to the wheels but I'll be happy with anything over 450.
Am I on the right track or have I been sniffing too many paint fumes?