JW23

I have a GT45 with a 1.05 ar and im trying to find out how it compares in dimensions to an On3 76mm with a .68 ar. I cant find any dimesions on the 76mm. Does anyone have any info on this?

I am trying to determine if I have enough room in my engine bay for twin 76's. if it looks like I'll have enough room I'll just lay the GT45 back for my Z71.

Preston99WS6

iTrader: (7)

The ON3 76mm has a 68mm turbine, simular in size to the MP76, Garrett GT76, or TC76 it will work choke a LS motor pretty good as a single but would work out great if you get another and run twins. If you decide to do a single setup run the GT45. To do twins relocate the fuse/relay boxes, and battery and you will have plenty of room.

JW23

Thanks but I have a 66 ChevyII with a heavily modified stock front clip so every 1/4" of space is prime real estate. These old cars have little room for anything other than a SBC.

Im building a 5.3 with Microsquirt for the car right now.

Preston99WS6

iTrader: (7)

Understood, 5.3 can work depending on what your doing with it.

If its a street car it might be a little laggy, if you are dead set on the on3 76 turbos, quick ways to get passed slow spool would be to run e85 or get a 6.0 short block, small primarys to turbo like 2", or find turbos with 57mm turbine to run.


If its a track car it should work well since you will be building boost off a 2 step

Ferocity02

iTrader: (60)

Twin 76's on a 5.3L would be laggy on the street. I believe a GT45 is physically larger than an on3 T76. Maybe look at on3 70's?

05_quick4door

iTrader: (1)

Gt45 on the left. 0n3 76 with a .68 hotside on the right.

JW23

I cant thank you enough for that picture Quick4door. I thought they were the same size but there is a huge difference... literally. I have been looking at the 70's and 76's. I thought about going 76's in case I build a bigger engine later on. Also if I didnt get the "big" turbos right off the bat I would want to upgrade later.

Preston99WS6

iTrader: (7)

The on3 70's use the same 68mm turbine so there wont be much difference in spool up. Housings will be same size as the picture above.

knuts82

The On3 76mm has a 65mm turbine not 68mm..

LT1RAY

iTrader: (21)

Yep, this is correct.

Preston99WS6

iTrader: (7)

65mm fat fingered it looking at the .68 A/R makes the on3 even worse for a single when campared to a GT76, TC76, MP76.

Makes it better for twins though.

JW23

How laggy do you guys think the 76's would be with my 5.3? The 5.3 is all stock besides a Stage 2 Tick Performance cam. I started rethinking last night that I may hate the late spool. You think full spool would be in by 5000? It would be good for my take off at the track. I only have a 27x10.5" ET Street on the car right now.

HRHohio

Wicked69 has had pretty good luck running Twin On3 70mms on his Chevelle. His thread:
https://ls1tech.com/forums/forced-in...on3-70mms.html

It's gotten a little long, but well worth the read.

Preston99WS6

iTrader: (7)

I would think it would be full tilt by like 4K, probably start around 3K. You got a good cam for it, curious if Martin speced it for a single or twin build.

JW23

It's the Stage 2 they have listed on their website. It's not a custom grind.
230/231 | .60x"/.59x" | LSA115+5

Cjk417

What has been done to your 66 front clip I'm putting twin borgwarner s 366s in my 63 deuce ..right now it's a stock front end with a pinto rack and autofab race cars coilover kit . Global west spherical bearing lower arm bushing and del lum upper arm bushings .i haven't drove it yet but I'm already thinking about selling the stock clip and going with a aftermarket mustang ii .im going with a 5.3 and might try a micro or megasquirt out .

JW23

I welded in chromemoly tubing from just in front of the shock towers on the fender side of the inner fenderwells down to the front frame rails. Then I completely cut ou the radiator support and inner fenderwell sheetmetal back to the shock towers. I made a tube radiator support and crossmember in between the frame rails. I had to make different bumper brackets and weld nuts inside the frame rails to mount the bumper.

There is a guy on here that has twins with a stock front clip and he didnt do much cutting at all. He cut holes for the inlet of the turbos and recessed the shock towers. I'll see if I can find his link.

I cut my trash out because I wanted easy access to everything. When I do my piping I can pull the tube radiator support and the whole front half of my engine bay is exposed.

JW23

https://ls1tech.com/forums/forced-in...rbo-build.html

SleeperDesigns.net

Just getting into the LS game putting a 5.3l in my 92' supra. But anyways I just ordered a 76mm with 1.0 divided housing. Hoping for 650rwph at about 14psi or so on stock 5.3. It will also get a quick spool valve machined into the exhaust housing to make it spool like better! I will let you know how the 1.0 housing looks when it comes in next week but I don't think it will choke the 5.3 too much. If it does I will get a 1.15 and try that.

Seth

Cjk417

Nice I was thinking about making a tubeular core support and running down tube bars to tie in to my coil overs that way I could get rid of my shock towers ,if I keep the stock front stub .sounds like your going to have a nice ride when it's finished .