4.8 twins or single
Thread Starter
TECH Junkie
Joined: Dec 2012
Posts: 3,614
Likes: 1,326
From: Iowa
4.8 twins or single I picked up a 1987 caprice classic 4 door and have decided it needs to make more power and be way faster than it was ever intended to be. I'm trying to decide what turbo(s) to run on this thing and figured there's not many better places to ask.
I'll start with a rundown of the build then get into the turbo's i'm looking into.
Stock bottom 4.8
stock port/valve 706 heads milled to 59cc
.045 MLS head gaskets
Static compression=10:1
LJMS Stage 2 4.8 turbo cam... 218/223 .598/.571 112+3
Stock truck manifolds flipped forward
Stock Truck intake
Ported stock throttle body
4l80e
8.5" 10 bolt rear. Haven't decided gear yet (probably about 3.00-3.55 range)
Here are the turbos I'm considering. Let me know if there is a better option for my goals.
I want to make 600 tire MAX
Somewhere around 550 would be totally acceptable
Light off pretty quickly, just be a fun tire fryer and light to light car. Making boost in the mid 2000 rpm range would be awesome
twin GT2871 (T3)
50/71 Compressor .61A/R
71/54 turbine .64 AR
twin GT3076 (T3)
57/76 Compressor .6A/R
84/60 Turbine .82 A/R
Single VS Racing/on3 style 76mm
76/102 compressor .8 A/R
74.5/65 Turbine .96 A/R
These are just some of the setups I've read other people using and so that's what I am looking into,
If there is a better option out there or something people have had luck with, don't hesitate to throw the options into the ring. I'm sure the A/R could be changed also if someone thinks that would be beneficial
Thanks for any advice guys!
I'll start with a rundown of the build then get into the turbo's i'm looking into.
Stock bottom 4.8
stock port/valve 706 heads milled to 59cc
.045 MLS head gaskets
Static compression=10:1
LJMS Stage 2 4.8 turbo cam... 218/223 .598/.571 112+3
Stock truck manifolds flipped forward
Stock Truck intake
Ported stock throttle body
4l80e
8.5" 10 bolt rear. Haven't decided gear yet (probably about 3.00-3.55 range)
Here are the turbos I'm considering. Let me know if there is a better option for my goals.
I want to make 600 tire MAX
Somewhere around 550 would be totally acceptable
Light off pretty quickly, just be a fun tire fryer and light to light car. Making boost in the mid 2000 rpm range would be awesome
twin GT2871 (T3)
50/71 Compressor .61A/R
71/54 turbine .64 AR
twin GT3076 (T3)
57/76 Compressor .6A/R
84/60 Turbine .82 A/R
Single VS Racing/on3 style 76mm
76/102 compressor .8 A/R
74.5/65 Turbine .96 A/R
These are just some of the setups I've read other people using and so that's what I am looking into,
If there is a better option out there or something people have had luck with, don't hesitate to throw the options into the ring. I'm sure the A/R could be changed also if someone thinks that would be beneficial
Thanks for any advice guys!
TECH Apprentice
Joined: Apr 2012
Posts: 333
Likes: 4
From: New Zealand
Go twins and go small, pay a little more for the R option (ball bearing) they are rated at 430hp each and you'll need that to achieve 700rw. If you can't afford the R go next size up, but def go twins. You won't be sorry.
There's plenty of guys will brag about having bigger units and faster singles, but yours will get it done, come on quicker, be super useable, throttle controllable and fun. Don't look back. At 600rw you'll be having way too much fun to care about whether a big single has a better top end. My 2 cents
And I'd look at a wave trac/trutrac diff - much safer than the old school LSD
There's plenty of guys will brag about having bigger units and faster singles, but yours will get it done, come on quicker, be super useable, throttle controllable and fun. Don't look back. At 600rw you'll be having way too much fun to care about whether a big single has a better top end. My 2 cents
And I'd look at a wave trac/trutrac diff - much safer than the old school LSD
Last edited by Bazman; Aug 29, 2018 at 08:24 PM.
You didn’t indicate a budget?
I don’t agree with the info above, but everyone is welcome to an opinion! Ball bearing designs offer very little in performance vs cost. They are also not rebuild-able if you scrap one. Most china “ball bearing” turbos usually aren’t even a full ball bearing design. Usually have the typical journal main bearing with a ball bearing support on the compressor side.
Twins are twice the work and plain unnecessary for a 600hp goal. I’d run a single cast S366. It will spool VERY quick, install easily, and meet your goal easily.
If you must go twins, look to the GT3582 with the small T3 .63 housings. You can get them for about $140 shipped and they are proven performers. I’ve got a set on a 5.3 on 15lbs and they spool quick and make great power.
The ON3 76mm is s poor design. Split between the exhaust wheel and compressor is to large making it laggy by nature. This is then off set by using a tiny housing and using higher back pressures to drive it. That said it would still meet your power goals. It’s just not a great unit. VSracing sells a 76/68 that would work a bit better if you don’t want to spend the money on the Borg Warner turbos.
Most of the guys with “spool issues” don’t have the hot side setup properly and/or have the tune off. With a 600hp goal you should be using 2” hot side piping. This keeps the exhaust velocity up and helps greatly with spool. 2” to each side of the scroll on an S366 would spool crazy quick with 10:1 4.8 and that cam.
I don’t agree with the info above, but everyone is welcome to an opinion! Ball bearing designs offer very little in performance vs cost. They are also not rebuild-able if you scrap one. Most china “ball bearing” turbos usually aren’t even a full ball bearing design. Usually have the typical journal main bearing with a ball bearing support on the compressor side.
Twins are twice the work and plain unnecessary for a 600hp goal. I’d run a single cast S366. It will spool VERY quick, install easily, and meet your goal easily.
If you must go twins, look to the GT3582 with the small T3 .63 housings. You can get them for about $140 shipped and they are proven performers. I’ve got a set on a 5.3 on 15lbs and they spool quick and make great power.
The ON3 76mm is s poor design. Split between the exhaust wheel and compressor is to large making it laggy by nature. This is then off set by using a tiny housing and using higher back pressures to drive it. That said it would still meet your power goals. It’s just not a great unit. VSracing sells a 76/68 that would work a bit better if you don’t want to spend the money on the Borg Warner turbos.
Most of the guys with “spool issues” don’t have the hot side setup properly and/or have the tune off. With a 600hp goal you should be using 2” hot side piping. This keeps the exhaust velocity up and helps greatly with spool. 2” to each side of the scroll on an S366 would spool crazy quick with 10:1 4.8 and that cam.
Thread Starter
TECH Junkie
Joined: Dec 2012
Posts: 3,614
Likes: 1,326
From: Iowa
I'm looking at the journal bearing turbos for the exact reason you stated. Cheaper, simpler, I can rebuild myself if need be, not enough gains for the ball bearing at my power level
I'd like to keep the turbo(s) under $500
I have read a few build threads with the 366 and they seemed to be maxx'd at about 540 wheel with a 5.3.
I think the 76/68 might be a good option, I just picked the 76/65 because I've seen alot of good results from guys. Can you explain why the split between exhaust and compressor makes it laggy. I thought this was actually one of the better spooling options...was I mistaken?
Thanks for advising the hot side advice. I have been debating between 2" and 2.25"
I know the 2" will spool better, but I don't want it to choke me out as I reach towards that 600 wheel power number. Do you think 2" will be an issue at 600?
I'd like to keep the turbo(s) under $500
I have read a few build threads with the 366 and they seemed to be maxx'd at about 540 wheel with a 5.3.
I think the 76/68 might be a good option, I just picked the 76/65 because I've seen alot of good results from guys. Can you explain why the split between exhaust and compressor makes it laggy. I thought this was actually one of the better spooling options...was I mistaken?
Thanks for advising the hot side advice. I have been debating between 2" and 2.25"
I know the 2" will spool better, but I don't want it to choke me out as I reach towards that 600 wheel power number. Do you think 2" will be an issue at 600?
“Better spooling” doesn’t translate into efficient power per pound of boost. S366 would stomp that turbo spool wise and make more power per pound as well as flow more overall.
The S366 will make 600whp on a 4.8 and it will do it quickly. They flow 70-80lb min at reasonable back pressure ratios. But if you want under $500 I’d be looking at the 76/68. I’d go with the T4 S475 clones VS racing sells but they are right at $500 shipped.
The wheel sizes have to do with leverage. Bigger the exh wheel the more energy it can extract to drive the compressor. If the turbine is smaller than the compressor it’s going to be at a disadvantage. One of the reasons the S366 is so good. 66mm compressor and 73mm exhaust wheel.
2” is MORE than enough for a 4.8 with 600 hp goals. I’m making 1000ish on 2” with a 370 cubes at 19-20lbs of boost. The 4.8 is 292 cubes.
The S366 will make 600whp on a 4.8 and it will do it quickly. They flow 70-80lb min at reasonable back pressure ratios. But if you want under $500 I’d be looking at the 76/68. I’d go with the T4 S475 clones VS racing sells but they are right at $500 shipped.
The wheel sizes have to do with leverage. Bigger the exh wheel the more energy it can extract to drive the compressor. If the turbine is smaller than the compressor it’s going to be at a disadvantage. One of the reasons the S366 is so good. 66mm compressor and 73mm exhaust wheel.
2” is MORE than enough for a 4.8 with 600 hp goals. I’m making 1000ish on 2” with a 370 cubes at 19-20lbs of boost. The 4.8 is 292 cubes.
A buddy of mine put a legit s366 t4 .91 on a 5.3 in his ‘65 c10 and he says it’s downright ignorant (in a good way) as far as boost. By the time your foots to the floor it’s there. That’s with 2.25 off each manifold to a merge that’s about 4” long. You can find the s366 for about $560 if you look hard enough.
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Depends on what else is done to the engine. Maybe at 15 psi. I’ve also heard of another guy that makes 15 max on a 5.3 with one. That’s with the gate pinned. They’re WAY smaller than even my t4 475 for packaging.
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TECH Junkie
Joined: Dec 2012
Posts: 3,614
Likes: 1,326
From: Iowa
Sorry for the multi post there. Mobile app issues.
Motor will be stock aside from cam and milled heads...Stock port
Packaging is a non issue...I have enough room under the hood of this car to stand and do jumping jacks
Motor will be stock aside from cam and milled heads...Stock port
Packaging is a non issue...I have enough room under the hood of this car to stand and do jumping jacks
I'm looking at the journal bearing turbos for the exact reason you stated. Cheaper, simpler, I can rebuild myself if need be, not enough gains for the ball bearing at my power level
I'd like to keep the turbo(s) under $500
I have read a few build threads with the 366 and they seemed to be maxx'd at about 540 wheel with a 5.3.
I think the 76/68 might be a good option, I just picked the 76/65 because I've seen alot of good results from guys. Can you explain why the split between exhaust and compressor makes it laggy. I thought this was actually one of the better spooling options...was I mistaken?
Thanks for advising the hot side advice. I have been debating between 2" and 2.25"
I know the 2" will spool better, but I don't want it to choke me out as I reach towards that 600 wheel power number. Do you think 2" will be an issue at 600?
I'd like to keep the turbo(s) under $500
I have read a few build threads with the 366 and they seemed to be maxx'd at about 540 wheel with a 5.3.
I think the 76/68 might be a good option, I just picked the 76/65 because I've seen alot of good results from guys. Can you explain why the split between exhaust and compressor makes it laggy. I thought this was actually one of the better spooling options...was I mistaken?
Thanks for advising the hot side advice. I have been debating between 2" and 2.25"
I know the 2" will spool better, but I don't want it to choke me out as I reach towards that 600 wheel power number. Do you think 2" will be an issue at 600?
I made 570 with a s366 non-intercooled on a blow through carb on a 5.3. With converter locked and a little more boost, probably could have broken 600. It's an awesome sounding tubo too! lol Best whistling turbo I've used yet. It's an absolute blast to drive in my c10 with it. Comes on super fast!
8 Second Club
Joined: Dec 2016
Posts: 16
Likes: 1
2007 4.8 w/150k miles, untouched bottom end and heads, BTR Stage 2, BTR springs, 7875 VS Billet, 4l80e w/HD kit, 8.8 w/3:73 gears, A2A, E85, truck manifold one side, LS1 to clear AC on the other. Just started tuning AFR on wastegate, timing not touched yet, 7lbs in first, 9 lbs the rest of the run. Trapped 129.xxx in the quarter, 3400lbs with me in it. Calculated to 560hp crank. I'd have to check a datalog when I get home to see what rpm boost starts building on the street. Can provide more detail if you want it.
Now 10.300 @ 135
Now 10.300 @ 135
Last edited by fegoins; Nov 25, 2018 at 02:39 PM.
TECH Apprentice
Joined: Apr 2012
Posts: 333
Likes: 4
From: New Zealand
I re-read my post and had missed you run an auto. Forcefed86 is right - a single will get the job done perfectly. I ran a rear mount single on an auto and it could boost from a stop without a trans brake - just squeeze and go. A manual has lag in 1st gear normally. In your app, with auto I'd go single too. For a manual I prefer twins
8 Second Club
Joined: Dec 2016
Posts: 16
Likes: 1
2007 4.8 w/150k miles, untouched bottom end and heads, BTR Stage 2, BTR springs, 7875 VS Billet, 4l80e w/HD kit, 8.8 w/3:73 gears, A2A, E85, truck manifold one side, LS1 to clear AC on the other. Just started tuning AFR on wastegate, timing not touched yet, 7lbs in first, 9 lbs the rest of the run. Trapped 129.xxx in the quarter, 3400lbs with me in it. Calculated to 560hp crank. I'd have to check a datalog when I get home to see what rpm boost starts building on the street. Can provide more detail if you want it.
Thread Starter
TECH Junkie
Joined: Dec 2012
Posts: 3,614
Likes: 1,326
From: Iowa
Getting all kinds of different feedback the more I talk to people.
What do you guys think about a set of GT3582 turbos? Maybe give me a little more headroom to grow if I want, and still spool fairly quickly?
What do you guys think about a set of GT3582 turbos? Maybe give me a little more headroom to grow if I want, and still spool fairly quickly?