@ 5 lbs of boost is an intercooler needed?
 

I know all the big hp guys need them but the blowers are spinning harder and beating up and heating the air.
With only 5 lbs of boost from a turbo would an intercooler be needed? Thanks for any info, RM

No, as long as you are running lower compression, 9:1 or little less, and some decent fuel, 91 octane or better, you will definitely not need an intercooler. I have run 8-9 psi of boost, on 93 octane fuel, with no intercooler for over a decade with no issues.

thanks for the info. I plan to run an intercooler as I can’t get good fuel where I am and my plan it to turbo a bone stock 5.3L LS1 engine. Which is I’m sure 9 to 1.

When I first installed my centrifugal super chargers I was told I did not need a intercooler because I was boating in cooler water and not building much boost (5lbs) so I installed them without the intercoolers , ran the boat not happy with the performance I added intercoolers and picked up 6mph.

what engine you running bbc?
what intercooler are you using? Thanks

https://cimg9.ibsrv.net/gimg/www.off...68d6ca7d18.jpg
BBC I made my own did not like anything that was being offered

that’s a clean looking set up.

The type I’m looking for is an in-line Intercooler as I plan to use the oem intake throttle body which has a large opening to the throttle body at the front of the intake.

im curious how much a centrifugal blower heats the air vs a turbo and Whipple style blower...

About 12 years ago I built a street car engine, sbf with a Vortech centrifugal. Was a healthy setup with 9:1 designed to run on 93 pump gas. I had a custom cam ground with passing strict ny dyno testing emissions. Basically the cam had no over lap. Plan was to run 10-14lbs. Didn't work out that way. Air temps were high 100s-200ish. The engine would detonate instantly. Kept putting larger blower pulleys on to lower boost. Got to the point I ran out of pulleys to use and had a custom larger pulley made. From memory, I got it down to 5-6 psi and it still detonated like crazy. Had to pull engine in short time do to black death on the pistons.

Bottom line, engine had to much cylinder pressure and today's pump gas is junk. I learned a lot from that build. Boost is not everything.

I don't know what the temps are on the other set-ups but with mine after a hard run you can not touch my charge pipe so it is at least 150'F

What do you mean you're sure it is 9:1? The LS1 is 5.7L, and 10.2:1. There are many different 5.3L Ls engines with compression anywhere from 9.5:1 - 10.2:1, none are 9:1 from the factory.

I’m mostly an internet mechanic but I’ve never heard of an LS as low as 9:1 so I’d double check that.

Many people on here haven’t had the best luck without an intercooler. It may work but you’re leaving a ton of performance and reliability on the table without one. The heat in the bilge and demands on the engine compared to a car are big contributors to the issue.

i plan to use the 5.3L gen3 LS engine. One of articles I read referred to the cast iron block 5.3 325ci engine as an LS1. I’m sure I can get the compression down to 9 to 1 using the stock pistons if I run a thicker cometic head gasket.
my goal is to build a twin turbo set up to run in these engines as they are the least expensive ls eng to buy at the boneyards as most guys don’t want the gen3 engines.
check my other thread on the LS Eng


a guy wanted to see how much hp a stock 5.3 Ls coulda handles. They ran 76mm turbos. And ran a bunch of Dyno pulls increasing boost each pull. It made 695hp @ 5.5 lbs of boost and they made over 1300hp on the last pull. I think they should have kept going until they blew up the engine lol

say you want 700-800 ponies. You can buy a merc for all the money and when you blow it up it’s big money to fix. Or I think a twin turbo set up for the LS 5.3 will live a long life at that hp level as It’s under 8lbs And will make that hp. It was proven in the Dyno tests Buy a junkyard engine hone the cylinders install new rings gapped for turbo set up and Shim up the oil pump spring, arp rod bolts, cometic head gaskets and you have a 1500 buck or less 800hp engine if you do your own freshen up work it would be closer to a grand! I would set mine on kill for 1,000 ponies and so what if i puke a motor. At that price I would keep a couple spare bullets in my garage lol.
Just tryna build a better mouse trap

Rm you seemed to have it all figured out!!! Set on kill and let us know how you make out. 😁

Im sure ls engines with good rods will hold up at that hp level.

I would be doing it with stock rods. The motor made 350hp more than that. It sucked That they didn’t keep going until it failed. To see what would fail and when. My guess is the powdered rods.

I think the LS is a much better engine design than the bbc platform. With A/m rods and forged slugs they make insane hp. The block is serious reinforced and has the six bolt mains.

the guy above said over 9 to 1 Cómp I would have detonation issues I was just saying I’m sure a stock ls motor is 9 to 1 or above. Which you just confirmed. As a result I would definitely Run on intercooler.

aren’t most currently built blower motors in the 8.5 to 1 range?

I never ran an intercooler for years on my 8lbs 10-71.
Intake temps never went over 150* at speed.
An intercooler dropped it down 30* (summer weather)
I don`t recall any speed increase but probably a safer set up with less chance of detonation.

what size are your engines?

well does it accelerate harder? Did you try spinning more prop?

thanks for the info, RM

The ls platform has been beat to death. It is well know what breaks at what hp/rpm/boost in a stock ls engine. Search the internet and you will find all the info you will need.

It is hard to compare a bbc to an ls engine or any other. Modern engines can run more cylinder pressure (in general) than an older designed cylinder head. It is not uncommon for a stock modern engine to run compression of 10:1-12:1 on pump gas from the factory. Try that with a bbc.

where are all the twin turbo LS engines in offshore power boats? I haven’t seen one.

comparing a blower motor to a turbo motor on how much boost it can take is like comparing apples to oranges. The added ho an engine needs to make in a blower motor and the added stress in the front of the crank for the blower drive add a huge load on the bottom end that a turbo doesn’t. Say a 1000hp. Lower motor how much ho does it take to spin the blower 125hp?

I look at the new turbo packages from merc and others, I think that is the future. Don’t see anyone one offering twin turbo set ups for an LS anywhere.

merc gets close to 40k for a 600sci. I think a reliable 600-800hp twin turbo kit for the LS would sell very well especially knowing that when it gets tired you can replace the engine very affordably.

Turboed ls engines are nothing new. Like I said, beat to death. Yes that is in the automotive world. Marine environment is another story. You think there aren't many for no reason?

If you use thick head gaskets to lower CR on an LS motor, you completely lose the quench turbulence that prevents detonation. You need to keep the squish clearance under .050" and use dished pistons.

You also need to come to grips with the difference between a 700hp LS set up to live in a street/strip environment vs performance marine duty. Marine usage demands full continuous output at higher speeds, with no load cycling.

A lightweight boat running wide open for shorter blasts can make do withdturbo'ed junkyard donors. You'll end up disappointed if you plan to push a serious performance hull hard 30 minutes at a time..

i have no problem putting a set of good rods and offed pistons in an ls.
I’d like to try to run the stock motor and probably will for the first pair. See how they hold up and go from there.
Old school sbc engines are nowhere near as stout as an ls engine and they seem to last forever in boat of every shape and size.
Thanks for the heads up on keeping min .050 on the squish. I spoke with shafiroff racing about that today he didn’t give me a dimension just told me to change pistons Instead of putting a really thick head gasket in it.
Since the engine make 695hp @ 5.5 lb of boost, I would set it up to run 5 lbs, I think it should live a long healthy life at that level.

Party on! Keep us posted with the outcome as we all appreciate the info. A build thread would be awesome! ;)

Im looking at what’s out there for water jacketed turbos. I’m sure there is one that will work for this application I just need to find It.

hell it it doesn’t work I can always sell the parts on eBay and go with old school 406 engines.

Please point us to the website that shows a 695hp LS at 5.5 psi of boost. At 6,000 rpm, that works out to 610 lbf of torque. A 400 ci LS motor will struggle to deliver 380 lbf of torque above 5500 rpm. Working backwards, you need to boost the motor to 156% effective torque capacity. Disregarding dynamic losses in the induction system, you will need a minimum of 8.4 psi of boost AFTER cooling the incoming charge back to within 10% of ambient temperature in order to approach what you describe.

I'm not doubting your recipe. I just very much want to see it, and the accompanying data.

Please link us up.

M

Check out my thread entitled

What’s out there for Chevy LS based engines

there are two videos of the guys with the LS dyno runs

I had a set of CHIEF built 502s with Blower Shop 6-71s with aluminum dart heads. They made 675HP on the Dyno. Never had intercoolers. Ran premium gas however. They had alot of reliable hours on them before I traded them in. This was a few boats ago.

how many lbs of boost did they make? Thanks

Go easy on the throttles big daddy!!

hey brother how you been?

I hope you’re well.

Still have your skater turbine?

I can’t go easy on the sticks! Lol

Just as the thread 5-6 lbs.

that’s interesting you didn’t need an intercooler at that boost level.
tommy was a hell of an engine builder. If the heads flow really well and you have the right cam, you don’t need to make crazy boost to make good hp.

I def will run an intercooler just make sure it doesn’t detonate as it’s a new combo and I don’t have Tommy’s experience

https://cimg3.ibsrv.net/gimg/www.off...b941753a0a.jpg

I found the article.
5.3 LS motor.
Flat top pistons.
Factory bottom end.

$2,700 heads.
$1,000 intake
$ 800 worth of injectors
Big throttle body..
620/281 hydraulic roller cam
$1,600 dual core intercooler
Twin 76mm turbos
RACE GAS.
695hp at 6600 rpm.
5.5 psi

With that huge intercooler, the motor was "seeing" 5.5 psi at 115 degrees. Before the intercooler, there was probably 8.5 psi at 200 degrees.

Your original post was questioning the need for intercoolers on a 5psi build. You need to understand that the magazine build was NOT a 5psi non-intercooled motor. It was a 8 or 9 psi non-intercooled motor WITH an intercooler. Without race gas, it would have holed a piston in short order.

In a boat, running 91/93 pump gas, you have a lot of things to balance to keep things happy at wide open throttle. Cooling is one of the most significant. Rising intake charge temps are a big deal unless you run short bursts or have sufficient intercooling. 6600 rpm boat engines also need huge oil coolers.

Keeping a stock bottom-end 5.3 together at 6600 rpm and 600hp is its own form of luck.

I would hate for you to beat up the combustion chambers of those nice expensive heads because you were dead set on using junkyard donors to prove some point..

Anybody can slap together something to do a few 1/8 mile runs a month in a S-10 with drag radials.

Building a 600hp engine to run wide open in a boat for 20 minutes solid takes a different approach.

Everybody has to learn at their own pace. It was a lot of years ago that I put a 100 shot of nitrous on a Merc 260/5.7 Alpha. Since the boat was light, it lasted for almost 3 bottles before it put a rod thru the block.
LS Gen 3 motors are superior to the 5.7 in every way, but I hope luck runs strong in your neighborhood.