F-Body Demon

iTrader: (1)

Hey guys, well I was wondering if anyone here knows if the crank from a 4.8L Vortec engine would go into a LS1 or LS2...or hell any other 3rd or 4th Generation GM Smallblock engine? Is their a big difference in the crankshaft bearings? Because it seems to me (from what I was able to find) that a 4.8 and a 5.3 share a block and pistons, the only diff is the rods and crank (way to go GM). Is this true?

Ive been drooling over the idea of a high rpm LS engine sitting in between the wells of my GTA. This could be it, assuming I could do the shortblock for under $2500 before machine work. Who wouldnt love a 327 LS engine!?

Ideas?

F-Body Demon

iTrader: (1)

WHOA!!!

http://www.crateenginedepot.com/stor...--LSX-C10.aspx

Okay well the answer is YES! According to the chart on this webpage, all GM Gen 3-4 blocks have identical bolt patterns and journal sizes. Sorry for wasting the space on the site.

MattODoom

iTrader: (1)

It seems to me that the ability of the engine to rev and make power up top is going to be a function of the top-end components. With an adequately strong bottom end, the stroke difference between 4.8 and 5.3 cranks shouldnt affect the revving ability

F-Body Demon

iTrader: (1)

Shorter stroke is lighter, therefore it will spin up faster. And it will get better gas milage.

SheldonZ28

iTrader: (1)

I think your working in too many different directions.

You want it to spin up faster and get better fuel milage? One or the other

But honestly, your going to loose alot of power and the extra RPM wont make up for it. Besides, my 3.66stroke/3.8x bore 5.3l motor spins to the moon and back near instantly. No need to try spinning these motors and faster

F-Body Demon

iTrader: (1)

hey guys im just scratching an itch with this idea. its a dare to be different thing. that and im a smokey yunick fan haha.

MattODoom

iTrader: (1)

Hey, I was just throwing it out there. I doubt the difference in weight between the two will make much difference in how snappy the motor is. You could always work the 5.3 crank to be lighter than the 4.8 crank, no?

brandoz28

iTrader: (1)

http://www.carcraft.com/techarticles...ine/index.html
makes peak power at 6800 RPMs, you really want to go any higher than that??

F-Body Demon

iTrader: (1)

You ever been behind the wheel of a V8 doing 7k+? It feels like the engine is pissed off and ready to kick your ***...if it wernt bolted down. So with this idea its not about making more horsepower, its about making the BEST horsepower. For the ride that is. More than 400 hp is pretty awsome however you put it. I dont need more than that...especially when its at 7 grand.

And the 5.3 crank is the same as a 6.0 crank ,they are both 3.66" Stroke.

MattODoom

iTrader: (1)

Ive been in a roadrunner with a 426HEMI shifting at 7,600. Whats your obsession with no-torque short stroke engines?

V8Rumble

iTrader: (2)

As long as you're aware that

* you're going to spend a fair bit more for valvetrain parts that will be reliable at over 7 grand;
* a shorter stroke is definitely not the most driveable way to make power;
* horsepower is horsepower, regardless of what the exhaust note sounds like;

and

* you have the money to spend, & don't mind doing so,

then I say go for it. I can't see a practical reason for doing it (it seems as though you're basically wanting 'a certain exhaust note' and 'to be able to brag that your engine revs to 7k'), but hell, it's not my car/my money/my dream, so who cares?

If it's your car & your money, make it your car...

(Just do the research first, so you know what you're getting into!)

brandoz28

iTrader: (1)

I have driven a car that revs over 7K i shift it at 7200 RPMs and it eats a couple pushrods every year. Just be prepared to spend the time and money upgrading and replacing things that aren't your normal "wear items" this means valve springs too...its no fun if you drop a valve, seen it on an old 327 that was shifted through a muncie, wrecked the piston, and shoved the valve through the head.

green92

F-body is looking into the idea the GM 302 design came from, is what im understanding. Basically it was a 327 block destroked with the 283 crank, and from what i have been told these motors would snap 7 and 8 grand easy and make great power all the way to that range. So if gm was able to produce a motor to handle this with the technology they had back in the 60's, why not try to do it now with a new generation of motors?

igotta355z28

iTrader: (1)

.......(Excerpt from a review about the 1969 Chevrolet Camaro Z-28 302 Cross Ram) "The good news was that the car had greater flexibility near the top of each gear and a higher top speed; the bad news was that freight trains could accelerate from a stand still faster...and perhaps quieter."

green92

Huh i thought they came out the hole screaming i didnt realize they were weak on bottom. I guess that why they only came with 4 speeds then.

igotta355z28

iTrader: (1)

no all power is up high thats y they had 4 speeds with big rear gears...and they were designed for the trans am races so power needed to be mid to high not down low...overall not good street engines....

V8Rumble

iTrader: (2)

Also - the 5.3 -in stock form- comes out to right about 325 ci. I know you're primarily looking for the new engine to be a high-winding unit, but I figured that someone was going to note that anyway...

F-Body Demon

iTrader: (1)

Well yes thats true...but the 327 I mentioned here would be a 3.27 X 4.006 unit, not a 3.66 x 3.78 like the 325 (5.3L). The shorter crank also has the great upgrade of a 1.92 Rod Ratio over the 5.3/6.0s 1.6 Rod Ratio. The longer rod ratio would help to crutch the loss of CIs and Stroke. And anyway this engine would only lose 5.5% of its CIs over a LS1 anyway...its a minimal loss IMO.

But after looking into it, it seems like the project will need custom pistons...which isnt something im very happy with. I like to stick to readily available parts (another one of Smokey's rules). Which has protected me from mistakes in the past. I'll keep looking but as far as it looks for me, this engine is just a set of pistons too far out into the exotic range for me.

wesilva

iTrader: (35)

Reviving an old thread but no customs pistons needed if you go this route and my calculations are correct. This is using an LS1 but the 6.0 is just a larger bore. All other dimensions are the same.

4.8 crankshaft is a 3.26" stroke.
4.8 rods are 6.278" long.

You would need a piston that had a compression height of 1.335 to 1.34 depending on how the block was decked. Stock LS1 pistons have a compression height of 1.34. So a short stroke LS1, LS2 or 6.0 can be done with stock parts.

F-Body Demon

iTrader: (1)

Sorry to re-dig a dug up post. But wesilva your saying that the LS1 pistons are 1.34, does that burn down to the 6.0 as well? If I could get a 6.0 and a 4.8 I could make it work with minimal extra parts....just when I thought I had it figured out...man.

F-Body Demon

iTrader: (1)

Double post.

wesilva

iTrader: (35)

The short answer is yes. The 6.0 shares the same compression height of 1.325 - 1.336 because it shares the same crankshaft stroke of 3.622" and the same rod length of 6.098".

The formula is fairly simple. Compression height is measured by the following:

Crank stroke divided by two: 3.622 divided by two = 1.811

Add that to the rod length: 6.098 + 1.811 = 7.909

Subtract that from the deck height: 9.245 - 7.909 = 1.336 compression height.

Now remember that the decrease of stroke is going to decrease compression. You will either have to mill your heads to the appropriate combustion chamber size or purchase heads with the combustion chamber size.

wesilva

iTrader: (35)

Now lets use the same formula for the destroked 6.0.

4.8 crank stroke of 3.26 divided by 2 = 1.63

1.63 + the rod length of 6.278 = 7.908

Deck height of 9.245 - 7.908 = 1.337 compression deck height. Basically the same compression deck height.

I've been through this already because my son and I are building a LS1 for maximum gas mileage and the inherent anti friction capabilities of the short stroke/long rod LS1 engine will give us the goal we are after. Those anti friction capabilities being favorable rod angle to minimize piston thrust scrub, lower piston speed and narrow ring package.

SheldonZ28

iTrader: (1)

I think we all knew it was possible, the point is, its a complete waste.

4" stroke LSx motors have been taken over 7k rpm safely.

To lay it simply, it hasnt been done, cause its not worth it, its a loose loose. You loose power, and you dont gain fuel milage.

If you've got an itch for a super high rpm motor, crotch rockets redline at like 18,000 rpm. Were talkin V8's here, and were workin with the newest technology.

The limiting factor to getting a LS1 to 7k rpm is primarily valvetrain.

If you have perfect valvetrain, you can throw in a forged 3.622 rotating assembly, then get a priority main oiling block if you want it to be a 100% safe 7k+ rpm redline motor.

Your thinking too hard for this, its simply not worth it. But a 6.0L and keep it as a 6.0L.

wesilva

iTrader: (35)

Here's a solution...

Buy an iron 4.8. They can be had for very cheap. Bore out the cylinders to the LS1 3.9 standard bore. The block will safely take that bore. Buy LS1 pistons. Modify the motor any way you choose like modified cylinder heads, cam, etc. If you don't like it...drop in an LS1 crank and rods and be done with it. All your out is your labor.

kad5118

I know that this is a ultra old thread but i am wondering if you ever got a round to goinag through with the motor deal.I my self also have a 4.8 that i am looking to throw ls1 pistions in.

wesilva

iTrader: (35)

Interesting if nothing else.

kad5118

yes that is very impressive well i thinking maybe with the 4.8 with ls1 pistons it should be close to the 500 hp range easy.then and maybe gain another 20 pounds of torque.They did a back to back test with the 4.8 vs the 5.3 both were using the same parts.Such as cylinder heads a cam a fast 102 intake with a TB and the 4.8 made 472 hp and 390 pounds of torque while the 5.3 made 484 hp and 420 torque I believe its close to those number.I really dont see where the 4.8 will lose power by adding the ls1 pistons.

wesilva

iTrader: (35)

In my opinion, there are two attractive applications for this combo. I like it boosted....especially turbochargers where you need to spool up quickly. The other would be for applications where you are traction limited....be it by the racing body's rules or by having, for instance, a pro-touring car with suspension and tires that are built for handling and compromise "hooking up" performance. These applications suffer when big low end torque motor punishes the tires and they are left backing out to maintain traction.

kad5118

I get what you are saying torque is awesome but is not the key with certain applications.I am really thinking and thinking about this setup for my GTA

Pocket

iTrader: (24)

Curious what the output would have been using a totally stock lq4 short instead of the 4.8 bottom end in that hybrid. The peak values are at common rpms for most na LSx engines

wesilva

iTrader: (35)

I had an '85 IROC with full Spohn / Global West suspension mods with Toyo R1 Proxies. The car handled like a demon around a road course or auto x but straight line performance suffered....especially with the built SBC 400. When it was time to freshen the 400, I sold off the bottom end and installed a forged large journal 327 crank and 6.25" long rods. The car was better able to put the power down. Never ran a quarter mile but it was fast. I did do the necessary mods to keep the valve train alive...ti retainers, bee hive valve springs, light valves.

wesilva

iTrader: (35)

Hard to say without the builder divulging what mods were used in the 332...such as cam specs, porting data, etc.

mikesanto70

A friggin Dyno sheet would have been nice too to look at the curve and where it fell off at!!!!!!!!!
Call that machine shop and ask them to post a sheet on their video page or just email one!!!!
I have been thinking of the same build for a 3rd gen with twin 62mm turbos and a 6L80/90E trans that could rev to the moon under boost, a forged 4.8 tt would be nice and should be able to take anything thrown at it!!

Paridoxiss

Hey new to the form. I have a 4.8/5.3 iron block currently in the machine shop for a flux-dip. What I want to know is if I bore this to fit ls1 pistons, would the Pistons work with the 4.8 rods and crank? Thanks

Paridoxiss

Sorry to bring this back up, I just noticed the date on this thread haha

wesilva

iTrader: (35)

The answer would be the same then as it is now....yes. Ha ha. You would have to have the engine balanced but it's a straight forward swap provided that your 4.8 rods are press fit and your LS1 pistons are press fit. Or your 4.8 rods are full floating and your LS1 pistons are full floating. Factory LS1 pistons are press fit and will not work on floating rods. But there are aftermarket replacement LS1 pistons that are floating.

Paridoxiss

Ok cool I had to ask because I was told elsewhere that the compression height was different and you would need custom made pistons or rods to make it work. I'm going to start a thread once I get the motor back from the shop. I'm having it bored to 3.898. I've seen so many people who where interested in this set up but gave up on the idea. Thanks for the reply as well wesilva

morrow

I'm just going to throw this out there... I have bean building road race engines for a while now... A buddy of mine built an ls3 with a 4.8 crank to run it in his 68 Camaro a few years ago for the ultimate street car challenge. Most fun engine he's ever had... Yes you loose low end power... But what you gain is a almost perfect torque band and hp climb... If your on a road coarse you don't want lots of low end torque that CAn and will blow your tires loose... You want a smooth steady climb in power... Which is exactly what this does... Power comes in around 3k to 3,5ook. And climbs up to 9k with a hp rating of 400 hp at 6500rpm and 600hp at 9k .... Granted that's all based off of your set up... The biggest issue is your valve train.. Build it stout.... You really don't want to suck a valve at 8k... And yes a standar lsx has bean spun safely to a high rev, but the thing is... How many times can it do it and for how long.... Keep in mind ... This is how they build the engines in f1

morrow

This is exactly what I will be doing in the near future after the body is finished on the Rs.R
I'm between a ls3 with a 4.8 crank or a ls1 with a flat plane crank.... Might build a budget ls1 with a 4.8 crank at first just to get it running... Then build a full race engine