I was daydreaming at work today (thinking about F5000 racing, 50 years on) and wondered if there was a way to build a five liter LS engine. Apparently the hot set up for F5000 was the 327 block with the 283 crank, but I'm unaware of any combinations of LS components to build such a thing. Anyone know?
There are only two different strokes AFAIK, 4.8 and everything else. (Not counting the 7 liter. Okay, three different strokes...
The 4.8 is already a 293. Boring it out to 5.7 spec would get you 311ci.
Looks like your best bet would be a 4.8 with an overbore. Or a 4.8 crank in an aluminum 5.3 block with an overbore. Not sure if anyone makes any 60-over pistons for the 4.8, though. That'd get you 303ci.
Stroke is still longer than a 327 
4.8 is 3.268", everything else is 3.622".
3.820" pistons(0.040 over) are common, but I haven't stumbled onto any 3.840" yet. I had considered building an aluminum 4.8 for my Challenge car when I found an aluminum block for $150 and a 4.8 for $250. I ended up finding an aluminum 5.3 for $300 instead, but an aluminum 4.8 would be out of the ordinary and you could sit there and say "naw, it's just a 4.8".
Edit: The Nelsons' 1000 HP LS beast is a 6.0 block with a 4.8 crank, yielding a touch over 5.4 liters.
To be honest, I am amazed that anyone offers oversize pistons at all for the 4.8. I can't see anyone rebuilding when good used engines are cheap and plentiful.
One could also get the crank reground, and ask the crank grinder to nudge the stroke out a little bit. Somewhere I read that the rod journals are the same as SBC, I wonder how much of a pain it would be to get Honda journal rods. The main difference between a 289 and a 302 is something like .13" stroke (2.87 vs 3) which is alllmost doable with a deep undersize. People also used to make cheap 315s by offset-grinding the cranks to 2.3 Lima size and using two sets of those rods, which are also longer and stronger. (I think the 315's stroke allows you to use common Chevy pistons)
'Course, this is all a lot of work just to get 3% more displacement before you hit the 5 liter limit. The grassroots effort method would be to just run a 4.8 as-is and spend the money saved on other ways to go faster. Or food and shelter, I suppose
i too dream of an aluminum 4.8. I would imagine that the 4.8 crank weighs a bunch less due to less counterweighting needed for the shorter stroke. There is going to be less windage losses in the crankcase, too.
In reply to Pete. (l33t FS) :
I think (don't know for sure) that the oversize pistons for a 4.8 and 5.3 are the same, so they're really offered for 5.3 use. Summit shows pistons as 4.8/5.3 on most of the stuff they offer. Also, I've read articles where engine builders used 4.8 pistons in 5.3s because the stock 4.8 piston are flat topped and offer a mild compression increase.
In reply to DeadSkunk (Warren) :
Chevy *probably* used longer rods in the 4.8, the same way they used longer rods in the 4.3 V8. Apparently it is easier from a manufacturing perspective to make rods with a different pin height than pistons of a different pin height. (The 4.3 had the same pin height as the 5.0/5.7)
This means you could make a 311ci short stroke LS1, or a 329ci LS2. If you wanted to prove a point. My understanding is that the head flow is good enough that there is no benefit to shorter stroke engines, so if you really wanted a small displacement LS2, just run a 5.3...
In reply to Pete. (l33t FS) :
Yes, I'm pretty sure the 4.8 rods are longer, and the pin height for 4.8 or 5.3 pistons is the same. The only real difference between the pistons is the 4.8 is flat, the 5.3 is dished. There's a Hot Rod engine build online where they kept increasing power to a 5.3 until it died and only afterwards did they discover it was actually a 4.8 when they used a bore scope to see what failed, and noticed the flat pistons.
In reply to DeadSkunk (Warren) :
Oh yeah, and the one where they wanted to see how much boost they could throw at a junkyard engine, and they did initial tests with a cam/lifter upgrade, saw that it made 450-odd horsepower at 7000rpm, which they thought was odd, until they pulled the heads so they could get the pistons out to open up the ring gaps and found that they had a 4.8.
450-odd horsepower is remarkably close to DZ302/Boss 302 territory. As a point of reference.
The beauty of the LS truck motors........add headers, a cam and a bigger throttle body and get 400-450 HP. My Challenge engine will (budget permitting) be an aluminum 5.3 with a cam from the LS7 Vette engine and a set of headers. I'd love to throw it on a dyno to see what the real results are.
stroker said:I was daydreaming at work today (thinking about F5000 racing, 50 years on) and wondered if there was a way to build a five liter LS engine. Apparently the hot set up for F5000 was the 327 block with the 283 crank, but I'm unaware of any combinations of LS components to build such a thing. Anyone know?
Vintage rules won't let you run a LS engine.
frenchyd said:stroker said:I was daydreaming at work today (thinking about F5000 racing, 50 years on) and wondered if there was a way to build a five liter LS engine. Apparently the hot set up for F5000 was the 327 block with the 283 crank, but I'm unaware of any combinations of LS components to build such a thing. Anyone know?
Vintage rules won't let you run a LS engine.
I was thinking of a "modern" version built on the cheap.
327 esque is easy. 4" LQ4/9 and 4.8 crank gets you a 328.
I don't know of any OTS 3" cranks but I'm sure someone would cut you one, then you'd have a over square 302
Most of the guys making smaller cube high rpm motors are using the 4.8 cranj
You can offset grind the crank for a shorter throw if you need to really fine-tune to stay 5.0L. Kinda kills the cheap part.
stroker said:frenchyd said:stroker said:I was daydreaming at work today (thinking about F5000 racing, 50 years on) and wondered if there was a way to build a five liter LS engine. Apparently the hot set up for F5000 was the 327 block with the 283 crank, but I'm unaware of any combinations of LS components to build such a thing. Anyone know?
Vintage rules won't let you run a LS engine.
I was thinking of a "modern" version built on the cheap.
I hate to tell you a secret but plenty of vintage racers cheat, especially where it's not regularly enforced.
Second the engines in those formula 5000 cars were modified to the moon. 5-600 horsepower was normal. Even with a LS you'll spend serious money getting one of those to last a season. Other racers will glance at your engine and realize you aren't playing fair. So it's doubtful you'll pass tech.
I can see one in autocross though. Or HPDE track events. Then just use either a 5.3 or 6.0 with a decent camshaft and go for it. If you use a 4.8 to stay under 5 liters there isn't that much extra power ( maybe 15-20hp) bringing it out to 5 liters to make it worth it.
There are computer programs that are accurate enough to get within 2% of actual that will give you precise numbers. I use performance trends when picking components for my racing engines
Opti said:327 esque is easy. 4" LQ4/9 and 4.8 crank gets you a 328.
I don't know of any OTS 3" cranks but I'm sure someone would cut you one, then you'd have a over square 302
Most of the guys making smaller cube high rpm motors are using the 4.8 cranj
4.8 crank in a 5.3 requires aftermarket pistons and cheap just flew out the window.
In reply to frenchyd :
4.8 and 5.3 blocks are identical and you can use the 4.8 stock pistons with either crank,with the appropriate rods. No need for aftermarket pistons unless you're sticking a 4.8 crank into the 5.7/6.0 bores.
https://www.summitracing.com/search/part-type/pistons/bore-in/3-840-in
Lots of pistons in that size, though most of these probably wouldn't be of interest. $800 for a set of eight forged pistons doesn't seem that bad though, really, right?
DeadSkunk (Warren) said:In reply to frenchyd :
4.8 and 5.3 blocks are identical and you can use the 4.8 stock pistons with either crank,with the appropriate rods. No need for aftermarket pistons unless you're sticking a 4.8 crank into the 5.7/6.0 bores.
If the pin height of the 5.3 and 4.8 is the same, then you just use the 5.7/6.0 pistons with the 4.8 rods. Just like putting an L99 crank in an LT1 to make a 5 liter LT1.
In reply to Pete. (l33t FS) :
You're probably right on that. I may have misspoke because the only build I'm aware of with the 4.8 crank in a 6.0 used aftermarket pistons, but that may have been because of the boost levels involved.
If you compare the stroke difference between the 4.8 and 5.3 to the rod length difference, you'll find the rod length difference is exactly half the stroke difference. That suggests the compression heights of the pistons are similar, so you may be able to use 4.8 crank and rods in the larger displacement engines to create intermediate displacements. Why would I want to do that.....no real reason, aside from LS engines are like LEGO and I can. According to Andrew Nelson the 4.8 crank is stiffer so will take more boost before behaving like a skipping rope, but for NA motors there's no real benefit that I can see. For a Challenge car you might be able to find one engine with a bad crank and another with a holed piston, both cheap , and cobble up a usable engine, but we're a pretty small subset of the LS community. Pre-Covid I could find 4.8s for $150, not now though.
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