4.2l LS?

Hi,

I'm planning a build for a race class that mandates two valve engines, and V8 engines can be maximum 4.2l displacement. 

Is there a reasonable way, with off the shelf aftermarket parts, to build at 4.2l LS?

The 4.8 LS has the shortest stroke of all the variations and you need 7/8 of that. You're looking at a custom crank to get to 4.2L . I'm not up to speed on what might be available, but I suspect there isn't much demand for short stroke cranks. Since you need to reduce the stroke by 0.409", that's too much to just offset grind the rod journals the required 0.2045" I think. A shop might be able to weld extra material and regrind it, but that's outside of my wheelhouse. However, there are lots of people on here who are more clever than me and I'm sure will chime in.

What about a 4.2L Vortec six engine? Readily available and make good power. See NIVLAC57 videos on YouTube for potential.

Edit: Never mind the 4.2 Vortec. I forgot your two valve limitation.

There's an Aluminum block factory displacement 5.3 L.

I'm pretty sure it has steel sleeves for cylinder walls.  Maybe a 4.8 crank and smaller inside diameter cylinder wall sleeves.  Also custom pistons.

Maybe 🤔 

In reply to DeadSkunk (Warren) :

I would 100% agree with this suggestion, except it violates the two valve rule.

Looks like a Vortec v6 is going to be the spec engine for this class.

There was a 4.3 liter old style small block Chevy.  I don't know how easy it would be to de-stroke it the small amount required. 

In reply to Indy - Guy :

The sleeves are cast in, so you can't press in new , thicker walled ones. I've never heard of pressing a second sleeve inside the existing one, but that doesn't mean it can't be done.

This sounds like a Rover V8. 

A shop that makes billet LS cranks might be able to machine up a shorter stroke version. The more i think about it, the more sense welding a 4.8 crank makes sense. You're looking at adding about 0.210 of material to the inside of the rod journals and offset grinding back to the stock 2.100" journal diameter. Then getting the appropriate pistons and rods.

I don't know how high you intend to spin the resulting engine but getting valve train that lives above 7k requires progressively more expensive kit. I would recommend pricing that in relation to your target max rpm first.

4.2 Aston with half of the cam lobes removed?

Keith Tanner said:

This sounds like a Rover V8. 

That was my first thought given the specs. They're not that cheap to make extra power from if one desires more than stock power. Well, at least without increasing displacement like TVR did.

DeadSkunk (Warren) said:

In reply to Indy - Guy :

The sleeves are cast in, so you can't press in new , thicker walled ones. I've never heard of pressing a second sleeve inside the existing one, but that doesn't mean it can't be done.

You bore the old sleeves out and press in new ones.

One can buy cranks down to 2.5" stroke, that and aluminum rods made to the right length would be cheaper than sleeving and you'd keep the bore.  Still not cheap.

For an off the shelf engine, a Ford 255 (small bore 302 made in early 80s) may work.

Pete. (l33t FS) said:

For an off the shelf engine, a Ford 255 (small bore 302 made in early 80s) may work.

This was my first thought as well. The internet says you can put LS heads on a SBF...

In reply to gumby :

You can in fact bolt the heads down.

The bank offset is reversed so you are on your own for an intake manifold, and between that and a reversed valve order you'd need a billet cam made by an understanding cam grinder.

For all the expense and effort, I'd can the idea of a V8, hunt down a Buick 4.1, and find some ex NASCAR parts on eBay.  Old Busch Grand National bits pop up frequently. Should be good for about 400hp without undue effort. (Ford also had an engine based on the same architecture as the 4.2 truck V6, but only in the sense that an R07 is based on the small block Chevy)

In reply to Pete. (l33t FS) :

Indeed. And to the original question, no there is no reasonable, off the shelf path to 4.2 LS

Since I am a font of bad ideas, a 5.3 with two intake rockers/pushrods/lifters removed is a V8 engine, that only displaces 4l...

gumby said:

Pete. (l33t FS) said:

For an off the shelf engine, a Ford 255 (small bore 302 made in early 80s) may work.

This was my first thought as well. The internet says you can put LS heads on a SBF...

You can. However the rest of the job gets a bit convoluted with making custom cams and intakes and headers. For less time, effort and $$$ you can buy good cylinder heads for the Ford smallblock and chose from a large offering of cam options.

In reply to NOHOME :

The issue with the 255 is you probably can't use the really good heads because the bore is, I think, only 3.5", so that limits you for valve size.  Potential power output is almost directly linked to intake valve size, too.

You could build a Buick V6 pretty easily to be at 4.1 liters, and there are decent aftermarket aluminum heads available (Champion, TA).  The Buick Stage parts mentioned above are very good but are getting rare.  The S2 heads require different cam, valvetrain, intake, and headers. 

The guy who helped me do my last Stage motor did a few for a guy running a Legends car (old ARCA circle track car) and they made just over 500 HP NA.  They were not cheap.

The original question appears to limit V8s to 4.2 liters, but do V6s get more?

Jesse Ransom said:

The original question appears to limit V8s to 4.2 liters, but do V6s get more?

Or less for the reduced weight? Same 2v restrictions or are 4v heads allowed?

If considering a V6 there is also the LZ9, a 12 valve 3.9 liter that is good for 240 HP stock

One question is what is everyone else running in that class?

porschenut said:

If considering a V6 there is also the LZ9, a 12 valve 3.9 liter that is good for 240 HP stock

Yes, the final version of the GM 60 degrees pushrod motor was where I was heading too.

I really want to make a Lincoln LS joke in here. (You know, 3.9 V8 and all). 

In all seriousness, who makes a class with such an obscure engine being the option? They must really not want you to run a V8. I think the only 2V V8 I have ever been around with less than 4.2 is in the old Buick Range Rover. mill And that engine is uh, not exactly a powerhouse. It was light apparently.