LS Headed 300: Brainstorming problems

General rule of thumb is 1HP per cfm on a v8.

I'd estimate 50hp just from the airflow gains but there's way more to it than that. The intake and exhaust manifolds, rockers, throttle body, etc all have to change. Key parameters are going to be size and length of the manifolds. Intake especially because now the head has a much larger and more efficient port which is going to do wonders for the power band above 2500, probable even from idle. Anybody can slap parts together and "it makes power" (crate engines) but getting all the parts to work together to make the engine perform takes planning and when you're done you have an engine with a couple different parts and machined a little different that is better than the crate engine is every way while making 50+ hp more. You will need to do this planning to maximize the head change. Miss match the parts/designs and it won't perform...It will likely be better than stock, but that is a pretty low bar... Get it all working together and you'll be shocked at how good it is.

Stock the 300 made less than 150HP. Miss matched parts with the head swap I'd say 200 no problem and 250 very likely. Get all the parts working together and I see no reason why it wouldn't make 300-350HP and be better in every way.

That may sound like a huge increase but it is a huge change. 1HP per cubic inch is not even batting an eye on nearly all engines....that can rev up. The 300 is on its face and not doing much after 3000rpm because its designed to be a work horse. You put the LS head on and suddenly you have airflow support to rev to past 6000 with a mild cam.

Mr_Asa said:

Ian F (Forum Supporter) said:

Maybe a crazy thought, but perhaps instead of trying to weld the heads together, plate off the ends of the passages and then use some high-temp o-rings to connect them? 

I'd be concerned I'd end up with a restriction in coolant flow.

Hmm...  maybe... but it's not like there aren't other tight passages inside the head. 

You posted a running engine video before , 

can you see how he did the water galleys ?

Is he the only one that figured this out or is it a secret " society"  and you are not a member :)

In reply to californiamilleghia :

The running engine was an AJ Hoyt head that doesn't have cooling passages.  Drag race only.  He has built a LS head though, he said he just welded the sections together.

I have this crazy idea that the power numbers will be about what they are for a stock 4.8 LS-style truck motor.  Stock cam, very similar displacement, probably about the same compression, I doubt there's enough inliner magic in this thing to really change peak numbers.  I could maybe see a bit more volume under the whole torque curve but that is an irrational leaning on inliner magic thinking.

Ok folks, I should be able to pick up the head sections from my machinist on Friday or Monday, then I'm going to bevel them and prep for welding.

I've heard from a friend working as an engineer at GM that the LS heads I have are cast from 319 alloy.  Brief looking around says that 4043 looks like it might be the go-to filler?  Other tips for welding?

asphalt_gundam said:

General rule of thumb is 1HP per cfm on a v8.

I'd estimate 50hp just from the airflow gains but there's way more to it than that. The intake and exhaust manifolds, rockers, throttle body, etc all have to change. Key parameters are going to be size and length of the manifolds. Intake especially because now the head has a much larger and more efficient port which is going to do wonders for the power band above 2500, probable even from idle. Anybody can slap parts together and "it makes power" (crate engines) but getting all the parts to work together to make the engine perform takes planning and when you're done you have an engine with a couple different parts and machined a little different that is better than the crate engine is every way while making 50+ hp more. You will need to do this planning to maximize the head change. Miss match the parts/designs and it won't perform...It will likely be better than stock, but that is a pretty low bar... Get it all working together and you'll be shocked at how good it is.

Stock the 300 made less than 150HP. Miss matched parts with the head swap I'd say 200 no problem and 250 very likely. Get all the parts working together and I see no reason why it wouldn't make 300-350HP and be better in every way.

That may sound like a huge increase but it is a huge change. 1HP per cubic inch is not even batting an eye on nearly all engines....that can rev up. The 300 is on its face and not doing much after 3000rpm because its designed to be a work horse. You put the LS head on and suddenly you have airflow support to rev to past 6000 with a mild cam.

I agree with all of that.

I also remember when 1 hp / cu in was huge numbers for anything that would be a streetable engine. We have come a long way!

wheels777 said:

03Panther said:

asphalt_gundam said:

General rule of thumb is 1HP per cfm on a v8.

I'd estimate 50hp just from the airflow gains but there's way more to it than that. The intake and exhaust manifolds, rockers, throttle body, etc all have to change. Key parameters are going to be size and length of the manifolds. Intake especially because now the head has a much larger and more efficient port which is going to do wonders for the power band above 2500, probable even from idle. Anybody can slap parts together and "it makes power" (crate engines) but getting all the parts to work together to make the engine perform takes planning and when you're done you have an engine with a couple different parts and machined a little different that is better than the crate engine is every way while making 50+ hp more. You will need to do this planning to maximize the head change. Miss match the parts/designs and it won't perform...It will likely be better than stock, but that is a pretty low bar... Get it all working together and you'll be shocked at how good it is.

Stock the 300 made less than 150HP. Miss matched parts with the head swap I'd say 200 no problem and 250 very likely. Get all the parts working together and I see no reason why it wouldn't make 300-350HP and be better in every way.

That may sound like a huge increase but it is a huge change. 1HP per cubic inch is not even batting an eye on nearly all engines....that can rev up. The 300 is on its face and not doing much after 3000rpm because its designed to be a work horse. You put the LS head on and suddenly you have airflow support to rev to past 6000 with a mild cam.

I agree with all of that.

I also remember when 1 hp / cu in was huge numbers for anything that would be a streetable engine. We have come a long way!

I don't want to argue or contest any rules of thumb.  But we typically see 2.05 HP for each 1 cfm head flow increase when measured at 28" H2O for a V8.  A 6 will see 1.53.  This is at peak power and rpm when the head, intake, exhaust and cam are matched for the rpm.

Just an example - a 350 with a head that flows 300 cfm will make 617 HP at 8200.  When the head flow is increased to 310 cfm the engine will make 638 HP at 8400 rpms.  

Interesting that you've seen up at the 2Hp per cfm range. I assume you're working with a well optimized package at that point and not surprised by the results. What back to back to back testing I did playing around on the dyno I found that the 1hp is close for a decent street engine. Which just further pushes the point that the more parts work together to optimize, the better the engine performs.

On a similar note I've had an engine on the dyno not quite back to back but 2 days for full teardown and clean because it tore the shaft system out of one head and needed that repaired. Before it made 960HP and the only changes that were made beyond the thread repairs was honing .0005 extra out of the bores and opening up the rod side clearance from .020 to .030 because of high oil pressure. It made 980HP after that which I expect was the reduced pump effort that bought the oil pressure down from 105ish to 80. Was neat to see since I haven't heard of anyone really test oil pressure hp/psi losses before.

Mr_Asa said:

Ok folks, I should be able to pick up the head sections from my machinist on Friday or Monday, then I'm going to bevel them and prep for welding.

I've heard from a friend working as an engineer at GM that the LS heads I have are cast from 319 alloy.  Brief looking around says that 4043 looks like it might be the go-to filler?  Other tips for welding?

Looking at the pictures of the cut heads the other day I had the thought that I wouldn't be shy about cutting intake flange side material out of the way for access to get a proper solid weld all the way around the coolant jacket. Looking again I think you'll need to grind the whole head bolt hole out of the way to do it too. Then build it back up to drill again.

Welding Tip: Its a used head so don't be surprized when contaminates come out of the aluminum and screw up 90 percent of your first weld pass....then several times after that too. This can be minimized with lots of cleaning but sometimes the heat of welding just has to get it all out. So don't get discourage if/when you weld and then have to grind it all back out and do it again. 

I'd also say bolting them to a thick plate of steel should help keep it all in place and act as a heat sink for when you're preheating and to help keep it from getting too hot when welding. More importantly it'll fight warping which is going to be the biggest problem after welding is finished.

Dialing in this stupid 120V spool welder.  Still, I think its promising.

Its too hot outside to be welding.

We have welding, folks! This is getting real. 

barefootskater (Shaun) said:

We have welding, folks! This is getting real. 

Yes it is, isn't it.

Something I thought of today that won't help you now.

Fill the sliced bolt/stud holes with weld, mill flat to the surface and weld together.

Or grind out the back side of the problem areas and then build up weld to where you need it.

Re-drill the bolt/stud holes and tap threads later.  I have no idea if this is a good idea or not but it would save the problem of welding inside a hole.  

In reply to noddaz :

If you look above, you'll see where I cut the exterior portion of the bolt hole away from the head.  I went as close to the water jacket as I dared (between 1/16 and 1/8th) and cut a valley into the head where the bolt goes.  Gonna fill that entire section with aluminum boogers and then re-drill those head bolt holes.

Thinking of doing a 3D print for a jig for the pilot hole at least.

I think getting 300hp out of this thing may not be as easy as we think. Don't forget the stock truck  ls intake is very capable, so to match the stock 4.8 output, you would need at least as good an intake, exhaust manifold, and camshaft, that doesn't even take into account the small efficiency stuff like weight of the rotating assembly, oil pressure, and ring tension and size.

Now if your porting the head and doing a bigger cam, it's a whole different ball game. 

I would think head only would probably be low 2s with a decent intake.

Either way it will be a monster improvement over the old tractor engine

I haven't forgotten this.  Just been workin on the boat and job searching.

Anyways, I did a thing.  Ran out of wire halfway through the final weld.  Such a PITA.

Gonna need to go find a piece of steel for the exhaust flange.  3/8" minimum?  Should I go for 1/2"?  What's a good thickness for an exhaust flange?

Can you use the intake and exhaust flanges to keep the head from flexing ?

if thats part of the plan then make them 1/2 inch

I bolted it to the block while I welded the sides and top, included a 1/4" plate for the exhaust.  I haven't hit the bottom yet, but so far the mating surface is nice and flat.  Put a straight-edge on it and didn't really see any gaps.

So I started to work on intake stuff.  The solid models available online are all just subtly off, combined with where I cut the heads it took several revisions to get to a flange that I could bolt on across the head cuts.

But I finally was able to get something that worked

Now I need to start working on an actual intake design.   I got a roughed up mock up, but from what I know of intake design this thing is way off.

Shouldn't the angle of the intake runners be raised (it seems like you are adding two turns)?

In reply to bentwrench :

Possibly?  I'm not completely clueless about intake design, but there's a reason I started this thread. https://grassrootsmotorsports.com/forum/grm/intake-design-and-building-how-to/186000/page1/

No significant movement here, although this happened.

pimpm3 is helping me by picking it up if this isn't enough info to qualify for Challenge stuff.

Damn, this is cool

Every now and then I get frustrated that I'm not in on the ground floor of this, but at the same time I don't care that much cause it means I can steal their designs

At least my intake is sexier.  I like the integration of the old Ford intake lid, though.

So there's at least one other absolute maniac out there, eh?

y'all are doing the good work. Keep the world interesting. 

bentwrench said:

Shouldn't the angle of the intake runners be raised (it seems like you are adding two turns)?

He needs independent throttle bodies!