Uranium238

I am a lurker on this board (and this is my first time posting), gathering information that will be used for a potential track car with an LS-swap. I am interested in doing a 4.8L LR4 build since complete engines can be had for less than the price of an IKEA sofa in my area. The motor would be swapped into a Porsche 944 for track duty on courses such as Thunderhill, Laguna Seca, and Sonoma Raceway. Texas Performance Concepts sells a conversion kit that even includes shorty headers for this swap, which is what I will likely be picking up to make this happen.

I have read articles that the LR4 is fairly durable, but does not have the torque a 5.3L does like the LM7. I do like the fact that the LR4 revs happily as we have one in a 2001 Silverado. This also makes me wonder if I can build this motor up to redline at 7000 RPM without breaking anything.

I'm not looking to do anything really crazy with this budget build, but would like to squeeze around 350-400HP at the crank out of it. I have been reading about cams, valve springs and heads that would assist in my goals, but really don't know what would be a good setup and an ideal pushrod length for any non-stock cam profiles.

As far as EFI goes, I am turning to Microsquirt for this.

My background is pretty much Porsche and Mercedes. The LS-swaps have hit many Porsche forums with some kick *** 944s out there pissing off the purists to high heaven. Somehow I think I am about to follow that same route. This is the perfect board to learn about these engines too.

Are there any recommendations for a budget 4.8L build to get me up to the HP numbers above and decent durability for track use?

Mercier

iTrader: (15)

IMO, your HP goals are reasonable. 7000RPM means upgraded rod bolts. Rod bolts mean resizing the rods which involves disassembling the engine. The argument has been had a thousand times here that some get lucky and replace the rod bolts without resizing. I am convinced it just isn't worth the real risk of pulling the whole thing back out/apart if you fall into the unlucky group.

That being said, if you can live with 6500RPM or lower redline, go with a 5.3 and a LS2 cam. 400 crank HP all day long with $60 valve springs and not much else that you wouldn't have been doing to the 4.8(I assume truck intake won't fit in the 944?). Factory-like reliability. Could do the same with the 4.8 and you would likely be more on the 350-360HP end of things with a few hundred more RPM but IDK if I would call it 7000.

Check this article out..great primer for what can be done with stock parts and a 5.3. Find some cheapie used LS1 intake valves and have the 5.3 heads cut out for a 2" valve and you'll gain a little on top.


http://www.hotrod.com/how-to/engine/1307-ls-cam-test-comparison/

It is slightly confusing the way they have it laid out but each test is that cam in the 5.3. It seems they are referring to a 6.0, etc. but what they mean is that cam originally came in a 6.0...the power numbers are that cam in the 5.3.

Now I want to build a damn Porsche.

yossarian19

For durability at the RPM you are going to want, upgrade #1 is probably valvetrain. I'd go ahead and put full roller rockers or at least a roller bearing retrofit on. Probably valve springs and pushrods, too.
You could just get the Summit trunion retrofit for under $150, the Chevy Performance Hot Cam kit (with springs) for $500 and see about getting LS1 valves put in your heads.
I'm no expert but that's probably all I'd do, put the redline at 6,500 RPM and see how she runs. If it costs more to put the valves in than to buy new heads, then put some #243 heads on. California labor costs, and all...

Uranium238

Thank you for the replies. Screw CA labor. This is not the first, nor the second time I have done an engine teardown.

I cannot believe a 5.3 makes 400HP with just an LS2 cam. Amazing! If I that route which is by far the cheapest, what intake should I use as the truck one will not fit under the hood? LS6?

Now I kust have to find an LM7 for the dirt cheap price of the LR4 I am looking at ($400)

Uranium238

Yossarian is this the hot cam kit you are telling me about?

Mercier

iTrader: (15)

Plenty of folks have been satisfied with the Hot Cam but for the $$, you are leaving power on the table. That kit still only comes with the LS6/2/3 ($60) valve springs so you are paying aftermarket cam price for a GM cam. Most guys get the Hot Cam for the sound specifically. Reality is that cam chop is sometimes a byproduct of a powerful cam but cam chop does not necessarily make a powerful cam.

If you don't mind spending some $ on a cam but dont want to invest in expensive valve springs, call and tell them you want max effort with the LS6 valve springs. I predict you will end up with a better matched cam than the Hot Cam for the same price.

My $0.02.

Mercier

iTrader: (15)

And yes, LS6 intake would be your best bet.

Uranium238

I would prefer to keep the costs down. I found an LM7 at one of those online junkyards for a couple hundred more. It even includes the harness and ECU which I THINK cpuld be tuned to adapt to the new cam and intake. I am also thinking of 36 lb injectors.

I am not asking for any serious power increases as a stock 944 transmission can easily break when abused. 400 is now my set goal.

So to confirm, an LM7 with an LS2 cam, LS6 intake, LS6 springs is the best way to get to this goal? Man this is really exciting

yossarian19

Keep in mind,
if you can't use the truck intake, it takes some trickery to run the truck accessory drive. I don't recall what's involved with which combinations of intake / accessory drive because my LS lives in a truck - so everything fits. Do some more reading on what you need to buy / build / modify to make an LS6 intake live with your planned accessory setup.

Be sure to post pics / build thread when you build it

Uranium238

Yes will do. I am searching now for accessory mounts. I think I would need a setup similar to an LS1.

Mercier

iTrader: (15)

There are a few folks that have made the truck accy drive work with the car intake. A little massaging was required and I think someone may make a bracket now. Possibly on eBay?

Real question will be fitment in front of the engine. Truck accessories sit out a little further from the block.

For the LS2 cam, you will need the LS2 front cover with sensor. Racetronix makes a cheap wiring extension that makes it plug right in. I think I mentioned before, that can be done at/under $100.

Uranium238

Can I use the stock ECU to tune it to the cam and bugger injectors? Also who would be a good tuner to do it?

I am in the SF Bay Area. I am mulling over making this a smog legal build and having it BAR'd.

yossarian19

There is no possible way to make this smog legal. The BAR insists that an engine that came in a "light truck" or "medium truck" emissions class vehicle cannot be swapped into a passenger vehicle.
You'd have to start with a CARB approved engine block for passenger cars or an original, aluminum, LS1 / 2 / 3 / 6 / 7 block.

Alternately, buy a GM E-rod engine and stick with CARB parts on the outside - or make it an off-road racecar and skip the smog entirely.

Yes, though, you can use the stock ECU - it just needs to be tuned. As for "who"... Couldn't say. I had Painless tune an ECU and it came back without the "fan on" temp programmed. I'm not sure I would use them again but I might, purely for convenience.

Uranium238

Okay, so that rules out smogging the sucker. I will have to buy a trailer and take it to the track. Not a problem later on after the build is done. As for the ECU, screw it. I will just use Microsquirt.. Just have to read up on it more.

MuhThugga

The 5th Gen Camaro accessories have the same spacing as the trucks.

Uranium238

Well I found out today that F-body attachments are the way to go. There is a nice setup I saw on Rennlist with the power steering located in front of the driver side valve cover. I even got some ideas on how to place the filter under the front nose panel of the car.

Uranium238

In a Hot Rod magazine link, they had claimed the LS2 cam on the 5.3L LM7 experienced valve float, but I think that was using LS6 springs. I will likely need the engine to rev cleanly to 6500RPM.

Any other suggestions for valve spring choices if I run the LS2 cam?

On a side note, I have been scouring craigslist and even found a Gen IV L20 for cheap. Those have variable valve timing if I recall and 300HP out of the box. I would rather not deal with VVT in my application as I want to keep this swap as simple and straight forward as possible when it comes to tuning the EFI.


Searching the forums also led me to a thread where a guy did a turbo build (not sure if it was an LM7) in a 944. Man that car was sweet! I would love to do something like that later on, but the wallet is always the limit!

Uranium238

ARRRGHH! Okay sorry to beat a dead horse here but I got offered an LS3 cam with 76-77k miles on it for $70. How much better is this cam over the LS2? I read the Hot Rod magazine test, and the numbers look better on a 5.3L. I also found some blue valve springs, which I think are the LS6 type for $60 too.

yossarian19

EDIT
Looking at the hot rod mag article, it really looks like they are about the same on a 5.3 engine.
At 4500 RPM, the LS2 is down single digits in torque while the LS3 cam is up single digits. The spread from 4500 onward is even narrower. I'd run whichever you can get cheap and understand going into it that until 4,500 RPM you are actually losing power compared to stock.

Mercier

iTrader: (15)

Spend as much $$ as you want and you'll never find a cam that will reach the goal of OP(more HP at higher revs) and still compete down low on torque with a stock cam. Aftermarket can be better but you have to expand your budget by a few hundred bucks. You still won't have stock cam low RPM power. VVT would help some but that's more cost and tuning. And we are in a light car now; not a heavy truck.

Valve springs, I think a fresh set of GM blue springs would do fine but if you want to step up affordably(never a bad idea), an entry set of beehives like Comp 918s or PSI 1511s would do well. If you get to that point on your build and need some, I have a few sets around that are NASCAR track test takeoffs that were only run once. Make you a handsome deal on them but they're pretty affordable new as well.

Keep in mind that valve springs can be changed om the car in 30 mins.