Uranium238

A deal for an LM4 was too good to pass up last night. I am sitting here in my patio now figuring out what to do with it.

Motor is going into a Porsche 944 and I am limited to 450HP for racing. Should I force feed it or keep it NA (if it's even possible to get 450 at a cheaper price than turbocharging)? I have two cams with the motor, an LQ9 and LM4 cam. Would prefer to use one of these if I go turbo.

Since the motor is going to be abused, I am thinking about buying the ARP main bolt/stud kit, and their rod bolts that need resizing... However I am not clear how to do that. I guess there's a manual for everything.

A little history about the motor..

-160k miles
-Mirror shiny bores too
-For some reason one piston has scratches on the side of it toward the bottom
-Seller included wiring harness


More to come as I keep digging through the box of parts.

I literally have EVERYTHING less the PCM.

Che70velle

iTrader: (6)

What’s your budget for this engine build? Sounds like fun!

JoeNova

1 7/8" long tubes, big cam, Dorman LS2 intake, 450 flywheel is do-able.

Che70velle

iTrader: (6)

Agreed. The weak link of these engines is the oiling system for track use. Dry sump is mandatory.

ddnspider

iTrader: (26)

How do they limit you to a HP figure and not a CI? Do you have to engine dyno the setup to prove it doesnt make more than 450?

Uranium238

Hey Joe the long tubes don't fit in a 944 body. Some people have had really good luck turbocharging hence my thoughts on going this route.

There is a company called Texas Performance Concepts that makes a swap kit for the 944 that includes shorty headers. I have pasted the link below. I think the primaries are 1 7/8 but don't know how good their headers are first hand.

http://www.texasperformanceconcepts....ation-Kit.html

Uranium238

I'm beginning to think turbocharging is the easiest route to go now for this. I was going to use an LS1 intake with fuel rails just because they are cheaper to get (than an LS6 or LS2). I already have the stock manifolds that are cast iron, which I hear can be reversed and piped to a turbo. They just need the flaking rust cleaned off of them, and then wrapped.

With that being said, the car will be used for road-racing, which would mean a low-lag, low-mid RPM spool rate. The 450HP limit was given to me by a friend, but I haven't had the chance to research requirements for SCCA's XP, which is probably where this car would be classed when done. Anyway, the car build is years from now, I want the motor to be priority first.

As for budget, since I got the motor so cheap, that allows a $2500 budget. Aside from ARP hardware for the bottom end, I was looking at roller rockers (gold Comp Cams) for durability to drop money on. That takes like 500 off the price there unfortunately.

KCS

iTrader: (20)

I wouldn't suggest using ARP main studs, they're not really necessary for what you're doing IMO. ARP rod bolts probably aren't needed either. When you upgrade to a stronger fastener, the bores need to be checked. That goes for the mains as well as the rods. You might end up spending a lot of money on the fasteners and machine work for no real benefit.

ddnspider

iTrader: (26)

I would go the stock rocker route with the trunion upgrade. Thats like $175 bucks. The stock rockers are strong and light. This just gets rid of the needle bearings from taking a crap. If you could keep the IAT's cool, a roots style blower would be perfect.

gnx7

iTrader: (28)

If you plan to road race race it just keep it n/a. Cooling an engine properly for 20-30 mins even n/a is a challenge and simple is good on race cars.

Don't waste your money on main studs/aftermarket rocker arms.
If the main/rod bearings look good then reuse them. ARP rod bolts can be added and you don't have to resize the rods. I've done this in plenty of engines without issues.
Brian Tooley Racing (BTR) sells a good trunion bearing kit to rebuild your stock rocker arms.

Mill the heads for maximum compression. As a general rule of thumb.... 11.25:1 works for 91 octane, 12:1 for 93, and e85 supports 13.5:1. 1 full point increase in power increases potential power output by 3%. Labor/parts alone is around $300+ (head gaskets, bolts (GM or ARP), machine shop resurfacing cost.

Get a real camshaft as that will unlock the power. Many good used ones pop on in the classifieds. If you have the tools/time/patience you can mildly port the stock heads.... otherwise if overall budget allows I believe Texas Speed will do it for $700-800 in labor with their CnC porting program.

Oiling is the weakpoint in these engines as mentioned. If you can run an Fbody oil pan with Improved Racing oil pan baffle or a rear sump oil pan that already has baffles even better. An Accusump as well would be a good idea.

Uranium238

The Texas Performance swap kit comes with a pan and rear sump. I wonder with a little bit of modding I can get the Improved Racing baffle to fit.

How are the windage screens on the Trailblazer? Because that is what I have here in the parts box.


Also, let's go with a real attainable NA power number: 420-425 flywheel. What do I need to get that? I'll pick up that LS2 intake as a good start!

My 862 heads appear to be great candidates for porting, so let's do that in addition to a mill. How much do I need to get this sucker to 11:1?

gnx7

iTrader: (28)

Katech does porting for $500! That is a steal from a very reputable race shop.
http://store.katechengines.com/cnc-p...eads-p589.aspx

Uranium238

Doesn't look like they include the valves though after porting, unless I misread it. Looking at PRC CNC porting through Texas Speed right now for $950 (probably higher due to the valves). Just don't know what cam to do if I go this route.

JoeNova

A stock gen 4 5.3 with nothing but headers and a 222/225 cam made about 430 HP on my buddies engine dyno. Thats flat top pistons, 799 heads, gen 4 truck intake, dyno headers, cam and springs. Very broad torque curve. You're going to have less compression and worse flowing heads/intake, but you can offset most of it with more cam.

Uranium238

Should I not port the heads then and put the money into flat top 4.8 pistons, yet still mill down my 862s?

Digging into the archives here, I feel like all the power I need can be made by just doing a basic rebuild, and slapping a turbo and reasonable injectors on it along with an LS2 intake manifold for hood clearance. I know a guy who will discount the machine work for milling the heads, and decking the block. Saves a few bucks, which should go directly to <PROPER> oiling. I'm not too worried about cooling on a swapped 944.

All I know is I have a free LQ9 cam that looks PERFECT at 60k miles, an extra set of 317 heads I'm not going to use, and an itch for more than 400HP.

Ya'll are doing a good job at making me want more power too by the way.

JoeNova

If you want 450 HP with a turbo, then cam/heads and whatever else is completely irrelevant. 100% stock long block with no accessories at 6 PSI will make 450 HP at the flywheel.

JoeNova

I've been 7800 on a 240k mile 4.8 with all original stock hardware. There are others who have been 8k+.

Trunion upgrades are good to replace the needle bearings in the rocker arms, but with LS6 springs and a low rev limiter, those aren't necessarily needed, either.

The VS Denmah kit uses a GT45 turbo. Really bad for what you're doing. They're big, laggy, and inefficient.

Uranium238

I deleted my last reply because I have basically two debates going on for this build. Ironically family and friends arguing either NA or Turbo.

Some people are saying just go the easy route and throw some flat top LR4 pistons in there and port the heads. Porting would be cheaper vs that 870 kit by Denmah, not including fabrication of piping.

JoeNova

I would rather do the hotside fabrication than swap press-pin pistons and port heads.

pdxmotorhead

So,, just gonna join the N/A crowd,, You may/likely already know this.. Turbo motors will eat you alive for cost to road race.. Just is.. A N/A build at 450 HP will make that 944 fast enough to see god in the braking zones, Your already going to need a 1200 dollar a weekend budget for tires that will hold up to that power in a light car like a 944.. I helped put a 4.3 Nascar GN V6 motor in a 944 years ago,, thing was a 160MPH front straight car, and it didn't take that much power to do it,, we got 1 to 2 race sessions out of a pair of Goodyears. (Slicks) Sanctioning body ended up making us put a 12 pt GT1 rated chromoly cage in it.. To replace the 6 pt ERW cage.. about 4500 bucks..
For the class of car your talking about, figure at least 3 grand in a welded cage, SCCA and NASA have almost banned bolt in cages..

There is massive weight to be lost in the 944 by removing insulation and undercoating from panels. Cheapest speed there is..You'd be money ahead just to buy a roller 944 car already caged and stripped race cars cost at least 2x to build vs buy..

25 year road race track rat.. Flagged/Crewed/Drove/tuned and fiddled with just about every class of road race car.. FV to GT1.. I've helped ground up build at least 2 dozen road race cars.. Races are won in the rule book...