ahritchie

iTrader: (1)

I'm finally ready to start planning a rebuild and adding Advanced Induction CNC ported factory heads and one of their cams to my 1999 Firehawk M6 #37; I want to keep it very simple, heads/cam, maybe intake, and replace rings/bearings and do a cylinder hone. LS7 clutch would also be in the works. I would also like to upgrade to ARP rod bolts in the bottom end for added insurance/reliability. I'm more familiar with the old school LT1 stuff however. The car already has the basics...long tube headers, cat back, and a lid.

First of all, I've got 2 LS1s, the factory installed one in the Firehawk now (167K no issues at all) and I bought a spare LS1 engine that simply had a blown head gasket (lower miles) from my buddy who works at the local dealership. I figured I would just build my spare engine since I got it so cheap ($200 ) and reduce downtime on the car....that way I'll STILL have a verified good LS1 if something bad happens!

First question; how much $$ am I looking at approximately to have a shop install new rings, bearings, cylinder hone and resize the rods for ARP rod bolts?

I'm aiming for 11.5 CR or better and 440+ RWHP, I plan on running a smaller cam as I like lots of torque down low and excellent drivability and I don't plan on upgrading the rear gears. I want to keep mods to this car to a minimum as it is a more rare Firehawk so it can be put back to stock quickly if wanted. Will the stock injectors support 440 RWHP?

Any thoughts or suggestions on this setup?

Ai 224 / 230 - .610" / .605" - 114 LSA
A great daily driver cam. This grind has a noticeable lope at idle, retains excellent manners, and makes power into the mid 6XXXrpm range. Most often run in LS1/346's and LS3's.


GM LS1 346cid/5.7L High Compression Heads & Cam Kit:
Ai 219cc HCR Full CNC Porting
PSI 1511 MaxLife Endurance Springs
New GM OEM Valve Seals
Any Compression Ratio from 10.4-12:1, or Ai optimized for cam selection
Any HR Camshaft - Ai Custom Grind, or you may specify a grind yourself
Ai One Piece 4130 ChromeMoly Hardened Pushrods 5/16" & .080" Wall Thickness
GM OEM .051" Head Gaskets
In-house QC inspection of your individual camshaft

Typically manages 440-460rwhp SAE corrected

HCI2000SS

iTrader: (2)

I bet that setup makes for some great power under the curve and will surprise a few people

ahritchie

iTrader: (1)

I've done a little more research and have heard questionable things about the stock LS1 pistons when it come to higher RPM/HP levels....as in cracked pistons

Is it reasonably safe to run stock pistons at 500 flywheel HP level and 6500+ RPM or should I be looking at forged pistons too?

JakeFusion

iTrader: (7)

Where did you research that?

Stock pistons crack when there is detonation. Especially with boost or nitrous. The stock rotating assembly (crank, rods, pistons) are plenty good for a 6500 RPM NA heads/cam street motor. Where you have issues is the rod bolts giving out or oil starvation and damaged bearings.

And 440 might be possible if you put a FAST 92 on top of the combo... but that's another $1200+ with the throttle-body. Otherwise, I think 420rwhp is more realistic.

Also, I wouldn't shoot for 11.5:1 with that cam. 11:1 is all you need. 11.5:1 would be better suited for a 234/240 type of cam.

ahritchie

iTrader: (1)

http://www.superchevy.com/how-to/ght...continued.html

^Also, I noticed theres a TON of threads about cracked #7 pistons and broken ring lands for LS1s by a google search.

I probably will get an intake/TB too. What is the safe limit for CR for a LS1 on 93 pump gas? I know the LT1's respond well to increased CR and can take up to 12:1 on pump gas if tuned right and the HP/TQ gains are worth it...more CR is more "free" power no?

Rise of the Phoenix

iTrader: (27)

You need not worry. Your pistons will be more than fine. Hell, boosted guys are making 700 to 800 rwhp on stock LS1's. As long as you don't have some total idiot tune the car, you'll be golden.

dr_whigham

iTrader: (49)

I'd ****-can the idea of the LS7 clutch... It'll stick to the floor at high RPM. That's a pressure plate issue, not a hydraulic issue.

Get a Monster Stage 2.

Darth_V8r

iTrader: (4)

^^^definitely!^^^

While you're getting this, also get the tick master cylinder and speed bleeder. The stock hydraulics suck on these cars.

Also, I would urge you to reconsider the cam. It has -1 degree overlap, and you will need overlap to carry power. Tick SNS 2 or cam motion Titan 4 have 227 degrees intake, but also make very good torque. The Titan has 3.5 degrees overlap, and the SNS has 11

Jake is correct about the compression. If you run that cam on 11.5, you will need lots of octane booster or racing gas

Darth_V8r

iTrader: (4)

Thought id clarify my camshaft comments. I ran the comp XER273, which is almost identical to the one you described. The idle I would describe as "somewhat noticeable". Don't get me wrong, it's a good cam for torque, but I don't think it'll reach your goals.

Made for very good cylinder pressure and strong mid range torque, but flat ran out of steam above 6000 due to lack of overlap. To hit 440, you are going to need to rev above 6000 and still carry good power. By going with just a bit more duration and a bit less LSA, you can gain the overlap while keeping a 40-45 degree IVC, which will help you maintain torque lower in the band.

If you keep overlap at 4 degrees or less a good tuner can tame it nicely.

Hope that helps

ahritchie

iTrader: (1)

Ok, I will look into other clutches. I'll talk to Ai, they do custom grinds as well to whatever you want I guess I've still got the reverse cooled LT1 mindset when it comes to CR, my other 383 LT1 has 11.4:1 CR and is considered "mild" as far as built LT1s go...but that's apples to oranges...11:1 or so it is!

Now, just have to find a machine shop to do a mild rebuild and resize my rods for ARP bolts so I have a solid foundation to start with!

ahritchie

iTrader: (1)

I've done a little more research and have come to the conclusion that it seems my "241" LS1 heads are pretty much obsolete these days and most people go straight to the LS6 "243" heads for porting.

If I do choose to stay with the 241 heads, I would want the High CR 219cc Full CNC ported heads package which ups the price a bit to $1200 and is good for 440-470RWHP.

Option two of course is to source some used 243 heads off ebay or somewhere as cheap as possible and get those ported with the CNC'd 226cc GM LS6/LS2 Cylinder Head Package good for 450-500 RWHP for $1000 + cost of used heads ($200-300?)

That being said, is there really a 30+ HP difference in these heads once ported?

HCI2000SS

iTrader: (2)

If both heads were done by the same ported then yes a 20-30 hp difference is about right

ahritchie

iTrader: (1)

Ok, looks like i'm on the hunt for used 243 heads....seems like a no-brainer to get that sort of gains for the price of some used heads.


One more question, part of me says "if it ain't broke don't fix it" in regards to the stock bottom end with 167K with good oil pressure, no issues, ect. The other part of me wants "insurance" of a rebuild and ARP rod bolts so if something bad happens it doesn't destroy my heads. As mentioned I'll be staying mild on the cam to keep RPMs under 6500....how risky is it to just slap heads and cam on a 167K stock LS1 to save a bunch of money and time? If it blows up I could always just put the stock "spare" LS1 I've got laying around lol.

HCI2000SS

iTrader: (2)

Theoretically if everything is in good working order you should be fine for some time, and since you have a spare I'd say go for it if you think it's all in good shape. If you didn't have a spare lying around I'd consider otherwise lol. That's just my opinion

ahritchie

iTrader: (1)

Thanks, I might just do that. It came factory filled with Castrol syntec synthetic and i've used nothing but that the many years I've owned it. I figure worst case scenario a rod bolt lets go, sends a rod out the side of the block and destroys the heads, I'm out the cost of the heads (~ $1500 or so) at some point in the future and have to swap engines. OR I spend that same $1500+ NOW for a rebuild and have a more solid foundation and still have to swap engines....But have better peace of mind. I guess it would be quite a bit easier to work on the engine while it's out of the car though. Decisions, decisions...

HCI2000SS

iTrader: (2)

Lol its never easy lol, but I think it's the right decision in your case

mOtOrHeAd MiKe

iTrader: (8)

That is a fine plan, you are splitting hairs in the 20hp range... and it isn't worth getting too worked up about.

I spec'd my cam to do the same as the one you have indicated above which looks like it is on LSL/LXL lobes. Mine just happens to be 226/230 113+3 on LXL/LXL lobes... such a minor difference; but, our goals are the same.

FWIW, I have a set of PRC Stage I 799s, stock gaskets, LS6 intake, BTR springs and SLR lifters, 1-3/4" headers, etc going on a 150+K mile '02 LS1 long block. Other than a new timing set and LS6 oil pump nothing is getting changed out for stock internals. Maintenance is what keeps these things together.

Don't sweat the little every HP for my dollar approach that happens too often around here. Build a solid engine and enjoy. I say this knowing that a stuck a bottle in the trunk to deal with the overkill-build guy and his 20 extra wheel HP.