Recommendations:MAXIMIZE Lowend -Offroad LS1

**rustynuts** · 12-02-2007, 05:11 PM

hey folks, fairly new to this tech board but have been lurking for a little while. i wanted to get your opinions on maximizing the lowend power from my ls1 and share the ways i've come up with to do this. this engine is going into my custom rockcrawler. my previous engine was a tb 350 .060 over with an rv cam, mild tune, stock heads, and headers. nothing special. it never had enoug power/torque for me. high rpms are of no concern. i don't want to have to spin my motor up to 4000 rpms to get to my power.

for starters, i cannot afford to go bigger heads, big bore, or a stroker crank at this juncture. the rebuild of my crawler is sucking my funds dry rapidly. going from maybe 275hp to 425hp (and similar tq) or so through 4:1 gear reduction and 42" tires requires the strengthening of my drivetrain which is also costly (cromo shafts, billet 300m ujoints, x2 steering axles as this thing is 4 wheel steer). so i'm trying to find that happy medium. running a built 700r4 with a 2000 rpm stall.

that being said, this is where i am to date. stock 5.7 ls1 from a '99 bird w/ a supposed 70k miles. compression tested and all 8 holes at 175 psi (fairly dry motor, hasn't run for awhile). i'm building my own custom long tube headers with low end in mind. they are 1 5/8" primaries about 34" long, to 2 1/2" collectors. i'm debating on dual exhaust vs merging to a 3" pipe to single exhaust for better scavenging/backpressure. open to ideas here.

engine has 853 casting heads and i'm thinking of doing a mild port job, as well as milling approx .030 along with .040 gaskets which in theory should get me close to 11:1 w/ a .036 quench. i plan on running 91 octane. to keep things economic, i'll leave the valve train stock as there will be no high reving. one of my concerns here is i don't know what those springs have been through in their 70k life. there wasn't a clear reason as to why the 21 yr old i bought the motor from pulled it and put a built engine in place. i could just be paranoid. i've heard stories of stock push rods being a weak link but this only seems to be when reving to the moon and missing a shift or accidental downshift. so, for my application, would the stock pushrods be acceptable?

my biggest ? lies with cam selection. while i'm sure alot of folks can recommend a descent cam, who's really going to "know" about a non street driven applicaton where low end is paramount. it seems my application is at the other end of the spectrum compared to 99% of folks here. open to suggestions.

another ? i have is regarding a mafless system. what's the advantage other than the obvious, no need for a maf, as i don't have one yet. is this something that would work for my application? if not, why? how necessary is a wideband o2? i have EFILive flashscan V2 and plan on tuning myself. but i only have experience tuning dmax diesels. also, fwiw, this engine will have no smog. 425hp is my goal, pending cost. i've attached some pics to give you a better idea of the application. i plan on doing most of this work myself, excluding the milling of the heads. any thoughts are valued. thanks in advance.

this is the original buildup thread for anyone intersted in the build:
http://www.pirate4x4.com/forum/showt...ht=wheel+steer

David

**99transamC/FIA** · 12-03-2007, 01:53 PM

WOW that is alot of typing!
425 HP should be no problem.
Call Comp Cams and get camshaft for towing App.(6.0l truck)
Stock valve train will be just fine(But i would consider upgrading the pushrods ,and spings) Trickflow's (pushrods 7.400 long)are only like $70.00 and i'm sure that summit racing or jegs has off brand stuff that will work just fine for what you are doing.
REPLACE THOSE JUNK SPRINGS.
New cam will not like old spring(.500 max lift).
A MAFless system will be easier to tune, and for offroad driving is going to be your best bet.
Machine sounds WICKED.
If you can send me some pictures.
Good Luck
dwhsmp@sbcglobal.net

**0rion** · 12-03-2007, 02:39 PM

I would call someone at COMP cams and tell them what you're looking for and I'm sure they can help you with cam selection. I would also HIGHLY recommend upgrading your valvetrain at the same time along with all the supporting stuff. Pushrods, springs, oil pump, and timing chain. It's always just a good rule to swap those out. Springs and pushrods probably being the most important of the 4 but I would do them all. They really don't add a ton of cost.
I would also run a MAF. You can do speed density and lots of people do including myself all summer but what the MAF gives you is flexibility. I was speed density/open loop this summer and the AFR's really fluctuate with the weather. You'll be much more consistent with a MAF and O2's.

**rustynuts** · 12-03-2007, 05:06 PM

Originally Posted by 99transamC/FIA

WOW that is alot of typing!
425 HP should be no problem.
Call Comp Cams and get camshaft for towing App.(6.0l truck)
Stock valve train will be just fine(But i would consider upgrading the pushrods ,and spings) Trickflow's (pushrods 7.400 long)are only like $70.00 and i'm sure that summit racing or jegs has off brand stuff that will work just fine for what you are doing.
REPLACE THOSE JUNK SPRINGS.
New cam will not like old spring(.500 max lift).
A MAFless system will be easier to tune, and for offroad driving is going to be your best bet.
Machine sounds WICKED.
If you can send me some pictures.
Good Luck
dwhsmp@sbcglobal.net

thanks for the input. check the shortcut in my 1st post. there's alot of detailed pics there.

Originally Posted by 0rion

I would call someone at COMP cams and tell them what you're looking for and I'm sure they can help you with cam selection. I would also HIGHLY recommend upgrading your valvetrain at the same time along with all the supporting stuff. Pushrods, springs, oil pump, and timing chain. It's always just a good rule to swap those out. Springs and pushrods probably being the most important of the 4 but I would do them all. They really don't add a ton of cost.
I would also run a MAF. You can do speed density and lots of people do including myself all summer but what the MAF gives you is flexibility. I was speed density/open loop this summer and the AFR's really fluctuate with the weather. You'll be much more consistent with a MAF and O2's.

that's two votes for comp cams. you are right, i should do the basic supporting parts. now's the time.

your comment about consistancy with a MAF and O2's is interesting. i don't know much about the difference running with vs without. considering my altitude changes (6000' to sea level) from one trip to the next, it sounds as though i should run the MAF/O2's.

any thoughts on the CR and quench for 91 octane? what are your thoughts on max dynamic CR (cam affects this i believe) for my application? i've read 8.5/8.6 max. any validity to this?

**Killer_bluebird** · 12-14-2007, 10:03 AM

I have to say you want to talk to Patrick Guerra on LS1Tech.com he has put some sick combos that produce a lot of low end torque. He can spec the perferct cam for your set up. His screen name is "Patrick G" or you can email him at camhelp@guerragroup.com

**rustynuts** · 12-14-2007, 09:44 PM

Originally Posted by Killer_bluebird

I have to say you want to talk to Patrick Guerra on LS1Tech.com he has put some sick combos that produce a lot of low end torque. He can spec the perferct cam for your set up. His screen name is "Patrick G" or you can email him at camhelp@guerragroup.com

10, 4.

i didn't talk to patrick but i did talk to jeff whom is also at thunder racing. i'm sure he's on top of it also. i ordered my cam from them. i'll post up once the engine's running for the thread/info purposes. thanks killer.