L18 8.1L Performance/Customization thread

[RootBreaker]

@Larry has done a fabulous job of doing a thread ' L18 8.1L swap resource thread ' and I am in no way able to compete with that!!!! and nor do I want too; however, what we need is this area maybe to keep that thread cleaner. I know i am guilty of asking questions there and it is a resource thread and needs to be cleaned up some..

so I am thinking of using this thread, mods modify as seen fit, to more so have people voice what has worked, what has not worked, etc. I am going to block out the next 4 plus this for 5 sections as I do not know how long we can make each section. Mods to remove again if not needed.

For myself, I am listing out part numbers and costs so someone can see everything that I have used and how much I am in on the upgrade.

Maybe we can then go back and cleanup the other resource thread and move parts here to get that a bit cleaner???


I am also thinking of another one for a 'junk collection 8.1 thread for the ask questions.... thoughts?


RootBreaker's Swap

Truck: 1978 chevy K20 camper special 8400gvrw
1986 k30 front clip from a 454 silverado
1982 c10 diesel cab/bed

I need to update this as I have purchased little, very little items.. but hey they were needed...


************************ Parts Purchased *****************************
2002 8.1L motor/harness/pcm/TAC/etc - facebook 8.1L group $700
Motor Mounts: Energy Suspension 3.1116R - Amazon $55
ORD Big Block Engine Cross Member - ORD $223.50
2002 Silverado diesel gas pedal - car-parts.com $60
Drive By Wire pedal to TCM cable - $26 - Amazon
6AN Billet Fuel Filter - amazon - $10
AN6 stainless braided fuel line - ebay - $50
454 stock exhaust manifolds - friend - $45
EP381 fuel pump - amazon - $30
2557583 pilot bearing - amazon - $20
Exhaust gaskets - fel-pro MS95840 - $13
Wires - Duralast lifetime - 4711 - $32
12559976 EGR Cover - thatgmpartsguy.com - $11
12580673 EGR Cover gasket - thatgmpartsguy.com - $5
MOCA 4PK1010 EPDM Serpentine Belt - amazon - $6
145a alternator - amazon - $78
Rear main - Evergreeen RMS10481 - amazon - $20
3705-05293265 - flywheel - partsgeek.com - $125
12563485 flywheel bolts - amazon - $60
Hillman M10-1.5x40 bolts (5) for Bellhousing and Engine - Free from friend new in pack
072960 3/8 to 3/8 Brass Pipe to Hose Adapter for Brake Booster to Vacuum port - $3.99 Autozone
Russell #644123 to adapt 6an lines $16 - Amazon
Russell #644113 to adapt 6an lines $16 - Amazon
Braded fuel line with 6an fittings - $50 - Amazon
Walker 41821 o2 sensor in exhaust adapters (2) - $34 - Amazon
Cherry Bomb Glass Pack mufflers (2) 12" - $70 - Amazon
2.5 in/out mufflers and tubing - $175 - Autozone
Harness rework and "Hot Tune" - Ebay - $450 includes shipping to and from
o2 sensors - (2) - $45 - Amazon
MAF - KAX 245-1107 AF10043 - Amazon - $35
MooSun 4" Cold Air INtake System - $60 - Amazon
3" sealed cone filter setup to connect to snorkel - $35 ebay
3/8 Barb fitting to connect brake booster line - $8 autozone
Hydraulic line compression coupler - $15 Ormsby yard work repair shop

______________________________________________________________
Total.................................... $2512


Gotcha's:

• normal brass coupler from Autozone for power steering high pressure is not meant for this high of pressure thus a heavier duty unit used
• Tach - functioning without a pull up resister - but is way off... ECU says 800rpms and tach reads 2500rpms
• passenger side temp sensor in block - has 3 wires on it, 2 actually go to ECU, someone said connect that 3rd to gauge in cab and it will work... cannot get it working for me

Side Notes:

• Gauges - oil pressure is a manual gauge. Had issues getting the correct adapter, thus I broke off my electronic oil sender, drilled and tapped and placed the 1/4" nipple and hooked up gauge.

 

[RootBreaker]

{For Future Needs}

 

[RootBreaker]

{For Future Needs}

 

[RootBreaker]

{For Future Needs}

 

[RootBreaker]

{For Future Needs}

 

[ZooMad75]

The only source for 8.1 performance parts is Raylar. Better have a fat wallet too.

Dart is the only one that makes an intake for a carb (though that's completely insane to do).

BBC headers still fit the 8.1 so there's a lot to choose from there.

The rest comes down to tuning.

I'm over simplifying a bit here but it's the only downside to the 8.1 is the lack of performance options.

That being said it don't need much. I'm perfectly happy with mine with the light tune it has and the stock cam. I could have stuffed a Raylar stage 2 cam in mine. Chose not too. I drove Larry's burb with that cam. If you want a hot rod to haul ass with, use it. That burb was an animal to drive. Put the hurt to bro-dozers everywhere. But it killed the low end torque. As in the curve started around 2000 rpm vs the stock cam at 1000. It was fun to drive fast but sucked lugging in the lower gears.

If you play off road and crawl around in low gear a lot don't do it. If you don't need the low end grunt and need to spin it faster, get the cam. Probably be really good in a mud truck.

Be aware, the stock tune will fight the cam. You will need to get a pro involved to get the system dialed in.

 

[sweetk30]

after driving my 8.1/nv4500 3500-hd for a few weeks now and pulling a 10k trailer a lot i think i am ready to bump the fuel pressure up a few pounds like others have done .

my question is does it make a decent jump in power ? and should i set it with the engine running at idle ? or another specific way ?

 

[ZooMad75]

after driving my 8.1/nv4500 3500-hd for a few weeks now and pulling a 10k trailer a lot i think i am ready to bump the fuel pressure up a few pounds like others have done .

my question is does it make a decent jump in power ? and should i set it with the engine running at idle ? or another specific way ?

It's not a radical change, but enough you'll pick up on it. Just hook up your pressure gauge and start the engine. You'll need a small security torx bit to make the adjustment. It may only take 1/4 to 1/2 turn to get the desired change. 66-68psi is a safe range. I bumped up to 70psi, but didn't see any more bump in power vs the increase in fuel use.

You may find that the pump might be weak too and won't push past 62-63psi. Even after adjustment. I've seen them run on pressure as low as 49-50psi, but they don't run too well and if you are watching the fuel trim with a scan tool, you'll see it running lean.

 

[rksjd8420]

Raylar just came out with a new intake manifold that uses the 4 bolt throttle body.

 

[ZooMad75]

Raylar just came out with a new intake manifold that uses the 4 bolt throttle body.

I watched that the other day. Raylar makes good stuff. But given the captive audience and lack of competition he can charge whatever he feels for the part.

 

[rksjd8420]

I watched that the other day. Raylar makes good stuff. But given the captive audience and lack of competition he can charge whatever he feels for the part.

Their other intake is $2900. I bet you could build a custom intake that adapts an lsa or lt4 takeoff super charger for that.

 

[ZooMad75]

Their other intake is $2900. I bet you could build a custom intake that adapts an lsa or lt4 takeoff super charger for that.

Just get the Whipple supercharger they sell. I've ridden in a 8.1 Whipple blown Yukon. Holy hell is it a sleeper even with the low boost pulley on it.

 

[Larry]

Cool thread….

Regarding the temp gauge, you sure didn’t read hacking in to the coolant temp sensor wires to run the dash gauge in my threads because I would have told you there is another ½” pipe plug fitting in the drivers side cylinder head that an earlier BBC temperature sending units screws right into then plug your original dash wire into that….

 

[RootBreaker]

Cool thread….

Regarding the temp gauge, you sure didn’t read hacking in to the coolant temp sensor wires to run the dash gauge in my threads because I would have told you there is another ½” pipe plug fitting in the drivers side cylinder head that an earlier BBC temperature sending units screws right into then plug your original dash wire into that….

so i tried takin mine out but it desitegrated!!!! spellin? lol

 

[RootBreaker]

The only source for 8.1 performance parts is Raylar. Better have a fat wallet too.

Dart is the only one that makes an intake for a carb (though that's completely insane to do).

BBC headers still fit the 8.1 so there's a lot to choose from there.

The rest comes down to tuning.

I'm over simplifying a bit here but it's the only downside to the 8.1 is the lack of performance options.

That being said it don't need much. I'm perfectly happy with mine with the light tune it has and the stock cam. I could have stuffed a Raylar stage 2 cam in mine. Chose not too. I drove Larry's burb with that cam. If you want a hot rod to haul ass with, use it. That burb was an animal to drive. Put the hurt to bro-dozers everywhere. But it killed the low end torque. As in the curve started around 2000 rpm vs the stock cam at 1000. It was fun to drive fast but sucked lugging in the lower gears.

If you play off road and crawl around in low gear a lot don't do it. If you don't need the low end grunt and need to spin it faster, get the cam. Probably be really good in a mud truck.

Be aware, the stock tune will fight the cam. You will need to get a pro involved to get the system dialed in.

i get that but I feel this will be a great dump zone to keep the awesome resource thread cleaner!!!

@ZooMad75 ...
My adjuster was rusty...
I got it turned and drove it cuz i had a hessitation to which went away... bit I went too high... got home buckin and kickin... checked and 74psi!!!..

managed to get it lowered but then stripped so $70 later and autozone non adjustable reg in... havent taken it out lately so i gotta....

 

[sweetk30]

so who is getting what for oil pressure on there 8.1 at full warm temp ?

i am doing around 35psi towing a trailer with 2,500 rpms and not towing i am getting almost 40psi . oil level is full but due for a change out .

and special oil you guys are finding better luck with ?

@Larry @ZooMad75

 

[Capt Ron]

65psi at idle on mine after fully warmed up but mine only has 60k miles.

 

[sweetk30]

Mine has 80,900 on it .

Plan is change the oil and filter first .

Just trying to get a idea on average specs from others .

 

[ZooMad75]

Mines over 60 normally, I use Mobil 1 with an ac delco filter. The normal GM rule of thumb on oil pressure applies still with 8.1's. 10 psi per 1,000 rpm is the standard.

 

[sweetk30]

went and grabbed 2 5qrt jugs of mobil 1 5w-30 truck and suv spec oil part# 124596 ( see pic ) . i also grabbed a napa GOLD ( wix ) filter #7099 for the change out also .

she took 6.5qrt of oil with filter change out . fired it up and let it run for a few and no leaks and then shut down and let sit for recheck of level . she does take the full 6.5qrt to do a swap on my truck .

road test verified what ever oil was in there was my low pressure problem and it wasnt full black or dark brown but was dirty color . before i was doing max 40psi and sometimes almost 30psi on highway trailer pulling duty . now when warmed up @ 600rpm i have 30psi and @ 1,000rpm i have 40psi and @ 1,500rpm - up its 55-60psi .

and if anyone is looking for a taller / more capacity filter here is some #'s for you from another site and i checked them on wix filters site .

7099 is 1/2 qrt = stock use spec
51060 is 1qrt = 2x capacity of stock
51794 is 2qrt = 4x capacity of stock