The "Tan Brick" aka my 1997 Express Cobra conversion

[Fast355]

You will like that cam setup , I have used a few , been playing with the 8.1 for a while now and it is a very good swap and power increase for an upgrade. Ray and Larry offer great parts and reasonable (for what they are) prices , problem is its hard to justify all that $$ for a tow pig I suppose , but I did it for the '01 . The 8.1 is IMHO the most underrated gas engine recently , surprised more aftermarket support is not out there , but then again maybe I'm not surprised.....



Understood.


Good luck Chris , I'm sure it'll be a cool ride.

TOM

Thanks Tom!

I may get a set of the Raylar roller rockers somewhere down the road.

I also believe it is an underated engine and I can't wait to have it running.

Here is what I found for the cam.























If it is as described and all servicable I will be very happy!

[Fast355]

I pressure washed the 8.1 today and popped it open. It was all factory down to the plugs. I about panicked when I saw how much oil it had been burning that is until I discovered the source. The intake gaskets were DONE and it was pulling oil into the intake runners at the intake gaskets. 6 of the 8 ports were soaked with oil. I am going to go ahead and pull it completely down and may do rings and bearings as well.

[JeepsAndGuns]

Is that normal for such a low mileage chevy engine?

[Fast355]

Is that normal for such a low mileage chevy engine?

I am starting to think so!!! The L31 in my 1997 Express rolled down the assembly line with died in 2004 at 57K miles due to hydrolock on startup breaking a rod and sending it through the side of the block at the oil pan rail. Intake gaskets were trash on that engine. 7 yrs old with only 57k miles. Saving grace of the 8.1 is the fact it does not have any water passageways in the intake.

[1project2many]

I think it has to do with time exposed to oil or coolant, not necessarily mileage. The silicone imprinted seals in the gaskets swell and split. Fel-pro makes a nice gasket for the L31 but I don't know if they have one for the LS engines.

[Fast355]

I think it has to do with time exposed to oil or coolant, not necessarily mileage. The silicone imprinted seals in the gaskets swell and split. Fel-pro makes a nice gasket for the L31 but I don't know if they have one for the LS engines.

I am confused! Not working with a LS1 here maybe someone else is though. I am working with the 8100 aka 496 big block which is a different animal. GM has a TSB to replace intake bolts and a revised gasket part number.

[1project2many]

My bad. I was distracted by a call and didn't catch what I'd typed. No magic Felpro gaskets for the 8.1.

[Nasty-Z]

There was a mid year change in 2004 for intake gaskets on these engines , don't know if you have seen the TSB on this or not Chris, but it is below , Intake gaskets on the early 8.1's were problematic .

Condition/Concern:
Higher than expected oil consumption even after the intake bolts were replaced per Bulletin 02-06-01-035.

Recommendation/Instructions:
Since this type of engine may be used under various load conditions, the acceptable rate of oil consumption is 1 quart (.946L) of oil every 100 gallons (379L) of gasoline. If the intake bolts were replaced per 02-06-01-035 and the excessive oil consumption still exists, replace the intake gaskets with part number 89017539. Use current SI instructions for intake gasket replacement and torque procedures.

Mid year 2004 changes to the cylinder head and intake gaskets were made, making a more robust seal between the cylinder head and the intake manifold. Early 2004 8.1L engines will accept the updated gaskets discussed in this PI, 89017539. The late 2004 8.1L engines that have the updated head and intake gaskets do not require a updated gasket. The differences in the engine are as follows.

2001 to 2004 1/2 8.1L L18 engines will accept the gasket Part Number 89017539.

These engines can be identified by inspecting the intake bolts or the intake gasket.

• The intake manifold bolts will be silver in color and measure 65mm long.


• The intake gasket will be flat with no type of locator that engage to the cylinder head


2004 1/2 to current 8.1L L18 engines will not accept gasket Part Number 89017539.

These engines can also be identified by inspecting the intake bolts or the intake gasket

• The intake manifold bolts are black in color and measure 72mm long.


• The intake gaskets are stamped seal with locating Dowels that fit into the counter bored bolt holes in the cylinder head for the intake bolts.


• Due to the more robust intake seal be sure to complete normal oil consumption testing. If oil consumption is excessive (more then 1 quart (.946L) of oil every 100 gallons (379L) of gasoline), complete SI diagnostics for oil consumption


• If a intake gasket is found to be leaking, use the most current parts catalog listings.


Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.




I use the metal / rubber gaskets on all of the ones I have assembled , found they work better than the originals .

HTH

TOM

[Fast355]

Thanks for the info Tom!!

I found the old saved files from the older GM Powertrain information I had saved on these engines. Including these GM Marine power charts. The 375 HP engine used the factory truck cam and achieved its power with a freer flowing intake and exhaust and a different rating system. The 425 hp used a hotter cam and in some years a forged crank. The forged crank was later dropped. The factory light duty truck/van/SUV engines are 340 HP and 455 TQ. What that tells me is with the intake/shorty headers, exhaust and tuning this 8.1 should be getting close to the 400 Net HP and 475 Net TQ range. That is approaching direct injected 11:1 compression 6.2 HP levels without reving as high, without a cam phaser or direct injection.

375 HP


420 HP (Mercruiser 425 HP) I love how the TQ curve starts over 400 ft/lbs down near 1,000 rpm and it hangs over 400 ft/lbs even up at the 5,200 rpm redline. Downshifting into 2nd accelerating to pass should be a breeze compared to the stock truck cam.