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Thread: The "Tan Brick" aka my 1997 Express Cobra conversion

  1. #61
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    Wow. That's a helluva find. What is the lowest numerical ratio available for the 14 bolt? I'd be looking to gear that thing for 1500 RPM on the highway. Maybe it's time to step up to a 6L90E to gain the extra gear reduction?
    Code:
    Gear  6L90 Ratio          4L80 Ratio
    1          4.027              2.48
    2          2.364              1.48
    3          1.532              1.00
    4          1.152              0.75
    5          0.852
    6          0.667
    R          3.064              2.07
    2nd compressor is usually aftermarket and can be removed. We have several buses with dual A/C (but nothing with 8.1). All sorts of mischief with dual a/c systems, like belt only available from A/C company at $100 each, and modified belt routing, and idler pulleys not available from anyone. Carier was big designer of systems for years but has now been bought and name changed to MCC. From my vantage they don't have anywhere near the parts or support network anymore. Other players stepping up and trying to fill voids but parts fitment and application is still a challenge. I've got a 250A, $1000 alternator here that was designed to work with a dual a/c and custom alternator bracket on a Ford. It doesn't fit anything else but I'm surely not throwing it away after spending that much $$ on it. I'll fabricate a bracket for something.

  2. #62
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    3.42 is the highest (Numerically lowest) gear available for the 14FF

    How about an Allison 1000 series and keep the 4.10's ? Works fantastic in my 8.1/Allison 2001 3500 Dually

    Allison 1000 Ratios
    1st 2nd 3rd 4th 5th 6th* R
    3.094 1.809 1.406 1.00 0.711 0.614 4.480
    * 6 speed available 2006-up but it is a retrofit to earlier models.

    TOM
    Last edited by Nasty-Z; 09-23-2015 at 05:50 AM.
    1994 3500 Dually , 502 (509) , 264HR , Edelbrock MPFI , PFI '7427
    2006 Forest river-Sierra 37' 5th wheel
    1999 Astro Van, L31 Vortec , 4x4 conversion
    1994 Pontiac Sunbird "Work ride"
    1993 K-3500 "Ex-diesel" 454/4L80E - '7427
    1992 454SS "Eh Stock" , Blower & '7427 swap .
    1992 S-10 434 SBC/Tremec - '7427
    1984 S-10 , SAS, 496/700R4/205 , D44/14BFF -'7427
    1980 Z-28 454/700R4
    1977 Olds 98 Regency 403/700R4

  3. #63
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    Quote Originally Posted by Nasty-Z View Post
    3.42 is the highest (Numerically lowest) gear available for the 14FF

    How about an Allison 1000 series and keep the 4.10's ? Works fantastic in my 8.1/Allison 2001 3500 Dually

    Allison 1000 Ratios
    1st 2nd 3rd 4th 5th 6th* R
    3.094 1.809 1.406 1.00 0.711 0.614 4.480
    * 6 speed available 2006-up but it is a retrofit to earlier models.

    TOM
    I just don't want the added power loss!! My 4L80E already has the dual stator 4.3 converter that stalls 2,300 rpm behind the 350. The 10.5" FF I have has 3.73s in it. I want 4.10s in the back but a good comprimise might also be a 2.96 first gear planetary set in the 80E.

  4. #64
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    On a side note I have a line on an entire cam/valvetrain from a very low hour 425 HP 496 Mag Mercruiser for $300 that was given the Raylar treatment. Cam/Lifters/Pushrods/Guides/Studs/Rockers and double roller timing set. The cam and matching tune is worth 50 HP in the 375 HP Marine version of the 8.1 making it the 425 HP HO. I am sure the rest of the gain over the 340 HP truck version is exhaust/intake/tune/loss of the mechanical fan. The cam does its thing under 5,000 rpm as well and has a nice sounding idle.

  5. #65
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    I did a little more research and decided what the heck and ordered the cam. Might be a shade big for many heavy haulers, but my Express is fairly light compared to a Dually or a Workhorse. Seems the cam is Mid 220s @ .050 on the intake, mid 230s @ .050 on the exhaust, .510/.510" lift and cut on a 114* LSA opposed to the stock 118* LSA big block cam. For $360.00 shipped for the whole take-out cam kit, it is hard to turn down. 425 HP 496 mag reaches 425 HP before it reaches 5,000 rpm.

  6. #66
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    Quote Originally Posted by Fast355 View Post
    I did a little more research and decided what the heck and ordered the cam. Might be a shade big for many heavy haulers, but my Express is fairly light compared to a Dually or a Workhorse. Seems the cam is Mid 220s @ .050 on the intake, mid 230s @ .050 on the exhaust, .510/.510" lift and cut on a 114* LSA opposed to the stock 118* LSA big block cam. For $360.00 shipped for the whole take-out cam kit, it is hard to turn down. 425 HP 496 mag reaches 425 HP before it reaches 5,000 rpm.
    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.....

    Quote Originally Posted by Fast355 View Post
    I just don't want the added power loss!! My 4L80E already has the dual stator 4.3 converter that stalls 2,300 rpm behind the 350. The 10.5" FF I have has 3.73s in it. I want 4.10s in the back but a good comprimise might also be a 2.96 first gear planetary set in the 80E.
    Understood.


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

    TOM
    Last edited by Nasty-Z; 09-23-2015 at 09:00 AM.
    1994 3500 Dually , 502 (509) , 264HR , Edelbrock MPFI , PFI '7427
    2006 Forest river-Sierra 37' 5th wheel
    1999 Astro Van, L31 Vortec , 4x4 conversion
    1994 Pontiac Sunbird "Work ride"
    1993 K-3500 "Ex-diesel" 454/4L80E - '7427
    1992 454SS "Eh Stock" , Blower & '7427 swap .
    1992 S-10 434 SBC/Tremec - '7427
    1984 S-10 , SAS, 496/700R4/205 , D44/14BFF -'7427
    1980 Z-28 454/700R4
    1977 Olds 98 Regency 403/700R4

  7. #67
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    Quote Originally Posted by Nasty-Z View Post
    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!

  8. #68
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    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.




  9. #69
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    Is that normal for such a low mileage chevy engine?
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

    93 Jeep YJ Wrangler, 4.0L, 5 speed, 8.8 rear, homebrew hub conversion and big brakes, hydroboost, 2.5in OME lift, 31x10.50's---the daily driver

    99 Jeep WJ Grand Cherokee limited, 4.0L, auto, 2wd, leather and power everything, 99% stock---the long distance highway ride.

  10. #70
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    Quote Originally Posted by JeepsAndGuns View Post
    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.

  11. #71
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    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.

  12. #72
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    Quote Originally Posted by 1project2many View Post
    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.

  13. #73
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    My bad. I was distracted by a call and didn't catch what I'd typed. No magic Felpro gaskets for the 8.1.

  14. #74
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    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
    Last edited by Nasty-Z; 09-28-2015 at 09:24 AM.
    1994 3500 Dually , 502 (509) , 264HR , Edelbrock MPFI , PFI '7427
    2006 Forest river-Sierra 37' 5th wheel
    1999 Astro Van, L31 Vortec , 4x4 conversion
    1994 Pontiac Sunbird "Work ride"
    1993 K-3500 "Ex-diesel" 454/4L80E - '7427
    1992 454SS "Eh Stock" , Blower & '7427 swap .
    1992 S-10 434 SBC/Tremec - '7427
    1984 S-10 , SAS, 496/700R4/205 , D44/14BFF -'7427
    1980 Z-28 454/700R4
    1977 Olds 98 Regency 403/700R4

  15. #75
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    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.


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