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

  1. #31
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    I drove it again this morning on my way to work. Out of a red light, aimed toward an on-ramp, I jumped on it. I noticed the axle wrap/wheel hop has been greatly eliminated. The thing screeched the right rear tire, the G80 in the 9.5" locked, felt like it jumped up, planted itself, and took off! I kept it planted on the floor for ~1/4 mile uphill on-ramp, glanced down at the top of it and was already rolling 85 mph. It happened so quickly and smoothly, I did not even notice I was rolling along that well. Cruising down the highway on my way to work, I noticed having new wiper cowls probably cut down 50% of my wind noise at 80 mph. Honestly speaking, I can't wait to get the rebuilt 1-ton suspension, brakes and rear-end under it and get the Hellwig rear sway bar ordered.

  2. #32
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    Fast, I have a 90 Astro van with hydroboost brakes. Would that unit be adequate for installing in a 1/2 ton 4x4, or should I look for a 3/4 ton or 1 ton unit out of another pickup.
    Square body stepsides forever!!!

  3. #33
    Fuel Injected! JeepsAndGuns's Avatar
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    Quote Originally Posted by jim_in_dorris View Post
    Fast, I have a 90 Astro van with hydroboost brakes. Would that unit be adequate for installing in a 1/2 ton 4x4, or should I look for a 3/4 ton or 1 ton unit out of another pickup.
    One of those would be perfect for a 1/2 ton. The astro van hydroboosts are a very popular swap for the fullsize jeeps (wagoneer, cherokee, J-10, etc..) Everyone who installs one loves it.
    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.

  4. #34
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    Quote Originally Posted by jim_in_dorris View Post
    Fast, I have a 90 Astro van with hydroboost brakes. Would that unit be adequate for installing in a 1/2 ton 4x4, or should I look for a 3/4 ton or 1 ton unit out of another pickup.
    Those Astro/Safari vans are basically 1/2 ton truck or 2nd generation F-car like brake setups. The Astros hydroboost sits at a downward angle on the firewall. Hydroboost is commen to find in the later G-vans as well. From about 1993 to 1995 it seems nearly all the G20s and G30s used hydroboost.

  5. #35
    Fuel Injected! JeepsAndGuns's Avatar
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    Quote Originally Posted by Fast355 View Post
    The Astros hydroboost sits at a downward angle on the firewall.
    Not all. Most all I see at the junkyard are straight, only a few have been angled down. Not sure if its a year range thing or what. The ones with the straight mounting plate are usually really easy to adapt to other vehicles.
    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.

  6. #36
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    Quote Originally Posted by JeepsAndGuns View Post
    Not all. Most all I see at the junkyard are straight, only a few have been angled down. Not sure if its a year range thing or what. The ones with the straight mounting plate are usually really easy to adapt to other vehicles.
    Weird...I only seem to see the angled ones here. I had both a 97 and a 2002 recently that had the angled ones. The old G-vans and Express vans I have seen were straight with mounting plates. Generally speaking they are all pretty easy to adapt. Especially considering you can even mount the booster itself upside down.

  7. #37
    Fuel Injected! jim_in_dorris's Avatar
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    Then I guess i will remove it before I send the van to the crusher
    Square body stepsides forever!!!

  8. #38
    Fuel Injected! JeepsAndGuns's Avatar
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    Quote Originally Posted by Fast355 View Post
    Weird...I only seem to see the angled ones here. I had both a 97 and a 2002 recently that had the angled ones.
    Made me curious, so I did a little looking online and it looks like the 95 and older had the flat mounting plate, and the 96 and newer had the angled plate.
    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.

  9. #39
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    Quote Originally Posted by JeepsAndGuns View Post
    Made me curious, so I did a little looking online and it looks like the 95 and older had the flat mounting plate, and the 96 and newer had the angled plate.
    My 10 year old Autozone water pump started leaking the other day. Got it swapped out under warranty. Got a good picture of the March underdrive pulleys.


  10. #40
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    Looking at picking up the 24x coil per cylinder conversion for this tank. I have a spare set of low mileage D585 style truck coils with the external heatsinks. I also have a spare 2003 Express van 6.0L harness to rob the coil wiring out of. Word on the street is the D585s give out 3x more spark energy than even the LS1 coils do and have dyno'd up to 10 hp over the LS1 stock coils no less the old L31s single coil distributer setup. I cannot wait to twist this thing to 6,000 rpm with great spark energy. I have seen claims of 20+ hp on a LT1 with the same setup.

  11. #41
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    Well its coming back apart again, still have a coolant leak that seems to be going into #4 cylinder after my overheat last spring and the Comp cast core 215/220 cam is hammering quite nicely. Pulled the stock cam from this crate engine out of the tube it has been sealed up in since 2007 and discovered it has the numbers 7395 stamped on the end of it. Always thought the engine ran like hammered crap on the stock tune and now I know why. It had a Ramjet cam in it, explains the +10% long term fuel trims I used to see that I attributed to the MPFI spider change that was done with the engine back in 2006. I have decided for now the ETecs are coming off, my ported canadian 906s are going on and the Ramjet cam is going in.

    Commission check from work just went through the bank and hit my account at midnight. I just ordered a list of parts from EFI Connection and a set of plug wires custom made for the swap from PCM of NC.

    https://www.eficonnection.com/eficon...px?ItemId=1337

    https://www.eficonnection.com/eficon...px?ItemId=1349

    https://www.eficonnection.com/eficon...spx?ItemId=810

    http://pcmofnc.com/index.php/perform...ion-swap-wires

    Ordered the wireset in Red and will be runing the D585 style coils with the heatsinks built on them. I am not expecting to see 18 ft/lbs average torque increase like I have seen with the LT1s (0411/LS2 coils compared to Optispark with the factory LT1 PCM and a MSD 6AL box) but I do know the L31 ignition sucks and the LSx coil per cylinder setup will ensure I am getting all the efficiency and power out of my setup that I can get. Should be a slick looking and running setup when I am done.



    This is the LT1 testing claim I saw.

    http://www.hotrod.com/how-to/engine/...ls-conversion/

  12. #42
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    Very soon she is going to be pulling herself around on a fully rebuilt 1-ton G3500 8-lug suspension and 10.5" FF 14-bolt with 4.10 gears, PYO 16" alloy wheels from a 2001-2008 GM HD truck wearing Cooper Discoverer AT3 LT265/70R16 load range E tires. 4.10s and a 30.63" tall tire should work out really well. Will put me right at 2,500 RPM @ 75 and a downshift to 3rd pulling a trailer uphill will put the Ramjet cam right into its sweet spot at 3,400 rpm.

  13. #43
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    You're having trouble with the L31 ignition? Maybe you've already mentioned it... Biggest problem we see is moisture in cap. Insert a hose nipple in one vent in distributor and connect to ported vacuum and problems go away. On LS powered vehicles the coils tend to fail around 150k miles. Then its chase, chase, chase after that unless you replace the set. For low cost maintenance the distributor is nice.

    Ramjet / HT383 cam that I installed in the bus is working well. We're seeing much improved fuel economy. Should have switched years ago. Might install more cams this winter if we have the time. Had to spend some time with idle corrections to prevent surging but otherwise minimal changes were done. 302 in Suburban also had surging issue... again, changing spark values for idle speed correction solved problem. Suburban is providing 20+ mpg on highway when not towing. Better than our 4.3 powered '95 Blazer ever was.

    I'm sure that full floating axle will be fun. Big brakes will be nice, too. One of these days I should take measurements to see if the '09+ rear disc hardware is a bolt on for the older vans.

    Edit: I see the CC test replaced stock pcm with an 0411. I'm not sure I'd attribute all the gains to the ignition as they did.

  14. #44
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    Quote Originally Posted by 1project2many View Post
    You're having trouble with the L31 ignition? Maybe you've already mentioned it... Biggest problem we see is moisture in cap. Insert a hose nipple in one vent in distributor and connect to ported vacuum and problems go away. On LS powered vehicles the coils tend to fail around 150k miles. Then its chase, chase, chase after that unless you replace the set. For low cost maintenance the distributor is nice.

    Ramjet / HT383 cam that I installed in the bus is working well. We're seeing much improved fuel economy. Should have switched years ago. Might install more cams this winter if we have the time. Had to spend some time with idle corrections to prevent surging but otherwise minimal changes were done. 302 in Suburban also had surging issue... again, changing spark values for idle speed correction solved problem. Suburban is providing 20+ mpg on highway when not towing. Better than our 4.3 powered '95 Blazer ever was.

    I'm sure that full floating axle will be fun. Big brakes will be nice, too. One of these days I should take measurements to see if the '09+ rear disc hardware is a bolt on for the older vans.

    Edit: I see the CC test replaced stock pcm with an 0411. I'm not sure I'd attribute all the gains to the ignition as they did.
    I vented the distributor years ago to a vacuum port I added in the throttle body just above the throttle blade. I hooked a vent hose into the TB bonnet similar to the way an opti spark is vented in later years.

    I think the FF 10.5 will be great too although my guess is that it weighs 450-500 lbs with the drums on it. The 13 x 3.5" drums should be a nice upgrade. I already put tue 8600 GVW front calipers and pads on it when I put the Hydroboost and 1-ton master on it.

    I totally eliminated idle spark correction with my 215-220 @ .050 cam and the idle has been rock solid. I had played with the values but the old cam really liked it just being diabled with all timing maps having the same values.

    My brothers 1999 5.7 with the LT1 cam and tuned black box was also very good on fuel, especially after a set of Hooker 1 5/8" long tubes and Hooker 2.25" dual exhaust went onto it. He saw 20-22 mpg on a few roadtrips. With the 40 gallon tank in the truck on a trip we went on we went through like 3 states before we had to get gas.

    Good the see the 395 Marine cam is working well for you. I never have been a fan of the factory L31 cam. I never felt it had enough duration split to work well with the factory heads.

    Finally I am guess you have a ton of cracked manifolds on these buses. Have you tried the Doug Thorley Bus headers on one yet? I don't know how long you plan to keep them in service but they are $615 and they come ceramic coated and well built with 14 gauge tubes and 3/8" flanges with headpipes to bolt up to the stock 3" pipes. I now often find myself pulling uphills unloaded in Overdrive that caused me to downshift to 3rd before. With 7,500# behind it I pull in 3rd gear with my 29" tall tires and 3.73s. The torques gain and MPG increase was very noticeable after adjusting the VE and MAF tables. The heads run cooler too, allowing me to dial in a few degrees more timing across the board.



    The last trailer I towed for ~250 miles was about 6,500# with an older Jeep Cherokee on it. Running 65 mph @ 2,600 rpm in 3rd gear I was able to get 14 mpg. I don't recall finding a single uphill run that caused it to downshift.I LOVE the torque.

    Last edited by Fast355; 08-09-2015 at 07:04 AM.

  15. #45
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    I vented the distributor years ago
    You know, as I read this I'm almost remembering you doing this. It sucks to get old.

    my guess is that it weighs 450-500 lbs with the drums on it.
    Yes. You will notice the additional mass. But no more worries about bearings chewing through axles or spiders letting go.

    With the 40 gallon tank in the truck on a trip we went on we went through like 3 states before we had to get gas.
    Nice. That would probably be 5 states if you were here in the northeast!

    We've only seen a couple of cracked manifolds. I know it's a problem for people but I believe the combination of in-town driving, relatively low average speed, and less than full load trips keeps the heat down. I've considered headers (those sure are purdy!) but the cost including shop time to install was fairly high compared to used manifolds and I really have to watch spending for projects like that. Most of our 5.7 buses are approaching end of life. If I get three more years out of the '99 and '00 models I'll be lucky. It's a shame to let them go because we're literally throwing them away. Local scrap yard gave me $300 for a complete one last week. Dually rear, 4L80EHD, running 5.7, 0411 ecm. Two weeks ago we sent one down with no engine, trans, or other parts and they gave me $200. If only I had a place to store component parts!!

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