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  1. #1

    Default Need to Replace Broken 1986 5.0 Block

    Good Afternoon,

    I'm the proud new owner of a 1986 GT Convertible. The car came with a free set of holes in the front of the block. So... I'm on the lookout for a compatible block in good, usable condition. I've gotten in touch with a guy who has an engine from a 91 T-Bird 5.0 that he's not going to be using and is selling. From what I can tell from searching this forum (and according to FoxChassis' post of 2/18/2017 in the "302ho questions" thread) the '91 - '93 T-Birds have the same 5.0 roller that my car has. Can anyone validate this for me or point me to a definitive resource so that I can be assured that I wont be wasting my money? I plan to rebuild my engine using the T-Bird block as a core. Future upgrades would be a MAF conversion and an intake/head/cam swap. But for now I just want to get the car driving so I can address the other issues. The car has been parked for the last 20 years. Brakes, fuel pump, tires, some interior work, etc.


    Thanks in advance,


    Grant

  2. #2

    Default

    Tbird motor will actually be a bit better.

    It will have notched pistons (although not forged like the 86 pistons) and has a camshaft nearly identical to the 93-95 cobras, minus 1.7 rockers as well as e7 heads. Some people seem to like the e6 heads, but e7's bolt right up and should gain you anywhere from 5-15hp.

    Sbf are nearly identical for most years. All 85up blocks should be roller compatible and the same block casting. Anything else that might be different you already have in old motor.

    Buy it.
    2 1986 cougars (both 4 eyed and 5.0)
    1 1987 cougar

  3. #3

    Default

    Thanks for the info. I'm going to get it tomorrow afternoon. Any quick tips as to what to look for? The engine is sitting on the ground. Will I be able to do a compression test turning it over with a breaker bar? I should be able to check the dipstick to see the oil condition. I have a bore scope I can take with me. My main concern would be a damaged block... Again...

  4. #4

    Default

    Without magnafluxing a block there is no definitive way to tell if a block is good or not, lots of indicators like metal stress etc, but it will take a true non destructive test to get real answers.
    1981 Mustang Hatch 3.3 "Orange Juice"
    1983 Mustang GT Convertible "Triple Black"
    1994 Ford ThunderBird SC
    1987 Firebird T/A
    1984 Firebird Forumla
    1988 Mazda RX-7 Infinity
    1987 Mazda RX-7 Turbo II
    1994 Eagle Talon TSI
    1991 Eagle Talon TSI
    2003 Pontiac Grand Prix GTP

  5. #5

    Default

    See how clean it is, oil will tell ya alot. I think you would learn more from pulling a head if they would let ya. If its got oil, it takes alot to hurt them. I have 350k miles on my old 86 and it passed emissions with no cat at 291k miles. I beat the crap out of if. Had another with 185k or so, dropped in a t-5 and broke 6 sets of motor mounts and drove over 50k miles in less the a year.

    Id also check the back intake, there is a pvc filter in there. If thats all clogged then it can effect the ring seal. I dont know if you could spin it over easily enough to get a good reading, but it would be a bit hard with the springs and heads on. You should be able to hear hissing.
    2 1986 cougars (both 4 eyed and 5.0)
    1 1987 cougar

  6. #6
    FEP Power Member gmatt's Avatar
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    Default

    ^^^^what they said^^^^ Pull a valve cover and the pan. Are you planning on rebuilding the shortblock? If you aren't, ask him if you can pull a bearing cap to check the condition of the bearings. If he won't, pass. Trust your instincts too. If he gives you a sketchy feeling, be wary. some guys are open and honest. I bought a complete used engine from a guy on this forum and it runs great.

  7. #7

    Default

    Thanks to all of you for all of the good information. I'm assuming when looking at the main bearings, I'm looking for scoring running along the races (spun bearing)? I t's been quite a while since I've been this deep into an engine. I figure that since I'm going to be up to my elbows in this thing, and assuming the internals are all good, I'll go with a complete rebuild. Can anyone recommend a good rebuild kit? I see some in the $250 range (Amazon) that include:

    Full Gasket Set, Pistons, Piston Rings, Main Bearings, Rod Bearings, Cam Bearings, Timing Components, Oil Pump, Freeze Plugs

    Is that something that I should consider? Do I need the new pistons (maybe just rings?) Is there a better kit out there in this range?

    Thanks again for all the help. It is extremely appreciated.

  8. #8
    FEP Power Member gmatt's Avatar
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    Default

    Spun will be obvious when you see it, look for worn too. Copper showing. Maybe let a machinist look at it for the other stuff. If the bore is OK, the pistons would probably be too, but who knows how this engine's been treated?

  9. #9

    Default

    Your easiest, and most effective soloution will be this.

    Go to your closest auto wrecker
    Get a GT40 era 302 - If the Fuel Injection is there, take it. If not, don't worry - someone here will have one to sell you cheap.
    Take it to local certified machine shop
    Get them to tank and flux the block
    Get them to bore the cylinders to whatever you want - Its not expensive and you are in there anyway
    Have them port and polish your e7 heads
    Get them to tank all the rest of the parts, and run a material density test on the pistons and connecting rods
    Buy /repair whatever is needed on the injectors side of things
    Have the shop grind you a cam to match your now improved setup
    Put it all together yourself

    All this - maybe 1500 bucks at a good shop and some of your weekends.
    1981 Mustang Hatch 3.3 "Orange Juice"
    1983 Mustang GT Convertible "Triple Black"
    1994 Ford ThunderBird SC
    1987 Firebird T/A
    1984 Firebird Forumla
    1988 Mazda RX-7 Infinity
    1987 Mazda RX-7 Turbo II
    1994 Eagle Talon TSI
    1991 Eagle Talon TSI
    2003 Pontiac Grand Prix GTP

  10. #10

    Default

    Thanks for the suggestions. And in fact, that's my ultimate goal. However, at this point, I just want to have the car be able to move under it's own power. I need to concentrate my limited funds on getting the car drivable before I worry about engine upgrades. I did pick up the 302 and I am in the process of tearing it down to take to the machine shop to have it tanked and magnafluxed. They're also going to mic everything, replace freeze plugs and deglaze the cylinders. Then I should only need rings and bearings and a couple weekends to bolt everything back together. However, there's a guy in my area (DFW, Texas) that hunts down the Explorers and pulls the engines. He has one on Craigslist, complete with all of the sensors and the computer, for $500. Once I get the car drivable and presentable, I will try to get an engine where I can do just that. Tear it down and have it "refreshed" and drop it in my car. But unfortunately my budget only allows me to get a "running" engine.

  11. #11

    Default

    I do have one more quick question tho. It was mentioned above that the cam in the T-Bird motor will be different from my current cam (86 Mustang). Will I be able to use that along with the newer heads? Or will the speed density cause me problems? OK.. Two questions. My thinking is that I should utilize the (cast) notched pistons in the T-Bird engine. This will give me more clearance if I can use the T-Bird cam, and If I use a larger cam in the future. I have no plans of forced air or nitrous. Or will the be required because of the newer head?

  12. #12
    FEP Super Member erratic50's Avatar
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    Watch firing orders. It's determined by the cam.

    Advance an HO cam no more than 4 degrees for a really snappy street motor with tons of low end.

    Retard the cam not more than 4 degrees if you want it to rev more freely up top and make a touch more power with a little less bottom end torque.

    1.7:1 rockers on the exhaust help a lot. Not as much on the intake side.

    You can pick up a ton of power with a different cam from COMP these days. the stock cam or even letter cams were considered good back in the day but if you already have it apart no reason to leave the cam stock.

    Forged pistons are usually well worth the money. I've ran a fair amount of NOS through my 86 5.0L back in the day .... then drove it tons of miles. Mine has just shy of 455K and I beat the crap out of it every chance I get. I still haven't tore it down to freshen it- haven't needed to. Crap like valve guide are shot but the shortblock is still quite solid. I'm running E6 heads with headers and Typhoon EFI and 65MM TB and 70MM MAF. It pulls willingly past 6000 and is actually a bit hard to keep off the rev limiter at WOT with this combo.

    if you are going to MAF with an upgraded intake, go to a 93 Cobra ECU from the Mcparts store. This will allow 24lb injectors.

    Important with the 70MM cobra MAF...... I still run 19's with an A9L and mine is forever lean at high RPM. I had to increase fuel pressure to compensate, but now it tends to be a little rich at part throttle.

    Good luck on your build!

  13. #13

    Default

    The cam will work fine and will be the h.o. firing order. It doesnt have quite the lift to reduce lopeing. This was done due to complaints of nhv with the supercharged 3.8 motor originally put in the 89-90 cougar xr7. Think of the tbird as a personal luxury car for old people. It was the two door town car of its day.

    If you decide to throw 1.7 rockers on there, it should be pretty much the same as a cobra cam in the 93-95 cobras.

    The h.o. cams changed a bit every year. They got slightly better power or economy just about every year, but all the changes were very minor. I doubt there is 5hp between the best and the worst. All of them will work well and be compatible with the 86 speed density setup.
    2 1986 cougars (both 4 eyed and 5.0)
    1 1987 cougar

  14. #14
    FEP Super Member erratic50's Avatar
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    Default

    Great point SD vs MAF. I thought I read it would be converted....

    Agreed - HO cams varied. 89 HO with 1.7:1 will lope just a touch straight up or retarded if idle is less than 750.

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