1. Registration trouble? Please use the "Contact Us" link at the bottom right corner of the page and your issue will be resolved.
    Dismiss Notice

3.8 Grand Nat question

Discussion in 'Early CJ5 and CJ6 Tech' started by schardein, Mar 25, 2005.

  1. Mar 25, 2005
    schardein

    schardein Low Range Therapy

    Success, MO
    Joined:
    Aug 11, 2003
    Messages:
    553
    Not sure if this is the right place....

    Some may know that I got a little carried away during my last off road trip, and the results are in: Spun rod bearing #6 (furthest from the pump) and scored rod bearing #4. So at the least I am looking at needing a new crank as mine is .010/.010 already and don't want to go anymore undersize.

    BUT, this guy has a 3.8 turbo Grand National motor he wants to sell me. Questions:
    1. Do these run lower compression because of the turbo?
    2. If so, are the heads different or the pistons?
    3. My normal intake will bolt on?
    4. Will a turbo cam run ok without turbo, or replace it?

    If it is the pistons, I won't pay as much since I will need to replace them. If it is the heads I can use mine. Or if the compression is the same I will really be in business.

    Any other points I missed please advise!
     
  2. Mar 25, 2005
    vanguard

    vanguard

    1. Do these run lower compression because of the turbo?

    Compression should be higher due to the turbo.

    2. If so, are the heads different or the pistons?

    Pistons are probably different, as are the crank and the connecting rods. Usually better/more material and stronger. Pistons may have different or extra rings.

    3. My normal intake will bolt on?

    Should. I'm assuming you don't want to run the turbo.

    4. Will a turbo cam run ok without turbo, or replace it?

    Hard to say. Others probably now more.

    Hope this helps.
     
  3. Mar 25, 2005
    mb82

    mb82 I feel great!

    Charlottesville Va
    Joined:
    Mar 17, 2003
    Messages:
    2,706
    i think he ment the compression when the turbo is not working or not there.
     
  4. Mar 25, 2005
    vanguard

    vanguard

    I understand. Without the turbo compression will be lower, but all the parts are engineered to withstand higher compression provided by the turbo.
     
  5. Mar 25, 2005
    Heimbig2

    Heimbig2 Member

    Richland, WA
    Joined:
    Jan 13, 2003
    Messages:
    195
    For awhile the cam timing was set 8 degrees off on the turbo models, not sure on the grand national ones.
     
  6. Mar 25, 2005
    michigan_pinstripes

    michigan_pinstripes I'm not lost, I'm wandering

    Clarkston MI...
    Joined:
    Aug 20, 2003
    Messages:
    605
    It will work just fine for you.

    The compression should be 8.5:1 on the turbo. The lower compression is needed because the compressor adds it back in under boost ;)

    Other than that, you can run the engine as-is with a EF intake and carb of your choice. You will gain a stronger crankshaft and rods. Compression is marginal but not that big of a deal IMO.

    A turbo cam is relatively mild and you shouldn't even notice. Specs are really similar to a naturally aspirated (non-turbo) motor.

    Don't be afraid of a .020/.020 milled crank. Many guys race this crank without failure.

    Get the serial number off that turbo motor and post it. Its located on the drivers side of the block under the head. What is he asking for it and what comes with it?
     
  7. Mar 25, 2005
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
    Messages:
    23,596
    Greg, what's your budget? How much compression did you have before the spun rod?

    Here are the Buick pistons: http://www.beckracing.com/slvpg13.htm This indicates the
    turbo engine only has a half-point lower compression ratio (at atmospheric).

    You can install a crank kit without removing the engine. A reground crank is pretty much de rigueur for a cast crank. If it were mine, I'd want to pull the engine and wash out all the oil galleries though. You may be able to get back a 10/10 crank with no core charge - depends on the condition of your crank. You will also (probably) need a rod to replace the one with the spun bearing. Hone the cylinders, reuse your pistons, new rings, new rod, crank kit, gaskets ... I think you can do it for less than $300.
     
  8. Mar 25, 2005
    w3srl

    w3srl All-around swell dude Staff Member

    Port Orange, FL
    Joined:
    Nov 6, 2002
    Messages:
    4,275
    I agree with everything Tim said except the part about replacing the crank with the engine still in the vehicle. While it can be done, and I've done it with an L-head 4, it is a real bear to do it, keep everything clean and get it right. It is much, much easier to accomplish with the engine out of the Jeep, and on a stand IMHO.

    The thing that I would be concerned with, other than how much bearing metal crap is now lying in the oil galleries is what the actual clearances are. The only way to check this easily and accurately is to torque the mains and the rods and use plastiguage to check the bearing clearances.
    This means installing, checking, reinstalling, checking, etc. Much, much easier out on a stand than on your back under the Jeep.

    You can do this job pretty inexpensively if you only need to do the crank and rods. This is the route I think I'd go, unless you can get that GN engine w/ turbo for sheep. ;) I know you have a big move pending, so I'm sure that enters in there too...
     
  9. Mar 25, 2005
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
    Messages:
    23,596
    Yeah - my mistake - I had a lapse, rushing off to a meeting. I was thinking rod bearings, not mains. Pull the engine. It's really easy to pull a CJ engine anyway.
     
  10. Mar 25, 2005
    w3srl

    w3srl All-around swell dude Staff Member

    Port Orange, FL
    Joined:
    Nov 6, 2002
    Messages:
    4,275
    You're not losing it Tim, he did say rods. But if the rod bearings are trashed, the mains aren't far behind...
     
  11. Mar 25, 2005
    michigan_pinstripes

    michigan_pinstripes I'm not lost, I'm wandering

    Clarkston MI...
    Joined:
    Aug 20, 2003
    Messages:
    605
    BTW --I have a .020/.020 crank here that I pulled out of my "freshly rebuilt" turbo motor (never run, just assembled). It wasn't a turbo crank so I opted to grind another one.

    $50 + ship to *gulp* the islands. I think you could grind yours for $100 which would be about a wash in cost.

    Go .020/.020 and get it balanced to the flywheel.
     
  12. Mar 25, 2005
    schardein

    schardein Low Range Therapy

    Success, MO
    Joined:
    Aug 11, 2003
    Messages:
    553
    Thanks for all the replies. The motor is out and apart. It had been rebuilt, balanced and bluprinted about 6 years ago when I got it. Let's just say I trust the guy that sold it to me. I pulled it myself so I know the history. I am really disappointed it came apart like this.

    I am strongly considering a complete teardown (heads and pistons/rods are still in it) hot tank the block, clean the galleys, have the rods checked (even the spun one looks alright) and going with a new 10/10 crank. Reuse my rods if the shop says they are good, and reuse my pistons, rings, everything else.

    Someone told me buicks have terrible oiling systems. The oil pump had a "wear plate" installed. I did notice that my oil pressure would be good at startup/warmup, but drop off as the motor got fully hot. Been doing that for about 2 years. Didn't think anything of it cause I always had at least 10 at idle and it came up when on the gas. Rule of thumb I was taught is 10 psi for every 1000rpm.

    Anyway, I think I am going to replace the timing cover as well, I have found some advertised and having a hi volume oil pump.

    On the other hand the turbo motor is supposedly a fresh rebuild and then sat for 6-8 years. I have no idea what he wants (he won't say) and not sure what to offer. It is basically a long block, complete but no accessories. Didn't get a good look, but no flywheel, exhaust, only the bottom piece of the intake (I think they were 2 piece??). Would $200 be an insult? I guess it depends on what I find when I tear it down....

    I run the heavy 225 flywheel rebalanced to the 231.
     
  13. Mar 25, 2005
    schardein

    schardein Low Range Therapy

    Success, MO
    Joined:
    Aug 11, 2003
    Messages:
    553
    Steve, about the move... the interesting thing is I don't know yet when, and I have this as well as a 95 YJ tub sitting in the driveway that is supposed to go on my 83 cj7......Ever have that feeling in the pit of your stomach this might not be good...
     
  14. Mar 25, 2005
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
    Messages:
    23,596
    Well, consider what you can fix your engine for, then offer accordingly. There's some risk involved in using an engine you personally have not rebuilt, so that's a factor too. Not saying that I'd reject the GN engine because of that, but it should figure in the price - more risk, lower price.

    If you hot tank the block, the hot tank solution erodes the cam bearings, so you'll have to have them replaced. I'd lean toward pressure wash (either at the shop or at the car wash) and rifle brushes through the oil galleries.
     
  15. Mar 25, 2005
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
    Messages:
    23,596
    Our friend D. Datson says "Also recommended for heavy use is a better oil pump. Stock pumps are just adequate for stock driving but not for higher RPM." "Rods, mains and valvetrain are all fed from the lifter gallies (sic) so Buick engines are very sensitive to low oil pressure." (Recommending the Kenne-Bell HD oil pump).
     
  16. Mar 26, 2005
    schardein

    schardein Low Range Therapy

    Success, MO
    Joined:
    Aug 11, 2003
    Messages:
    553
    I can get the turbo engine, block and lower end only for 175. It does not have an oil pan, and mine won't fit cause it is a 20 bolt block vice 14.

    Did some research. All the v6s were 8:1 compression, even the turbos, according to chiltons and motor manuals.

    The heads are 25518445 which is apparently very common, looking at the buick v6 history page. I bet mine are the same and plan to reuse them.

    The block is 25524140, which translates to 1985 rwd buick, NON TURBO, again according to the v6 page. Interesting, the turbo intake and valve covers are on the motor. On the back of the block is cast 85 (year?) then 3.8, then 4.1 (the bigger v6 available 81-84 or so.

    So I will look at the crank tomorrow, if it is not a turbo crank with rolled fillets I may have to lower my offer.
     
  17. Mar 27, 2005
    michigan_pinstripes

    michigan_pinstripes I'm not lost, I'm wandering

    Clarkston MI...
    Joined:
    Aug 20, 2003
    Messages:
    605
    That is the same block I have. It is a late 1985 20 bolt turbo block. All cross references show the 20 bolt in 1986-87 only. The 1986 "109" block gained a turbo return hole and the lifter galley had more meat with oil drainback holes drilled, not rugged cast like the 140. This 140 apparently was a transition block to the "109" The guy I bought the "140" from claimed he pulled it out of a 1985 Grand National he parted out and sold the rolled fillet crank. I'll be interested to see what you find --it should be a turbo crank. An original rolled fillet crank (un-cut factory installed) is worth $200 minimum on the used market. The 445 heads was the final casting on the RWD carb and turbo motors. Good stuff. Pocket port those heads for great results. My engine guy is going to bowl hog the underside of the bowl below the valves for $50. This is an old Smokey Yunick trick for 25-30 HP (per Pat Ganahl's book).
     
New Posts