4bt alternator bracket questions "help please"
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    Default 4bt alternator bracket questions "help please"

    4bt top view.jpg "this is my view for clearance" i can always route the intercooler pipe different if the cummins alt and bracket get in the way

    my 4bt first snapped the alternator bracket bolt, i replaced it, about a month went by and it snapped the bracket. My set is out of a chevy bread van so i have the GM alternator and freightliner long arm to hold it in place. i would like to go with a cummins configuration this time because of these 2 issues and the alternator has been rubbing into my intercooler pipe over time. i know i am at the right place and the people here can help me. i am trying to find out what year alt bracket and the arm dodge makes will bolt right on to my 4bt. mine is an 86 with turbo and inter cooler. i added pics to help explain. i am not a super good mechanic, just an average joe. any info will help and i thank you greatly for replying. i did replace my ac compressor not long ago and a 1995 compressor bolted right up. i have seen alt brackets with 4 bolts and an arm but mine has 3 bolts as the pics will indicate…wanted to know what years 5.9 parts may fit my motor. let me know what to do. also does anyone know how much these 3.9's will pull? if i need to post more picture please let me know or message me and we can talk. thanks
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    Last edited by flymflam; 11-27-2012 at 02:13 PM.

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    Looks like you're using the Frieghtliner mount (AC compressor above the water inlet), which uses a seperate lower alternator mount of a different design and slightly different location than what you've put together here. Id guess your alternator mounting was not quite aligned with the other pulleys, setting up a vibration that eventually fatigued the metal to the point of breaking the bolt and mount. Do a search for Freighliner mount here and you'll get the Cummins p/n's and pics of the assembly with proper lower alternator mount and L bracket support.

    Here you can see the Cummins lower Alternator mount, as it mounts to the top of the Freightliner (Medium Duty, F700, F800 etc.) mount with the two bolts at the top of the mount. There's also a small L bracket at the top that ties the whole mount assembly to the upper thermostat housing, to reduce twisting forces due to belt tension.

    http://www.4btswaps.com/forum/attach...9&d=1289498212
    Last edited by viking427; 11-27-2012 at 07:10 PM.

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    so is it best to convert my set up over to a cummins like on 6bt or find the frieghtliner mount? i have a 95 cummins ac compressor that is mounted below. i do know the alt bracket that snapped is the original 4bt. any help will do, thanks for the reply Viking

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    The Cummins a/c bracket puts the compressor so low a lot of apps find it into the frame rail. The mid-mount bracket is sought after and rare in the yards. I have a spare in the shed I've been saving for a rainy day. Just went out there and these are the #'s on the alt. bracket. The alt. bracket is 3921510 and the L bracket is 3924068. In addition to the trucks viking427 mentioned I believe you can find them on some Sterlings, and some school busses.
    Hope this helps, and if you decide not to use it do not throw or give it away.
    Al
    01 Dakota Quad cab, 4bt, NV 4500, NP241dhd , Gear Vender P style, 392's, HY35W, M&H spacer, 366 Gov. Spring.
    Being smart is easy. Just think of the dumbest answers and say the opposite. .

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    If you have a manual you will note the ac/alt mount is bolted in a particular order. If this sequence is not followed the manual states undue stress and breakage can occur. Did you follow sequence? I would also use a straightedge to make sure everything is in alignment. I've had to use shims and washers before. You'd be surprised how a 1/16"+ can f**k things up.
    69 Bronco 4bt/IC/HE221, NP435/203/205, 3.54 D60s OX locker F and Detroit R, military H1 beadlocks and 38" rubber
    "sealing the deal on this forum section as a whole..(and/or his entire membership here){which has been an issue before}ps: you were warned.... Redhedbronco reported for vulgarity character attack."-47Ford-1.5Ton Rats dwell here.
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    Yes, it looks like you are already using the Freightliner mount, just with an odd large "L" bracket at the top that I havent seen before. Not sure who had your stepvan before you, but it looks like they were creative - that mounting setup is not standard Fritolay/UPS/FedEx 4BT stepvan issue.

    Two potential problems - 1) What you're using as your lower alternator mount (that keeps breaking) is actually a 4BT/6BT upper alternator mount. 2) What you're using as your upper alternator mount (curved piece) looks too thin (gasser application maybe) to resist the torsional twisting and stress the thick ribbed belt and 4BT vibrations will apply to it.

    Id get my lower alternator mount down onto the top of the Freightliner mount where it belongs using the proper Cummins part numbers for both lower and upper alternator supports, which were designed for use with the Freighliner mount. Both oem brackets are beefy and hold the alternator solidly in its proper position and orientation to resist movement.

    Conchy has given you the Cummins p/n's for the lower support and the small "L" bracket. The only one you still need is the upper support - the long swept curved piece - that p/n should be in the archives here but Ill see if I can find it. And yes, hold on to that Freighliner mount, they're uber expensive new and used.

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    Curved support is # 3920862
    Al
    Ps,,,FYI the alt bracket bolts to the top of the large a/c mount. The L goes from the rear alt bracket bolt to the water inlet to stabilize and secure it.
    Last edited by Conchy Cracker; 11-28-2012 at 12:06 PM.
    01 Dakota Quad cab, 4bt, NV 4500, NP241dhd , Gear Vender P style, 392's, HY35W, M&H spacer, 366 Gov. Spring.
    Being smart is easy. Just think of the dumbest answers and say the opposite. .

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    cool guys thank alot. looks like i can find these parts. i think the reason i have such a long creative curved freightliner bracket is because it is not the right delco or other GM alternator. what is the proper alternator to put on this configuration? is my water inlet the right one for the this application also? points out towards radiator.. thanks again
    Last edited by flymflam; 11-28-2012 at 12:26 PM.

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    It's going to take a straight up water neck. The alt. Is a 21si but the delco off my chevy bread trk also fit. Not sure what it was, but prolly a 21si also.
    01 Dakota Quad cab, 4bt, NV 4500, NP241dhd , Gear Vender P style, 392's, HY35W, M&H spacer, 366 Gov. Spring.
    Being smart is easy. Just think of the dumbest answers and say the opposite. .

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    okay so i need to also get the waterneck that points straight up? any one have that part number? and is there an elbow that fits on it for the hose to point back towards the radiator? i mentioned before i am not much of a mechanic, just getting started actually. thanks cracker

    so far this is what i got: The alt. bracket is 3921510 is now 3930820 "number has changed according to a local cummins dealer" $30 and the L bracket is 3924068 $10 & The alternator bracket is designed for a 21si or 22si J180 style unit. seems an alternator will be around $120.

    now just need to clarify the waterneck problem. wonder why this configuration has the one i got?

    would the correct water neck part be: Cummins Water Inlet Connection 3903102?????? "this is where i need help now"
    will it take a different water neck than the one i have because the brackets are going to bolt on different and come in contact with the straight out water neck that is shown in the pictures?
    Last edited by flymflam; 11-28-2012 at 03:32 PM.

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    Here's the straight up 4BT (and industrial 6BT me thinks) outlet;

    http://www.ebay.com/itm/Cummins-Ther...#ht_165wt_1291

    They turn up frequently in the classifieds here and fleabay. Post a "want to buy" ad. Same with the Alternator.

    Just have a muffler shop custom bend lengths of 2" pipe instead of searching the earth over for just the right shape radiator hoses you need. Use a few 4" lengths of silicone hose or turbo "hump hose" to connect them up. They look cleaner, but you need to leave enough flexibility in them the shaking engine wont rip/bend/tear them.


    Here's the 89/90 Dodge 6BT thermostat outlet. It may also work for your setup IF it clears your upper (curved) alternator support;

    http://www.ebay.com/itm/Cummins-3-9-...#ht_230wt_1291

    No, that p/n 3903102 is the lower water inlet.

    READ READ READ and "search" is your friend. Answers to almost every question you've asked is in the archives, spend a few weeks in there til your eyes hurt, then come back to visit us

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    Flymflam, if you go to a Cummins dealer and have him bring up all the parts for the Ford/Freightliner ac/alternator mount you'll have close to 40 parts counting all the bolts. It is a heavy duty part with lots of bracing. The main part #'s are 3930822 for the ac block mount, 3920862 for the upper alternator arm, 3930820 for the lower alternator mount, 3921382 for the lower water inlet, 3285102 for the upper water outlet, 3930838 for the tensioner mounting plate, 3978021 for the belt tensioner,and numerous small parts. All together, if you bought it piece meal from Cummins it would be in the $500 range. Believe it or not, the most expensive part is the tensioner @ $149.02. This why most of us search for a used one. I paid $200 for a complete set up with both water necks which I felt was a fair deal. Several things you need to know about this unit. First, the bracket bolts to the block using the same holes many use for the passenger's side motor mount. Second, the alternator used with this set up must be a J180 mount found on 21si, 22si, 24si, and other delco alternators. Third, the Dodge ac compressor will not bolt to the ac mount. It is designed to accecpt a medium duty truck ac compressor. All in all this makes a very neat set up on a 4bt. Gets the ac away from the frame. When I said this thing is heavy duty, I would emphasize the heavy. With the ac and alternator bolted onto it the thing proboably is in excess of 100 lbs. Cummins doesn't make anything lightweight. If you are doing a Chevy install, the guys usually opt for the lower water inlet that points straight out instead of the 90 deg down version. Frames on those get very tight in that area. Here is a photo from one of the member's installs showing the set up.
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    I also make an alt bracket for the high mount ac set up that lets you use the dodge waterneck, I bet you could run the straight forward outlet through it also.

    I also had to make the bracket (not in pic) that attached the alt bracket to the water outlet, the Ford f800 part number wouldn't work with the dodge outlet.


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    Char1355,
    That sure is a purdy motor right there.
    01 Dakota Quad cab, 4bt, NV 4500, NP241dhd , Gear Vender P style, 392's, HY35W, M&H spacer, 366 Gov. Spring.
    Being smart is easy. Just think of the dumbest answers and say the opposite. .

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    Conchy, I though everybody would like that , including you. Best example of that set up I could find so I saved the photo. Love those bumble bee colors. You take good pictures.

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    That pix it has the turned down lower water neck. Had to go with a straight out to clear my frame.
    Thanks fer the compliment.
    Al
    01 Dakota Quad cab, 4bt, NV 4500, NP241dhd , Gear Vender P style, 392's, HY35W, M&H spacer, 366 Gov. Spring.
    Being smart is easy. Just think of the dumbest answers and say the opposite. .

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    The 90 deg turn down works ok with the Fords, but you usually need the straight out for GM's and other narrower frames.

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    with the set up you guys are talking about i will have to relocate my tensioner etc…. its already dropped in FJ60. i may need to fab what i can and go from there. i am going to post more pics and get more opinions from you guys, lots of help from all you already and i really appreciate it.

    this is the only issue i have with my conversion so i am hoping to fix it like it sits and keep going. only other issue is i get 25mpg and would like to hit 30 consistently. i am using the 4 speed toyota tranny.. etc.. has a ranger overdrive also.
    Last edited by flymflam; 11-30-2012 at 02:46 PM.

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    I have seen this set up with the tensioner in other locations but it doen't give as much belt contact with the crank pulley as the low mount tensioner. Cummins made many different alternator mounts besides this one. Since your's broke, I'd check the belt alignment. Just don't see tons of those breaking.

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    what a nice bracket

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