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Discussion Starter #1 (Edited)
79 Chevy K10 4BT Conversion

I am in the middle of a 79 Chevy K20 SWB "restoration". I bought it running with a 400 sbc, th350, and np203. I wanted to install 6 cyl. cummins but was scared away by the weight and size. I know it has been done. I changed everything after reading this and other forums about the 4bt.

I rebuilt the 400 and even bought a 700r4 and np205. Every thing was in the chassis and even had the exhaust run. Once i made up my mind I yanked the motor and put it in another truck.

My current plans are to run a 4BT, SM465, np205, and a gearvendors over/underdrive

I plan for this to be a daily drive that will some bassboat and jeep towing.

I plan on running 3.73's and 33's to start and maybe go up to 35's to get the highway rpms closer to 1800 rpm (i gather this is the sweet spot). I have a few pics but do not have a motor yet.


Tranny Gear 0.78
rpm 2000
gear 3.73
tire size 34.5
mph 70.55561971


What do you guys think?
 

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Are those numbers for 2000 rpm using the GV overdrive?
(not familiar with the SM465 top gear ratio)

If it is, then I would go to 3.42 R&P.

I am planning on the same overdrive which gets more power
to the rear wheels, much like a semi-truck. Real good for
towing, and great for highway mileage. (gears are electronically
selectable on the fly when using an automatic, not sure with
the manual).

Any pics of your GV and adapter?
 

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sounds like you have a great vehicle in store. Post some pic's and good luck!!
 

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Discussion Starter #4
Are those numbers for 2000 rpm using the GV overdrive?
(not familiar with the SM465 top gear ratio)

If it is, then I would go to 3.56 R&P.
The following chart is from Gearvendors's website:

M465 4-SPEED MANUAL
Axle Ratio 4.56 4.10 3.73 3.42
Trans Ratio Final Drive Ratio
1st 6.55 28.91 26.86 24.43 22.40
2nd 3.58 16.32 14.68 13.35 12.24
Over 2.79 12.73 11.45 10.41 9.55
3rd 1.70 7.75 6.97 6.34 5.81
Over 1.33 6.05 5.44 4.95 4.53
4th 1.00 4.56 4.10 3.73 3.42
Over 0.78 3.56 3.20 2.77 2.67

Sorry I tried to create columns but it all squished back together in the post.

I had already installed 3.73's for the original plan with the 400sbc and 700r4. I will keep them to experiment. From what I have read the "sweet spot" is for a stock 4bt and any power increases may change that fuel consumption curve. I don not plan do do much to it but I do want to upgrade to an aftercooler and relocate the turbo like Mootank has on his ranger. Tweek the pump and so on looking for 400 ft lbs. I will keep the 3.48's in mind.

I am finally getting close to having enough money to buy a motor but no GV unit yet.
 

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I went to http://www.f-body.org/gears/ and punched in some numbers.

The 3.42 at 1800 will get you 69 mph in 4th-over and 54 in 4th. The 4bt has adequate torque to cruise on level surfaces with the sweet spot around 1600-1800 for mileage.

3.42 at 1600 will get you 62 4th-over and 48 mph in 4th.

3.42 at 2000 will get you 60mph in 4th, (just select out 4th-over).

Definitely worth considering for getting the most out of GV overdrive and a diesel, which, believe me, are big investments.
 

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Discussion Starter #6
A little progress

I plan on adding info like some others have to keep a log of the project. I would put the cost in there but I have changed my plans so much I do not have a clue anymore.

Over the weekend I sand balsted the gas tank support frames and painted them with POR 15. Has anybody used this long enough to see if all the claims are true? Set the new tanks and strapped them down. Installed the original (to me) skid plates. This will be a great test for some of the POR15 claims on durability. They were really rusty. I washed them and let them dry and them painted with out sandblasting.

I will post pics this evening.

I also talked with Gear Vendors last week. Really nice folks. I want to run a Flight stick grip from an F4U Corsair as the shifter handle. (I had the Idea before the Tuttles on American Chopper). I plan to use the trigger for the OD switch but after talking to GV I had to do some thinking. The system requires a toggle switch rather than a momentary contact. An electrical eng. I work with suggested a spequenced relay. Click ... and it stays on Click again ... and off. Problem solved. I need to figure out how to use the "bomb" button.

NO 4BT yet. I may have to trade or sell something.

Next task will be to plumd the fuel lines and get the cab back on the truck.

Are there different types of lift pumps on the cummins? If so how many lines do they require? 1,2 or 3?
 

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Are there different types of lift pumps on the cummins? If so how many lines do they require? 1,2 or 3?
You've got 2 different mechanical lift pumps, one's a standard diaphragm type, the other a piston type. (Then you can also get into the aftermarket stuffs, but..)

As far as fuel lines go, you need one supply and one return, no matter which pump you have.
 

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Discussion Starter #8 (Edited)
Tear down picks

Here are a couple of picks of the truck coming apart at xmas 05. I will get some of it now in the daylight soon.

Machman Thanks for the info.
 

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Discussion Starter #9 (Edited)
Progress

No 4bt yet, but when I do finally get one I can get right to making mounts. I just finished rebuilding a SM465 and NP205. I install a twin stick kit from JB Custom Fab.

I sprayed the bottom of the cab with the lizard skin stuff.

Next step is to smooth the firewall and paint it black. I then plan on spraying the Lizard skin sound control and ceramic bead stuff inside the truck.
 

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hey, I own a 75 Chevy k20, 6" lift, and 35's. I plan on following this thread and I am looking forward seeing you finish it. Your truck is looking good. Keep up the good work, cause I will need it. Thanks
 

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I did my swap about a year and a half ago, and I love it! Did it in about the same truck only an 82 model. I had a SB 400/SM 465/205 before, now I have the 4bt/Gutbag/Dana 300 (first chance I get I'm slappin' a NV4500 in). The 4bt is 1,000,000 times better than the 400 ever thought about being, and 23 mpg beats 8mpg any day! If you have any questions let me know. Looks good so far.:)
 

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Discussion Starter #12
82 Model

Hot Dawg,

Sounds like a sweet rig. Do you have any pictures?
 

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Slick1725

Yes, I've got a few pics. I'm in Korea right now so give me a few days and I'll try to post them up. We're having a war exersize all this week and I am in a gas mask gettin' shot at!:nuke: I'll try to hook you up this weekend though.

You might have to send me your email address, I don't know how to post pics on this site.
 

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Discussion Starter #14
Long time due!

I have been working when I can on my truck project. I have sold 2 vehicles, a bass boat, and a 4 wheeler. Traded another to get rid of payments and we had a baby. So I have slowly but diligently been progressing on my truck.

Short summary of updates:

-Got the body back together sanded down and epoxy primed.
-Sprayed in lizard skin sound and heat stuff.
-Blacked out under the hood
-Converted to hydraulic clutch
-Installed a used Gearvendors Overdrive
-Just finished driveshafts
-Found 3 more vintage rims so I could have a spare

Whats to come:

-I think I am financially ready to buy a 4BT finally. That is the next purchase.
- ORD style front Bumper and a rear with a swing away spare carrier.
- Continued work on body and paint.

I have pretty much set my goal for the truck but it will take one more "stimulus" check (tax return) to get a lift from ORD, tires, and AC.

I will be posting more pictures. The 1st one attached is after much stripping, sanding, and scraping. The other is an alternate use for an engine hoist.
 

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Discussion Starter #15
Pictures

Took some pics this afternoon.
 

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Discussion Starter #16
Pictures

More pics - Manual Hydraulic clutch conversion
 

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Discussion Starter #17
Pics

Overdrive and under the truck
 

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Looks good
I question the gear vendors od? If truck is for around town and not for distance driving ok. I can tell you from experience that the gear vendor will only last 120,000 to 150,000 max if you use your truck as a truck.
It is hard to get parts for them when you are on the road. and yes I changed the oil and cleaned both filters every 10,000.
jim
 

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Discussion Starter #20
GV

What caused your failures/what failed? Was the truck in operable or did you just loose OD?

I will probably not put more than 20K on the truck each year and I do not intend to pull much other than an aluminum boat or a car every now and then.

If I get into long road trips I could stash a longer drive shaft and the original fixed yoke.

With a little more info on your issues I might be able to do a preventive rebuild or something at so many miles.

Thanks for the input
 
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