Author Topic: Gas tanks and spring swaps  (Read 1093 times)

Offline 1967KaiserM715

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Gas tanks and spring swaps
« on: January 12, 2019, 03:28:15 PM »
I am planning on doing a HD 63/64 inch rear spring swap from a later 1 ton truck into a 1986 Chevy K30. this is a single cab, 8 ft bed truck with the 56 inch rear springs currently and a 20 gallon tank.

Right now it looks like I need to move the front spring hanger forward 10", this will of course interfere with the 20 gallon tank. If I do a 16 gallon tank can that gain me the ten inches needed to clear? on other words, is the 16 gallon tank 10 inches shorter then the 20 gallon?

Worse case, I have seen some guys to an inside frame rail tank swap from later cab and chassis dually trucks, frame rail width actually remains the same for all cab and chassis dually trucks, at least to 2006/7 because they all used a 40.5" spring perch width.

Thanks in advance.
Current Vehicles:1985 GMC K10(Daily) 1991 GMC K2500(Daily) 1975 Beetle(not running) 1985 Mercedes 300D(not running) 1952 M35    1967 M715(not running)
 1986 Chevy K30(under repair)

Offline 75gmck25

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Re: Gas tanks and spring swaps
« Reply #1 on: January 16, 2019, 08:51:22 PM »
I don't know the length of the 16 gallon tank and whether it would get you the clearance you need.   However, there are stock GM tanks in 25 gal, 31 gal and 40 gal that fit in the back between the frame rails, if you remove the spare tire brackets.   The 25 gallon was used on some cab and chassis pickup trucks, and the 31 and 40 gallon tanks are from the Suburban.  I've run across several articles online from folks who made the conversion and put the gas filler up just inside the back of the bed near the tailgate.

Bruce

Offline 1967KaiserM715

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Re: Gas tanks and spring swaps
« Reply #2 on: January 18, 2019, 04:55:05 PM »
So I finally found some info, and I'm probably going to screw up the values, but a 16 gallon tank is roughly 43 inches, a 20 gallon is 56 inches.

 Final spring measurements put me at 6 inches forward.  So a 16 gallon will fit fine, with probable room to spare.

I am trying to avoid a rear tank to maximize rear ground clearance, but I'm still going through some planning changes as I move forward with this project.

Some pictures after relocating the front spring hanger. The rears did not need to move, and I may do a shackle flip in the future, but this only moved the axle rearward 1/2" at best.

I measured multiple times, there is at worst only a 1/16" discrepancy from side to side, all depends on where and how I was measuring.

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Current Vehicles:1985 GMC K10(Daily) 1991 GMC K2500(Daily) 1975 Beetle(not running) 1985 Mercedes 300D(not running) 1952 M35    1967 M715(not running)
 1986 Chevy K30(under repair)

Offline 1967KaiserM715

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Re: Gas tanks and spring swaps
« Reply #3 on: January 18, 2019, 04:57:55 PM »
Nothing is 100% finished either, I still need to move the bottom mount and drill some more holes, but I needed the truck off the trailer and able to roll around.

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Current Vehicles:1985 GMC K10(Daily) 1991 GMC K2500(Daily) 1975 Beetle(not running) 1985 Mercedes 300D(not running) 1952 M35    1967 M715(not running)
 1986 Chevy K30(under repair)

Offline VileZambonie

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Re: Gas tanks and spring swaps
« Reply #4 on: January 18, 2019, 05:00:28 PM »
Why are you putting in longer springs?
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Offline 1967KaiserM715

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Re: Gas tanks and spring swaps
« Reply #5 on: January 18, 2019, 05:39:37 PM »
Why are you putting in longer springs?
Flex, and softer ride without sacrificing load carrying capacity.

I was going to do a thinner spring pack, with more overload springs, but talking with my local spring guy with my plans, he recommended longer springs, the length helps give a softer ride.

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Current Vehicles:1985 GMC K10(Daily) 1991 GMC K2500(Daily) 1975 Beetle(not running) 1985 Mercedes 300D(not running) 1952 M35    1967 M715(not running)
 1986 Chevy K30(under repair)

Offline Jerr-conn

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Re: Gas tanks and spring swaps
« Reply #6 on: January 29, 2019, 11:13:02 AM »
Kaiser man--- you realize you will have to shorten your driveshaft about 5"" also? Hope you
Get the right gas tank.good luck. Look forward to seeing finished pics.    Jerry
Jerry

Offline Jerr-conn

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Re: Gas tanks and spring swaps
« Reply #7 on: January 29, 2019, 11:21:55 AM »
Kaiser man---remember, you will probably have to shorten your driveshaft and relocate your rear
Shock brackets. Send finished pics.
Jerry

Offline 1967KaiserM715

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Re: Gas tanks and spring swaps
« Reply #8 on: January 29, 2019, 12:21:41 PM »
Kaiser man---remember, you will probably have to shorten your driveshaft and relocate your rear
Shock brackets. Send finished pics.
Nope, axle location remains the same, I was originally thinking both the shackle mount and forward spring mount would have to move, but using 88-98 style 63/4 inch springs, the axle pin to rear shackle measurement remains 32", same as all 56" springs from 73-87 trucks, only the leading edge  to axle pin changes. This means only the front spring hanger has to move, and everything else can remain stock. This was also one of the reasons why I decided to continue with a spring length swap.

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Current Vehicles:1985 GMC K10(Daily) 1991 GMC K2500(Daily) 1975 Beetle(not running) 1985 Mercedes 300D(not running) 1952 M35    1967 M715(not running)
 1986 Chevy K30(under repair)