86 C20 SM465 to NV4500 swap

[WoodyK5C20]

Just purchased an 86 C20 with 5.7 @ 300 hp backed up by a SM465. 2100 rpm at 60mph and I watch the gas gauge sprint to empty at a high rate of speed. I have been looking into swapping the SM465 for an NV4500 and get lost in the details.

I have a hydraulic clutch on this 2wd truck with 3.42 gears. The engine RPM calculators say that with the NV4500 I can go from 60mph to over 80mph at the same rpm so that would help me not get run over in Atlanta traffic or give me much better gas mileage at 60mph.

Seems that there are different NV4500's out there in newer and older and Chevy and Dodge versions.

Looking for someone to let me know if the clutch setup/bell housing or driveshaft need adjustment/adapters to pull off this swap. Does the hydraulic clutch need to move or be adapted?

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Mainly looking to keep the hauling capacity and be able to drive it daily in Atlanta traffic.

 

[78C10BigTen]

Im affraid i have no info on this subject but welcome and very nice truck!

 

[SDJunkMan]

Welcome!

I too am thinking about a NV4500 swap, but I am planning to do it on a 4x4. Doing it on a 2 wheel drive should be pretty straight forward if you are already set up with a hydraulic clutch. Two of the major problems I have found are mating the transfer case and clearance between the slave cylinder and the front driveshaft, neither of which will effect you. You shouldn't have clearance problems with the floor since you already have a stick shift.

The Advance Adapters web site has a lot of information and discusses the differences in the 4500's.

 

[WoodyK5C20]

Thanks I'll check it out.

 

[84 M1008]

I think the advice adapters #712576 adapter kit is your best option.$418.00 The SM465 has a different bolt pattern to the bell housing. You can also have the stock bellhousing drilled and tapped to accept the NV4500. That would require a smaller centering ring I believe.

 

[Madhorn]

I have done this same swap in my 77 K10. Advance Adapters is a great source of information and parts. Just a couple things to keep in mind.
*you will need a bell housing
*the drive shaft will most need to be modified. I suggest a new one from a reputable shop.
*may need to modify the cross member.
*the shifter on the 4500 is further back so the floor will need some modification.

 

[Shorty81]

Welcome, darn nice Chevrolet you got there. I've had many 465s but never swapped em out.

 

[1985c20]

2100 at 60mph really isn’t revving that high. That’s probably a pretty decent rpm for the power vs mpg war. If you go any lower you will most likely be lugging it out and that will net you less mpg. The optimal cruising Rpms depends on how the motor was built. But you should consider the price of gas vs the price of the conversion. Usually it takes years just to break even

 

[mcarlo86]

2100 at 60mph really isn’t revving that high. That’s probably a pretty decent rpm for the power vs mpg war. If you go any lower you will most likely be lugging it out and that will net you less mpg. The optimal cruising Rpms depends on how the motor was built. But you should consider the price of gas vs the price of the conversion. Usually it takes years just to break even

I would agree with this. 3.42 gears with those big tires is already in the realm of "economy/highway" gearing. I think you may find that after spending a lot of money and time doing the swap, you will end up driving in 4th gear most of the time unless you have a tail wind. I had a '90 Chevy with 3.42 gears with a 5 speed manual when I was in college back in the day (with 235 75R15's - which is quite a bit shorter than your 3/4 ton has) and I still rarely used overdrive unless the driving conditions were ideal. I noticed that when I would shift into OD at 60 or so, I would actually have to use more pedal (ie more gas consumption) to maintain speed than when I was in 4th. Just my 2 cents. Sweet looking pickup though!

 

[SquareRoot]

Do it. It'll be the perfect excuse to build that torquey 383 or better yet- 6.0 swap.

Welcome to the Rabbit Hole.

 

[WoodyK5C20]

2100 at 60mph really isn’t revving that high. That’s probably a pretty decent rpm for the power vs mpg war. If you go any lower you will most likely be lugging it out and that will net you less mpg. The optimal cruising Rpms depends on how the motor was built. But you should consider the price of gas vs the price of the conversion. Usually it takes years just to break even

At 60mph I am going at least 15mph slower than the slow traffic in Atlanta. Normal cruise speed in the Mercedes diesel is around 85 and to not be dangerous if I am running around 80 I am pushing 2700-2800 rpm's and I don't like pushing the 5.7 that hard all the time. In normal driving locations the SM465 is just fine.

Thanks.

 

[mcarlo86]

2700-2800 rpms isn't pushing it hard at all for a small block. That's right in it's sweet spot. My '68 C10 with a 327, 3.73's, SM465, and 235 75 15's runs over 3K at 65-70. Been driving it like that for 25 years. Just saying that you have a truck and the gearing set up you have is about right for highway cruising as is. You could take the money that a OD swap would cost and easily buy a decent car for daily driving too. Just sayin'.