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6.2 to BBC swap

Duntz00

Duntz00

1/2 ton status
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I've got a 82 K25 with a factory 6.2/465/208 setup, I'm pondering on pulling the 6.2 and putting a 366 BBC Chevy in it out of a log truck.

Yes I know the 366 isn't a very desirable motor but it will be cheap enough, I think... :dunno:

So, is there anything that needs to be changed like the engine crossmember, wiring harness, etc.?
 
The 6.2 is set up the same as far as motor mounts,etc,as any small or big block,it should bolt right up OK...the 366 big block I believe is a tall deck motor,that has many "one off" parts that wont interchange with other big blocks like a 396,402,454--like the intake for one,and they have 4 ring pistons,different connecting rods,and various other differences....it will likely be a tight fit on the drivers side,the valve cover being taller may interfere with the firewall,nothing a few hammer blows wont fix..

A 6.2 may lack some wiring for things like a carb idle solenoid ,an HEI distributor,but you can use the injector pump pink wire to power the HEI and the other wiring like the alternator harness are the same..you can "delete" the glow plug wiring if you want too,it wont be needed any more..

Many consider the 366 a "boat anchor",(some say the same thing about 6.2's too..:blush:)..but they are a pretty rugged engine,used in many 2-1/2 ton trucks that rack up lots of miles at higher rpms..they might not be stump pullers,but they are hard to kill..
 
If you got a good 366 i'd use it... perfect for a torquey 4x4. We have one in a 87 c60...gutless with 400 bushels in the box. Lol! But it gets it done!

What Bob said sounds right to me. :waytogo:
 
Why do you want to swap out the 6.2? Just asking as comparatively those two motors are very close in performance. The difference being fuel economy. The 366 will drink a LOT more fuel. If the 6.2 is gone then ok but I have seen a good number of them come to life with just a little work. New injectors and a once over has made more than one 6.2 live another half a million miles. Injectors perks one right up. Just my .02... I might be biased a little.
 
ya 366 and 427 from big trucks are a bit fun . they take there own front drive brackets for stuff . there also made for a lower rpm scale of power range .

as said if the 6.2 is dead and you have all the parts then swap it i guess . but there will be some mods involved .

i am looking for a good running 366 or 427 tall deck that had a water cooled air compressor for air brakes on it from 1986-1990 vintage . . .
 
Main reason for doing it is looking for a little more power, really want to put 6.0 ls motor in it but that's not in the cards....

There is nothing wrong with the 6.2 other than needing a fuel line fixed. Injectors were changed at 80k, truck has 180k on it and yes it is the actual mileage because I bought it from the original owner. They confirmed the mileage was accurate. I've actually got a set of long tube headers for the 6.2 that I never installed.

@sweetk30 I will check the 366 truck to see how it is setup, it is a complete truck with a 5speed manual and 2spd rear.
 
another thing a old timer mechanic told me was every 6.2 he did a pump/injectors/ turn up the pump timing got a timing chain set. about everyone he did was whooped .

when he gave them back the guys would say oh my wow its got so much power now.
 
sweetk30 said:
another thing a old timer mechanic told me was every 6.2 he did a pump/injectors/ turn up the pump timing got a timing chain set. about everyone he did was whooped .

when he gave them back the guys would say oh my wow its got so much power now.
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I'd say this one is probably due a timing chain, I probably need to change the glow plugs too. It's very hard to start in the winter unless it is plugged in.
 
I think you'll find that although the the 6.2 diesel and 366 are different in hp ratings, the torque ratings are really close. D
 
Agreed--I see so many 4x4's with engines that have 3/4 race cams and intakes & carbs that would be much better suited for a Camaro or other light car for drag racing,than a truck that will spend much of its life pulling weight and driven around town or at normal highway speeds..

One guy I know spent thousands on a 396 he had "sitting around" ,he had it bored out .030 over,I told him that was risky,they were so thin to start with--after a crack was found in one cylinder,it was determined it was a 402,probably a 396 that GM "goofed up" and bored out to a 402..came out of a '71 Chevelle..

He decided to have it sleeved,and put it in his '73 K5 with a cam that was practically "full race" and some other heads that were the rectangular port ,and a Weiand intake that had an open plenum and the Holley 750 double pumper mounted diagonally on it..a bunch of swap meet parts he got at a good price,but poorly suited for his needs--he had a cabin up in maine and used the K5 to go there every weekend and do some off roading ..

The engine sounded awesome,but coupled to an SM465 and 3:08's,it was a herky-jerky slug around town,it idled at 1500 rpm (barely),and once you got to open it up above 45 mph the thing took off like a rocket..low speed driving "around town" would foul plugs eventually,and it was no fun to drive anywhere but on the highway over 60 mph..

I let him drive my bone stock '74 C-10 with a 454 & TH400 ,he said "wow,I guess I should have left the engine stock,that thing pulls like a freight train right off the line!--(it too,had 3:08's)...

When I told him I had gotten almost 15 mpg with the 450 cfm Holley Economaster I put on it on long trips,he really got mad--"I'm lucky to get 5-8 mpg!"..
I told him he should have left the peanut port heads on it,they flow plenty well enough for "normal" driving,and that I would have gotten a Competition Cams "off road RV and towing cam"...not a lumpy "race car" cam.....and kept a Q-jet & the intake on it--he did swap those back on it after his Holley gave him some grief,and said it did help a lot,was better off road and got a little better gas mileage..


Everyone seems to think a 6.2 will get over 20 mpg...not in my experience--maybe a 1/2 ton 2wd with tall gears or a 700R4 will,but my '82 K2500 with a TH400 is lucky to get 16 mpg if I drive like grandma..
I have had big blocks in the past that could get almost that many mpg...all things considered I'd rather have a BBC in it that could actually spin the tires,and pay a few bucks more for gas--and it would start in the winter with no hassles..
 
My 6.2 recently got 17.3 mpg normal highway driving 20 miles each way to work with 35s 4.10 gears and a 700r4 and 3/4 ton axles. It's a slow ass underpowered turd on hills. On a long, big mtn pull recently I dropped from 65 to 35(my wife was like OMG this is embarrassing). If I did the injectors/pump and a turbo I'm sure it will be perfect. I love it for low speed lug it around on the trails stuff. Just needs a little more nuts when you want it. Plus I don't have to worry about buying any of that fancy fuel injection stuff the gasser guys all need and I can burn hyd oil/transformer oil/atf/whatever I want in it.
 
My 6.5 regularly gets 17-18, my 6.2's average about 14-16 most of the time and we pull hills everyday.

I think the actual cost of the swap would be about the same as just freshening the diesel. That was really all I was trying to convey. I too get Faith's up in the " grass is greener" thing with engines. I always and will always prefer diesels to gas engines. Lots of reasons and history there but in the end it has to make sense to you. If it does then rock on.
 
I just filled up my truck yesterday--I had driven it 151 miles,most all of it under 45 mph on "back roads",and city driving stop & go..
I fill it right to the gas cap when I fill it,and mark down the mileage because the fuel gauge doesn't work (it buries the needle a 3 o'clock,sending unit is NG)...it took 9.282 gallons to fill it,which comes out to be 16.1 mpg...

It gets the same mileage pretty much no matter what type of driving I do,or it it is loaded down or empty,just like every other GM truck I've had..no matter what engine you have in a square body 3/4 ton 4x4,a 3+ ton "brick" ,it is unlikely you'll ever get much over 16 mpg ..
I do know guys with TBI 350's in later model 1/2 tons getting 17+ mpg consistently...and their trucks wont bog down on hills..

I feel GM should have just used the Isuzu straight six diesels they had in larger "straight jobs" instead of making the 6.2...they were much better engines and more powerful,yet they get about the same fuel mileage..
 
Agreed. TARussell had an '02 w/ manual & 4.10's and it got as good of mpg's towing a truck than mine (manual w/ 3.73's) gets unloaded. :doah:
 
nvrenuf said:
Agreed. TARussell had an '02 w/ manual & 4.10's and it got as good of mpg's towing a truck than mine (manual w/ 3.73's) gets unloaded. :doah:
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Do you have a chip in yours? A good towing tune will make all the difference in the world for fuel mileage. My 24v was at about 16-18 before I installed a simple super chip tune. Now on economy it sees 20 plus. Towing tune helps a good bit too.
 
Vombrown said:
Do you have a chip in yours? A good towing tune will make all the difference in the world for fuel mileage. My 24v was at about 16-18 before I installed a simple super chip tune. Now on economy it sees 20 plus. Towing tune helps a good bit too.
Click to expand...

No, it's bone stock. I'd like to get a Smarty Jr for it but every time I have the money I always seem to spend it on my Blazer. LOL
 
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