Hey guys. I have an 84 k5 that I am rebuilding to be a daily driver. The plan is to run 35s and 4 inch lift. Transmission is a th400. I have 2 very nice but very different motors and can’t make up my mind on which to use. I have a very low mile 6.2 diesel that runs perfect and a freshly rebuilt 400sbc. My daily commute is about 20 miles of winding country road with a top speed of 60 but mostly around 50. Give me your thoughts. Thanks for reading!
CK5
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Help me decide on a motor.
- Thread starter Texar2
- Start date
MEMO43
1/2 ton status
I would run the 400sbc
parts galore at your favorite parts store
less swapping out
ie cooling system
fuel tank
fuel delivery system
hydro boost for brakes?
they will both be around same mpg.
what motor was in it before sbc of sorts?
parts galore at your favorite parts store
less swapping out
ie cooling system
fuel tank
fuel delivery system
hydro boost for brakes?
they will both be around same mpg.
what motor was in it before sbc of sorts?
X2 on the 400 SB...
I had one I pulled out of a '78 K10 Burb that was rotted to death and put it in my '77 GMC K2500 and liked it very much..it was not good on gas ,but my current '82 K2500 with a 6.2 has never got much over 16 mpg either,and its a dog ,very gutless on hills and take offs..
The 400SB I had replaced a '74 454 I had in the truck that developed a strange wrist pin type knock,and I never really noted any big difference in the power or torque,and the 400 was lighter overall..
The only drawback to a 400 SB is they can overheat fairly easily and since the cylinders have no water jackets in between them they can crack easier..however mine got overheated many times when I had the snow plow on it till I found a cure and was lucky it never even blew a head gasket...you'll need the correct flex plate or flywheel and balancer for the 400 SB,they are externally balanced unlike all the other older SBC engines..
If your in TX maybe the 6.2 might be ok ,you wont likely have to deal with cold starting issues,but I'd save that for an off road buggy or truck,the diesels are great for mud bogging and climbing hills with no fear of wet ignition wires or distributors and the injection makes them much better for any off roading that would encourage a carb to flood on a gas engine...be prepared to have extra starters,glow plugs and hoarding spare parts though,6.2's are getting more scarce and if you end up needing to buy "good used parts" they aren't cheap and easily found any more..at least in my area..
I have become less & less a fan of them after owning one 17 years..many times I wish I put that 400 SB in the truck when I got it,and still do..
I had one I pulled out of a '78 K10 Burb that was rotted to death and put it in my '77 GMC K2500 and liked it very much..it was not good on gas ,but my current '82 K2500 with a 6.2 has never got much over 16 mpg either,and its a dog ,very gutless on hills and take offs..
The 400SB I had replaced a '74 454 I had in the truck that developed a strange wrist pin type knock,and I never really noted any big difference in the power or torque,and the 400 was lighter overall..
The only drawback to a 400 SB is they can overheat fairly easily and since the cylinders have no water jackets in between them they can crack easier..however mine got overheated many times when I had the snow plow on it till I found a cure and was lucky it never even blew a head gasket...you'll need the correct flex plate or flywheel and balancer for the 400 SB,they are externally balanced unlike all the other older SBC engines..
If your in TX maybe the 6.2 might be ok ,you wont likely have to deal with cold starting issues,but I'd save that for an off road buggy or truck,the diesels are great for mud bogging and climbing hills with no fear of wet ignition wires or distributors and the injection makes them much better for any off roading that would encourage a carb to flood on a gas engine...be prepared to have extra starters,glow plugs and hoarding spare parts though,6.2's are getting more scarce and if you end up needing to buy "good used parts" they aren't cheap and easily found any more..at least in my area..
I have become less & less a fan of them after owning one 17 years..many times I wish I put that 400 SB in the truck when I got it,and still do..
Thanks for the replies. Glad to hear some real world experiences with both. I had my mind set on the 6.2 but I didn’t know the 400 was going to look so nice once I pulled a head. It may make a nicer daily driver. I have a set of 3/4ton axles with 4.10s that would work well with the 400. Anybody else?
The '77 GMC K2500 the 400SB I had went in also had 4:10 gears,and it was quite peppy with stock tires,you could squawk the tires going into second gear with it on dry tar without even opening the 4 bbl secondary barrels..even the 454 it had previously had to be opened up wider to do that..both engines were bone stock other than an Edelbrock carb on the 400..
i had a built 400 sbc one time . 30 over / forged and knife edged crank / weight balanced rods / the WHOLE lunch box of upgrades . . . she was a animal for torque . use to run that in a k10 long bed on 9" lift and 1tons with 4.10 and 38" swampers . had a built th350 trans and no problems with the combo .
skip the 6.2 diesel and do the 400 sbc . mine i used a 80's tall rad 3 core and no problems keeping it cool .
skip the 6.2 diesel and do the 400 sbc . mine i used a 80's tall rad 3 core and no problems keeping it cool .
Thanks again. I was thinking I would use the diesel rad since it’s huge. Im about to pull the cam to see what it has. Im hoping for low rpm torque so I can run 37s, 4.10s, th400 and still get on the hwy if need be. Anybody know what stall I should pic?
I'd keep the 6.2 radiator and hydroboost if your truck is so equipped..|
I like the low stall speed torque converter the diesels use ,GM also put them behind BBC and even some 292 straight sixes in RV's and vans to keep the fluid temps lower and take full advantage of their torque curve around 1600 rpms..they feel "tighter" and you aren't annoyed by the engine sounding like the trans is always slipping until you wind it up higher..
I like the low stall speed torque converter the diesels use ,GM also put them behind BBC and even some 292 straight sixes in RV's and vans to keep the fluid temps lower and take full advantage of their torque curve around 1600 rpms..they feel "tighter" and you aren't annoyed by the engine sounding like the trans is always slipping until you wind it up higher..
Well the th400 is from the m1008 so it has the diesel converter so that would workout. Thanks for the input!
That will likely have 6 bolts coupling it to the flexplate...you could run just 3 out of the 6,or buy a flexplate with the 6 hole pattern..if they make one for the externally balanced 400 SB...
I would run the 400 as well. I have had a couple of them, there are still 2 around my place. With proper tuning, I have never had an overheating problem. I don't work mine hard, but not scared of full throttle.
As said, stock converter with a torque cam.
Be sure to check the bolt pattern on the flexplate against the converter. As far as I know, there is a dual bolt pattern that is not the same as the HD or diesel bolt pattern. I believe that the 6 lug converter has all 6 holes on the same bolt circle. A dual pattern covers TH350 and TH400 with two slightly different bolt circles.
As said, stock converter with a torque cam.
Be sure to check the bolt pattern on the flexplate against the converter. As far as I know, there is a dual bolt pattern that is not the same as the HD or diesel bolt pattern. I believe that the 6 lug converter has all 6 holes on the same bolt circle. A dual pattern covers TH350 and TH400 with two slightly different bolt circles.
First the disclaimer: I've owned 109 cars, trucks and motorcycles with 3 of those being Gen 1 K5s, 8 of the being Gen2 K5s, 1 being Gen3 and my current and final K5, a Gen2 frame and windshield cowl with Gen3 drive train. I'm almost 60 and have more opinions than hair, and you know what they say about opinions. Having said all that....
I've had both engines and both have pros, but lots of cons. Out of the starting gate I would opt for the 400 for the HP potential but the potential for cooling issues is high, especially if the motor and heads have never been apart and hot tanked.
The 6.2s were dogs but pretty reliable, but being glorified gasoline engines instead of designed from the ground as diesels left lots to be desired.
Maybe considering selling them both and taking that cash to add to more cash then buy yourself a crate 383 (or build it yourself).
If I couldn't do that but wanted a solid daily driver, I'd look for a solid 350. Existing (as opposed to living) outsids of Houston, heart would be a huge favor for me.
Best of luck no matter what!
I've had both engines and both have pros, but lots of cons. Out of the starting gate I would opt for the 400 for the HP potential but the potential for cooling issues is high, especially if the motor and heads have never been apart and hot tanked.
The 6.2s were dogs but pretty reliable, but being glorified gasoline engines instead of designed from the ground as diesels left lots to be desired.
Maybe considering selling them both and taking that cash to add to more cash then buy yourself a crate 383 (or build it yourself).
If I couldn't do that but wanted a solid daily driver, I'd look for a solid 350. Existing (as opposed to living
) outsids of Houston, heart would be a huge favor for me.Best of luck no matter what!
Go with the 400.
I have a 400 in my 77 Jimmy with 2.02 heads, 4x4 Comp Cam and all smog legal and it makes a lot of torque down low. I run 35's with 3.73 gears and I averaged 10.5 mpg in the mountains west of me and I wasn't easy on the throttle. The Jimmy also weighs right close to 6400 lbs. Throttle response is nice, you lay on the throttle and it will move. Dual exhaust with glasspacks and the 400 has a nice sound to it. Just make sure you have your steam holes drilled in your heads and go with a HD radiator and a good water pump, which you should anyways. Never been a fan of a V8 diesel unless it was a 6.9 or a 7.3.
Joel
norcal
19Tim69
1/2 ton status
Without a doubt... run the 400...
Unlikely. They do like different gear ratios, so maybe with the wrong gears the 6.2 will dip into the carefully driven 400 range. With the right gears, the 6.2 can get 50% better. That's basically what they're for.
Not exactly true, even though your conclusions are spot on
beags86
Eastbound and Down
6.2 = boat anchor. Obsolete junk.
400= can't go wrong with an sbc.
400= can't go wrong with an sbc.
19Tim69
1/2 ton status
I agree...and who are you going to pay to work on the anchor? I had a 6.2L in a bucket truck & I never saw better than 10 MPG & not very many shops wanted to wrench on them either
Lolz_cats
Uga duga
If you do run the diesel th400, make sure you switch out the vacuum modulator for a gas style. I swapped my blown up 6.2 for a sb350 and have it mated to the original diesel trans and it seems to work fine.
It's not fair to compare a 6.2 in a bucket truck to a 400 such in a k5.
I would be in the same situation as the op.
I think both are a very viable option especially if the 6.2 is a good runner.
I have both in my arsenal and I like both for different reasons.
My 6.2 diesel equipped truck gets good mileage and off road feels effortless.
The chalet blazer I had with the 400 was very responsive but I couldn't keep up with the fuel, even ran out on the highway once in Utah after 100 miles of headwind, I had the 25 gallon tank.
You do the math.
I now have a turbo diesel suburban and I love it but I am having trouble with the transmission
I have the same issue when I try getting a shop to do anything on my 6.2 ,the few guys I know & trust I'd let work on it,back away from it like it was a live rattlesnake..they dislike diesels period,after having some bad experiences (like burning up a starter after a simple fuel filter change due to not knowing the bleeding process as an example)--they refer you to a "diesel specialist" who gets $110 an hour..
My truck is also 39 years old,rusty,and they know it'll be a pain in the azz to do any repairs ,they either quote me a ridiculous price,or tell me "buy another BETTER truck" ...they fear it'll end up half apart "stuck" on the lift if a NLA part cant be found right away..
So,I end up busting my own azz to either "fix" it,or ghetto fab some crude repair to keep it rolling..
I stupidly sold a good running 400 SBC for $150 when I was hard up for money 7 years ago,never should have done that..it'd be in my truck now,and to hell with the poor gas mileage,I don't go far anyways any more..
