350 vs 383 vs 400

[bgh831]

Anything besides stock and you just playing so it is entirely up to you and what you like/want. Keep the 400 rebuild it even it's perfect for the type of driving your gonna due minus the MPG's.

 

[Mishri]

hah yeah.. getting some better MPGs would be nice, right now i think i got 12mpg on the highway.

$619 new for some vortec heads doesn't sound too bad. the used ones for $200-300 is sounding more in the range i'd look for spending. it's amazing how cheap things are for these older vehicles... doing H/C/I and exhaust for under $1,000 sounds pretty awesome.

I hadn't driven the truck in a few weeks so I took it out last night, it is running pretty well around town, although there is an issue, battery was dead when I went to start it, must be a short somewhere or my dad connected the electric choke to an always on source, i can check that easily enough. also the choke might not be operating properly, i have to give it some gas till it warms up for awhile. I'll see what the edlebrock manual says about setting the fast idle since it looks like it's wired properly.

 

[Christian Nelson]

Ok, after hearing more about this, NO, DO NOT rebuild this engine. There's no reason to, that you've listed. Your statement that it just doesn't seem to have as much power as your newer truck is not a reason to be looking for troubles. Several reasons can account for your "butt dyno" feeling less power from this truck than your newer one. Your gearing, the newer truck has a 4 speed, overdrive transmission. Many of these have a lower 1st gear, and because of that, feel like they launch much better. Also, they sometimes put lower differential gearing in them since they have that overdrive, allowing the final drive ratio to be about the same, with much more percieved throttle response. Your older truck has a 3 speed transmission, for it to attain highway speeds without screaming down the road at redline, they have to have higher differential gearing, making it feel less responsive than if it had lower gears. another reason, vortec heads, 40+ bolt on horses are on your newer truck. EFI, even though some guys will swear up and down they can get a carb to perform every bit as well as an EFI, I have yet to see this in real life. EFI, throttle response, and fuel mileage are better, the "butt dyno" will see a difference, even if you have similar HP at WOT. Lastly, when was the last time this older truck had a tune up? Gunk in the fuel lines/carb? plugs, plugwires, distributercap/rotor? Do you have an after market ignitions system in it for hotter spark? All sorts of directions one can go LONG before the topic of rebuild the engine ever needs to be brought up.

 

[Mishri]

I said i'd like to get the '76 up to the speed/acceleration of my '97 SUV, I don't expect them to be the same, even though the '97 is just a v6. gearing in the '76 though is 4.11s, which is probably why it rips off the line but struggles at highway speeds with it's 3 speed. I'm basing my speed comparison of time to reach speeds, and how it struggles to hold 80mph WOT.

My reasons for wanting to rebuild it was, it's been 24 years and 150,000+ miles since the last rebuild and I'm not convinced it's running top notch, and while i was in there doing a re-build why not go in and give it a little bit more horsepower? Which is when the guy I was going to have do the rebuild suggested going with a 350 he has sitting around.

It does have new fuel lines and carb was installed about 6 months ago (an edelbrock, I haven't looked at the cfm, but I'm guessing my dad chose the right size) it has new plugs, plug wires and distributor.

Some of this also comes down to, I want it to be like new(or better) again, I'm trying to restore it to awesome condition since my dad has just been letting it sit around and rot and it's always been his baby.

Him giving me his truck was a big deal, my mom put it this way of how big of a deal it is that he entrusted it's care to me.

when my dad married her he said these are the order of things of importance to me, my truck (the '76), hunting, football, then you.

she eventualy made her way up past football. i say this just to give you an idea of the sense of responsibility I have for making this truck awesome again and what I should do to make it that way. I want to do things right and make it as good as I possibly can. Although I'm looking at budgets, it's not like I couldn't throw $5,000+ at it this year. although I'd prefer to just get everything working right and to fix up the body/truck bed which is rotted/rusted through in area than to spend $2,000 on an engine not be able to do the rest. I have a long list of things to fix though, so I figured I should make sure the engine/transmission was top notch and then worry about the rest, like the speedometer, fuel guage, temp gauge, doors not closing properly, windows not rolling down, backup light missing, broken tail gate, bent hood, windshield wiper fluid has a hole in it... etc.

At this point I think I am better off fixing known issues rather than worry about an engine that still gets me from A to B based on some conversations here and elsewhere.

I'd love to be able show up to a camping trip with him going from this:

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to this:

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but it's also important that it runs and works properly as well, this is basically a restoration process with upgrades, doesn't have to be factory.

 

[HotRodPC]

I'm not fond of 400's. The siamese cylinders is enough to scare me away, especially after a bore making hte walls even thinner. One good overheat and they run hot by nature, and you're done. Money wasted and down the drain. The 383 is not a bad option and adds more torque to the 350. I'd be on board with either the 350 or the 383, but not the 400. Scrap that block or make a cool coffee table of it.

 

[Mishri]

Haha thanks, yeah the deal isn't entirely off the table.

I haven't discussed pricing but I believe the deal is I trade him the 400 for the 350, my dad says he should do it for free since the 400 is worth more, but i'm sure he'll want some money.

It's something I'll have to consider, I'm going to take the truck out camping this weekend with my dad, how well it performs will help me decide what is important

I'll be bringing an LMC catalogue with me so we can see what goodies I should get for it(likely order what I can from rockauto.com). I'll have to make another thread in the exterior section about the rusted cab corners, doors and front fenders... it's rusted through. and the truck bed is rotted out., i'll have to put plywood over it so i don't lose anything.

but like i said, after doing some consulting I think I am better of focusing on what is broken first.

 

[bgh831]

377 (400 block 350 crank) high RPM with vertec top end with FI conversion would be really cool and junk yard doable

 

[HotRodPC]

377 (400 block 350 crank) high RPM with vertec top end with FI conversion would be really cool and junk yard doable

That's a destroker motor. And to do it you'd have to have the crank mains welded up then turned down. I've never liked the idea. But then again, I've never cared for SBC400s. I had a 4 bolt main 400 once. I scrapped it. I regret it now. People pay big bucks for a virgin 4bolt SBC400.

Does your SBC400 have 2 freeze plugs one each side or 3? The 3's are a 4 bolt main.

 

[bucket]

That's a destroker motor. And to do it you'd have to have the crank mains welded up then turned down. I've never liked the idea. But then again, I've never cared for SBC400s. I had a 4 bolt main 400 once. I scrapped it. I regret it now. People pay big bucks for a virgin 4bolt SBC400.

Does your SBC400 have 2 freeze plugs one each side or 3? The 3's are a 4 bolt main.

Jeg's sells (or sold) bearing spacers to run the 350 crank.

I had a 400 and liked it, never had any troubles with running warm either (like everyone says they do) except for when I had a bad thermostat that wouldn't open all the way.

And I was told the 2 bolt blocks are actually less prone to cracking than the 4 bolt blocks. Not sure how true that is.

 

[HotRodPC]

I know of some 400 that ran their asses off, but I just can't get past the Siamesed cylinders and steam holes in the heads. Now that you mention the 2 bolt being less prone to cracks, I've heard that too, and less prone to overheating, and more likley to be thicker walls for boring. I forgot about the spacer available back in the day too. Back then, one our racer buddies had a little Mercury Capri with a SBC400 and a ton of NOS on it. He ran high 9's low 10's and drove it to work everyday.

 

[Christian Nelson]

I wholeheartedly can get behind you taking care of the known issues first, then dealing with whether you should rebuild/swap engines on it.

I think your biggest problem with going 80 mph, is your 4.10 gearing you mentioned. This will give the truck good power for pulling, and off the line, but since you don't have an overdrive like your newer truck, your rpm's are way up there, likely out of your power band, and possibly running out of fuel if you have a 650 or smaller cfm carb on it. You say Edelbrock, the common edelbrok people put on SBC's is the 600-650. Might be a tish small for a 400, running at 5,000 rpm's.

If you get a 350, you will have the same problem, the rpm's are too high, and with a 383 stroker, it's even worse, they are built for low end torque, not WOT high revs.

Easiest solution I can think of for you if you want to make a change to your highway drivability, would be to swap in a set of 3.73 differential gears. This should give you a bit more on the top end, without sacrificing too much low end power.

Another alternative but not necissarily easy, or preferred, would be getting a 700R4, and keeping the 4.10's.

My reccomendation would be to go with 3.73's, if you are planning on doing a lot of interstate speed driving.

I had a truck with 4.10's, 350/TH400 it was great for towing a cattle trailer with a goosneck, rarely needed to downshift going up hills with a full load of cattle, but you didn't really wanna go much above 55mph on it, and this was with some tall (I think they were about the same as 33's) tires on it. And, it DRANK the gas. Only truck I had that was worse, was one I got that had 4.56 gears in it, and that thing, I thought I would blow the engine going on the interstate, trying to do 65 in it, unless I had the 38.5 swampers on it.

My most preferred gear ratio is 3.73 for most purposes on these trucks. If it's 2 wheel drive, and you aren't hauling heavy loads, you can even go with the 3.08, and be even happier at the top end, but your bottom end may not be as hard of a launch. With the 400 though, you may have enough grunt to not be a problem.

From your description of the issue, this is where I would focus my attention (after you've taken care of the stuff you know is wrong with it)

Good luck, make your dad proud!

 

[Stroked]

$300 seems like a good deal for a set of Vortec's, but if they need any machine work done you're going to be getting close to the price of a new set.

And don't worry about the Edelbrock. 600 cfm is plenty of carb for most any 350. It's probably enough carb for the 400 too, unless you plan on spinning it over 6,000 RPM's.

EDIT: I somehow got switched around and was thinking you had a 350. Lol. Haven't had my coffee yet this morning.

 

[Mishri]

Thanks for the input guys. I'll take a look at the carb tonight, see which one he bought. I'll also have to look for the freeze plugs, never have before, I might not be able to see them under all the oil build up

 

[Stroked]

That sounds like the 350 I just bought. Lol. I spent 10 bucks at the carwash trying to get all the oily grime off of that thing.

 

[Guardian]

I have had a couple of the 400 blocks and didn't have any issues with overheating. I have seen quite a few that had heating problems but most were self induced.