350 vs 383 vs 400

[Mishri]

So right now I have the original 400ci v8 in my '76. A guy I work with who everyone says is an awesome mechanic has said he'd help me get everything working right again and running well.

So I wanted to just rebuild the 400 and i'd like a little bit more power over factory, it does have an aftermarket cam right now installed in the early 80s. it was last rebuilt in 1988 and I just think it feels down on power from what i can remember. my dad says it only has 50k miles on it since the rebuild but im pretty sure it has 150k miles on it, that was 24 years ago and he daily drove it for awhile.

anyway, on to the question.

So the guy willing to help me with the rebuild says he has a 350 with a good set of heads we could drop in there instead (i'm guessing he'd take the 400 off my hands) he also said we could put a 400 crank in it and make it a 383. My dad says he'd prefer to keep the 400 in it because its not a very common engine but if he would do the swap for free and it's a brand new engine it might be ok.

What are your thoughts? trade for new 350 or just pay the guy to rebuild the 400? I'm leaning towards keeping the 400. Also i would hopefully be helping him with the rebuild so I can learn. I simply don't have the tools or knowledge to do a great job is the only reason I don't want to try it by myself.

I think the offer of the 383 would include me buying a new 400 crank as he wants the 400ci engine. and he may even want paid to swap out the 350 for the 400, I don't know yet.

also my daily driver is a 98 GMC jimmy, and compared to that the truck is pretty slow, so i'd just like to get it up around it's acceleration/speed. my toy is a modded 2012 mustang 5.0, so I don't need anything as fast as that

Thanks for the advice in advance.

edit: also, my dad said I should just do a compression test, if it's good then there is no point to rebuilding it since it doesn't look like it's burning oil. it's leaking oil out of the valve covers but that is an easy fix.

 

[Stroked]

Take the 350 and use the 400 for a boat anchor

 

[crazy4offroad]

No replacement for displacement!! Dont listen to Jared!

 

[Stroked]

Lol, I figured I would stir somebody up with that post.

But seriously, I would trade just for the fact that it's cheaper. If you're wanting a strong motor, then there's nothing wrong with a properly built 400.

 

[Mishri]

Haha, yeah I think i'd like to keep it, the 350s are cheap and everywhere, 400 has some uniqueness and will deliver the power I need. I'm just taking it out camping and hunting, nothing to serious. so even the stock 200hp or whatever it was is sufficient. it'll see some muddy roads and thats about it, it's illegal to drive more than 100 yards off the road here where we camp so I wont be able to have any real fun with it I might be doing some towing and hauling with it, no racing, but being able to pass people on the 2 lane hwy up there is kind of important to me, but not a huge deal if i get stuck doing 55 in a 65, it's only a 1 hour trip anyway.

Unless somone else chimes in with something different I think I'll just stick with the 400 and pay for the parts and whatever he wants for labor to fix it up.

The next question is, considering what i'll be doing with it do i want to do heads/cam/headers or leave it stock, or maybe just throw a new cam in there? it's powerful enough to get most jobs done, we've pulled out trees and stumps with it. so maybe I should just do the rebuild and call it good.

 

[Stroked]

Heads/cam/intake/etc, will really wake it up. Just make sure you drill the new heads for steam holes. That's probably the most common mistake I hear about.

I can't give much other advice cause I've never owned or worked on a 400.

 

[Mishri]

now I talked to someone else who says if its running okay don't worry about, just replace gaskets to stop the oil leak and work on other issues. which it has many of. It's possible the engine is fine. Hmm.. decisions, decisions, where to start, engine rebuild so I know everything is good or focus on known problems?

My idea was, if I rebuild the engine then i'll know it'll be good for another 100k+ miles and I wont have to worry about it. On the other hand, it could still be good for another 100k+ miles and i'm just wasting time/money when I could work on the other things I need to fix.

 

[crazy4offroad]

If it has good compression you might try a new cam, incase the lobes are worn out on the one in it. If the compression isnt so great, have the bores checked for out-of-round and out-of-taper and if they are in spec you can get by with a re-ring/re-bearing rebuild job. Out of spec naturally will need bored and new pistons/rings.

 

[bucket]

I wouldn't worry too much about the compression because a junk set of heads could be the reason for low compression on a couple cylinders too. If oil pressure is good at all times, I'd just pull the heads and see what the cylinder walls look like. If there's no ridge at the top, I'd just do a new cam and heads. I would also splurge and go with a roller cam setup, and probably go with a set of Vortec heads too. It's not hard to drill the steam holes in the heads yourself, just use the new head gaskets as a template.

 

[Mishri]

Thanks for the input, I did a little looking at the vortec heads. Sounds like with the right head/cam/headers/intake you can get 450hp out of them (the article wasn't clear if it was bhp or whp, i'd assume whp)

they cost around $800 right, plus the other stuff probably looking at $1500+ to rebuild it with the heads? seems like a bit more than i'd like to spend right now, especially considering i really only want 250-300bhp. I mostly want to keep my low-end torque high, I don't care that much about peak hp numbers. just a little more oomph over stock would be good.

My thoughts are for now rebuild it, new cam, possibly a new intake manifold if they are actually better with stock heads. and if I can find cheap/decent headers go with that. On my car LT headers cost around $1200, im guessing I can find much cheaper for the truck though right? haha. I'd like to keep the engine rebuild under $800 if possible.

what do you guys think? realistic expectations or would I be better off just leaving it stock if I'm not doing heads?

 

[Stroked]

Without looking, I'd say you could get a set of headers for less than $200

 

[Christian Nelson]

I wouldn't rebuild it unless you know it needs it. Too many people just rebuild for no reason n my opinion. If your compression is good, leave it be. If you have bad compression, verify it isn't just a valve leaking before you rebuild. 150,000 is barely broken in, unless you've been driving with no air cleaner in a sand storm for those miles.

The rings and bearings on an engine are usually pretty much the last thing to check. (You check rings by squirting oil in the cylinder and see if compression changes) unless you ran your oil REALLY low, or your oil pump quit, or got plugged, your main and rod bearings should be good as well.

I agree with your dad.

If you want some power out of this thing, pull a set of vortec heads, EFI system out of a 99+ pickup from a U-pull it junk yard, or buy a wrecked truck, and put a hot cam in it, and you will have to program the chip, and you will have one HOT machine then.

 

[oopsman_09]

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[crazy4offroad]

Vortec heads are cheap, not $800. I picked up a pair recently for $200. It is also a cheap way to boost compression, since they have 64cc chambers and I figure your stock heads have 74-76 cc chambers. If you want to keep your carb you have to get an intake that is made for Vortec heads but you can expect around 40 HP just from bolting them on. The pic of the cherry red turbo is exactly why I couldnt run one, first mudhole I hit with a red-hot turbo would be the last, when it cracked. Now I wouldn't rule out a 75-150 shot of nitrous though...

 

[Stroked]

Vortec heads are very high on my list for my current engine build. You can buy a brand new pair from Summit for $619. So I definitely wouldn't pay $800 for a used pair.

I keep saying someday I'm gonna turbo a 350. Just for chits and giggles.