Looking for tips / recommendations on 350 build.
 

Hey there,

I currently own a 1971 C20. It is my daily driver / work horse truck. It currently has what I believe is an all stock 307 with an unknown amount of miles on it. Rite now the truck is running fairly good. I am looking to get a 350 block, put it on my engine stand, and build it over a long period of time while still using my current engine in the mean time. I am not looking for high performance, just a nice reliable rebuilt 350 that would make a great work truck. The current 307 has a fair amount of torque, but nothing to brag about. It has a 2bbl rochester carb, stock heads, stock exhaust manifolds, etc. I have build a few old Ford engines in the past, but this will be my first SBC. My main questions are regarding what block / heads should I look for? What vehicle(s) has the ideal 350 block / heads if any for rebuild purposes? (Assuming there are differences in 350 blocks.) As you can tell my knowledge of the SBC is very little. I would like to take my time with this build, gather as much knowledge as possible, and at the end have a nice reliable engine to drop in my work truck.

I may be considering putting a TH350 or TH400 behind the engine. I currently have a 3 on the column, and as much as I love it, it has given me nothing but issues. (Mainly linkage problems, etc.) Plus, manual transmissions can get old pretty quick in SoCal traffic.

Like I mentioned, I am not looking for something high performance, but at the same time I am not against standard modifications such as 4bbl, possibly headers / aluminum intake / etc. assuming it is within reason. Something that I can load with flooring and pull my trailer comfortably.

I am not looking to go a fuel injection route.

Any information or points in the rite direction are much appreciated.

Thanks in advance.

Re: Looking for tips / recommendations on 350 build.
 

You are going to get a few differing opinions on what to do. First you should take as look at what it is going to cost in your area for all the machine work plus parts to completely rebuild a 350. In some parts of the country it is cheaper to simply buy a GM crate 350 engine. If I were in your situation I would look for a '96-'02 L31 Vortec 350 to build. Going this route gets you the best small block production head made, plus you have the ability to run a factory roller cam. With compression of 9.3-9.4 and this cam, you will have a good reliable torquey small block.

https://www.summitracing.com/parts/n...7395/overview/

Of course you will need the Vortec specific intake manifold, a 600cfm carb and a HEI distributor.

This is the basic engine I am talking about except with a carb instead of the EFI.

https://www.summitracing.com/parts/n...5815/overview/

Re: Looking for tips / recommendations on 350 build.
 

The sbc is a great motor to build and work on...there are almost no limitations on directions or performance...and it is a very economical engine to fix up, build or modify.
Are you doing this for the sake of economics? or interest? or?
...as mentioned the 'crate engines' are pretty cheap relative to what you might spend in building one....or at least competitive and a lot faster and easier to get done.

As for the transmission...you would be better served to get past the TH350/400 option and move up to the 4 speed automatics like the 700R series or the 4L60 transmissions. You will get better mileage and performance out of them.

Coley

Re: Looking for tips / recommendations on 350 build.
 

I think CaptainFab nailed it for you, I feel you would spend that sort of money and effort rebuilding one you pieced together...

There use to be a SBC offered which cost around 1500 bucks, mostly stock and offered into older vehicles. Summit or Jegs use to sell them but I did not see them listed....Good Luck in whatever you decide and have fun !!!!!

Re: Looking for tips / recommendations on 350 build.
 

I'm with CaptainFab on this one as well. I'm building mine, but that's because I had a good Vortec 5.7 core to work with. I also opted to go with the HT 383 cam to get a little more out of it.

Re: Looking for tips / recommendations on 350 build.
 

I appreciate all the feedback. Assuming I went the route of the Vortec but do not want to buy a crate engine, what truck / engine would I be aiming for from a parts yard? I can get engine machine work done for close to nothing and I enjoy putting things together myself. My father has a 02' GMC Sierra 2500 HD with a 6 liter Vortec and that thing still runs like a clock after a quarter million miles, so I could see them being reliable engines. Just curious as to what donor to look for.

Re: Looking for tips / recommendations on 350 build.
 

96 through 2002 (limited applications in 2002). If you want the 4-bolt main look for a 3/4 or 1 ton truck or van.

By the way, the 5.7 Vortec and the 6.0 Vortec aren't the same engine design, but the 5.7 is a great engine.

Re: Looking for tips / recommendations on 350 build.
 

One thing I didn't see mentioned is that a GM crate motor comes with a 3 year/ 100K warranty. It dies, they replace it. I was going to rebuild mine but after doing the math the crate motor is just a bit more and the warranty swayed me.

Re: Looking for tips / recommendations on 350 build.
 

The L31 Vortec 350 was installed in '96-'99 trucks and '96-'02 Express and Savana vans. And yes the 3/4 and 1 tons had 4 bolt main blocks.

Re: Looking for tips / recommendations on 350 build.
 

Go captainfabs route. I also asked this question and after more than a year of contemplating am getting ready to take his advice. You just cant beat 2k for a long block with vortec heads that you can slap your own intake/carb/efi combo on and also have a warranty. I looked at lots of options. build myself from bottom up, top end kits on a used engine, LS engine etc and I think Captainfab is spot on with his recommendation. Its a roller engine that with a cam swap, long tubes, eddie rpm, and 650 cfm carb could crank out 300plus hp and close to 400tq. For 1100 bucks more you can throw a mildly built th350 trans behind it from summit and have a reliable engine/trans combo that should last you a long time.

Re: Looking for tips / recommendations on 350 build.
 

If you do decide to go the junkyard Vortec route there are a few things you should be aware of. It's pretty rare to find used Vortec heads that aren't cracked; my machinist got new, heavier castings for me for about $200 each. You'll need a new intake manifold (different bolt pattern) and flexplate or flywheel (Vortec has a 1-piece rear main seal). If you find one with the fuel pump hole drilled consider yourself lucky (I found one, so they're out there); otherwise you'll need an electric fuel pump. The temperature sending unit won't fit, but forum member A1971Blazer does a really nice job of turning them down on a CNC lathe. You'll have to do a little bit of massaging to get your accessory drive brackets to work, but they will. However, if you're considering a serpentine drive, it would be a good idea to pick one up from your donor vehicle. Your stock exhaust manifolds will work (I'm using Dorman 2.5 center dump rams horns on my Blazer). Your stock motor mounts will also work. Your distributor will need a mellonized gear (available separately, but included with many aftermarket HEI distributors).

On mine I'm running the HT 383 cam (more torque, plus it has the fuel pump lobe), a Cloyes double roller timing set, and I put in a bronze tipped fuel pump rod.

I think that's about it, but if you have any questions, just ask. Good luck.

Re: Looking for tips / recommendations on 350 build.
 

Can I widen my scope of search if I don't care about a 4-bolt main?
I mean,.. I have never heard of someone breaking down because they only had a 2-bolt main.
I beat the crap out of my 283 when I was a teen, so now that I'm old and want to build a cruiser, with decent mpg, where else should I look for a L31?
Thanks
-Robert

Re: Looking for tips / recommendations on 350 build.
 

New they are just under $2000 dollars with free shipping. That is probably the route I would go.

BUT be forewarned that the warranty may not apply if it is not installed in a 96-02 application where it was originally. Especially if you cam swap, intake, run a carb instead of FI, etc.

SOME of the production Vortecs are actually drilled for a mechanical fuel pump. I just looked at one this week that had the blockoff plate installed and another that didn't because the hole wasn't drilled. So if you find a drilled one and build it, you can have a roller cam and you can run mechanical pump.

But the GM warranty is awesome as long as you have the motor installed in the correct application. The standard 350 is about $1600 delivered and sometimes Jegs runs sales on eBay around $1350.

Re: Looking for tips / recommendations on 350 build.
 

L31 has a 1 year 12,000 mile warranty if installed without modification. 3 year warranty if you install it in a 1996-2000 GM Pickup.

I purchased my L31 for $1879 on Ebay. (I got $100 Ebay rebate for 5/4 day + $100 gift card). I feel like I'm going to have about $2700 total in the swap.

I think a resourceful person could get this done for $2200 total. I'm just not patient enough and I like shiny new things.

Re: Looking for tips / recommendations on 350 build.
 

The 1/2 tons have 2 bolt main engines.

Re: Looking for tips / recommendations on 350 build.
 

So update here. I went with the l31 crate per cap fabs reccomendation. It was on sale for 1900 bucks on jegs free shipping. I would recommend a brand new one if you can afford it. What a difference from that wire out 283. With a brand new top end, flex plate, arp fasteners, torque converter, hei, headers and serpentine setup from the junkyard i am somewhere in the neighborhood of 3500 bucks. I could post a parts list if you need one for reference. This thing is beautiful and brawny. It WILL burn the tires right off if you want it to. I feel little need for a cam swap. There is plenty of power down low and it pulls well through the entire rpm range most ppl will use in a truck.

As for warranty, my understanding is it's 12 months 12,000 miles if not installed in 96 to 2000 truck/van/original application

Re: Looking for tips / recommendations on 350 build.
 

One think to considered, IF you are replacing or spending much money on cleaning up the crank, it is just as cheap to build a 383 with and iron or cast steel crank. The extra cubes really help torque production for a work truck.
Other have mentioned Vortec heads and are spot on with that advice. Don't need to port them or anything else. They will make your SBC much more responsive and efficient. Good luck with the build.

Dan

Re: Looking for tips / recommendations on 350 build.
 

Really great advice. This is what I would have done if I didn't have my crazy idea of trying to clone a 1970 Corvette LT-1 / Camaro Z-28 350 for my 1970 C10.

Car Craft has had nice articles on rebuilding these very economically. They are pretty good for wear even with very high miles, so that saves a lot on machining costs. And they respond really well to cam changes. Comp cams even has a cutter so you can trim the top of the valve guide down yourself to allow for higher lift cams.

Re: Looking for tips / recommendations on 350 build.
 

Oh! I missed the update before I posted. Congrats on a successful upgrade!

Re: Looking for tips / recommendations on 350 build.
 

I just don't want to spend the money and energy on a traditional sbc, and yet I'm not sure I want to go as far as an LS.
So I'm thinking the L31 is a nice middle of the road solution.

Re: Looking for tips / recommendations on 350 build.
 

Are the heads that come with the L31 crates from jegs or summit less apt to crack?

Re: Looking for tips / recommendations on 350 build.
 

They might or might not.
Likely not.
They’re new. Should be good for a 100,000 miles or more. Way more!
A ton more miles than you’re gonna drive.

Re: Looking for tips / recommendations on 350 build.
 

Agreed. I've never heard of Vortec heads cracking badly enough that someone had to replace them as long as the engine is running. You just wouldn't want to put money into a set of cracked heads. I have a Vortec engine in a 2001 Express 3500 van that has somewhere around 170,000 miles on it.

Re: Looking for tips / recommendations on 350 build.
 

What auto transmission most likely came with the L31?

Re: Looking for tips / recommendations on 350 build.
 

In the C/K 1500's it will be the 4L60E. In the C/K 2500/3500's it will be the 4L80E.