Re: What GM create engine to buy for 3/4 ton 72 C20
 

This^. I have had mine for about a year now and couldn't be happier with it. Mine is in a 1970 c10 long bed and it will get down the road. I have a Summit Stage 1 intake, Holley 4 barrel and headers with 2 1/2 inch exhaust.
ETA- The center bolt valve covers like the one piece rear main seal don't leak like the old style does. I didn't like the center bolt valve covers at first but now I prefer them over the old valve covers. No need to tell me yours don't leak because everyone knows they leak sooner or later, usually sooner.

Re: What GM create engine to buy for 3/4 ton 72 C20
 

I have no idea about the differences in the 195 and 260 crate engines.

I too have a negative vibe about center valve cover hold downs. The after market vortec heads we used on the Blazer were dual bolt pattern, so we used original valve covers. We had to redo the exhaust and oil filler tube because of the angle of the heads. The rear AC compressor brace wouldn't work either.

The 290 crate motor we used on the K10 worked great as an install. I had all the same emotions about the engines you mentioned. It has a nice lumpy idle and works well. It's not the torq monster we would like but is fine for pulling the boat and atv's.

Re: What GM create engine to buy for 3/4 ton 72 C20
 

Thank you everyone for the feedback! I think I have made up my mind and will go with the L31-R. Some questions I have is what parts I need to make this engine work in the 72. My engine mounts currently in the truck look nasty any suggestions on mounts? Will this bolt up to the SM465 with no issues with the correct(?) flywheel? Another question I have is how the serpentine system would work. My truck doen't have power steering or AC and I intend to keep it that way. It uses a old school simple thin belt setup that only goes to the alternator. Can I keep this simple setup and same alternator or I need to buy a serpentine kit for the L31-R? If I do have to buy a kit do they all come with power steering and AC provisions? What do I do with it? Also I would need a water pump, intake manifold for carb, new carb, exhaust manifold/headers?, HEI distributor, electronic fuel pump, air cleaner, and plugs and wires. Any suggestions or anything I'm missing for this. Also will the starter thats in the 350 in the truck now work with L31-R? Will the radiator be the same? Any additional wiring needed? I also saw somewhere you have to plug a hole in the block for a sensor? Any mods I should make to the L31-R before it goes on for more hp/ torque? Thanks

Re: What GM create engine to buy for 3/4 ton 72 C20
 

You should be able to use the factory style mounts, I did. I also added chains to my motor because I read the mounts are prone to breaking. I have a V-belt setup, I had some old brackets and just matched up some to work. Yours should be easier without power steering. Use a water pump made for your model truck, I have a problem with mine, lower radiator hose hitting the frame. I used the thick Felpro gaskets(forget the part #) for the intake and Edelbrock part #9300 gasket sealer. This is what Edelbrock recommends for their E-Tec heads which is basically the same thing. You will need a new flywheel made for a 1 piece rear main seal. Right now I'm running a Holley Mighty-Mite fuel pump which is pretty quiet. I have only run it for a few weeks but no problem with it yet. The bigger Holley pumps are loud as He!!.The starter should work depending on what exhaust you use. I'm running a mini-starter but don't buy a MSD mini-starter, two different cousins have had 4 to go bad in no time. If low end torque is what you want leave the motor alone and put a low profile duel plane intake (I used a Summit Stage 1) and good exhaust. I used long tube headers and 2 1/2 exhaust.
Just one more thing, If you don't have your heater hooked up be sure to run a by-pass hose from your intake to your water pump.

Re: What GM create engine to buy for 3/4 ton 72 C20
 

My block came out of a 4 speed truck. You're welcome to the flywheel, clutch disc, and pressure plate if you want them for the cost of shipping (PM me if you want pics). Stock engine mounts work fine - you can still get a set through most auto parts stores. The bolt pattern on the Vortec heads is slightly different, but you should have no problem making your alternator bracket work. You will need a new manifold - the Edelbrock 2116 if you're running the Quadrajet carb. The same water pump your stock engine has will work with the L31 (but get a new one). If you don't already have an HEI distributor, I would definitely make that upgrade (whatever engine you get). I'm using rams horns manifolds - you should have no problem with your stock manifolds as long as they're in good shape. Your starter and radiator should be fine (as long as they're in good shape). Your temperature sending unit will not fit in the head, but user A1971Blazer does a really nice job of turning them down on a CNC lathe to the correct thread size. You'll need to install an electric fuel pump, and I would recommend you put it on a relay tied into an oil pressure switch so it cuts off if there's an accident. I bumped up my cam just a bit to the Ramjet 350/HT 383 cam, primarily because my block was drilled for a mechanical fuel pump and the stock cam didn't have a fuel pump lobe, but the HT 383 cam should give me a nice boost in torque and a little more HP.

Re: What GM create engine to buy for 3/4 ton 72 C20
 

A little more info on the GM crates. Note that the L31 we've been talking about that lists for just a hair over $2000 is the base L31 - but it also has a slightly more expensive brother (I assume this is the L31R some have referenced - it's specified for 3/4 ton and up, whereas the base L31 is considered a 1/2 ton replacement). Anyway, L31R = L31 HD (same engine, just different terminology depending on where you're looking). From what I can see it has the exact same specs, but you get 4 bolt mains for your extra $200. If I were to go the GM crate with vortec heads budget route - either of the L31s is hard to beat bang-for-the-buck-wise. The HT383 has some impressive numbers (but an equally impressive price - more than double an L31).

Here they are:
L31 https://sdparts.com/i-19928727-gm-en...te-engine.html

L31 HD https://sdparts.com/i-19928425-gm-en...te-engine.html

HT 383 https://sdparts.com/i-19928346-chevr...SABEgKvj_D_BwE

Some interesting notes:
- The L31s have a hyd roller cam/383 has a hyd flat tappet
- 383 has a forged crank/L31s are cast
- L31s require electric fuel pump (as mentioned above)
- 383 includes manifold and ext balanced flexplate (not sure if L31s include a flexplate)
- 383 and L31 HD are 4 bolt mains, L31 is not.
- L31 CR=9.3:1 / 383 CR=9.1:1 (MUCH better than the 195/290 hp crates' 8.5/8.0:1 CRs)
- Both have decent lift cams, 383 is more aggressive, thus the hp delta..

Bottom line, I'm not building a race truck - but the extra 100 ft-lbs of torque of the 383 sure would be nice. However, very best bang for the buck imho is the L31 HD.
I think a set of center-to-perimeter bolt valve cover adapters may be in order... :) Anyway, just wanted to share. Hadn't heard of the L31 HD before - and I'd spring for the extra $200 to get 4-bolt mains personally, whether I needed them or not. I believe that $200 also gets you some upgraded exh valves and cyl head improvements (although I'm not sure what those improvements are). If, when the time rolls around and I happen to have won a small lottery, I might spring for the 383, but if it were gonna happen tomorrow, I'd go with the L31 HD. Significant improvement over the original 350 and for about the price of the Gen 1 195 or 290 hp GM crates. I guess maybe I can live with a vortec manifold bolt pattern and externally balanced flexplate after all!

EDIT: Note in the table below for the HT383 cam - it is a mis-print. HT 383 has a hyd roller, not a hyd flat tappet cam.

Re: What GM create engine to buy for 3/4 ton 72 C20
 

I have the L31 in my 55 Chevy 210 2 dr. It is a very capable, smooth running little engine, but is a little anemic. It does fine, but the response to the go pedal is a little light to suit me.

The roller cam was the biggest factor in the purchase of the L31, but if I were to do it again, I would gladly pay for more torque and HP.

You can build a 383 cheaper than that HT383 and have a roller cam. I love the 383 we have in the Blazer.

Re: What GM create engine to buy for 3/4 ton 72 C20
 

Jocko, the HT 383 has a hydraulic roller cam: http://www.chevrolet.com/performance...l-block-ht-383

If you want to save some money but get more HP and torque, buy the HT 383 cam and put it in your L31 block. That will get you close to the 383's numbers - at a much more friendly price.

Re: What GM create engine to buy for 3/4 ton 72 C20
 

I have been thinking about calling Comp Cams and ordering a roller cam set up for my L31.

Re: What GM create engine to buy for 3/4 ton 72 C20
 

[QUOTE=truckster;8082963]Jocko, the HT 383 has a hydraulic roller cam: http://www.chevrolet.com/performance...l-block-ht-383

Thanks - that’s certainly what i was expecting, was surprised that Scoggin Dickey listed it as a flat tappet. Ok, scratch that detractor! Good point on 383 cam in the L31. Has anyone does this that can confirm you won’t kiss a piston in the slightly higher compression L31 with the slightly higher lift of the HT383 cam? I highly doubt it, the lift isn’t “that” aggressive, but would be a comforting data point. I’d probably go with the 383’s intake also. Considering GM Parts prices - by the time you add a flexplate, manifold, electric go, and cam, you might be tickling just south of the 383’s price tag, and you could use a mech pump with the 383 :). Still, sure don’t need a forged crank for an old truck, so there are some savings to be had with any L31 approach.

Re: What GM create engine to buy for 3/4 ton 72 C20
 

[quote=jocko;8083021]That's what I have in mine. I haven't fired it up yet, but my machinist confirmed it's good to go and it turns without hitting anything.

Re: What GM create engine to buy for 3/4 ton 72 C20
 

According to a Scoggin Dickey, L31 should have a roller. Is that more bad gouge? (Or are you just seeking a more aggressive roller?)

Re: What GM create engine to buy for 3/4 ton 72 C20
 

I want more power, and a 55 Chevy is supposed to have an engine that lopes.

Re: What GM create engine to buy for 3/4 ton 72 C20
 

Ah copy, thanks. Completely understand!

Re: What GM create engine to buy for 3/4 ton 72 C20
 

[quote=truckster;8083046]Thx Truckster. Noted - good info.

Re: What GM create engine to buy for 3/4 ton 72 C20
 

Yes you will need a plug that will go in to the timing cover because you are deleting the Sensor. you will also need a Melonized gear for your Hei distributor ,because of the hardness of the Cam in the L31 , I think you might want to go with the serpintine set up as the L31 was designed for it and you can go to your local pick n pull yard and get everything you need in a Hours time for around $100 ,if you try to go with your old V/belt set up it will cost you more money to convert and ton of agravation trying to line up the pullys and finding the correct pullys . also serp set up is more reliable ,

I just put a L31 in my 68 a few months back ,So I am just going by my personal experience installing the L31 vortec , So far its a great little engine that is driven everyday

Re: What GM create engine to buy for 3/4 ton 72 C20
 

Have you checked out Summit? No shipping but I believe there is a $100 core charge. Also you will need a way to unload the motor out the back of a semi if you want it delivered to your house. You may find it a little cheaper but Summit is an A1 company to deal with.
https://www.summitracing.com/parts/nal-12530283
Don't pay any attention to the HP ratings. If you install a 4 barrel carb and good exhaust you will get 300 hp easily but the torque will be way more. Torque is what you want, HP sells cars Torque wins races.

Re: What GM create engine to buy for 3/4 ton 72 C20
 

depending on the overall gear ratio, horsepower is the most important measure. Because of the math, an engine that is tuned to have peak horsepower below 5252 RPM will ALWAYS have more torque than horsepower, and engines with peak horsepower above 5252 RPM will ALWAYS have more horsepower than torque

Re: What GM create engine to buy for 3/4 ton 72 C20
 

Confused yet jocko?

Interestingly, there is not a "wrong" answer in all this.

It's all in what you want.

Re: What GM create engine to buy for 3/4 ton 72 C20
 

Ha, no not confused. I didn't even start the thread! Ha, hope I haven't butted in too much. The reality of my situation is that my K20 has a pretty raggedy replacement engine in it, couldn't even trace the numbers on it, but am guessing late 70's/early 80's passenger car. I've stumbled onto a no-kidding running 72 350 with all the a/c goodies attached that I could make a deal on - but it has a little over 200k on it with 1 rebuild about 40k mi ago. Nothing wrong with that - I'd get what, to me, would be what I'd have been dealing with when new - just not new. I'm not worried about numbers matching - but I am kind of on the "period correct" bandwagon. Anyway - the availability of the local 72 350 has kinda forced my hand even though I'm nowhere near tearing down the K20 for a rebuild. But - a bird in the hand... I should either crap or get off the pot with this engine. So, it's forced me to think about crates now rather than when I'm ready to install in the future. And, while I enjoy rebuilding old engines, if I went with the 72 350 and redid it, I'd still have a 200k+ motor (and that's ok) but likely with a .060 overbore by the time I'm done. Not too concerned with that, but a brand new crate might be a better approach. Am guessing rebuild of the stock 350 would yield similar #'s to the 195/260/290 Gen 1 crates. nothing to write home about, but a capable driver. Since I intend to stuff a camper on the K20, it would be nice to get a bit more than what the stock 350 (or a crate 290) would provide. Although I really do like the 195 with a cam swap approach. Still, probably not much better than original stock 350.

So, my initial aversion to one piece rear seals and vertical intake bolts has subsided a bit (as long as I use the perimeter valve cover bolt adapters). I really think it will come down to either the HT383 (if times are good) or the L31 HD (if things are just what they are today). I'd be happy with either. All said and done, it's really only about a $1K-1300 difference once you add in the flexplate, fuel pump, intake, etc. So, would I spend that for an extra 100+ lb ft of torque. Hmm. Maybe! :)

Appreciate all the insight from those that have installed either of these engines - very helpful. I'm gonna think on it a little bit longer and perhaps let my procrastination on the 200k mi 350 make the decision for me :)

EDIT: Thanks Gary - yes, I have checked out summit - was just posting specs from GM sites. Summit is where I go first to buy IF they have it - they tend to have the best prices. They beat Scoggin Dickey by almost $200 on the L31R. And, they just opened a store in Arlington, a hop skip and a jump from my house :) They do have deliv service with a tommy-lift or whatever you call that thing.

Re: What GM create engine to buy for 3/4 ton 72 C20
 

I lost track of the OP. Sorry Gary.

Re: What GM create engine to buy for 3/4 ton 72 C20
 

Honestly, in a truck, when was the last time you spun an engine up past 5k to get max horsepower?. Very rarely if any of my engines see even 4k with a manual trans.

Re: What GM create engine to buy for 3/4 ton 72 C20
 

Best price I've found on the L31 R: $1971
https://www.ebay.com/itm/GM-OEM-NEW-...BYyYeE&vxp=mtr

Re: What GM create engine to buy for 3/4 ton 72 C20
 

Yeah I tend to agree with you jocko. L31-R or the HT383 I think are the best options for low end torque, vortec heads, and hydraulic rollers. It’ll just boil down to how much you got to spend.

Re: What GM create engine to buy for 3/4 ton 72 C20
 

Agree with you, they have the lowest price, that is where I got my L31 from (Radley Chevorlet ) a few months back. They are great to deal with they had my engine at my door in 7 days, they also advised me that GM had a rebate program at that time , they took care of that also and about 2 weeks later I got a GM visa cards in the mail totaling $150.00 on them, So the engine costed a little over $ 1,800