86 Sierra Classic. Bad Block... Now what?

[4WDKC]

My choice would be to rebuild the original block.

It's a simple recipe to make great power and it's more fun AND rewarding to "repair" than to "replace".

Chances are extremely high that your engine is rebuildable ... if it didn't seize at high RPM.

If it matters I own both Holley and Weiand intakes and pick either of those over an "elderbrok".

While I agree with you it seems good machine shops are getting harder and harder to come by. That coupled with the lack of warranty crates are becoming reasonable. I just had a shop setup vortec heads for my tbi motor, less than 500 miles on the heads and 2 valve springs broke in 2 places. Now I am on the hunt for springs to work with my cam/heads and give me the pressures I need. If the springs they used hadnt had an inner dampner it would have dropped 2 valves and cost me my engine.


Without knowing how you will be using this engine/truck Id be looking at something like this
https://blueprintengines.com/collec...s/gm-350-with-vortec-heads-roller-cam-1pc-rms

 

[rpcraft]

While I agree with you it seems good machine shops are getting harder and harder to come by. That coupled with the lack of warranty crates are becoming reasonable. I just had a shop setup vortec heads for my tbi motor, less than 500 miles on the heads and 2 valve springs broke in 2 places. Now I am on the hunt for springs to work with my cam/heads and give me the pressures I need. If the springs they used hadnt had an inner dampner it would have dropped 2 valves and cost me my engine.


Without knowing how you will be using this engine/truck Id be looking at something like this
https://blueprintengines.com/collec...s/gm-350-with-vortec-heads-roller-cam-1pc-rms

Can you still buy the GM performance Vortec heads from Scoggins/Dickens Chevrolet like you used to?

 

[SquareUp]

got ahold of a local engine builder..

I am going to fix my block, install new pistons.
Going aluminum heads and intake.
headers.
going to cam it up a bit.
new carb.
reseal the tranny and change filter.
stall converter
reseal the transfer case.

I doubt it'll be a 450hp motor by any stretch, but he said that itll be a huge difference from what I had. I'm pretty happy that I'll get to keep the original block with the truck.

I will keep you guys posted on the progress.. as of now I have a table full of parts.. lol

 

[DavesJimmy]

So broke down the motor this evening... I have bad valve guides on the head. and a scored cylinder wall and wear on the block.. Looking at a crate motor.. however.. I am not sure which route to go..

Motor will be sitting in front of a TH350. Stock. Looking for some direction. Everyday driver.

Any help would be appreciated.

Get a gm 350 crate engine. Thats what i did. Save ya time and money. I got the long block and used all the stuff off the old engine except the water pump.

 

[Rusty Nail]

Granted you're new and I don't know you mannn..
BUT guessing from the tone of your posts, I think you will be happier this way. It's much more rewarding, like I said.

The split is normally very 50/50 repair or replace...obviously only YOU know which you will like better. Did you ask the truck?
Repair certainly lends value to your asset.

If I or WE can offer further assistance / other information - speak up! We ALL share love for square body trucks.

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[75gmck25]

A crate motor is the fastest choice, and probably the least risk. However, you don't have the fun (and pain) of making all your own choices. A GM L31 Vortec 350 crate engine is about $2,200, but it has a mild cam and will only be rated at the HP of a late 90's stock 350. A crate Vortec from Blueprint or ATK is about $2,600, but with more compression and more cam they are rated at about 375 HP.

Do not waste your money on a new base GM 350 crate, or the GM 350/290 HP crate. You won't save much money, and you will be giving up several key improvements that were made with the L31 crate (1 piece rear seal, Vortec heads, roller cam, etc.).

One source of reasonably priced aluminum heads is Blueprint heads, which you can get from Jegs and Summit for $899/pair completely assembled. They are set up for dual pattern intake bolts, so you can use either Vortec intake or your original intake. The will handle higher lift without additional mods, and will work with a roller cam.

I would also strongly suggest a swap to a roller cam. It will cost more, but gives you the flexibility to use modern fast ramp cams without worrying about lobe wear. There is a good reason that GM switched to all roller cams in the 90's for SBCs.

Bruce

 

[CiscoKid]

I just installed an L31 engine (12530283) over the past few weekends. Got it finished this past weekend. Don't have any drive time yet. I'm a newbe at this so it took a while as I took my time and asked lots of questions. Main reasons I went with a crate, I'm not a mechanic and don't have the skills to rebuild an engine to specs. The crate engine only cost $1729 ($1879 less $100 discount and a $50 Visa card from Radley GM) and I've read it's close to 300HP with intake and exhaust. Also, has a roller cam, Vortec heads and 4 bolt mains. My original engine had a flat cam so the roller cam and net cost of $1729 after discounts was a no brainer for my circumstances.

 

[tanyourhide]

People generally dont get squarebodies while thinking "im gonna put a computerized motor in this truck" i buy squarebodies specifically 70's squarebodies because i have watched too many regular joes scratch their head at their 90's chevy pickup, all becuase of the computer.
So i say jf your gonna get that fancied up electronic crap then roll on down to the bank and get a note on a new chevy. Its faster

 

[Frankenchevy]

I just installed an L31 engine (12530283) over the past few weekends. Got it finished this past weekend. Don't have any drive time yet. I'm a newbe at this so it took a while as I took my time and asked lots of questions. Main reasons I went with a crate, I'm not a mechanic and don't have the skills to rebuild an engine to specs. The crate engine only cost $1729 ($1879 less $100 discount and a $50 Visa card from Radley GM) and I've read it's close to 300HP with intake and exhaust. Also, has a roller cam, Vortec heads and 4 bolt mains. My original engine had a flat cam so the roller cam and net cost of $1729 after discounts was a no brainer for my circumstances.

this is what I did. paid about the same.

People generally dont get squarebodies while thinking "im gonna put a computerized motor in this truck" i buy squarebodies specifically 70's squarebodies because i have watched too many regular joes scratch their head at their 90's chevy pickup, all becuase of the computer.
So i say jf your gonna get that fancied up electronic crap then roll on down to the bank and get a note on a new chevy. Its faster

you don't need to computerize an l31r vortec. its just a long block. I got it because it's the most modern gen 1 type 350. so for the most part, it can look like a 70's or 80's 350. it's nice buying something made by gm with zero miles and a warranty. most machine shops around me wanted over $4k to rebuild my sbc with average parts. then you have to worry about their work. to each their own, though.

 

[75gmck25]

As already explained, the L31 Vortec SBC works very well as a carbureted replacement for the older SBC's. There is no need to use EFI or other electronics. The only thing it does not have is support for a mechanical fuel pump, so you have to switch to an electric pump. You also need the flywheel for a one piece main seal block, and a Vortec intake, but they are readily available. Once its installed, very few folks could tell visually that its a newer version of the SBC.

The complete L31 Vortec 350 would be $1900 from Jegs. while a fully assembled set of Vortec heads (which flow much better than any earlier iron heads) would cost about $700 from Jegs. Both are a good value.

Bruce

 

[Jrgunn5150]

I don't trust machine shops. A couple times getting burned with four digit bills and subpar work was enough for me. Egg shaped, tapered cylinders, tolerances set all wonky doodle... And then rebuilds never seem to go 200k, but originals do?

I generally prefer a crate engine if reliability is the goal. The Goodwrench 260 I put in my 87 back in 07 is still in there driving around today.

 

[4WDKC]

While I agree with you it seems good machine shops are getting harder and harder to come by. That coupled with the lack of warranty crates are becoming reasonable. I just had a shop setup vortec heads for my tbi motor, less than 500 miles on the heads and 2 valve springs broke in 2 places. Now I am on the hunt for springs to work with my cam/heads and give me the pressures I need. If the springs they used hadnt had an inner dampner it would have dropped 2 valves and cost me my engine.


Without knowing how you will be using this engine/truck Id be looking at something like this
https://blueprintengines.com/collec...s/gm-350-with-vortec-heads-roller-cam-1pc-rms

this is what I did. paid about the same.


you don't need to computerize an l31r vortec. its just a long block. I got it because it's the most modern gen 1 type 350. so for the most part, it can look like a 70's or 80's 350. it's nice buying something made by gm with zero miles and a warranty. most machine shops around me wanted over $4k to rebuild my sbc with average parts. then you have to worry about their work. to each their own, though.

As already explained, the L31 Vortec SBC works very well as a carbureted replacement for the older SBC's. There is no need to use EFI or other electronics. The only thing it does not have is support for a mechanical fuel pump, so you have to switch to an electric pump. You also need the flywheel for a one piece main seal block, and a Vortec intake, but they are readily available. Once its installed, very few folks could tell visually that its a newer version of the SBC.

The complete L31 Vortec 350 would be $1900 from Jegs. while a fully assembled set of Vortec heads (which flow much better than any earlier iron heads) would cost about $700 from Jegs. Both are a good value.

Bruce

The mech fuel pump is why I recommended the engine above, and it has a warranty.

People generally dont get squarebodies while thinking "im gonna put a computerized motor in this truck" i buy squarebodies specifically 70's squarebodies because i have watched too many regular joes scratch their head at their 90's chevy pickup, all becuase of the computer.
So i say jf your gonna get that fancied up electronic crap then roll on down to the bank and get a note on a new chevy. Its faster

The reason i bought the one I have is because it is fuel injected all the crew cabs I look at have to be 87+ because I dont know **** about carbs and dont have anyone to learn from. I figured I can learn to tune on the tbi and if I blow it up I can swap in a efi engine easier than if the truck was originally carbed.

After rebuilding an engine with flat tappet cam I can tellyou its nerve racking always wondering if you have wiped a lobe, if youre a purist put the block in the corner and two youre on the wrong site . holy **** thats alot of smileys to sort through. Either way use a roller cam .