punzak9

So I just talked to my builder today and he said he cleaned the rings ect, and they’re at their max. Thats before cleaning out the carbon which could make them a little worse. Sorry Im not very technical with engines but hence the reason for this post....Anyways, he recommended boring the cylinders .020 / .030 over, new pistons and rings. He said he could have a rebuild kit made up if I wanted but said he’d give me time to think about the options. I know I could ask the builder all these but for the sake of his time and to get more feedback I wanted to post here.

So few quick questions.
1) 350 .030 over is a 355. Right?
2) Would I be able to use the stock crank after its bored (if its in reusable condition)
3) Would changing the crank to a 400 make the 350 .030 over a 383?
4) He suggested flat top pistons if I wanted more performance and to keep compression down.

I am back and forth going 383 over a 355 because I feel like the 383 would have much more of a snowball effect on the car (rear/tranny/ect) compared to staying with the 355. I know price wise its not a huge difference.

Surge

To answer some of your questions yes a .030 350 is a 355, you would be able to reuse the stock crank if it’s in good condition. A 400 crank would make it a 383 but I believe then you’d have to run a 400 balancer and you would need the mains turned down to fit the 350 block. But that’s old school hotrodding, Most people nowadays just buy a new 383 crank that’s drop in and go. Flat tops would give more performance by raising your compression ratio. My 2cents is I would go for the 355 if you’re not looking to upgrade the trans and rear anytime soon.

AlkyIROC

1: yes
2. yes
3. yes and no. Providing you can even find a stock 400 crank, it's cast and not as strong as a steel crank. The mains would need to be machined down to fit into a 350 block and you would need to use 400 con rods on the 350 pistons. Cheaper to just buy an aftermarket 400 stroke crank, rods and pistons kit to make a 383. The factory 400 crank is also designed for a 2 piece rear main block. If you have a newer block with a one piece rear main seal, the crank won't fit.
4. Flat tops are also better then the factory dished pistons. They'll bump up the compression ratio slightly and you'll still be able to run regular gas.

Depending on the condition of the parts, the cost to build a 383 is the same as a 355 however you also need to be aware of all the costs to build a new engine. Proper machine work and assembly costs money plus parts for gaskets, seals etc will all add up. In the end, it can be a lot cheaper to just buy a prebuilt replacement engine with a warranty.

The cheapest 383 engine from Blueprint with iron heads is $4000 which includes Hypereutectic Pistons, roller cam and a steel crank. Cheapest aluminum head 383 engine is $4500

GeneralDisorder

iTrader: (1)

How do the bores look? Just because the rings are worn out doesn't mean you need to jump right into an overbore. If the bores look good and have cross-hatch visible just clean up the pistons and install a new set of rings. 5 cubes isn't worth the effort to buy oversized pistons, etc. If it's that far gone that it needs a rebore then just get a crate L31 Vortec that won't destroy your drivetrain and wallet and call it a day.

GD

punzak9

Thanks for the responses so far. It helps having clear cut answers.

@GeneralDisorder the machinist said he highly recommended a .020/.030 over bore. I simplified it in my response as “worn rings” cuz I cannot remember exactly what he said. He’s a local guy who came recommended by a guy I know who had engines built by him and he builds some kind of race engines on the side. So I trust his opinion and that he’s not screwing me, seeing how thats all I have to guy by. But he does take the time to explain everything to me even though I dont overly understand it. That is my basis for boring and getting new pistons.

punzak9

I really am torn but do think I’ll just stay 355 instead of 383. As much as I’d love to and for as small as the initial cost between the 2 engines would be, the drivetrain snowball is just too much for me I think.

GeneralDisorder

iTrader: (1)

Yeah that's what every machinist says. I build engines, install them, and dyno/tune them. I almost never bore blocks oversize. It's usually cheaper to just find a used Vortec block with good cylinders. Taking material out (especially if there's no reason to do so) just reduces the strength and thermal capacity of the block needlessly. See here:

http://www.snowvalley.20m.com/bikes/dnthone.htm

GD

AlkyIROC

No machinist should bore a block without having pistons in hand first. You need to match the piston to the bore so without a piston, you're only guessing if the clearance will be close enough.

There are a lot of other reasons to bore a block. Even if there is still crosshatching in the walls, there could be a taper down the cylinder or even a groove near the top of the cylinder. A slight overbore will clean up the cylinders but will also require new pistons to match the new bore.

There's a big difference between assembling an engine and building an engine. To build an engine properly, it's assembled and taken apart multiple times to check different clearances. That's also why it costs a lot more when a machine shop builds an engine. A backyard rebuild may be cheap but it's unlikely going to last 100,000 miles either.

punzak9

Just to clear things up.

It is a machine shop doing all of this. He has my block and stock pistons. As said above I forget the technical terms he used, but said that it could work but is at the very limit. He isnt pushing me into anything, but he is giving me his opinion and suggestions. He isnt doing any work to the block not having the pistons. I am going to get a quote from him pricing out a kit of the items that would be used before anything is done.

I was under the impression that boring an engine was no big deal. Seems like builds on these threads do it all the time.

GeneralDisorder

iTrader: (1)

It's no big deal to bore an engine. If that's what is absolutely needed. It is BETTER to not bore it if you don't have to. Because you avoid much of the unpleasant break-in process that results in wear EVERYWHERE inside the engine as invariably you have to wear down the peaks of the final honed finish and you get grinding compound from the bits of honing stones, etc. It is best avoided unless it is absolutely required. If the cylinders measure out within spec as the vast majority of fuel injected engines will - even after 200k miles of operation - leaving it alone is the best option. New rings of course. They will seat just fine.

And yes if you are going to bore it you either buy the pistons and bore it to match them, or you have to place a custom piston order with JE, Wiseco, Arias, etc.

GD

punzak9

GD, thank you for the explanation and suggestions. Im going to give him a call today and go over all 3 options again. (Leaving it with new rings, going 355 and going 383).

Drew

iTrader: (58)

Welcome to the money pit. This is the reason I always tell people not to bother rebuilding a small block chevy. It's not that the local machine shop is always looking to drag you over the coals, it's that they lean a certain direction to provide you something that will probably last longer and they aren't too concerned about what it'll cost you. You're really at their mercy to get the job done right, to get the job done quickly, and the $$$ it'll cost you. That's assuming they don't lose your parts, lie to your face, or dismiss you wants/needs/goals with the build.

For what GM charges for a Vortec crate engine, there's no reason to enter into a Grimm bargain with a machine shop and a craigslist engine with 255k miles on the clock.

GeneralDisorder

iTrader: (1)

I agree completely with Drew. I do it because I have the tools, the experience, and a relationship with a machinist where I TELL HIM what he WILL do for me and his opinion is of little concern to me. I take his measurements and his opinion under consideration, but I throw him enough business that he does what I say because he wants me to bring him more engines. As a shop I have leverage in that respect.

BUT EVEN STILL - the minimum required machine work on my used (very good condition) 98 Vortec L31 cost about $1650 and I didn't even touch the cylinders. That's before you consider head work - that was another $600, and the cam, timing components, rockers, pushrods, valve springs, etc. Sure I bought some trick parts and the sum total will be more than what you would get from a basic L31 long block from GM but the TIME investment and the money..... it is ABSOLUTELY a money-losing proposition if you just want a basic rebuild.

This is pretty much true of all cars. As a shop I don't "rebuild" basic engines. I DO build custom one-off engines but the cost is astronomical. I have customers with $25k into their engine. But for basic rebuilds - I buy them from the manufacturer. Subaru is a great example - we get reman short block assemblies fully dressed with oil pan, pump, and all the block plugs, etc for like $2300 and they come with a 3 year / 36k warranty. I couldn't rebuild one for that price let alone carry the warranty. It's a waste of time to even try.

GD

punzak9

GD and Drew, thank you both for the input. I definitely respect your opinions knowing my lack of knowledge compared to yours.

I think however that long before this post I put myself in the hole. I probably should've asked questions, such as these, but I thought I gathered all the info I needed from reading tons of threads. I bought the complete L98 engine last year off a guy on these forums for $600. So I was already into it there, not knowing the info I do now. Even before this post I disassembled the block and sent it out to get checked because I didnt want to drop in a block that was on its last legs.

Yes, this was supposed to be just a rebuild. However the more research I got and still get, and after my phone call with the machinist again today, I think I might just jump all the way up to a 383 build. He doesnt have all the engine parts (just the block and complete pistons because thats all I gave him starting out). Going with new pistons and getting a “kit” made either way for the 355 or 383, he said the cost for a new 400 crank would be a little more than having the stock crank gone over and ready to be put in. The cost in the machining price was the same to bore since its the same (obviously), and only $100 difference to notch the block for the 400 crank shaft.

punzak9

So I was already in it about $800 before this post between buying the L98 and the initial cleaning and check of the engine. If I didn't do any of that yet I would have definitely followed your new block suggestions.

GeneralDisorder

iTrader: (1)

Why not sell it (cleaned and checked) for the same $600 you paid for it and just write off the $200?

I say just get a crate L31 and a Vortec TPI base and call it good. The L31 is 250 HP right out the box.

The 383 (built and tuned right) is going to SHRED your drivetrain.

GD

punzak9

GD and everyone else who responded,
I really appreciate all the input, suggestions and advice. For better or worse I think Im going to go with what I have so far and turn it into a 383. I know the domino effect for the drivetrain but I think it will be worth ig in the end.

cardo0

My vote is just have the motor re-ringed and re-bearinged (if that's actually a word). I say this because you are not sure what you want to do and stroking the motor is going to require large dish pistons to control compression ratio and alignhoning and balancing. After all that the computer will need a new tune also.

What I'm saying is to save a lot of $$$ and frustration just go with a simple rebuild. Boring the block and adding new oversized pistons doesn't add to much to the cost but if the block bore is still in spec then save your $$$ and clean the original pistons then re-install with new rings. That's what specs are for! Every machine shop wants more business whether you need the work or not.

Replacing with a GM crate motor is another good idea but you want to match the camshaft and compression of the motor the computer is tuned for (which ever one that is) so you won't have to retune the computer right away. BTW tuning is something that can help any motor and a good place to start learning before any modifications will require it.

Hope this helps more than it hurts.