Thread: Another newbie needing SBC 350 build help

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Hello all, I am about to pull the motor from my 86 Jimmy (been blowing oil out the dipstick) and I want to completely rebuild it. It's a 350 with 305 heads (confusion about what block I had. Bought it thinking it had a 305 because of the VIN), summit racing headers, Edelbrock aluminum intake 2701, and an Edelbrock 600 carb 1406 (electric choke). I'm basically looking to increase reliability first and power if I can, without sacrificing reliability. I mainly use the truck for moving stuff, cruising, and off-roading. I'm looking for advice on heads, cam, crank, pistons, and assembly. Again, I'm a newb on this stuff so you may have to explain it to me like I'm 5. Thanks in advance for any advice! I look forward to making progress on this project.

(pic of the beast. I miss driving it)

I've nearly got the drivetrain removed. Right now the plan is to look over the bottom end and make sure the crank, pistons, seals, and rods are undamaged. I plan on replacing any seals here. I'm also looking at getting an Edelbrock top-end kit 2022 instead of piecing together a heads, cam, lifter, rocker set.

I like the nose art- reminiscent of the flying tigers.

Originally Posted by Camojimmy

I'm a newb on this stuff so you may have to explain it to me like I'm 5.

Jimmy, between the main group of fellows and gals on this board who regularly chime in, there is probably a thousand years of hot rod experience. I know I contribute over 60 years myself. (I'm 74 and began at age 13). Most of us are delighted to teach new people what to do and what not to do. The only thing that we require is that you listen up and pay attention, while answering our questions and posting your replies in a timely manner. If you don't say something every few days, we lose interest. I welcome questions from you about why I suggested one thing or another, that's the way you will learn how to do things for yourself.

Personally, I have little interest in adding onto parts that you already have, unless they will contribute to the end product in a manner that I would do on a project myself. Let's begin with the block. Is it absolutely carved in stone that you have to use a 305? If we're going to build a motor from a bare block, then it makes a lot more sense to start with a 350 block. I mean, it's not like they're expensive or anything. Hell, you can find them laying around in vacant lots or you can trade someone out of a block with something that you don't need anymore that the fellow might like to have. I traded a Polaroid Land Camera for a complete 1958 Chrysler Imperial one time. I used the 392 hemi out of it for an MGA roadster project and sent the rest of it to the boneyard.

I have also been known to give fellows my cellphone number on PM, so that if they get stuck, we can talk it out. I'm glad to do that for a fellow who is really into their project and pays attention. Robert Dobbs was the last fellow on this board that I did that for. He's building a 383 Camaro for drag racing. Shall we begin?

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CamoJimmy,
Everything Richard stated was spot on. He's been a huge help to me in my project and I still have a lot to learn from him. Like he said, the forum members on here are very knowledgeable and can/will be a great asset to you in your endeavors. More than likely, these guys like Tech have already been down the same road that you are on and have a wealth of information to share if you're serious about learning and accomplishing what it is you are wanting to do.

Thanks for the responses! Techinspector1, I think the block is a 350. When I first bought the truck I was led to believe it was a 305, even the VIN for the truck says it came with a 305. The last time I had the heads off (had them off twice, second time noticed the stamp) I noticed a stamp that had "GM 5.7LG SGI" stamped on it. I then measured the cylinders and they were close to what 350's are (4" I think). But because I thought it was a 305, I actually bought some stock 305 heads for it after the first time I had them off (the ones on it cracked at some point). So now I'm wanting to go back to 350 heads while I'm also figuring out the high crank pressure.
I plan on inspecting the block and transmission more closely to find stamps and get exact info from them.

Posted pictures are the block stamp and my current progress:

I stripped the block this weekend. Found my engine code and looked it up: 14093638 Small block V8 1987-95, 2 bolt main, roller or flat tappet cam, 1 piece rear main seal. I also investigated my transmission and it is a 700R4, will look at getting it refreshed.

I guess what I need help with now is what parts to get as far as cam, heads, lifters, rockers, and pistons. I'd like to go aluminum heads and a roller cam setup. I could also use a checklist to have for the machine shop. I scratched a piston while cleaning it :/ so I'll be looking for new pistons too. Not sure what size yet until I get the block checked out and possibly honed or bored. Was recommended flat heads to increase compression.

Any advice is appreciated!

Update:

Block and crank are at the machine shop/engine builder. I'll be getting some flat top pistons and a roller cam from there too. While it has been there I've been working on replacing worn out parts and painting everything.
I also ordered some Edelbrock aluminum heads.

whats the head CC's ? and valve sizes?

70cc combustion chamber. 2.02" valves. The heads come assembled. I'll have the springs adjusted for the cam too.

Jimmy, before the shop does a lot of work to the block, you need to have them measure the block deck height on all four corners of the block to determine whether the block is square or not and also to determine the stack of parts you need to use. This is where you make or break the build. Please find out this info and hit us back with it. Please don't buy any more parts until we make a plan. Otherwise you could paint yourself into a corner.

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What does measuring the block corners tell me? Do they just need to be even?

The first thing is yes, they need to measure the same corner to corner, but you also need to know the block deck height so that you can determine the stack of parts that you will use in the block as well as the piston deck height (measurement from the crown of the piston to the block decks where the heads bolt on with the piston at top dead center). We're pretty sure we will need to machine the block decks, but we need to know by how much.

Here's where we're headed with all this: All of the major aluminum cylinder head manufacturers specify a composition head gasket for use with their aluminum heads and most measure from 0.039" to 0.041" compressed. This compressed gasket thickness just so happens to fall right into the range of squish/quench that most all hot rod engine builders shoot for, 0.035" to 0.045". Although there are some hard-headed fellows out there who don't see the reason for composition gaskets with aluminum heads, the fact is that the aluminum heads will move around quite a lot more than the cast iron block that they will be attached to. So, in order to allow the head to move more than the block, we need the thicker gasket. Now, that's where the other part of this comes together.....

From the factory, the 350 Chevy and all other Gen I small block chevies will measure ~9.025" block deck height. That's the design blueprint measurement. In reality, the block could measure any other measurement from the factory. All it takes is for the mill operator to accidentally leave a small iron chip in the register from the previous operation and you have a catty-wampus block. And the other variable is that if you have not owned your block from the day it was manufactured at the factory, then you have no idea what other owners have done to it. Measurements on the four corners could be anything at all and if they are not the same, then the heads will sit catty-wampus on the block and the intake manifold will sit catty-wampus on the heads. If the intake manifold is not sitting square on the heads, there can be a gap either at the top of the head ports or at the bottom of the head ports. If the gap is at the bottom, you'll never find it with a combustible agent and the motor will suck oily crankcase vapors into the cylinder every time the intake valve opens. If you were to pull an oily spark plug out of the motor, you would begin to suspect that the valve guides were too loose or the valve guide seal was not doing its job, but the truth of the matter is that is could be the bottom of the ports that are not sealed up because the whole block is out of whack.

Now, since we know that we want the squish/quench to be somewhere between 0.035" and 0.045" and we also know that we want to use a thicker composition gasket to prevent fretting the soft aluminum, it makes sense that we must engineer the piston deck height (measurement from the crown of the piston to the block decks where the heads bolt on, with the piston at top dead center) to end up with what we want. Let's say that the stack of parts we want to use measures out to 9.000". That's 1.74" for the crank radius, 5.7" for the rod length and 1.560" for the piston compression distance. Add those 3 values together and you will find a stack measurement of 9.000". Now, we must cut the block decks so that we will end up with a 0.035" to 0.045" squish/quench to make the motor detonation-resistant on pump gas. For instance, if the block deck height measures out to be 9.020" on all corners, then we would want to cut the block decks down to 9.000", the same measurement as the stack. This is called zero-decking. This leaves the piston crown exactly even with the block decks and the squish/quench is then determined by the compressed thickness of the head gasket. With a zero deck, if you were to use a gasket with a compressed thickness of 0.039", then the squish/quench would be 0.039". If you were to use a gasket with compressed thickness of 0.041", then the squish/quench would be 0.041". If we used the 9.000" stack of parts in the 9.020" block deck height block, and then used a 0.041" gasket, then the squish/quench would be 0.061", too wide to control detonation on pump gas. It is also possible to find piston that have an increased compression height that might make a stack of 9.005" or 9.010" or even 9.015" If I were to encounter a block that was square and measured out to 9.020, for instance, and I had a stack of 9.015" I would probably not cut the decks, and use a 0.039" gasket for a 0.044" squish/quench.

Most machine shops will be reluctant to cut the block decks to zero because they feel that the block may need some correction down the road and they don't want to cut the block so that the piston pushes out of the block at TDC. Truth be told, there is nothing wrong with pushing the piston outside the deck surface by a few thousandths, so long as the top to the top ring is still sliding on the cylinder bore and not the head gasket. The other truth is that 350 blocks are cheap and easy to find.

This photo shows how you would measure the block deck height at home, with a 12" caliper. This photo shows using a digital caliper, but my favorite tool is a dial caliper. The problem with anything electronic is that every time you reach for it, the batteries are dead. The last 12" dial caliper I owned, I bought used on ebay for $80. You would measure all four corners as shown in the photo, LESS BEARINGS, then add the RADIUS of the main bearing bore to your finding with the caliper. the diameter of the main bearing bore for a 350 Chevy is 2.641", so the radius would be half or that, 1.3205". So, you would measure from the main bearing bore to the block deck, then add 1.3205" to your finding. That would be the block deck height for that corner of the block.
http://jamisonequipment.com/sites/de...s/BHM-24-1.gif

If you can't understand what I'm trying to teach you here, say so and I'll give you my cell number so we can talk it out. If you don't want to do that, then just measure the block decks on all four corners and post the finding here. We can work this out.

If you had waited to buy headers, I could have counseled you not to buy headers with thin flanges. You want minimum 3/8" flanges to prevent the material from curling up like a potato chip and spitting out the gaskets. Slow down dude, you're messin' up because you don't know what you're doing. The other thing I would not have advised you to do is to purchase those E-Street heads. They will flow about the same as a set of L31 iron production heads.

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Thank you for all that! I'll call the shop today to ask about their methods. They had mentioned decking it to be flat with the pistons too. The shop is an engine building place as well as a machine shop so I imagine they'll be helpful with all this stuff too. Again, thanks.

Spoke with the shop yesterday. They said they do measure on all corners and plan to mill it down to 9" as you mentioned. We discussed which gas I wanted to use and the compression ratio I'd end up with. I'm looking to stick to 87 octane as it's easy to find around me and the compression ratio will be somewhere around 9-9.5 to 1.