SBC Primer

[Dave70968]

So...if a guy had an idea tickling the back of his brain to build a small-block Chevy in a year or two, and didn't really understand what he's getting himself into, where might you send him to start getting educated? Assume he's familiar enough with cars to do most moderate repairs himself (i.e. not just a brake job, but rebuild brakes down to bare axles, etc.) and is reasonably capable of learning from a good book (with pictures) if he has somebody patient who'll put up with him asking questions.

Thinking something carbureted, or mechanical injection at worst; not interested in electronics. I want something as reliable as the proverbial stone axe, something I can find parts anywhere if it does break. Not looking for all-out power or racing, but I'd definitely like something enthusiastic. Application would be a Jeep conversion (ideally mated to a standard transmission). Not excessively worried about gas mileage, as it'd be a toy, not necessarily a daily driver, but the "Jeep" side of things is further down the road, and something I can probably sort out on the Jeep forum(s). I just don't even know where to start with the engine.

(Amusingly enough, I am reasonably handy with piston aircraft engines, but they're dead simple, and I've spent a fair portion of my life around airplanes; I really don't have that kind of experience with cars, though I'm not completely clueless--my experience in cars is just more with MGs than Chevys.)

 

[swampratt]

I build the old school reliable 350's for myself all the time.. and my buddies seem to like them also.
It is getting a little harder to come up with good cores to build off of.
There is a lot of power to be had in cylinder head work.
Get this book for cylinder head .
https://www.amazon.com/Chevrolet-Small-Block-Cylinder-Motorbooks-Workshop/dp/0879385472

There are books on blocks also.
But a lot of that is old school and the old school parts that worked very well then are not the same quality they once were.
Pistons I used were USA made Sealed power 345NP that piston today is not the same at all.

Stay away from the Hypereutectic pistons unless you build a low 9.5 compression or less deal.
I always shoot for a minimum compression of 10.3 and my 57 chevy 4 door has 10.87 actual compression and a cam that closes the intake valve very early.

Cylinder wall prep is a huge player in longevity . If you finish hone the walls coarse like 240 grit or even 400 grit you will have early wear.. basically the cylinder wall will slick up with the rings and if you finish coarse at 240 grit the final after rings are bedded in will be much smoother..think about where all that coarse surface grit went.

The filter does not filter 100% so do not expect it to catch the debris.
The cam lobes are basically oiled by splash oiling.. one reason during cam break-in you need to keep the RPM above 2000 and prefer 2500-3000 during breakin.. speaking flat tappet cam.
Roller cam is different.

If you do not plan on reving above say 6500rpm ever then the factory roller block would be a good bet and run a factory roller cam like the GM Hot cam.
Or a similar type.
I like rpm and so 7000+ and many times over 7500rpm is what trips my trigger ..the factory roller cam spider and factory type lifters will get in trouble.
I run flat tappet.
Here is an excellent read on roller cams.
http://garage.grumpysperformance.co...up-on-hydraulic-roller-lifter-selection.5522/

Here is a good sight to learn stuff from.
http://www.chevelles.com/forums/

 

[Dave70968]

I build the old school reliable 350's for myself all the time.. and my buddies seem to like them also.

A 350 was initially at the top of my prospects list; it looks like my initial reading was good.

It is getting a little harder to come up with good cores to build off of.

Fortunately, I have nothing but time on my hands; I'm not even looking to start for probably a year, though I'd certainly pick up the right core if I found it and stick it in the garage. That said, what should I look for to separate the good cores from the bad cores? Anything I can look for without taking the heads off, or do I need to actually inspect the bore? Any particular danger signs to watch for? I'm guessing a scuffed or scratched bore is an obvious danger sign, but what else?

There is a lot of power to be had in cylinder head work.

So I've heard, and I'm certainly interested in it conceptually, though I don't necessarily plan to use all of the available power. I'd love to have something that I derate in normal use by 25% (number pulled out of thin air). Again, looking for longevity as much as fun.

Get this book for cylinder head .
https://www.amazon.com/Chevrolet-Small-Block-Cylinder-Motorbooks-Workshop/dp/0879385472

Added to my list.

There are books on blocks also.
But a lot of that is old school and the old school parts that worked very well then are not the same quality they once were.
Pistons I used were USA made Sealed power 345NP that piston today is not the same at all.

Stay away from the Hypereutectic pistons unless you build a low 9.5 compression or less deal.
I always shoot for a minimum compression of 10.3 and my 57 chevy 4 door has 10.87 actual compression and a cam that closes the intake valve very early.

I had to go do a little reading on the metallurgy, but why do you dislike hypereutectic pistons? They seem to have some significant advantages (not arguing; I want to understand).

As to compression ratio, that sounds like it's up in the range that requires premium gas. I'd like to avoid that. Aviation has the same problem, with the additional issue that autogas has a higher vapor pressure than avgas, so even with low-compression pistons, you just can't use autogas up above about 8,000-10,000 feet without problems; avgas is 100 octane, "low lead" (if memory serves, about half the lead the old 100 octane had). We're in a serious crunch right now trying to find an unleaded fuel that'll work across the fleet, but even with some showing promise, it's still ~$5/gallon.

I want something that'll run on anything from premium to Uncle Jed's moonshine if it comes down to it (facetious, but close).

Cylinder wall prep is a huge player in longevity . If you finish hone the walls coarse like 240 grit or even 400 grit you will have early wear.. basically the cylinder wall will slick up with the rings and if you finish coarse at 240 grit the final after rings are bedded in will be much smoother..think about where all that coarse surface grit went.

The filter does not filter 100% so do not expect it to catch the debris.

Understood completely. I doubt I'll be doing the honing myself; I wouldn't mind, but I expect it's a high-precision job beyond my skillset and toolbox, so that'll be between me and the machine shop.

This seems like the place to discuss overboring; given that we're only talking thousandths over, I assume that's not so much about increasing power in and of itself as it is about presenting a new, unscratched cylinder wall? And slightly larger rings to match the overbore?

The cam lobes are basically oiled by splash oiling.. one reason during cam break-in you need to keep the RPM above 2000 and prefer 2500-3000 during breakin.. speaking flat tappet cam.
Roller cam is different.

If you do not plan on reving above say 6500rpm ever then the factory roller block would be a good bet and run a factory roller cam like the GM Hot cam.

How long is break-in? In aircraft engines (say, a Lycoming O-360: four-cylinder, opposed-four configuration, 360 cubic inches; about 180 HP), break-in can be ~25 hour (or more), run at 75% power or more (redline is typically 2700 RPM). We also typically run straight mineral oil rather than ashless dispersant for break-in.

Or a similar type.
I like rpm and so 7000+ and many times over 7500rpm is what trips my trigger ..the factory roller cam spider and factory type lifters will get in trouble.
I run flat tappet.

Yeah, that sounds more like a race engine than what I had in mind. Not that there's anything wrong with that, just not the application I'm thinking for this build. I'm looking more for not-quite-daily-driver to moderate off-road (think hunting Jeep suitable to go to either side of that application).

Here is an excellent read on roller cams.
http://garage.grumpysperformance.co...up-on-hydraulic-roller-lifter-selection.5522/

Here is a good sight to learn stuff from.
http://www.chevelles.com/forums/

I appreciate the links! I'll definitely get to reading.

 

[swampratt]

You need to go for a ride in my old school built 57 chevy.
It has about everything you want I would bet.

The octane thing is not as critical as you would think with the right combo of parts.
The hypereutectic cast piston is advertised as being stronger than regular cast piston ..they add more silicone to the alloy and that makes it harder.
Harder is not stronger in certain applications.
If you get into detonation with a harder piston it will shatter like tempered safety glass.
Yea you can live fore a while maybe in that situation.. but it is not like old school cast where you can actually beat the bearings out from detonation with the old cast piston and the piston lives..
A hypereutectic piston normally has more than 12% silicone some up to 20% that makes it very hard and not very resistant to impact loads.
Yes it is more scuff resistant.. but keep the air filter sealed up and oil clean and scuff resistant is a non issue.

It expands less than the cast piston and you can run tighter cylinder wall to piston clearances but this tight clearance is a bad thing in my book..as things heat up clearances get tighter.. you can allow the clearance with more expanding pistons and end up the same.
Hypereutectic piston tops run much hotter than cast or forged Downside is you need to gap the rings wider.
As you can come into a situation of butted rings.

More heat in the combustion chamber is good to a point.. but too much of it being generated and you get in trouble.
The cast iron head SBC gets along fine without the added heat.
You can find heads with very efficient chambers and you can turn old school heads chambers into a modern chamber that works very well. Talking old double hump or some 305 heads.. the 76cc and 70cc heads are too square to get there.

Reading on pistons.
http://blog.jepistons.com/2618-vs.-4032-material-differences

then this.
http://blog.wiseco.com/-what-makes-a-racing-piston

Smaller chambers are less detonation prone..I have tested than a few times in my builds.
Less surface area in the chamber because it is smaller and that is the key.
That is how I can run higher compression with pump gas.

Then you have rod to stroke ratio.. this also helps out in the compression department..Longer rod dwells piston at TDC longer and this makes the engine less detonation prone.
Rod to stroke ratio on the 350 is good. I have ran 12:1 on 91 octane with smallish cams 270H to be exact 224@ .050.. it had 245 psi cranking pressure. happy camper..I shifted it at 6900rpm daily.
In less than 2 years i put 75,000 miles on it.
Yes i drove a lot years ago.. wife would log over 70,000 a year and I would also. Lots of time for testing things out.
Get this I changed oil in cars every 2 weeks. 3000 miles.
Line your wallet.

I used to run Oldsmobiles and tossed stones at the Chevy.
I got a 78 nova handed down to me ..Finally it was mine and It was going to get a 455 olds.
But I had researched the small block chevy for about 2 years and decided to try my hand at a 350 chevy build.

WOW!!! my first one ran excellent. I could swear it would beat a W30 455 I just built for a buddy.

I called him up and told him ..and the race was on.
It was even steven until 135MPH where I topped out and he went on and ran 152 MPH.
HHHMMM I had a little 268H comp cam 20.5 MPG if i could keep my foot out of it. Q jet intake and carb and cast iron manifolds.

Imagine if i really souped it up. Which i eventually did .. kept tweaking it and swapping cams and heads.
Finally got it to run 11.50's in the 1/4 with a 370 gear and I could hit 176MPH in 3/4 of a mile.
Yea in that trim i put another 70,000 miles on that block that started with 100,000 miles and then logged 75,000
It then went into my 47 dodge truck and 6 years of driving then into the 57 chevy.. each time it entered a new vehicle i would put fresh pistons and rings and bearings in it.

Never bored and crank never turned.. cylinder walls never honed except what GM did to them in 1969.
cast piston and molly rings.. simple stuff.

 

[swampratt]

I learned a lot from my Uncle Ralph.. he raced stockcars against The King and others and when i was in diapers or before that.

He wrote a letter to Sealed Power and asked them what the best surface finish was to seat their Molly rings.
They wrote back and the answer was : You know that 100,000 mile polish that looks shiny and golden from oil seasoned into the cylinder walls that is the best surface to seat our molly rings.

Yep.
He said when he pulled engines apart and seen a good looking cylinder wall he would not touch it.. he would slap a set of the E251K rings in them and go. Those rings fit many 4" and close to 4" bore engines.

Those rings are not the same as they used to be.. ones today look like they were cobbled together by blind children.
Coating looks horrible and no up or down on the top ring and not the same oil expander.

Best core engines I would get came from running old cars from auctions or bargain post ..way before craigslist.
Used to be able to buy a 120 dollar car and drive it home.. pull the SBC from it and the trans and sell other parts then scrap the body and put money in the bank.

I do 2 break in periods for flat tappet cams usually 20-30 minutes each. I use Joe Gibbs break-in oil also.
Then use another good oil for runing ..not much Zinc in oils on the shelf today and they are always changing the formulas.
VR racing is still good Gibbs has their hot rod oil and a really good LS oil.

Keep open valve spring pressures under 300 and you will be good. 345 open on race stuff for flat tappets being max.
Well for me and the cam and lifters I run.. You can go more with special cams.

I found the old school lobes like the comp magnum and high energy do not require a lot of spring pressures.. especially if you keep the valves light and stock 1.5 ratios for rockers.
You can run 80 closed seat pressure and 280 open and still run a lot of RPM.

Big block chevy with say the 280H and up require a heavier spring but we are not talking BBC here.
Some quick rate cam profiles may want more spring pressure ..I have not ran those as the old "lazy" cams work fine for me.

Crower or howards lifters are good ones. basically a good Delphi or johnson lifter

 

[skyhawk1]

Well swamprat I might have to get you to look at this one if you've a mind to. Just got it for my god daughter, her grand parents raised her and her grandpa built this in the early 90's. Had to sell a few years ago and my girl just found it last week, just had to have it. Grandpa in nursing home now and she is dying to go take him to lunch in it. Been setting for a couple years, cleaned fuel out, changed oil etc. but running a little rough. Probably needs card rebuilt.
32 Ford

 

[swampratt]

I would love to make it run better so you can take the old guy out if you have not already.
I am available most week days during the day.

 

[Dave70968]

Depending upon when you have in mind, I wouldn't mind watching and learning something.

 

[swampratt]

I think you would be interested in these 305 heads i am finishing up.. see what all is involved in making them work well.

 

[Dave70968]

I very well might be. I have irons in the fire through next Thursday or so, but would love to find a time you're free.