1970 vs. 1978 350SB

[Southpa]

Hi folks, been a while, eh? I'm finally getting my engine rebuilt by a local outfit. I've done lots of work on the truck myself, but where it comes to the engine I figure I better leave it in the hands of people who can do it right . It was long overdue, still running but sounded pretty sloppy.

We're looking at a 1970 350 "010" cast w/ 4 bolt main. Among other minor things (will list later) there was a crack in the block. They didn't want to risk grinding and welding as they wouldn't be able to provide the one-year warranty ie. not always a sure fix. So they found another 4-bolt main 350 block and assured me it was similar vintage as my original engine. My main goal is to keep things as original as possible. If I knew the block was cracked I would have gone out and bought a Crate and have done with it.

Anyway, the suffix code on the new engine tells me its a 1978, any real big difference here? Both engines have the same casting and bearing caps. But I see large differences in HP and torque ratings between the two. I know one (1970)is gross HP (255) and the later 1978 is net HP (165). I don't mind using a 1978 motor, I guess a lot depends on how you set it up in the first place. I'm going for a stock rebuild w/ the ramhorns, no stroking or anything and I'm replacing the original intake with a Edelbrock Performer intake and the old (assuming original) 4MV Rochester with an Edelbrock 650 cfm offroad carb. I was told with that setup you can install and basically forget about it.

They also found:
one seriously cooked exhaust manifold, I mean melted and then cracked cast iron, under the heat collector.
Bottom of the timing chain cover was worn thru from sagging timing chain.
Two lobes on the cam were worn almost flat
Hole in one of the valve covers, was wondering where all that oil was leaking out.

I was driving this truck all this time (since 1995) on unleaded gas without hardened valve seats, surprised its lasted as long as it did!

[special-K]

From what I've heard,after '71 GM reduced the nickle content of their blocks. This may not be accurate. Maybe someone else knows better. The cracked block doesn't exactly support that info,though. I think the '78 block will be fine.

[oldschool18]

heres what I know and it might not be correct it is what was past down to me........your HP ratting has nothing to really do with the block but with heads and cam ect... The blocks are pretty much all the same and you should be fine with the 78, your 70 motor was before all the emissions and it prob had large port heads and the 78 had small port heads. Take the heads off the 70 and put on the 78 and it would be the same motor just have the heads redone with hardened seats and if you got the money get them ported and polished and as for anything else you could bore the motor out to get a little more out of it. Are you planning on doing a stock cam and intake and carb?

[geezer#99]

THe new block will work as well as the old one.
If you're keeping it stock put the original intake and quadrajet back on, The Eddy 650 is not a set it and forget it carb. They're touchy with fuel pressure and have a built in secondary bog. Both things fixable but why bother . Keep it stock.
REbuild the quadrajet. If you don't know how or can find someone who can then pm me.
I'll slide down and we'll get her going for you.

[WIDESIDE72]

What year did GM start putting the dipstick on the passenger side? Was it later (80-82)? That would be the only issue as to originality.
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[68c10airstream]

i got into auto mechanics with a friend at the machine shop in the mid 70's and we talked in length about the "010 on the block and he said (without scientific knowledge) that he felt it was the nickel content. He also said you could tell when you took a hammer to the 010 and it would ring like a bell, boring bar had to work harder and get warm cutting an 010, compared to the now (at the time) late 80's early 90's what he termed gray dead blocks. No ringing bell, easier going with the boring bar and repeat early failure from cylinder walls wearing out. Flat top pistons, an rv ROLLER cam style with roller lifters if your machinist is confident recommending a brand, etc, or your stuck with flat bottom lifters and adding ZDDP with every oil change, or possibly delvac or rotella-t oil designed for the 18 wheeler crowd. Look on the internet and find the article titled "when good cams gone bad". That will sum it up. My suggestion is if you are going old school find another 010, and deal with the above. Good luck Brian F.

[Southpa]

OK thanks for the info and advice! I was assuming the "010" in the casting no. (that's the embossed 8 digit number on the upper rear, driver's side) was nickel content too, but the guys doing the engine said its not so. Its just the same run of block style, dipstick on driver's side, 4 bolt main etc. and they went for quite a few years. I was just wondering about those HP ratings but I guess it boils down to how you build it. Original heads are fine and going back on and cam will be RV type, I have a "slightly used" (4000 mi.) Competition 268 cam I wanted to use but they did not recommend it. The lifters got all mixed up and once again, warranty issues... I only paid 50 bucks for it about 10 yrs ago. For anyone local to me it can be had for next to nothing, got the spec sheet with it too.

I was having some warmup issues with the original 4MV, basically the old style choke (coil spring expansion) was pretty finicky and a mechanic buddy told me that the E-brock w/ the electric choke worked better. We'll see how it goes. As far as originality goes, I was mainly referring to the heads and block. Anyway, I'm going to stay the course. Should be driving it by next weekend...so they say.

[Daves70]

The 78 block is the same. If you get the heads off the 78 and the casting # ends with an 882 then those are good flowing budget street heads and work well with flat top pistons due to thier 76cc chambers.The nickel content is an 010 or 020 and is found behind the cam chain and gears,I'd bet they both say 010.The block casting # may also be 3970010 on both and GM used that block for years.You can still use a flat hydrolic cam today as long as you follow proper break in and use a zinc additive or one of many racing oils that have came out recently.

[Lattimer]

From a power standpoint, a 350 block is a 350 block. Its what you put inside that matters.

The later engines had flow issues due to emissions compliance, and the power suffered. Hence the wildly different power ratings.

[68c10airstream]

Ok, here i go with schooling from the seventies. If you want the truck to run nice during damp cold days 40-50 degreef. you need to address what is called EFE. That stands for early fuel evaporative. What it entails is this, intake with a heat crossover passage open between head to head, heat stove over most likely the rh manifold and hose to a closed aircleaner with the duct hooked up between air cleaner to stove. Nobody does it unless they want originality. If you are going to run an electric choke, and an open air cleaner and drive in warmer weather, a aluminum intake with spacer in between carb and intake. The quadrajet relies on intake heat to relax the choke, unless it's electric. Oh, forget using an old camshaft. New camshaft and new lifters are a must. Cams are ground with a 4 degree uphill slope to rotate the lifter. Old school cam to old school lifters, Roller cam (no 4degree uphill slope) to roller lifters. Good luck

[68c10airstream]

Me again, the 010,020 is cast into the block as raised numbers behind cam gear. Also besides ringing like a bell he also said if you shined a light in the cylinder holes it would glisten (shine ) brightly like it was chrome plated. I currently run a 5.3 2001 ls in my 68c10. my prior engine was a 94 350 roller block, fast burn 96 and up vortec heads, quadrajet carb, ramhorn manifolds and a jerry rigged heatstove and special aircleaner. It worked ok, but vortec heads have no heat crossover passages so cold damp mornings left a little to be desired, but with a special light rv roller cam grind, 9.5 compression, hyperutectic pistons with narrow low drag piston rings, it pulled nice from 2500-5500 rpms on 87 octane and no spark knock, but i was running on the frail edge with 87. That was a feature engine build through hotrod magazine titled DANGER MOUSE. I copied it with my own intake and carb. Good luck Brian F.

[special-K]

I don't know what the advantage of all this ringing like a bell,etc is cuz all I know is the 350s from the '90s ran longer miles than earlier motors. My '90 Blazer's 350 had 193,000 miles on it when I sold it and it had full power,ran smooth,no leaks,no smoke,no noises.
The nickle content could matter when building up a stronger motor. The HP ratings dropped when they went from using gross to using net. A '70 350 was rated at 100 more hp than a '72. Has anyone noticed that difference when driving them? The dipstick moved to the other side in '85,didn't it? If this is a 4-bolt it was a truck motor,I believe. I was always told post '75 only trucks had 4-bolts,but maybe the high performance did too? These days people feel the 2-bolts are just as good. I know a guy who runs 2-bolt 400s built to 406 in his 8 second Vega and that's all he's run for the 20+ years I've known him. Yes,he does blow motors. He'd blow anything up to go .01 faster

[68c10airstream]

Hi special k, You pretty much answered your own question on the newer motors lasting longer. Basically it comes down to emissions. Fuel injection has had a major reduction in unburned fuel finding its way into the crankcase. That dilution is what washes the miniscule oil film on the cylinder walls off and wears them out. Newer motors use low drag narrow piston rings that sit higher up the piston to reduce the unburned fuel that lays in the area between the top of the top ring and the top of the piston. Oh, back to the seventies, 1970 was the last year that gm had high compression motors, mopar held on one more year. Just look up specs in an old motor manual and you will notice the change. By 1975 when unleaded came out, egr valves, catalytic converters. pistons were not flat tops any more, they were what we called soup bowls to reduce compression ratios down into the 8's. Also newer engines run hotter which helps with longevity. I can go on and on but it may not be received well so enough for now. This is probably my 10th posting on any forum ever so i will go cautiously. Thanks, Brian F

[68c10airstream]

special k, the man with the ringing bell story could be reached at goodman industries in winona minnesota. His name is jim tapp if he isn't retired yet. What a machinist. He took me under his wing when i was a subaru mechanic in high school (yes, 17 years old working next to a 40 year old mechanic that didn't want to go to factory school) as subarus were riddled with headgasket and main bearing problems. So at 17 i went to chicago for factory training during christmas break. Those were fun days.

[68c10airstream]

Oh special k, tell you vega friend to look up grumpy jenkins articles on small block builds. His favorite block is 63-67 chevy 2 blocks. I loved these cars, had many and grumpy used these blocks because he could bore a 327 out 120 thousanths and not hit the water jacket. These blocks are unique and different then any other small block as the filter pad sits about 3 1/2 inches higher in the block so the clutch bell crank can go on under the first gm short spin on oil filter. Jim tapp saved a few of these as the were the holy grail of small blocks. And yes high nickel content. Thanks, Brian F. originaly from austin minnesota

[special-K]

That all makes sense and confirms what I often pondered about newer engines lasting longer. I was stuck more on a theory that the fuel injection had something to do with not allowing raw fuel leak down like a carb can. It all makes sense.

I'm big on using the older blocks myself. I'm about to do a 383 and decided to use the 010 motor I have rather than the '72 motor. I have a "built" large journal 327 (010) waiting to go in my '67 project. My '71 tow truck has a '70 255hp (010) in it,too.

The compression was dropped as well as how they rated hp. Yes the power did drop but it sure wasn't 100hp. I use flat tops when I rebuild anyway,so piston type doesn't matter to me. I just bought a 400 for $150. All I want from it is the crank,rods,and balancer. Unfortunately there was no flex-plate,so I still need that. I think Southpaw will be fine with the '78 block. Definitely better than repairing a cracked one,IMO

I tried to find Jeff's Vega searching Google,but no luck. It's a black car named "Hanky Panky II". Hanky Panky was a Chevelle he had 20+ years ago. He mostly runs at M.I.R. cuz our local track caved to the wussies who were afraid they would run out of track,so they run 1/8 mile...which I hate as well. Drag racing is 1/4 mile,if you ask me.

On your internet posting skills...You're doing just fine. Well worded and no fouls thrown. I'll look forward to more posts. My "ringing bell" comment was basically to say in the end most will never see the difference. I've had perfectly good service from SBCs of all origins. I just used my '90 Blazer example cuz I bought that new and knew it's entire history.

[Spoof]

Hi Southpa,
Haven't seen you around much lately, glad you're still running your GMC. Me too, although it's rear end is unreliable right now.
If you're interested I have a short block 350 from 69. I believe it's a virgin too, and I think it's a 4 bolt main.

Cheers

[Southpa]

Thankyou for the offer Shane but I was in on Friday and they already had the '78 motor half put together. Its amazing how things can add up too! Oh well, in for a penny I always say. That's one thing I like about this place, when I first logged in so many years ago I learned more about my truck in 4 days of reading than 4 years of driving. You guys rock! I sure would like to know how many miles (hard miles too) were on that old motor. Was just over 100,000 ( very likely 200,000) when I bought the truck in ,95 and I watched it go around twice.

[Spoof]

Yep, you got good innings on that one. You'll enjoy the new one I bet.

[GASoline71]

I think cats get too wrapped up in the whole "high nickle block" thing. A block is a block. It'll last forever if you treat it right.

I helped build a 4 bolt main 350 that turned 485 dyno'd HP and 444 lbft of TQ out of a block from a 1978 truck. So it's all doable... if done right.

Gary