Let's rebuild a 350! (maybe), PT.1

What originally happened was that the engine started to run funny---erratic vacuum gauge readings swinging wildly in pulse with the engine. Also, would stall out below 900 rpms.

So, this prompted me to take the engine out and put in on a "test stand." The last time i tried to run the engine, i added more water to the radiator, but then water started to come out of the dipstick tube(there was apparently a small hole in the tube):



Water came out of the pan like so after the oil drained out:



The reason for the orangeish color is not due to rust----this is the new Dex-cool extended coolant.

Deciding i needed to start taking it apart to investigate, after taking the valve covers off i noticed that the pushrod for #4's exhaust rocker was bent and the rocker was loose. This prompted me to take off the head to investigate further:



Basically, what happened is that cyl#4's exhaust valve somehow got in contact with the piston and actually broke off and imbeded itself in the piston:





Also, if it makes a difference, cyls 2 and 6 were full of oil and probably a mixture of oil and water:



Add'l notes:
i took this right side head off 4 yrs ago to replace head gasket (which turned out to be unessesary due to mis-diagnosis of another problem) i am pretty sure that i used sealant on the head bolts; Looking at the bolts, there appears to be sealant on them. However, i DID NOT re-torque the heads after running them for a while. i have recently read you are supposed to do this.

i'm trying to be practical here and decide to rebuild or get a new, reman(or even used) engine.

So, please list all the possible reasons for the above AND in the order of likely hood.

 

pretty sure it was NOT caused by you not re-torquing the heads.

Sometimes parts just break....like valves...


I'd be looking for another engine, probably has some damage to the block making the water come out.

 

1) Reason for above. - Something broke. (exhaust valve)
2) Practicality. - Throw that long block away. It's not worth rebuilding.
3) Final Plan. - Find another sbc 350 they are cheap and easy to find.

 

Magna flux the block and heads, before you spend a dime on it. You probably have a crack somewhere.

 

Yeah---it looks like a total teardown is in order.


Any other thoughts?

 

I would not spend another dime on that engine. 350s are cheap. start over.

 

I ran an Automotive machine shop for 6 years. The only way you get water in the pan is #1-blown head gaskets, #2-cracked heads or block. If you don't see obvious damage to the head gaskets allowing that much water into the pan, magna flux or better yet pressure test the heads. If no cracks, pressure test the block. As has been stated above DON'T start a rebuild until you KNOW the block is good. You can probably pick up a running SBC for not much more than the testing will cost.

 

My guess is that after the piston hit the offending valve, it in turn cracked a cylinder wall.. or the head, or both. See what you can see yourself, but magnafluxing costs money, and that money would be better spent on another non-exploded 350 and the subsequent machining.. so I agree with oldschool66, squirrel, and badshifter and mtshasta steve

 

^Agree with all the above who said just get another motor. 'tree-fiddy's' practically grow on trees.

 

Could you describe pressure testing in more detail?

 

What do you think caused the piston and valve to meet in the first place?

 

Looks like the head of the valve broke off, and mayhem ensued.

 

The term 'hung a valve' comes to mind,, something in the valvetrain went away,
valve spring or lifter would be my guess, valve could have seized in the guide also... which would leave the valve open and then hitting the piston when it came up,, might find out after tear down, maybe not,,

 

Ok, i'm not saying that insist on rebuilding this one; If scrapping it is the most practical way, then fine.

However, just out of curiosity and to see what the heck happened, plus taking it apart really doesn't cost much i decided to take it apart.

As an interesting twist to the story, every lifter on that side of the engine slid out no problem EXCEPT #4's exhaust, suprise, suprise. i can't get it to move at all.

i haven't tried spinning the engine yet---don't have a stand; Will probably get a $45 harbour freight job asap.

Will report back in a few days as i work double shifts every other day (yet make less than before)

 

Hey, I dont blame ya, I'd wanna know too,,
Plus all the inquiring minds do too,
Lifter siezed in the bore,,, now the mystery thickens,,,,
Did a quick search on seized lifters and found this,, very interesting, maybe a lesson to be learned here:
"Many daily-use or street/strip hot rod engines are built up from 35-40-year-old engine blocks. The average builder never checks the lifter-body-to-lifter-bore clearance. It may have doubled. Pro guys bush the lifter bores, but most homebuilders just dust the bore with a brakehone to make the bore smoother and remove varnish. If there's more than .001-.0015 clearance, you could be in trouble." Barry Robotnick

 

Ok, i did some more disassembly and.......... (note: pictures should re-size down in a few minutes/hours)

Cyl, #4:







i don't know if it matters but this was a 4-bolt main crate 350:

 

was it a Mexico motor?

 

The pictures of the water coming out of the pan cringe my heart, I've had this happen on a 400 Pontiac, except the water got mixed in with the oil and came out as a milky sludge which was even worse. If you're looking for a detailed engine rebuild process online, have a look at this link, it's a 454 chevy. http://restorecarsfast.com/enginerebuild/

 

Si ---"Hecho en Mexico" stamped on block and heads. Goodwrench 350.

 

ouch. cyl don't look so good....

 

Looks like the rod and piston are a bit tweaked as well, locked up ya think? Get the slug out and look at the cylinder wall and also the #4 combustion chamber. I don't advocate saving this one, just curious.

Bob

 

Yep, damn, I feel your pain, on the bright side, 350 blocks are plentiful and mostly cheap for a stock block and heads. Check the classified ad section here on the HAMB even,,

 

Can i re-use the pistons? Except #4 of course. What about bearings?

 

What I would do is:
Inspect Inspect Inspect,,
Bearings are about the most inexpensive entity in the engine, but they're also one if not THE most important that will guarantee engine life,, if they are primo, no nicks, no scrapes and no errors, no copper showing, then yes, you can re-use them, Obviously not the one that hit the valve, or the rod it is connected to, INSPECT for other damages, You will need to know whether or not the engine has ever been rebuilt or refreshed before, On the back of the bearings there should be some nbrs and info that tells you whether or not that crank is std or .010 under maybe .020 under. Never take anything for granted, as far as Pistons, yes you can reuse them also, again, look for scrapes and damage down the sides and skirts. Clean the pistons with Super Clean or Simple Green, or Carb cleaner, dont use wire brushes. Same for the cam, crank, timing set, etc, The oil pump should be taken apart and inspected also, but again, they're cheap. Was this a STD bore engine? .030? You can Get another piston of the same design, same size (std, .030, .040 etc) were these dished pistons? Make sure you get one of exactly the same design, The crank should be good, If in doubt ask, take pics, You will need to find a block that has the same bore as those pistons, So you have some things to check into. I have found Craigs list to be a great source for parts,, I have rebuilt a few of them in my life, I have micrometers and I know how to use them . I recommend you get some and do the same. When you are armed with precision tools, and knowledge you will be able to deduce your situation by yourself. But I am sure that there will always be folks ready to help on the HAMB.. If you want to talk, go ahead and pm me, we can talk over the phone.

 

The more and more i read, it seems like decent, usable sbc cores can be had for $75-200. And machine shops should have some on hand or know where to get some?

i think i can re-use my oil pump, pan, intake, balancer, flexplate, possibly crank and possibly heads. But even if i needed to replace EVERYTHING, it seems and decent running engine could be built for $650? This is assuming i go with used heads as well.
Am i right on this assumption?

The purpose of this engine will be, in order of importance:
1) Primarily a back-up transportation engine.

2) Something to race on the weekends, powering a 3800lb car to at least mid 13 second range, then possibly 12, then possibly 11 but no faster than 9.99.

 

I don't think you can build a decent engine for $650.00, especially one that will go mid 13s.
You probably need to talk to a local machine shop to get labor prices, then grab a Summit/Northern/etc. catalog and figure parts.
Most decent "hot rod" engines I've built start around $3000.00 and the price goes up REAL quick.

"Speed costs money, how fast do you want to go?"

Larry T

Just looked at my Moroso Power Speed Calculator. Looks like mid 13's at 3800 lbs. would take around 300 hp to the rear wheels. That wouldn't be real tough. 10 flat would take around 700 hp to the rear wheels. That'll be a little harder.

 

You've got three choices-but you can only select two of the three

Good,Fast,Cheap
If it's good and fast-it won't be cheap
If it's cheap and fast-it won't be good
If it's cheap and good-It won't be fast

Now make you're choices

 

14 seconds is easy to do with inexpensive parts, 13's and even high 12's is possible with around 300-400 hp, however to break into the 11's and get into the 10's does take some special parts, more hp, and a little more than common know how, or, more money. The other HAMBer that said "Speed cost money, How fast Do you Want to Go? is absolutely right,, I encourage you to be diligent, read those books, see what people are runnin for parts and the speeds they're goin, remember too, you gotta start somewhere,, 14's should be easy, and for a beginner, thats the goal I think you should shoot for in the beginning, but first get your short block squared away. You got my number if you wanna talk,, later

 

Next question, do the rod journals on a SBC pretty much have to be at BDC (rod journal position, not piston position) to be able to take the pistons/rods out?

As you might be able to see in some of the previous pics, cyls #5 and #6's rod journals were pretty much at bdc or 6'0clock if you were looking at the engine right-side-up. And they came out pretty easy.

As you can also see in the previous pics, or can use your imagination, #3+#4's rod journal is at TDC; i was able to get #4 and #3's rod cap bolts off, but i could not quite get #3 out. i got the piston about even with the deck, then it stopped---it may have been coming in contact with the bottom of the cylinder.

#4 will move about 1/8" then it stops. i'm thinking this is due to the cracks in the cylinder wall. Also, because of those cracks, i'm thinking it's difficult to turn the crank.

 

the pictures of the #4 cylinder that were taken from the crank side looked like there was a nasty crack in the cylinder..

i have also read accounts on other forums of this dexcool eating up older head gasket material..

honestly that shortblock is pretty much scrap, wouldnt waste the time tearing it down.. with the cylinder being cracked, bent rod, more than likely the crank is bent, or its atleast tweaked and will need to be reground to true it up..

for the money i would more than likely recommend a new gm crate short block and have your heads completely rebuilt..