SBC / engine building questions (1 Viewer)

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DesertLake

DesertLake

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Have any of you guys built a SBC? Feel like giving some guidance?

Possibly a bad decision, I bought a nearly complete 4-bolt 350 from a friend, supposedly only needing pushrods and rockers. He had it built at some shop a few years back then didn't use it.

I cracked it open and started checking end play, and lo and behold the forward pair of rods are at about .016 or .018, depending on if I use my feelers or dial. Spec is .008 to .014. :mad: I'm guessing this isn't correctable without replacing the rods or crank or both. Is this a big or small problem?
 
DesertLake said:
Have any of you guys built a SBC? Feel like giving some guidance?

Possibly a bad decision, I bought a nearly complete 4-bolt 350 from a friend, supposedly only needing pushrods and rockers. He had it built at some shop a few years back then didn't use it.

I cracked it open and started checking end play, and lo and behold the forward pair of rods are at about .016 or .018, depending on if I use my feelers or dial. Spec is .008 to .014. :mad: I'm guessing this isn't correctable without replacing the rods or crank or both. Is this a big or small problem?
Click to expand...

the crank end play is determined by bearing ware, even though it is out of specs i think it will be ok. are the bearings new
 
Yeah the bearings are new, and I haven't even checked the crank end play yet. This is just the rod end play. Tomorrow I'll start looking at the crank. Once I've got the end play checked, time for the plastigage.
 
alot of times when people freshen up a motor they dont check those specs they are just concerned with oil clearance , but its a good idea for you to check these measurements to see if you got what you payed for
 
A lot of times you can pull piston/rods from one hole and put them in another with a companion rod that is wider/thinner to get your specs in. A few thousanths here and there can fix a potential problem.

While you are in there, check to make sure they put the bearings in correctly, and make sure they have the rods indexed correctly. Too much side play indicates they ground the crank out of spec in width between the fillets. While you can probably bolt it together and run it forever with a hi-volume pump, if it makes you feel better, you can do some work right now and save some worry down the road.

I don't think I would lose a lot of sleep over it, but I would want to check it out and see if I have a pair of rods that are a little on the tight side, that I could swap into the loose journal, provided they would take up the slack.

If the heads are already bolted down, then just check everything good and torque things back to spec. .002-.004 too much side clearance probably won't kill you. It just might need a little thicker oil, or a higher volume pump to keep the pressure up when it gets hot and you idle around. In a stickshift rig that will see lots of time at 1,000 rpm under heavy load, there's a lot more need for oil pressure than one that has an auto behind it.
 
Just to help end any questions looming in the back of your mind, you may consider replacing all the bearings while your in there. A set from Summit won't set you back much and you'll know what you have.
 
Yeah, that's what I was thinking. I should probably pull the crank from my old 350 and see if its any better. With all that free time I've got...
 
Oh what the f-

I finally pulled the heads and started removing the pistons today to see if I can find a combination of rods to take up the slack. First I re-measured the connecting rod end play for all 4 journals, and got:

1-2
 
Oh what the f-

I finally pulled the heads and started removing the pistons today to see if I can find a combination of rods to take up the slack. First I re-measured the connecting rod end play for all 4 journals, and got:

1-2 .024
3-4 .015
5-6 .011
7-8 .005

Okay, so 1-2 measured worse than I though this time, but maybe swapping with 7-8 will fix it, 7-8 is too tight anyways.

I remove piston 1 and see this:
1193273445_2B9yC-L.jpg

A little hard to tell from the pic, but the forward face of the rod is pretty gouged up - not sure how big of a problem this is, but if nothing else increased friction right? It definitely looks like it has been abused with tools. Maybe I should get a new set of rods.

Then I removed piston 2, and saw this:
1193273549_X62w9-L.jpg


WHAT THE HELL! I think someone once tried to remove this crank without pulling the pistons first.

Looks like I'll have to put the old engine on the rickety stand and see if its guts are any better...
 
That looks a lot like a rod bolt gouge from dropping the pistons without a protector on the bolts, then getting the rod jammed in between the block and crank. That, or sloppy work taking the piston out of the hole.

That particular spot is probably not too bad of spot to be missing crank journal. Looks like it might be on the coast side of the crank throw which is less loaded than the thrust side. That rod with the sides all torn up looks like hell.

I would measure the rod widths and compare them. It's entirely possible that someone screwed up the rod and then sanded it down, or had a machine shop sand it down so it wouldn't gall up and seize.

If that one rod is skinnier than it's supposed to be, or at least skinnier than it's brethren, you need a new rod.
 
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If I didn't throw them away, I've got a set of used rods for a smallblock around here somewhere in my stash of junk. Otherwise I'd just buy one from a machine shop. They should just about give one away since you are gracing their door looking to have a piston pressed onto their rod.
 
I have the rest of the pistons out, #1 rod looked the worst, but several weren't much better. I once took apart a seized (with bonus caved in pistons) 351C, and did damage like this getting it apart. All of this makes me think bad things about the rest of the engine.

Any machine shop recommendations? At this point I'm assuming new rods, but I'd like them to have a look at the crank.

Damn it's hard to suppress the butthead laugh while discussing engine parts.
 
I've never used the one in Gardnerville, but I have heard o.k. things about them. There are others, one I can recommend, but they aren't cheap, is in Carson, off Goni. Something Marine or ??? like that. I can drive there, but I can't remember the name.

Good guys, seem to know their stuff and they have 2 dyno's so that's a good sign. The owner impressed me a lot, and one of their machinists lives right here in the valley. They aren't cheap, but then again, you are seeing reason #1 why cheap isn't always good when it comes to machine work.
 
AIMS on Glendale just east of Rock (across from Baldini's and down a little) is a good machine shop fairly priced - and very quick imo.

Will, in a previous post you mentioned that the engine pushing an auto tranny will not need the oil pressure that the manual tranny will. Can you explain more? I've never had an auto in a truck until last week. Is the auto slipping allowing the engine to maintain higher rpm?

Paul
 
That's the gist of it. A std trans will drag the engine down a lot more rpm, to the point it dies from too low rpm. Rarely can you get an auto trans vehicle to idle slower than 6-700 rpm loaded. In fact, unless you have an aftermarket 900 rpm stall converter it's almost impossible to load the engine at that rpm with any substantial load. With a stick, you can get one down as low as 3-400 rpm while idling over obstacles, where the engine is just hammering the crank trying it's best to keep running. At that rpm, you really need close bearing clearances and a good pump to keep the pressure up high and keep the bearings from hitting the journals.

I would demand that an engine hold at least 20 psi of pressure at 1000 rpm under load. With a high volume pump and decent clearances it's not out of the question to see that much pressure.
 
All of which is why I don't want to mess with a questionable crank. AIMS will look at it, and are also going to inspect the heads. I can't even tell what volume these World S/R heads are, and it is cheaper for them to fully inspect the heads than it is for me to buy head stands and a Buret and the odds and ends to measure measure the volume. They are backlogged, but the way I work they will still be done before I would have been. Hell if I can figure out how to get the block into the back of my Neon I'll haul that down there too.
 
Nice guys at AIMS. I took the crank and heads down, they looked at the damage and said it should be fine, pretty much as Will described. They also ID'd the heads for me: World S/R (I knew that part) 76cc with no modifications, so this is going to be an 8.5 or so engine. The guy also pointed out that the World heads will take a lot more abuse than the Vortecs that I was originally planning before I picked this up, so I'm going to run with what I've got. Except maybe the connecting rods, he'll have a look at those. If they are worth using I'll go back to the mix and match plan to even out the endplay.
 
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