SBC engine build rant

[Jblack6527]

Maybe wrong place, move or delete if so.

To make this as short as possible, me and my best friend built a 400 SBC for his hot rod a couple years ago. It was intake, roller cam and refreshed heads off another motor on a rebuilt bottom end with new parts.

Float hung on the carb and filled the oil full of gas on start up, we drained it but the damage was done and it spun a rod bearing about 15 miles in.

Back to the machine shop, and one new crank, rod, rings and bearings later we finally managed to get the motor reassembled and got the engine back in the car and fired up today.

Holy shit does it smoke like a freight train. We expected some smoke being new build and rings and all, but this is terrible. We set timing, got the carb close and took it for some laps around the neighborhood hoping the smoke would ease off as it got some heat in it.

Cut a few hours out, and we've burned around 3 quarts of oil in 20ish miles.
Not super easy miles, but never over 4500rpm.

Any ideas what gives? This isn't either of our first engine, and we took our time assembling the thing.
Sounds like from Google that either we did something wrong with the rings(upside down or lined the gaps up) which we were careful and paid attention, or something with the machine shop.

 

[reptillikus]

I'm thinking ring issues. What oil did you use for break-in?

 

[Jblack6527]

I'm thinking ring issues. What oil did you use for break-in?

Royal purple break in oil.

 

[grumpy356]

you get the ring gap right and clock the rings?

 

[M92PV4U]

Correct rings for oversized pistons?

 

[xjmark]

What color was the smoke? Blue or white? A friend of mine had a 377 (400 block, 350 crank) built by a reputable builder and it wiped out the bearings within the first test drive both times.

What the builder found was that there was an air pocket in the 400 block casting that was opened up by boring it .030 over.

After the 2nd rebuild, he pressure plated the block and ran a propane torch in each cylinder to find that one of the cylinders leaked coolant into the crankcase once the engine was up to temperature.

This one never smoked more than a normal rebuild, but it's something to think about. Those 400 blocks are thin and finicky.

ETA... the blocks are thin.

 

[Ummduh]

Did you re-hone the bores with the new rings?

 

[Jackie Treehorn]

Do the heads you put on have the steam holes that 400s need?

 

[Jblack6527]

you get the ring gap right and clock the rings?

Bought pre gapped rings, but we did check one in each hole. I don't remember numbers, but they were in spec.

I'm 95% sure we did. That was my job, and I remember doing it. Can't promise anything as we assembled the bottom end a few months ago.

 

[Jblack6527]

Correct rings for oversized pistons?

Yes.

What color was the smoke? Blue or white? A friend of mine had a 377 (400 block, 350 crank) built by a reputable builder and it wiped out the bearings within the first test drive both times.

What the builder found was that there was an air pocket in the 400 block casting that was opened up by boring it .030 over.

After the 2nd rebuild, he pressure plated the block and ran a propane torch in each cylinder to find that one of the cylinders leaked coolant into the crankcase once the engine was up to temperature.

This one never smoked more than a normal rebuild, but it's something to think about. Those 400 blocks are thin and finicky.

ETA... the blocks are thin.

Smoke is blue, and smells like burning oil.

Did you re-hone the bores with the new rings?

Yes.

Do the heads you put on have the steam holes that 400s need?

Yes. Shop drilled them for us the first time we assembled it.

 

[Chevy_man]

Did you recheck ring gap? No chance the shop decided to take it another .010 over because someone missed a memo?

 

[Quick & Dirty]

Does it have a PCV system? Are there proper baffles wherever it's drawing from?
A leakdown test will check if the rings are sealing.

 

[xjmark]

The obvious answer at this point is Lucas.

Heavy Duty Oil Stabilizer – Lucas Oil Products, Inc. – Keep That Engine Alive!

 

[Jblack6527]

Did you recheck ring gap? No chance the shop decided to take it another .010 over because someone missed a memo?

We were lazy and didn't check every ring, but we did check one per bore.
Shop is just one guy, but we did double check bore size. Lol.

Does it have a PCV system? Are there proper baffles wherever it's drawing from?
A leakdown test will check if the rings are sealing.

It does have a PCV, tee'd off the back of the carb with the power brakes because there are no other vacuum ports on the intake. There are baffles in the valve covers.

 

[M92PV4U]

Does it look to have excessive blow by?

 

[Mikel]

What do the plugs look like? Compression?

 

[Norm]

Rings, if it has not seated in 20 minutes its not going to.

Is it a fresh bore? If not a fresh bore molly rings won’t seat. Cast will work in a less than perfect bore but moly likes it perfect as in machine hone, not dingle ball hone.

The only other possibility is PCV, disconnect and see what happens.

 

[GM Guy]

refreshed heads off another motor

Forget the valve seals? Or old set of cracked to hell seals?

 

[M92PV4U]

Forget the valve seals? Or old set of cracked to hell seals?

I was thinking bad valve guides.

 

[Jblack6527]

Does it look to have excessive blow by?

Didn't pull valve cover breather to feel, but nothing on the valve cover around them. Doesn't blow the dipstick out anyway.

What do the plugs look like? Compression?

We were going to pull the plugs next. Ran out of daylight and motivation yesterday.

Rings, if it has not seated in 20 minutes its not going to.

Is it a fresh bore? If not a fresh bore molly rings won’t seat. Cast will work in a less than perfect bore but moly likes it perfect as in machine hone, not dingle ball hone.

The only other possibility is PCV, disconnect and see what happens.

Was a fresh bore/hone, and shop knew we were using moly rings and allegedly honed accordingly.

Disconnect PCV for what reason? To see if it's sucking oil?

Forget the valve seals? Or old set of cracked to hell seals?

Definitely has valve seals. Pretty sure we put bought new ones when the heads were redone.

 

[Jblack6527]

I was thinking bad valve guides.

This could be a possibility, I would hope the shop checked them, they replaced the valves and springs.

 

[Norm]

PCV can suck a lot of oil, just plug it off and it should be obvious quickly if that is the problem.

Did you install the rings upside down? There is a mark on them because there is a bevel on the edge.

 

[Jblack6527]

PCV can suck a lot of oil, just plug it off and it should be obvious quickly if that is the problem.

Did you install the rings upside down? There is a mark on them because there is a bevel on the edge.

I know about the mark, and was careful about how I installed them, but it's possible I could have messed one up.
I sure hope not, would make me feel stupid.

 

[gt1guy]

Float hung on the carb and filled the oil full of gas on start up, we drained it but the damage was done and it spun a rod bearing about 15 miles in.

You may have washed the rings with fuel. That would have kept them from at the least, ever seating.

 

[Jblack6527]

You may have washed the rings with fuel. That would have kept them from at the least, ever seating.

The block was sent back to the machine shop and rehoned, new rings and bearings were installed.

 

[Mikel]

Besides the above, pull carburetor and look at the intake runners / intake valves with a borescope.

 

[Jblack6527]

Besides the above, pull carburetor and look at the intake runners / intake valves with a borescope.

Looking for what exactly? Oil?

 

[Mikel]

Looking for what exactly? Oil?

Lots of it. From different sources. If dry, it would point to rings.

 

[arse_sidewards]

Sometimes new rings can take hundreds of miles of hard use to seat properly if the bore is real smooth (i.e. new rings in an old engine without a hone), which it probably is from your mullet-fueled misadventure with gasoline.

 

[Jblack6527]

Sometimes new rings can take hundreds of miles of hard use to seat properly if the bore is real smooth (i.e. new rings in an old engine without a hone), which it probably is from your mullet-fueled misadventure with gasoline.

The block was rehoned after the adventure with gasoline