i started to have an issue with my 406 this weekend. if it gets above 208 degrees it'll start to smoke. the smoke isn't really blue or white. its kinda a mix between the 2 and it smells weird. it doesn't get a miss or anything when this happens either. once it cools back down the smoke stops. any suggestions. i've only had the engine for about 2 months now and its suppose to only have about 10000 miles on it. i'm going to try and start with the head bolts to make sure they are torqued correctly.

does the smoke smell sweet. if so you have coolant entering your cylinders. check to see if the machine shop that built the motor used heads specificly for a 400 block. if they didn't did they drill the steam vents into the heads??

i really couldn't tell from the smell of it. it smelt different than oil and coolant. i bought the engine from a guy i know who builds engines and race cars for a living. i know the heads are 882 casting heads.

I would be pulling the heads to see if steam holes were drilled. unless that guy specifically remembers drilling them. otherwise you will toast that motor.

i'm about to just sell it for what i can get out of the whole truck......thanks for the info though.

i'm about to just sell it for what i can get out of the whole truck......thanks for the info though.

It is really simple to pull the heads and check that the steam holes were drilled in the heads. Sounds like it may be getting hot......and no steam holes would do that on a 400 SBC....

.....you said you started to have problems this w/e....the motor has 10000mi. on it....how many miles have you got into it? Do YOU have much drive time on it....meaning how has it been for you before this?

before this past weekend it has been fine. the whole time i have had the engine it hasn't been over 200 degrees. i've had the engine for about 2 months. i've probably got about 5 trips out with it. i'd say that if it is smoking when it gets above 208 that i just about have to have a crack somewhere. i'll probably pull the heads to check them and if i can't figure something out there i'll probably just sell it the way that it is.

I'll give you 100$ for it :)

i'm about to get aggravated at it enough to sell it for that.

Going to go out on a limb here......as not being with it 1st hand....I am thinking head gasket or cracked head. Hopefully for your sake just a head gasket. You say it smokes....not really blue (oil) but not really white (coolant)....and it smells weird.....to that I say coolant.

Seriously, take it down, it is easy enough. Or at a minimum pull the plugs see if they look "steam" cleaned and while the plugs are out....pressurize the cooling system with a press. tester let it set and see if...#1 it holds press. and #2 see if a cyl. fills with coolant. It may not because like you said it needs to heat up 1st. But you never know till ya try.

Investigate what the problem might be......and report back.

Going to go out on a limb here......as not being with it 1st hand....I am thinking head gasket or cracked head. Hopefully for your sake just a head gasket. You say it smokes....not really blue (oil) but not really white (coolant)....and it smells weird.....to that I say coolant.

Seriously, take it down, it is easy enough. Or at a minimum pull the plugs see if they look "steam" cleaned and while the plugs are out....pressurize the cooling system with a press. tester let it set and see if...#1 it holds press. and #2 see if a cyl. fills with coolant. It may not because like you said it needs to heat up 1st. But you never know till ya try.

Investigate what the problem might be......and report back.

definitely agree on the coolant.

MoreTec says those heads are from a 74-80 350/400 and are 76 cc chambers. If they used the same casting for both applications would the steam holes already be there? Do the head gaskets come with the steam holes in them? I do not remember if the gaskets are universal since I am one of the few who have never had a heating problem with my 400 sbc. Maybe because it has the 4 core big radiator.

No, typically the gaskets are not universal. They do have gaskets specific for the 400 (steam holes punched) and then some that steam holes NEED to be punched. Basically if a gasket is used without the holes it is the same as the head not being drilled....steam can't escape.

i'd like to start tearing into it this weekend but i dont know yet. hopefully just be a gasket issue.

The steam vents could just have trash in them. I've heard of this happening a lot and also people putting gaskets on without holes punched for the steam vents.

Yes, that was one of the problems with stock 400's AND poor maintenance....scale would plug the steam holes causing an overheat. The bad 400 raps really comes from head swaps without steam holes. BUT, he only has 10K on it (could still be poor maintenance) and I hope the machine shop didn't leave any garbage in the block after machining....


EDIT: We could go back and forth ASSuming what the problem may be.....Slider Buck get into it and report back. We, here at PBB, expect a full debriefing (full written report) by Monday 2/25 0800... :)

Thats funny! A full report to be at least 1 full page double spaced in 12 point font. Ha Ha. The advide about checking the plugs for being steam cleaned is really the starting point. That way you know you have moisture getting into the combustion chamber, that and cranking it over slowly after the plugs are out to see if you have any water/coolant coming out of the plug holes. Good luck and keep us posted, because we want to know, and help.

well i got it all tore apart but didn't find anything wrong other than they are 333882 heads without steam holes. i'm going to take the heads to a machine shop one day this week to get checked out and have him drill the steam holes for me. i looked all in the cylinders figuring i would find a crack in there somewhere but it might be so small that i can't see it. id say if it is a crack it is very small. it wouldn't even smoke till it got to 208 degrees.

Not having steam vents was the problem, I'm suprised that motor even stayed together

Now, aren't you glad you kept it and didn't unload for $50?

EDIT: Oh yeah, we're still expecting the full debrief on our desks Monday 0800. Yes, you've found the likely problem. But, now you need to reassemble to verify that was the sole problem. I am sure that'll be in the full debriefing on Monday 0800......issues>inspection> problem found>reassembly>repair verification.... :)

not so sure that i'll have a full report by monday morning. i'm going to drop the heads off to a machine shop tomorrow and he'll get to them around tuesday or wednesday. hopefully have it back together by next friday. he's going to clean them, drill them for the steam holes, and magna flux them for cracks.

start checking around the tops of cylinders for cracks, while you have the heads off.

one sign is a clean piston top.

start checking around the tops of cylinders for cracks, while you have the heads off.

one sign is a clean piston top.

any amount of water in the cylinder should make it all clean shouldnt it?. So a clean piston could just be a sign of the bad head gasket as well right?

Dont they make something that a DIY guy can use at home to show cracks?

any amount of water in the cylinder should make it all clean shouldnt it?. So a clean piston could just be a sign of the bad head gasket as well right?

Dont they make something that a DIY guy can use at home to show cracks?

a flashlight. and a magnifying glass. oh... you might also look for dark lines that dont match up to any honing marks.

well i just got back from the machine shop. he said that both heads gaskets were leaking. it was between both the middle cylinders. there is also some intake valves that aren't sealing off all the way so he's going to do a valve job while he is at it. also taking .015" off of the heads. then when i get them back i'm going to gasket match them. i couldn't believe how much material there is on the intake side of the heads that can be removed. probably be working on them for awhile.

well i just got back from the machine shop. he said that both heads gaskets were leaking. it was between both the middle cylinders. there is also some intake valves that aren't sealing off all the way so he's going to do a valve job while he is at it. also taking .015" off of the heads. then when i get them back i'm going to gasket match them. i couldn't believe how much material there is on the intake side of the heads that can be removed. probably be working on them for awhile.

if you have the ability, and the tools, you might take the valves out and do a little work on the bowls under the valves, as well. cleaning them up can provide you with a lot more performance advantage than you might think.

match the intake to a gasket, then match the head to the same gasket. it is not a requirement to polish the runners, as the rough surface tends to help keep fuel in suspension. I would suggest using a cartridge roll to finish with, but dont make the finish mirror smooth.

dont take any material off the floor of the runner, if you can help it. the air needs to rise up before diving past the valve into the cylinder.

i thought about porting around the bowl area but i'm afraid of messing it up. the machinist was going to leave all the valves out for me if i wanted to do it. i think just gasket matching will do good enough for me. that 406 was already plenty enough for that toyota. he figured with doing a valve job, milling .015" off, and gasket matching i'd get somewhere around 20 horse extra. i aint looking to get much more out of it.

take as much as you can get.

this is free.

all you need to do is smooth out the contours. just dont hit the valve job and make any turns gradual and consistent.

well i'm slowly getting it put back together. i got the heads gasket matched and put back on. the intake is cleaned up and ready to be put on next. hopefully have it done tomorrow night sometime. i'm trying to figure out what to do about a water pump. advance auto sells one for a 70 caprice with a 4 barrel that i'm thinking about going with. they list one for a 2 and a 4 barrel. what is the difference? does the 4 barrel one flow better?

well i'm slowly getting it put back together. i got the heads gasket matched and put back on. the intake is cleaned up and ready to be put on next. hopefully have it done tomorrow night sometime. i'm trying to figure out what to do about a water pump. advance auto sells one for a 70 caprice with a 4 barrel that i'm thinking about going with. they list one for a 2 and a 4 barrel. what is the difference? does the 4 barrel one flow better?

hard to say.

the water pump mounts for the upper alternator bracket might have changed on that model. Some pumps have a boss for a bolt to be installed to adjust tension on the front of the cam cover, but i doubt that was it.

the upper alternator bracket mount might be offset about 3/8" to the rear which changes the geometry on the bracketry, making the alternator freakish, sometimes. if you run into a wierd bracket, this might be the cause. over the years, ive found a few of them.

Yep, that is probably it. I recall buying a pump, painting it and bolting it up to realize it was the wrong one. I solved it by using a spacer behind the bracket. Two exhaust manifold washers if I remember correctly!

Sorry,I just found this,I have saw several sets of 882 heads without steam holes, I built a 406,Back in the early 90's for my brother with 186 heads and I drilled the steam holes in the 186 heads.Glad you found your problem,I hate to see a 400 block wasted.:D I think, I still have 2 sets of 882s without steam holes.

Sorry,I just found this,I have saw several sets of 882 heads without steam holes, I built a 406,Back in the early 90's for my brother with 186 heads and I drilled the steam holes in the 186 heads.Glad you found your problem,I hate to see a 400 block wasted.:D I think, I still have 2 sets of 882s without steam holes.

What do you think of using the 350 crank and rods? I got the parts and I think a 377 would be a good engine to build. Basically a basket case buildup with on hand parts. Looks like the main bearings would be the most expensive parts.

What do you think of using the 350 crank and rods? I got the parts and I think a 377 would be a good engine to build. Basically a basket case buildup with on hand parts. Looks like the main bearings would be the most expensive parts.

I've been wanting to build the same motor, they sound like they have a lot of potential to being an high power and reliable motor.

while the 377 does provide potential higher RPM power, and it does have more power than a 350, the 400 version would still provide more lower end torque (*what most people use, and need in a 4x4).

so... a 377 might be a great idea. but its a sacrifice.

I have all the stuff to build the 377. I do not have the 400 crank. I know the 400 would be a better torque motor and the 377 would be able to buzz some, but would the 377 with a 350 crank and rods be easier to build than trying to find a 400 crank?

I have all the stuff to build the 377. I do not have the 400 crank. I know the 400 would be a better torque motor and the 377 would be able to buzz some, but would the 377 with a 350 crank and rods be easier to build than trying to find a 400 crank?

well, if you have some of the parts, then do it, as long as you realize youre doing it on a budget. also realize that you will have to limit your power output due to the marginal quality of stock components. Since you wont be buzzing it to 7500 rpm all day, you probably wont need much more than stock stuff.. right?

know that the 400 piston is heavier. It has the same compression height in stock form as the 350 piston, which means if you use 400 pistons and 350 rods, you can use a stock crank. you cannot use 400 rods and 350 crank, as the rod is 5.565 inches long, instead of 5.7 inches long.

if you have press fit pistons on stock 400 rods, you run the risk of losing a piston by disassembly to fit the 350 rods. the pins sometimes gall when you try to remove them.

so, now that you have the stock parts together, you can get the bearing spacers and put bearings in your 400 block. this shouldnt be too much hassle.

so, with stock rod bolts, the combo is good to about 6800 rpm, or until you let off the gas suddenly and the piston pulls the rod bolt right through the stock nut. *(the vacuum created on the piston top may result in catastrophic failure of the rod bolt). This may never happen. or, it may show up real quicklike. I know guys who have run stock rods and stock bolts for years. I know guys that have blown up 34 engines before they were 25..

ok... cast crank?

some cast cranks live for a long time at 7800.... i know one did... but it was balanced. I know another that lived for a long time at 6600, it was also balanced. Have you thought about balancing the rotating assembly to compensate for the heavier 400 pistons? 200 bucks out of your budget *MINIMUM* to balance it.

those are basics.

if you are going to lug it around the hills like an old garbage truck engine, itll probably live forever without major performance enhancements like balancing, and high dollar rod bolts.

so, if thats the case, you have a low rpm large bore 350....that measures 377 inches. shit, run it.

The only reason I want to build the 377 is better high end power plus I've heard of people beating them to hell and staying together when a 400 would not

well i finally got it all back together. the darn roads are such a mess i can't even get into it to see what it feels like now. hopefully get it in the trails this weekend sometime to see how everything is now. i went with a WP490HD water pump. its suppose to be a heavy duty/ extra cooling pump. it was only $50 so we'll see i guess if it works any better. i know at about 600 rpms before it wouldn't hardly flow anything but now it moves a bit more coolant at that rpm. thanks for all the info and suggestions guys.