I just installed a 400 sbc in my t-bucket.a few questions, its got a rapid vibration in it, i think i have the wrong flexplate in it, it had a counter weight, but i had to dremel out the bolt holes to align them!!The weight looks fairly hefty.If anyones got a correct 400 flexplate & could give me the measurement of the weight i can tell. Also whats the litres on it? is it 6.6? what cars did they come in, this ones a 1979 or 80. And lastly someone told me that you want the temp up about 200o on it,he said the heads won't cool good if the temps too low!! is that true? Thanks JimV
Yeah it's 6.6 litre.The weight on the flywheel is critical,or you can use a 350 flywheel with a balance plate sold by Summit or others .These engines are real happy at 180 degrees.They do run hotter than other small blocks because they are a siamese bore,no space in the block casting between the cylinder bores.This does not mean you need to run them hotter!These engines make a ton of torque but if you're planning on RPMing it a lot you need to buy a steel crank-$1000.You can rev them to 6 grand regularly with no problem.
oh helll yeah...sbc 400 small blocks are great torque makers..but like terry says....6000 is about all i'd go with a cast crank. the 400 i had ran @ 200 degrees all the time, no matter what the outside temp was (with a 195 t-stat, and a 4 core radiator) the 400 i had was midly built (performer intake, holley 650, performer cam, stock rocker arms, stock pistons, stock crank, small tube headers, and a 125 h.p nitrous set up.) in a 71 chevelle, with 3:23 gears, and a turbo 350 trans, it ran consistent 12.90's in the 1/4. i loved that little 400..... the 400's are externally balanced so the correct flywheel and harmonic dampner are important. these motors came mostly in impalas, but i think some chevy blazers may have had them as well.
So did you add a bolt-on weight to your old flexplate, or did you buy a 400 flexplate? Sounds like your problems can be solved with a proper 400 flexplate. Several places have SFI versions for reasonable prices, they're thicker material. PS- you know the balancer is different too, right?
400 was last used in passenger cars in 1976, 77-80 was in pickups only. having to waller out flywheel bolt holes sounds kind of wierd....chevy used the same bolt pattern on all V8 engines from 55-85, including the 400. 400 and 454 had external balance, and a dowel pin in the crank to make you put the flywheel on the correct way. You can put a 454 flywheel on a 400 and it will be balanced wrong, but the bolt holes should line up.
here are a shot of a 400 flex plate and balancer....you didn't by chance end up with a late model 1 piece 350 style flexplate did ya ...as they have a weight as well.......brandon
Once you get the proper flexplate and balancer on there, you'll be fine. I ran a 400 (+.030", makes it a 406, actually) in my street/strip car for 22 years. Used a 180 thermostat and it always ran 180-195. Anyway, I tortured the stock cast crank with 7K shifts, every time it left the driveway, for all those years. Finally spun a couple main bearings last fall. So it can be done, but eventually, you'll pay. Casting variations (core shift, etc) are very common in the later model 400s. I was very lucky to get away with torturing mine so much. Now I'm building a new one, from an early (3 freeze plugs per side) block - much better quality, and MUCH more expensive! I say: Don't wind it to the moon, throw away your tach and temp guage, and relax and enjoy the ride...
it has the right damper on it.when i got the engine it had a clutch flywheel.i'll look into the vibration tomorrow.I just got the sawap done & was played out. JimV
I think my problem is the flexplate i have might be for a 454 BBC!! does the 454 have only one set of bolt holes in it? 6 at the same height?(dia.) Is the weight more on the counter balance? Holes line up now that i elongated them.Seems fine except i don't know if the balance weight is the same. jimV
I wasnt aware that Chevy ever sold a 400 with a standard tranny. I used to work at a speed shop in the 70's and the owner took the weight off of a flex plate and welded it to the back of a standard flywheel then ballanced the whole rotating assembly. There is also the chance your engine has been internally ballanced with mallory metal to use a non balanced flywheel. In that case you will need a 350 flywheel. Do some research and see if this could have been done in the past.
400 Chevys used to be a fairly well-kept 'secret' back when I first got into cars...until Bozos started robbing the cranks out of 'em to build their 383 engines! ("Oh! 400 cubes is way too much for me, thank you...but 350 isn't enough. Hmmmm....383 oughtta be just about right!!!" ) Back then. people used to love to tell all of the stories about how 400s overheated all the time, cracked heads and blocks, blew apart at 2000rpm, popped head gaskets on a weekly basis and all sorts of other misconceptions. The rumors spread like wildfire until they came to be taken as 'fact'...and the 400 SBC became the unwanted 'bastard child' of the small block family. That was cool. A few of us used to go around picking them up for free or buying them for chump change because nobody else wanted anything to do with 'em! All was good until more and more guys started running them and putting some serious hurt on the competition...then savvy racers and Street Heroes started giving the old 400 a serious second look!! Nowadays, they can be a bit harder to find, and a tad bit more expensive...but enough people still believe the old wive's tales to keep them semi-reasonable...you just need to look a little harder to find 'em. No big deal. In short, they DON'T overheat if the cooling system is up to snuff, they DO require the correct 400 sbc flex plate or flywheel (I have seen at least TWO 400s with manual trans flywheels in my time), they DO require their own head gaskets and any 1st gen sbc heads will bolt on, but 400 heads have 'steam holes' in them, and you need to drill those holes into any non-400 heads you install on a 400 block. Aftermarket heads are available with the steam holes already drilled. The ONLY 'bad' thing about the 400 is that it likes to drink the gasoline! I drove a 79 GMC 4x4 with one of those motors in it and it sucked both tanks dry in short order...but it could move a mountain with a touch of the throttle!! It never got over 180 degrees (with a 180 stat) and never broke, puked coolant, popped a head gasket or anything else! Get the right flexplate on there anfd you'll be real happy with it!!
My stepfather used to run a 400 sbc, .030 over, and destroked with a 350 crank in his super modified. Someday, as an homage to him, I would like to build a similar motor (pump gas though) with a Hilborn MFI to drop into my '58. He said it was plenty beefy enough and had to stay out of it enough because it always wanted to break loose.
400's are GREAT engines, my choice of all the chevys, I love torque. I have a question though (don't mean to hijack the thread). A friend of mine just told me about a truck for sale with a rebuilt 400 in it, but he said it has the newer "center bolt" heads on it. He wasn't able to drive it (broken frame) but said it ran well, and didn't overheat or act up while running. The guy selling it said he bought it that way and it never gave him any problems. I assume the rebuilder drilled the steam hole if that's the case. Anybody ever run the newer heads on a 400?
when it comes time to rebuild you 400 find a set of small journal 327 rods and have the crank offset ground and you can get up to 426 ci, set of camel hump 202's with the steem holes drilled, a high lift short duration cam with a short lobe seperation and you can have your own stump puller.
You could drill the steam holes in the newer style (1987ish) center-bolt sbc heads and run them on a 400 if you wanted too, though I've never done that and likely wouldn't. 400s came from the time of unleaded fuel, and any of them built after 74 will be compatable with today's gasoline. Also, the stock 400 heads are fine for a driver or mild performance mill. If I were to change heads on a 400, I'd go with aftermarket heads for a more serious mill. Make sure that rig really has a 400 in it...the balancer will be a dead giveaway. It could just have a 305 or 350 in it...and it wouldn't be the first time that some seller knowingly (or unknowingly) tried to pass one of them off as a 400.
I thought the same thing, but the first thing my friend checked was the balancer and it had the cut out. He's a chevy guy and knows them well, but like you, I couldn't understand why the later heads, unless the old ones were cracked or something or he didn't want to spend the $ to rebuild them and had these lying around or something. It's what's keeping me from making an offer.
Late model ('86 up) weight looks different...has a sort of notch at each end. One of those would have to be hogged inward out to fit bolts. I think both 400 and 454 early weights are similar to picture shown.
On the standard shift flywheel deal--Chevrolet used to sell one for 400 small blocks over the parts counter under part number 3896394, but discontinued it a few years ago.
I put a set of World Products Sportsman II iron heads with the angle plug option on the 406 in my 40. They give you very exacting instructions on drilling the steam holes. They do not go straight down they are angled. I had no problem doing them with a hand drill
i forget right now just what companies are making them but there out there, http://ncarboni.home.att.net/Engine.html
The 400 SBC are Great like one other guy said shifted @ 7000+ With a stock cast crank for 4 1/2 years The old lady is now up on jack stands with a freash'ed up Engine in it for the last 5 Yrs now. just got way out of hand on the coast to travel and race. 60 Ft was 1.49Sec ran 11.40s @ 122 MPH in the 1/4. You'll love it Hope you find your problem I also think you have a 454 fly wheel instead of the 400. Good Luck.
there is something wrong if you had to mees with the holes to get the flwheel on, the holes may be clocked to only go on in one position and you did not have them lined up so you "fixed it".
basicly what i did was elongate the holes.The flexplate holes where 11.50" the convertor is 10.75 so i elongated then( inward) 3/8" i put washers on the bolt head side & it seemed to work perfect!! Seems #7 cyl. isn't firing, i just found that out so tomorrow morning i'll look into it more.Thats where my roughness is coming from its not a vibration. I ran it today down the highway & into alittle traffic & the temp never went about 200o. mostly stayed right at 190o Big differance between a mild 350(was in there) and the stock 400!! especially in a T bucket that only weighs about 1400lbs.I had a 305 in it at first & putting the 350 in made a big differance, now its unbelievable!! JimV
If you are looking to replace the heads I just came up with a book of Chevy engine builds that had a long rod 406 in it w/ Vortec heads. If I remember right it put out high 400's for HP and low 500s for tq. Maybe that's the "centerbolt" heads mentioned earlier in this thread. And they are comparatively cheap too (for new parts anyway). I'll have to look in the book when I get home.
Okay, I'm home now. I found my book, it's "How to build Big Inch Chevy Small Blocks" by Graham Hansen Published by SA Design (SA 87, ISBN# 1-884089-86-0, printed in China, Damnit!) . It's got lots of stuff in it and would be especially usefull to anyone that hasn't built an engine before. I bought it at Barnes and Noble for $19.00. "7 Complete Engine Buildups: 383-454 Cubes!" it says on the cover. Okay as for the build 400 SBC short block with SCAT 4340 I beam rods, Probe dished pistons w/ Total Seal 1/16th inch rings. Compression was 9.5:1 Total timing was 35 Degrees. Cam was by Lunati, Hydraulic Flat tappet 230/230 [email protected] w/ .455/.455 inch and 114 degrees of lobe seperation. 1.5:1 Harlan Sharps on "Stock iron Vortec" heads w/ 1.94 X1.50 valves. Intake was an edelbrock RPM Air Gap Vortec w/ a 750 Holley HP and the headers were 1 5/8 Hedmans with a 2 1/2 inch exhaust. Now for an appology I can't find in the book where it says how long these rods are and it wasn't high 400s for horsepower. Thats what I get for woking in the middle of the night when I should be sleeping. So it made 427 Horsepower at 5000-5100 and 525 Lb-ft at 3600-3700. The chart goes from 2400 to 5500 and starts w/ 216 HP and 472 Lb-ft and ends with 421 HP and 405 Lb-ft. Not a high RPM screamer by any means but it should be fun as the torque is available anywhere in the curve. You could probably substitue less expensive pistons and rods for this power level if you didn't want to upgrade the heads later without going back into the short block. As a side note I seem to remember a Chevy High Performance article on building up a 400 and they got the flexplate indexed wrong on the crank (said they had it ballanced without the "alingment pin" in the flexplate and then installed it in the car sith it 1/6 of a turn off). It destroyed itself in short order. I wouldn't expect that to be your problem (as I wouldn't think it would still be running now) but I just remembered this, in case your vibration isn't just a sleeping #7. As for the alignment pin, I haven't seen one on a 400 (or anything else for that matter) as the only complete one I have still has the TH 400 that Chevy bolted to it in Detroit. Hope ths helps. Nexxussian
Geeze, I didn't mean to re write the book here! And one of these days I have got to get off my dead butt and do my intro!
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