need advice 400 sbc

[sev85]

Hey guys its been awhile since i have posted here but i need some quick advice i recently blew up my 350 sbc i found out from casting numbers is a 2 bolt main from a 72 vette the block is saveable but i need a motor asap i have the chance to get a 400 small block for 150 complete motor runs and turns over comes with torque converter should i buy it?

i have a 1982 gmc high sierra long bed th350 stage 1 kit 203 transfer case with part time kit gm corp 10 bolt front 3.42 gears and a gm corp 12 bolt rear also 3.42 gears 4 inch rancho lift kit with 15x10 outlaw 2 wheels currently has 36's going down to a 34 or 35 mainly used for driving around some light off road and not really trying to go outrageous maybe 350-400 hp is pushing it

heres some questions i have

I have a aluminum edelbrock rpm performer air gap intake will it work fine on the new 400?

i have a set of 462 2.02 intake 1.6 exhaust heads will they be ok on the 400?

i will be using a freshly rebuilt edelbrock 6310-03 600cfm electric choke carb will it be enough for the 400?

a set of 1 5/8 to 3 1/2 inch collector hedman long tube headers to go on it to true dual exhaust 2 inch pipe with glass packs be ok for the 400?

and will the stage 1 th350 be ok on the 400?

i also will be installing a double chain timing gear set before the motor is installed and a brand new hei distributor

also i have a gm performance mild cam and lifter set should i install it before dropping in the new 400?

sorry for the book but i am supposed to head out to get this motor in an hour or two so any quick advice before i go would help greatly!!!!

thanks in advance!!!!!

[Dead Parrot]

Most things should bolt up as both are SBC. IIRC, you will need the balancer from the 400 as it is balanced differently then most other SBCs.

If you really want a 'get on the road now' motor, I would skip things like cam swaps. To do that properly leads to cam bearings, new lifters, push rods etc. Even if this 400 runs, you won't know how good it really is until you fire it up. It would really suck to find out that it runs but is making a 'whirrin' noise after spending time and money bolting fancy parts on it.

Think of the 400 as a stop gap while you save your cash for a new crate motor with the specs that you really want. You can always fix it up later.

[sev85]

So for 150 it's a decent buy to get it on the road..... Ok awesome and I have been wanting to do a 400 swap for awhile what's the pros and cons of a 400 over a 350?

[old blue 86]

Don't forget that 400 heads head steam holes.

[Drewkimble48]

400's a fun but make sure to have a good cooling system. Also, I can't remember if it was stock or not but I know on my 400 I have steam holes where the heads bolt on and when I rebuilt mine, I bought a set of aftermarket heads and had steam holes drilled on them so definitely keep that in mind. From the sound of things, your on a budget for now but a 400 is a great build up if thats what you would like to do in the future . I've been meaning to dyno my truck to see what I'm pushing but, i feel pretty confident that the 400 is at least pushing 500 hp at the crank. I at least know i burn the tires into 3rd.

[sev85]

Thanks I didn't know 400s had steam holes so my 350 sbc 462 casting # heads will need to be drilled to work on the 400?

[sev85]

So the casting number on this block is 3951509 I have looked all over the net and it seems everyone has different information on what 400 this casting number is can anyone help?

What year was it made? 2 bolt or 4 bolt main? Which is better 2 or 4 bolt man? And how dificult would it be to put my 2.02\1.6 valve heads on it?

[Drewkimble48]

Originally Posted by sev85

So the casting number on this block is 3951509 I have looked all over the net and it seems everyone has different information on what 400 this casting number is can anyone help?

What year was it made? 2 bolt or 4 bolt main? Which is better 2 or 4 bolt man? And how dificult would it be to put my 2.02\1.6 valve heads on it?

per mortec.com this is what I came up with on the 400
3951509....400...74-80...2
2 bolt main from 1974-1980 is when it was manufactured

as far as the heads it shouldn't be an issue with those size valves. If I remember correctly, that's the size valves mine are. You will just have to watch how much compression you run to prevent valve to piston interference.

[craig113]

3951509....400...70-71...4 Bolt Main
3951509....400...74-80...2 Bolt Main

[BigBlocksRule]

Pre-1076 509's are a bit thicker than others are are the one most sought after by hotrodders. Should be 2-bolt which is preferred in 400's. You will need steam holes in the heads, have the shop do it. Better yet, find some cheap vortec heads and you'll be set.
They're hosses, bigger bore and longer stroke than a 350. Night and day difference.

[sev85]

bigblocks thank you and thank all of you for your input i am picking the motor up first thing in the morning its a 400 sbc from a 1972 rv i was told and the th400 with it but im gonna stick with my built th350 run my rpm air gap intake my headers my double chain timing set and run the factory heads that are already on it and install my hei distributor from my 350 until i can afford a complete rebuild with vortec heads or a nice set of aluminum heads and a mild cam

I'm glad to hear it will be a big improvement on my 350 yes it was a strong motor with the 202/1.6 valves flat top pistons and double chain timing set with a mild cam but the rings are just to far gone to consider using it more to drive the 10-12 mile round trip for work everyday and i really dont wanna destroy a very solid good running block

[sev85]

hey guys i finally picked up that 400 today it is from a rv from around 77 78 according to the old man i got it from it turns over great thankfully but i have some questions

the date code is D188 and the casting numbers are 3951509 according to nastyz28.com it is a 400 sbc from April 18 1978 and is a 2 bolt main 1970-80 3951509 400 150 low hp 265 high hp car,truck

will my brand new 350 distributor work on this motor because the distributor that came with it is way bigger in diameter but both are hei so i guess it doesnt matter that much but can i use my new one?

also the flywheels are different and the torque converters are different will that change it working with my th350 i already have in the truck using the torque convert and flywheel that came with the 400?

sorry to keep bugging everyone im still learning alot about these older chevy trucks and the plethora and diversity of everyone's knowledge here way surpasses mine thanks again for any help!!!

[BigBlocksRule]

You need to keep the correct balancer and flexplate/flywheel with the 400, it's externally balanced where a 350 is internal. Should bolt up to your converter, they're neutral balanced regardless of engine balance. Are they different size? Bolt pattern? Your 350 could have the small flexplate.

[sev85]

yes they are entirely different bolt patterns and sizes of torque converters the 350's is tiny like a dinner plate compared to the 400s huge converter and the 350 torque converter is also only 3 bolts that use nuts and lock washers and the 400 torque convert is 5 or 6 bolts that screw directly into threaded slots on it

[Dead Parrot]

Which transmission was in the donor vehicle? Since it was an RV, might have been a TH400 transmission.

Any SBC compatible distributor should work as far as the motor is concerned. Fitting it next to the firewall is a different matter.

[sev85]

the tranni was a th400 and and it was from a 78 rv

and the distributor that came with the 400 is twice the size as the one i bought for the 350

[RPOZ11]

Pressure test the block for cracks.
These notoriously run hot.
Remember you will be taking on the history of that motor and any problems unforeseen.

[BigBlocksRule]

Throw out the small block radiator and add a big block. You will have no overheating issues.
400's run hotter than others because they generate heat like a big block and folks try to cool them with a radiator that's big enough for a 305.

[sev85]

ok well the radiator i was using for the 350 is a 4 core dual or triple pass aluminum racing radiator because i do alot of slow crawling and idling with the truck so i had cooling concerns in the beginning so i got this radiator its way bigger than the stock dual core and i am gonna run dual electric fans with a thermostatic switch for dual stage cooling i picked up a 8 inch and 10 inch dual electric cooling fan with mounting bracket and im looking to get the switch this afternoon or tomorrow

[BigBlocksRule]

Sounds like you're set.

[sev85]

hey guys finally got that 400 in and running here is a video of it running sorry the video is terrible it got dark on me about the time i finally got everything hooked up and ready to run

also that 400 not a whole lot was actually interchangeable as i had expected about the only thing that fit and worked was the intake carb and headers the distributor didnt fit the gears were different and the timing chain cover didnt fit either nor did the brand new oil pan i purchased for it...!?!?! tad confused but oh well its in and runs good tell me what you think

View My Video

heres a picture of the whole truck

[IMG][/IMG]

[bnoon]

There are 2 oil pans for the early 2 piece rear seal engine blocks, driver's side dipstick, or passenger's side dipstick. If you really messed up you can get an '86+ one piece rear seal oil pan and that one won't even come close to working on a 400.

The timing chain cover must match the balancer, with the only real difference being the size of the balancer at 6" or 8". Universal ones have adjustable pointers and work with all gen 1 sbc including your 400.

EDIT: Sounds like a little bit of a cam in there, not too bad at all for an "interim" motor. Good job at 150 bucks!

EDIT 2: The TQ converter differences between a TH350 and TH400 are none, both will work in either transmission. The difference comes with the flex plate to converter bolt pattern. I use a 3200 stall in my TH400 and a dual pattern flywheel (10.75 seems to be the most popular pattern, I forget what the other pattern even measures). Car and light truck applications typically use 3 bolts to connect the converter to the flexplate and have either a large or small bolt pattern on the flexplate and it's mostly early vs. late, not a TH350 vs. TH400 difference. Heavy duty trucks/buses/box trucks/dump trucks/etc typically use a heavy duty 6 bolt converter because of the heavy loads they carry. The 6 bolt converters tend to stall a few hundred RPM lower than the stock 3 bolt ones on cars/trucks when swapped onto the lighter vehicles. You would have better off the line performance with the smaller converter too just from reciprocating weight reduction, let alone the stall difference, but it will not hurt anything.

[sev85]

awesome good news on the torque converter because i really dont want to pull it back out!!! this thing was a nightmare from minute one almost every exhaust manifold bolt broke and one snapped off in the head and i had to drill it and got lucky enough to easy out it but not before 6 drill bits ate the dust... =(

the motor does sound kinda lobey but i just figured thats how it idled but several people have mentioned it sounds like it has a mild cam and thats why the distributor gear was different and i had to use the one that came with the motor

right now it has a edelbrock 650cfm carb with 1 inch spacer, edelbrock rpm performer air gap intake, hei distributor, installed a new double chain timing set cam and crank gear as well, hedman 1 5/8s headers, i gotta go get new plugs and wires but other than that i think im fairly set for what i was hoping for a mild street/offroad rig high torque and moderate mileage

also one last quick question it only runs about 30 psi of oil presuure unles you rev the rpms up and it only climbs about 10 psi im told this is normal for older chevys as they only require about 10-20 psi of oil pressure is this true?

secondly this thing seems to take forever to warm up and never really gets warm either maybe 150 on the temp gauge if that but i only ran it for about 10-15 mins maybe less and it has a massive radiator

i will post pics soon but hopefully this weekend i will be installing the new carrier in the font end and installing the new springs for the rancho 4 inch lift and now looking for a set of 35 inch super swamper tsls to replace the worn out 36x13.5x15 iroks on it now

[bnoon]

Originally Posted by sev85

and thats why the distributor gear was different and i had to use the one that came with the motor

Yes, this is true.

Originally Posted by sev85

also one last quick question it only runs about 30 psi of oil presuure unles you rev the rpms up and it only climbs about 10 psi im told this is normal for older chevys as they only require about 10-20 psi of oil pressure is this true?

30 at idle is totally fine for any SBC engine and 40 under throttle is totally what you're after with a fresh mild build. 20 would have some wear on it, at 10 I'd be looking for a rebuild with new bearings to bring pressure back up. You don't really want higher pressure than 40 unless you have a higher capacity pan, otherwise you'll push all of the oil to the heads too quickly and not have enough in the pan. Too many guys run high pressure pumps at 60-80 psi with stock pans and no oil control mods and end up burning up an engine because all of the oil is in the heads and too little at the bearings. You're perfect where you are.

Originally Posted by sev85

secondly this thing seems to take forever to warm up and never really gets warm either maybe 150 on the temp gauge if that but i only ran it for about 10-15 mins maybe less and it has a massive radiator

At 150 degrees and only 10-15 minutes you should be fine. Number 1 because the analog gauges aren't the most accurate to read. I've seen them be off by more than 20 degrees before. Number 2 because it's cooler weather and you'll be running hotter next summer for sure. Number 3 because you are running an aftermarket aluminum intake that has a better cross over design and air gap... and it's aluminum for better cooling. I run a factory big block radiator with my pretty hot built 350 and the stock temp gauge barely reaches the one quarter mark in 100 degree heat (but is still one of the quickest vehicles I've ever had to defrost the windows in winter, heater works GOOOOOD!)

EDIT: Is your temp gauge sending unit in the head still or moved to the intake? That can make it read lower too.

[BigBlocksRule]

Dizzy gears are all dimensionally identical, only differences are what they're made of. Can't run incompatible materials, it'll wear the gear out and you'll be SOL.