I want to build a 400 small block

[disorderindminor]

I stroked a 305 to a 334, that was a waste of time, the machine shop got the piston ring end gaps wrong for the keith black pistons and it took the corners out of the valve reliefs, never even made it 200 miles on the new engine.

My friend fred gave me the 400 small block for free out of his old field beater truck before he scrapped it. Its a 1971 400 small block, its currently attached to a 400 turbo trans and those 2 reside in my 1984 cutlass supreme. I want to build that 400 into a 406, This summer im removing the front clip of my G body and putting in my gen V 454 H.O in it temporarily. I know the heaterbox needs modifying but i've seen 454's sitting pretty neatly in cutlass's. That engine can sit in there for a year or two while i do the 406 right. It will probably cost me alot more than im going to make over the summer being as i work 2 part time jobs and have alot of "crap" that nickle and dimes me to death (ie the cutlass).


So anyways for the 406
i plan to reuse these parts from my 334 dissaster:

-Flowtech Headers with 2 1/2in primaries
-Flamethrower HEI ignition
-Holley 4150 carb (650 cfm)
-Edelbrock Performer RPM intake
-Comp Cam 24H grind camshaft (might look into lunati roller cams and retro fit isky roller rockers, not too horribly out of budget but stretching).
-Mellings High volume oil pump


Oddly enough my headers conflict with my mini starter, and i can only use the big heavy stock starters. The alluminum mounting flange hangs out farther for some reason, not sure why, perhaps has to do with the dual bolt pattern arrangement.


So yeah I dont even know where to begin, last time i built an engine it was mostly taken care of by the machine shop. They put a scat 3.75 crank, bored the block +30 installed the kieth black 30+ pistons and rings (ring gaps were wrong leading to 2 pistons getting toasted) They put new cam bearings in, all the bearings cam and crank and rod bearings were clevite 77, the block was also clearanced for the extra stroke BUT i messed up by buying 5.56 rods so it had a shorter stroke resulting in a slug of an engine. The rods are scat 4340 chromoly H beam connecting rods that are bushed for free floating wrist pins. The engine started blowing white smoke like i blew a headgasket at a regular 55mph cruise down my street so i went home, pulled off the heads and discovered the carnage that was done.

Either way i did somethings right and some things wrong and i NEVER want to waste money doing that again, i want to build an engine right this time.

I figuer either world products cast heads or some AFR aluminum heads, 2.02 valves

I dont know how the stock 400 crank holds up, i know it has diffrent mains than 350 cranks so if i order a new crank from eagle or scat i need to besure to note 400 mains.

I would let a set of 5.7 or 6 inch rods, im not sure how that works out but i know thats how you make the 400's make power. If anyone has any experience with this let me know.

Im thinking JE or wiesco pistons, the speed pro's with the teflon patch looks promising but i will need to do more research on it.

Lunati or isky roller valve train possibly with comp cam roller rockers if things get tight on a budget.

I might want to change my intake manifold and carb setup.

As for distributors im really happy with the HEI flamethower setup i have.




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[mebe007]

how did you end up with the wrong ring gaps and which way were they off, too much or too little?

 

[Coveted]

Makes me anxious to finance my 496 with a blower on it so bad.

 

[disorderindminor]

how did you end up with the wrong ring gaps and which way were they off, too much or too little?

with kieth black pistons your supposed to go an to take an extra 10 thousandths off the ring gap, so the ring gap was way to small becasue the guy who put it together at the machine shop payed no regard to the little yellow piece of paper that came with the kieth black pistons


so does anyone have any 400 SBC recipies they would like to share?

 

[78Calais]

My buddy stroked a stock 400 block to make a 421ci motor. It has a 4.155" bore and a 3.85" stroker crank with 6" rods. He runs AFR 190R heads that would basically be the same as their new 195's. I don't recall the pistons he used but the compression ratio is 10.5:1. He has a Crower roller cam with 0.585/0.596 lift and 290/296 advertised duration. He's running a Performer RPM intake. It made 505hp and 515tq. It's in a '64 El Camino and he's run 11.61 @ 115.42. The only reason I can recall some of the specifics is that it was in Chevy High Performance magazine on page 86 of the Feb. 2003 issue and I'm looking at that as I write this. I also have another buddy with a 406 in his 65 Malibu and that has Keith Black flat tops and a comp cam 280H magnum and some factory heads and that is a simple but stout motor too. It's especially fun since his SS still has the 283 badges on the fenders so when we used to go cruising when we were younger the stock Iroc's and 5.0's would always try to mess with him thinking they had a chance against an old 283 but they were in for a surprise. Bottom line is that I think you'll like the 400 much better than your last motor no matter if you build it mild or wild.

 

[disorderindminor]

I do very much agree, It definitly feels like a truck motor though, lots of torque.


Do you know if you need to get the block clearenced like when you stroke any other small block? I assume so

Im really thinking about putting this one together my self but having the machine shop take care of the following:

Clean Block

Deck, Hone, and Linebore the block

Install New Cam Bearings

Get the block clearenced for my rods

Get the rotating assembly balanced and assembled.


I then plan to take my block home, Put in what ever cam and lifter setup i end up with, i need to do alot of research but i basicly want the ugliest sounding thing i can find, From my understanding the cam shaft should be your starting point when building engines but even though im almost done with my associates in automotive engineering i dont rember much about the lift and duration and how it effects everything. I focused my studies more on automotive instrumentation 😳 (basicly running dyno's and MTS units)

If some one wants to give me a crash course in cams or send me a link twards any direction it would be appreciated.


So once the cam is installed with adaquate assembly lube i need to do the timing chain, timing chain cover

Then do the oil pump

seal up the bottom end with the oil pan and gaskets (though i've never built an SBC and overcome the rear main seal leak).

I can then flip the engine over, put the heads on, put in the pushrods, and rocker arms (how do i factor in rocker arm ratio with the cam im using in terms of duration and lift).

once thats figuered out, i can put on the harmonic balancer

Intake manifold and carb +distributor

Waterpump and mid mount alternator bracket from blown up 334.

pulleys.

and Thats pretty much it?? then its ready to go in.

 

[85 Cutlass Brougham]

Well, if you plan to run the 400 length rods, you will not want to rev it too high because the rod-stroke ratio is not that good. My experience with one is one that was built by a machine shop years ago for a friend's 84 Z-28. ( I actually built and spec'd most of the car including the paint.) His used the standard GM 5.7 in rods from an other than 400 SBC with a set of Kieth Black Hypereutectic pistons that were made with the right compression height. That thing was FAST, once taking down a Ferrari Testarossa from an 80 MPH roll. It topped out somewhere north of 170 with a 3.27 gear and a T-5, which he found out when racing against some bikes. He ran the World Products S/R Torquer heads, a Performer RPM intake and a Edelbrock 750 carb with Hooker Competition headers (shorties) and a large single exhaust and a stock Y pipe for a HO 305. Unfortunately, this was in 1995 and I forget the cam specs, except that it was made by Crower, had more than 230 @ .050 and had a slightly lopey idle but was streetable. If I were to do it again today I would not use those heads because there are now better choices.

Also, 400's tend to run hot and need decent cooling systems. We ran a custom 5 core copper-brass radiator with the factory electric fan, I believe an Edelbrock water pump, and a 160 degree theromostat in the winter and a restrictor in the summer. They also need the steam holes to be drilled in the heads to match those in the block and head gasket. Sorry, but that's all I can think of for now. The 400 is a great street engine because of it's torque. If you can set the car up to take advantage of it ( don't put really short gears in it), you will have a fun car. Just remember that it's strong point is low end torque, and even with the 5.7 in rods you really won't want to go above 6,000-6,500 RPM at the most.

 

[disorderindminor]

Well, if you plan to run the 400 length rods, you will not want to rev it too high because the rod-stroke ratio is not that good. My experience with one is one that was built by a machine shop years ago for a friend's 84 Z-28. ( I actually built and spec'd most of the car including the paint.) His used the standard GM 5.7 in rods from an other than 400 SBC with a set of Kieth Black Hypereutectic pistons that were made with the right compression height. That thing was FAST, once taking down a Ferrari Testarossa from an 80 MPH roll. It topped out somewhere north of 170 with a 3.27 gear and a T-5, which he found out when racing against some bikes. He ran the World Products S/R Torquer heads, a Performer RPM intake and a Edelbrock 750 carb with Hooker Competition headers (shorties) and a large single exhaust and a stock Y pipe for a HO 305. Unfortunately, this was in 1995 and I forget the cam specs, except that it was made by Crower, had more than 230 @ .050 and had a slightly lopey idle but was streetable. If I were to do it again today I would not use those heads because there are now better choices.

Also, 400's tend to run hot and need decent cooling systems. We ran a custom 5 core copper-brass radiator with the factory electric fan, I believe an Edelbrock water pump, and a 160 degree theromostat in the winter and a restrictor in the summer. They also need the steam holes to be drilled in the heads to match those in the block and head gasket. Sorry, but that's all I can think of for now. The 400 is a great street engine because of it's torque. If you can set the car up to take advantage of it ( don't put really short gears in it), you will have a fun car. Just remember that it's strong point is low end torque, and even with the 5.7 in rods you really won't want to go above 6,000-6,500 RPM at the most.

I cant decide on a 5.7 rods or 6 inch rods.

I guess that kinda depends on what the stock 400 crank can take, 3.75 crank with a 6 inch rod should be a fiesty little engine, but id like to make somwhere around 500hp. If i have to get a new crank i'll end up going with a scat crank and connecting rods, lunati would be ideal but i think i need to keep this budget under 4 grand (being as i only have 5 grand in total and i think 1 grand needs to get dumped into me tubbing my rear end (semi) right).

Say im aiming for 10.5:1 CR what pistons should i run,
what AFR head would i want to run with this setup?

What would be a good cam with this setup? Something between 230-280 duration it seems, probably around 260 so its not tooo peaky. Peaky isnt fun.

So anyone got any heads and cam ideas shoot ideas this direction




Im running a brand new 4 core radiator for my car, it keeps the 400 cool as is with a flexlite fan, and thats without a highvolume pump, if i did something id definitly think about getting a high volume pump but i can never come to the conclusion that electric pumps pull as well a good belt driven fan. I guess to cut down on things that rob power i can switch to electric water pump, electric fan, electric fuel pump.

Probably the only fiesable way to reach 500 now that im thinking about it.


I plan to run the car on a 3.73 gearset, if it gets wylde i can always get a 4:10 but i doubt it. The 400 turbo trans steals alot of power to spin and is more weight than a th350, it would probably make my mill seem a 1/4 more effective to run a th350 but the th400 is the smoothest transmission i've ever owned in any automobile i've ever driven. Running a 2,500 stall

 

[85cutlass]

put a bead of silicone on the rear main seal that should prevent any leaks.

 

[85 Cutlass Brougham]

Is this going to be a track car or a street car? Also, why would you need to tub it when so many people run 9's in stock style suspension cars? I would put the money in a 9 in rear instead of tubbing it.