Thread: 400 Small block questions?

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Building a 400 small block for my Dad to put in his 55 Bel air. Want is streetable with some good torque for fun on the street. Running a manual transmission with approx 3.50-3.73: rear gear.

Block is .030. Stock crank turned .010. Stock rods with APR bolts. Pistons give about 9.5:1 with stock 76cc 400 head. Cam is hydraulic and mild to moderate trying keep it a torque motor. With 406 CID Question is how well do these stock heads work and what mods are necessary to use them. Already have 2.02/1.60 manly valves to have installed but what if any porting should be accomplished?

Or should I just trash these heads and buy something new. I am open to suggestion on buying new, but pistons purchased already yeild about 9.5:1 (sealed power stated 9.7:1 to be exact)and wanna keep this motor on pump gas and reliable. Most after market heads arent offered at 76 cc form what I have seen. (yes know I have to have steam holes drilled for 400) Want to give the old man just one last good solid car to have fun with. He's 59 now and drives a vette but still talks about his 1st new car at 21 which was a 65 GTO with 389 and 3x2s so want to help give him another rod to have fun with.

I dont know, kinda sounds to me your buildin a nice low rpm torquey motor, the stock heads with 2.02s installed should work pretty decent. If you already have em, & there good, & already have the valves in em, I think Id use em

depends on what your doing.... If your using the 400 short rod the engine could really benefit from a larger runner head..(180-195) well so clould the larger 350 rod...more so the short rod....

A shorter rod means faster piston speed which in turn needs/uses more air.....

That why the 400's suffered so much they needed way more head than they had....

A shorter rod moves the piston away from TDC faster than a longer rod....

All in all I would opt for a nice 180 cc runner head In cast iron....

I hope you have better luck than I did!!! I think if I had it to do over I'd build a 383.

Just curious, what kind of flywheel are you going to run?

Delray,

What kind of problems did you have building a 400?

Delray...alway stick with bigger

I do recommend if you are going to use the stock head having it machined and using stainless steel 2.02 & 1.6's preferable Manly street flows... these will wake those heads up....I ran a Crane 216 @ .050 dur cam and advanced 8 degrees on top of the 2 ground in ( 10 total) This will act a 540 out of the hole and will run good til 5500.....

What about aluminum?

The 400 likes a longer duration cam than a 350 would. I would suggest something in the range of a 274 advertixed duration for a mild street motor.

You can spend a lot upgrading the stock cylinder heads with big valves and screw in studs. Once you've installed the large valves you need to have the heads hand ported to allow the valves to flow properly. Just putting 2.02 valves in a head that had 1.94's without any port work will give you less flow than stock due to valve shrouding. When you are all done you will still have a set of crack prone heads that don't flow very well. Better, and likely cheaper in the long run, would be a set of aftermarket heads. Dart offers both steel and aluminum heads with 72c.c. chambers.

Aluminum work well....I would opt for AFR's 180's or 195's...

For a torque motor I'd go the 180's route...those heads with a 230@.050 cam and your set up you'll be very close to 500hp and way more torque than you'll know what to do with....did the same combo myself.....(taken from the Hot Rod setup)

Canfield cylinder heads may be worth looking into.

i've run several 400's from stock blocks with stock cranks to brodix aluminum blocks with callies cranks and oliver rods and with the short rod and fast piston speed at top dead center you can't go wrong with an aluminum head with 180 to 190 cc port volume as it will keep the port velocity up and more efficiently fill the cylinders. you can use a cam with 230to 240 duration @.050 and be very streetable on pump gas also with the aluminum head you can run 10 to 10.2 or so compression without detonation and if you buy a head(i'd run airflow or brodix) with smaller combustion chambers you can always run thicker copper head gaskets to lower the compression ratio... hope this helps

I know this is a LITTLE off subject, but you guys sound like you know what you are talking about.....
I've got a set of Bowtie heads I want to put on a 400. My machine very trusted machine shop said i didnt have to drill steam holes.....EVERY where else i look, says you must. Any Thoughts on this. This is going in my circle track car, so keeping it cool is a must!
Thanks for your help....
Brad

CAM SPECS are as follows for anyone else that wants to add additional input or opinions

224/234 @ .050

.465 int lift
.488 exh lift

114 lobe sep

drilling steamholes is an absolute must if you wish to avoid major problems. about the heads ... are they as cast or are they ported ...do you know what the flow numbers are and at what lift ...also, youshould have them flowed with the manifold on to see if what you intend to use is compatible or is it resticting flow... it's of little use to have big flow numbers at say .600 or .700 lift if your cam won't see even .500 of lift.