400/406 Builds

[Marv D]

Nick, I saw a set of cnc ported 186 casting camelhumps that were built for a friends small cubic inch dragboat went 218/137 @ .6" lift on a Superflo SF600 bench. That was with some spec they had to live by limiting the port to (best my memory recalls) at 165 or 170cc (something like that),, where they start at mid 150ish cc in stock, as cast form. I remember Roger saying some of the castings they started with went almost 200cfm as cast, but the sloppy casting and inaccurate means of the day,, the #'s were all over the place.

I've seen some of the reports around the net that they got 461's and such up to 260-270cfm with ultra secrete trick cnc programs,, but I've never seen anything but 'internet' claim those numbers.

In short I'm not trying to bash anyones machinist or build, just saying a 400 inch motor is BIG cubic inches and using a head designed for 327 inches should in it's self offer some thought of it's limitations.

[nicks diner]

Ty Marv, I'm not looking for an all-out racer just around 450 would be nice and I am definitely considering new heads like the Capt has advised. Looking at AFR 190.

[manimal]

World Products Sportsman II's are good heads as well. You will have to have the steam holes drilled.

[Captainfab]

Which Comp extreme 4x4 cam did you use?

Originally Posted by jjzepplin

I built mine quite a while ago but here goes-.30 over silicon skirted forged flat-tops-file fit rings- ARP everywhere I could put them-Rods resized-line honed block- Stock heads redone with 2.02/1.60 stainless valves and bowls blended-unshrouded-screw-in studs-1.6 roller rockers hardened pushrods stock crank turned and polished .10 .10 clevite bearings and steel marine head gaskets high volume oil pump and 4x4 pick-up and baffled pan for hard-steep angles-Comp 4x4 extreme(mild lope) cam hydraulic lifters Carter electric fuel pump with oil pressure cut off switch and 670 cfm Holley 4x4 carb on air gap intake with rear plumbed to the front thermostat housing for full rear engine coolant flow.
Missed a few things but she still has gobs of compression and runs on pump gas just fine with the curved Hei dizzy. Built everything myself so I am sure all of it is in there.
Might one day stuff a bigger cam in but it runs so good why screw with it?

[64chevmn]

I bought a 64 C10 last fall with a 400/406 small block. The engine started as a 400 4-bolt main small block; 10.2-1 compression, 292 comp cam, roller rockers on top, Edelbrock aluminum heads, Edelbrock RPM intake, Holley 750 carb with hooker headers. I only put about 50 miles on the truck before I tore the truck apart, but it "screamed" down the road. I plan on taking taking the oil pan, valve covers and timing cover off to make sure everything looks "ok" before I re-gasket everything. I plan on taking it to a engine dyno to see what type of power it makes and fine tune it before I drop it back into my truck this spring. The previous owner claimed it was around 500 Hp at the crank, so I will be surprised to see what it actually makes on the dyno. It runs ok on pump gas, but it ran much better on 100 octane.........

Dan

[Captainfab]

Which Edelbrock heads are on your engine?

Originally Posted by 64chevmn

I bought a 64 C10 last fall with a 400/406 small block. The engine started as a 400 4-bolt main small block; 10.2-1 compression, 292 comp cam, roller rockers on top, Edelbrock aluminum heads, Edelbrock RPM intake, Holley 750 carb with hooker headers. I only put about 50 miles on the truck before I tore the truck apart, but it "screamed" down the road. I plan on taking taking the oil pan, valve covers and timing cover off to make sure everything looks "ok" before I re-gasket everything. I plan on taking it to a engine dyno to see what type of power it makes and fine tune it before I drop it back into my truck this spring. The previous owner claimed it was around 500 Hp at the crank, so I will be surprised to see what it actually makes on the dyno. It runs ok on pump gas, but it ran much better on 100 octane.........

Dan

[jjzepplin]

Originally Posted by Captainfab

Which Comp extreme 4x4 cam did you use?

If I remember right there were a couple choices back then and I went with the 1st selection. I would have to look up the specs as I kept all the paperwork.
I figured it wouldn't see much high rpm usage so a good lope was not going to be a good thing rock crawling.
Then I moved to flatlands.

[64chevmn]

The heads are Edelbrock performer 60739

[Captainfab]

Thanks for that info.

So those Performer RPM heads have 170cc intake ports and 70cc combustion chambers with 2.02/1.60 valves.

Originally Posted by 64chevmn

The heads are Edelbrock performer 60739

[64chevmn]

Captainfab,

I need to change the rear-end in my 64 truck with a new one due to 50 years of wear. I found a 1969 complete rear-end with 3.07 gears; with my engine set-up I posted do you think I will loose too much low end torque going from 3.73 to 3.07's?

[Captainfab]

That depends partly on what trans you are running and what size tires. The 400/406's typically make good torque, but with the cam that is in yours, your low end torque may be down a little, as compared with a milder cam.

Originally Posted by 64chevmn

Captainfab,

I need to change the rear-end in my 64 truck with a new one due to 50 years of wear. I found a 1969 complete rear-end with 3.07 gears; with my engine set-up I posted do you think I will loose too much low end torque going from 3.73 to 3.07's?

[64chevmn]

Turbo 400 with a 3000 stall convertor; tire size will be around 225/70-15 or close to that size for the rear

[Captainfab]

I don't have any personal experience with a 406 with a 292 cam, but I think there is a possibility that the 3.07 gears may be just a little too high for that combo. They may work out, but if I were to choose, I would go with 3.42 gears with that engine and trans combo. I doubt you'll be getting much traction with those skinny tires.

[68post]

I have what is supposed to be a rebuilt 400 stock bore, but a non-stock cam (which I haven't got to verify yet). I do have 2 sets of heads. Stock vortec or Twisted wedge gen1.
Which truck gets the engine will determine the cam, heads, and intake used, and whether I use the 800 holley spreadbore or a modified Qjet.

I'm guessing if it goes into my '94 K1500 - I'll either need a 9.5" sf six lug rear or weld the tubes and beef my 10 bolt , but the PO left the 231 tc in it when he changed to a carb'd 350 and a NV4500. Is the NP231 pretty weak ?( too weak for my 350 also ?)

[Captainfab]

I don't know much about the strength of the NP231, but typically if you step up to larger than stock tires, and or lower gears, is when you find your weak links. What is your intended use of the '94 K1500?

[68post]

Originally Posted by Captainfab

I don't know much about the strength of the NP231, but typically if you step up to larger than stock tires, and or lower gears, is when you find your weak links. What is your intended use of the '94 K1500?

No mudding, just street and snow playing , off-roading may be a crawl thru the woods or pasture. It has 33's and the stock 3.73's.

[Coley]

....good point to Manimals comments about the steam holes.
It was my understanding too that any heads used on the 400 sbc's had to have the mating steam holes (special siamezed bores) in them to keep the engine from overheating.
Is this not required?

Coley

[Captainfab]

With 33's and 3.73's, there shouldn't be too much extra strain on the trans TC from that end. But if you do put that 400 in this truck, that will be some extra torque on the input side. I would suggest posting a question about the NP231 over in the Offroad and 4x4 section.

Originally Posted by 68post

No mudding, just street and snow playing , off-roading may be a crawl thru the woods or pasture. It has 33's and the stock 3.73's.

On a street driven SB400, you really need to have the steam holes in the heads. I would never consider running heads without steam holes on a street driven SB400

Originally Posted by Coley

....good point to Manimals comments about the steam holes.
It was my understanding too that any heads used on the 400 sbc's had to have the mating steam holes (special siamezed bores) in them to keep the engine from overheating.
Is this not required?

Coley

[68post]

Originally Posted by Captainfab

With 33's and 3.73's, there shouldn't be too much extra strain on the trans TC from that end. But if you do put that 400 in this truck, that will be some extra torque on the input side. I would suggest posting a question about the NP231 over in the Offroad and 4x4 section.

Thanks, good idea !

[nicks diner]

Ok finally got the specs.
406 4 bolt
gm crank and rods balanced
KB flat tops 10.5 1
NEW DART 200 cc SHp mildly ported 64 cc
comp cam hydraulic roller 523 lift 519 exhaust
Comp 1.6 roller rockers
air gap
Holley 850dp
full headers
373 gears posi
350 3 speed

Whatta you think?

[68post]

With the proper piston to deck height you'll have closer to 11.7 - 1 compression , a 76cc chamber would be perfect with flattops.
The 850 holley isn't a good street carb for anything smaller than a 454 , and not great then either .
A Holley 780/750 vacuum carb or a 750 or 800 tuned-up Qjet (first choice), even an 800dp or an 830dp holley carbs will be more responsive. Better yet the Demon high-end carbs are better than all but the very newest and best Holleys.

What is the cam's .050 duration ?

[nicks diner]

Originally Posted by 68post

with the proper piston to deck height you'll have closer to 11.7 - 1 compression , a 76cc chamber would be perfect with flattops.
The 850 holley isn't a good street carb for anything smaller than a 454 , and not great then either .
A holley 780/750 vacuum carb or a 750 or 800 tuned-up qjet (first choice), even an 800dp or an 830dp holley carbs will be more responsive. Better yet the demon high-end carbs are better than all but the very newest and best holleys.

What is the cam's .050 duration ?

243 257

[Captainfab]

IMO you still have too much compression for pump gas. And now you have way too big of a carb. But you said your machinist is well respected and a friend of yours, so I won't say any more.

[northern]

Originally Posted by nicks diner

Ok finally got the specs.
406 4 bolt
gm crank and rods balanced
KB flat tops 10.5 1
NEW DART 200 cc SHp mildly ported 64 cc
comp cam hydraulic roller 523 lift 519 exhaust
Comp 1.6 roller rockers
air gap
Holley 850dp
full headers
373 gears posi
350 3 speed

Whatta you think?

I like it. I have one that is close to yours but with a comp solid lifter cam. Same KB's. 64 cc camber Dart Iron Eagle, rpm air gap and a 750 holley.

[nicks diner]

Originally Posted by northern

I like it. I have one that is close to yours but with a comp solid lifer cam. Same KB's. 64 cc camber Dart Iron Eagle, rpm air gap and a 750 holley.

yes my mechanic has two to three different carbs that he will try out and see which is best for the motor and for the street. How is your motor on the street? plenty of power? Did you run any times at the track?