400/406 Builds

[Captainfab]

With the small combustion chamber on those heads, you must use a dished piston. A 600 cfm carb is a bit small for a 404 cu in engine. For a cam I would suggest something similar to the one I used in the build in post #1.

[burnin oil]

I cammed my motor back a little and run a 274 duration solid cam. The 830 double pumper is barely to big for this cam but worked well with the old one. I ran around for about 2 months on the primaries only, disconnected the secondaries, while tuning and it ran alright. Once I rehooked the linkage I gained a mile to the gallon and it runs a lot better. She just wants more than 400cfm that is available on the primaries. Do some digging and you will find that the Holley vac secondaries will never hit the full potential unless you run the lightest spring. The heaviest spring will nearly never open the back side.

[bigmac73]

post #88 no inputs or opinions, come on guys give me your thoughts....

[Cautrell05]

Originally Posted by Captainfab

With the small combustion chamber on those heads, you must use a dished piston. A 600 cfm carb is a bit small for a 404 cu in engine. For a cam I would suggest something similar to the one I used in the build in post #1.

Unless I find something bad on tear down I'm just going to re ring the stock dished pistons. Carb is up in the air. The options right now. A 650 holley, I was wrong earlier, a mostly stock autolite 4100 and a modified big bore 4100. The holley needs a full rebuild, both autolite carbs ran well on my street stock. And if they piss me off to much I will but a new one.

[Captainfab]

I think we need a little more info such as pistons being used, what trans and stall converter as well as your intended usage. Also what fuel you want to run.

Originally Posted by bigmac73

here is what I am working with -

Dart Short block 400 (03114002)
AFR 195 or 210 head eliminator street head
Howards OE style lifters (91113)
Howards Roller Cam either a 180885-10 or a 180265-10
Comp Ultra Pro Rocker Arms (1602-16)

any more thoughts on the cam selections please feel free

Originally Posted by bigmac73

post #88 no inputs or opinions, come on guys give me your thoughts....

[bigmac73]

http://www.summitracing.com/parts/drt-03114002
what ever pistons come with the short block, and I have a 2200 RPM stall now and a built 350TH, which is fine with the howards 180885-10 cam , and I already run premium 91 with my current engine now(per Manufaucture)

[burnin oil]

Flat tops will build some serious compression in a 400. You really need to know the cc's of the reliefs and how far down the deck the pistons go along with head gasket thickness. In HS I had a warm 400 that had hyp flat tops and 76cc iron heads that ran detonation free on 87. The only issue was intermediate dieseling at shut off. Tighter heads will shoot the compression really quick, especially with a zero deck height. Don't forget that hyper piston are not very tolerant of detonation so stay conservative on the timing curve and add some till it runs the best.

[Cautrell05]

anybody know what the dish size was on the stock 400 pistons?

[Captainfab]

I agree with burnin oil. You will need all the info necessary to be able to calculate the dynamic compression. You will also need to know what combustion chamber sizes are available from AFR on those heads. I'm not an expert, but I believe the AFR heads' flow ratio between intake and exhaust is so good that a split pattern cam is not necessary. If the dynamic compression is too high with the Howards 180885-10 cam, you will have to go with a cam that has a later intake closing to bleed off some cylinder pressure. This is often a more radical cam such as the 180265-10, but cams designed specifically for N2O or boost, will have a later intake closing and bleed off cylinder pressure without having a higher operating range.

Originally Posted by bigmac73

http://www.summitracing.com/parts/drt-03114002
what ever pistons come with the short block, and I have a 2200 RPM stall now and a built 350TH, which is fine with the howards 180885-10 cam , and I already run premium 91 with my current engine now(per Manufaucture)

[Captainfab]

I don't remember off hand, but with a stock deck height and about .041 compressed head gasket, you can use a head with 64cc combustion chambers and run pump gas. Of course there are variables, but it will work.

Originally Posted by Cautrell05

anybody know what the dish size was on the stock 400 pistons?

[kjdolphins]

I'm gonna get this thread fired back up because of my recent interest in 400/406's I'm playing on putting one together here shortly in the future and all of this information has been really helpful!

[GMR-PERFORMANCE]

Static means nothing until a cam is put into the equation .. I run 11.1 static on pump gas on the street and drive it without issue.. Cam is a 243/247 duration @ 50 adv numbers mean about nothing as they tend to print it how they want and keep facts less than accurate adv on this howards hyd roller is 292 , you need to look well beyond what most do to know if the "set up" will work correctly. Then you need to have the proper parts to control ign timing.. Just because you bought a MSD ign doe not mean much as most lock them out and run a ign box to control timing.. I run a MSD grid with ( so yes its locked out) . RHS 220 heads AED 4150 that is a 950 super mod HO carb SO 750 base plate 950 body that has been taper bored . 4l80E trans 4100 stal convertor with lock up, Rattlesnake D3 trans brake, full auto upshift, 373 gear in a moser 35 spline 9 inch, ohh and two guns on top of the little small block,. Does great for a all around hot rod, cruiser, hwy hauler..

as for the engine buy a new block the Dart SHP is very strong , takes care of all the issues with the factory stock block.. If you do not want to go that route build a 383 then.. Better off in the long run.. But I said different and went though a stock block or two.. Your money throw it away how you want, there is a reason that the Dart is used so much for these builds..

[jjzepplin]

I love how mine sounds like a big block. Sometimes I forget it's a smallblock. I like to hear the little engines rev trying to keep up as my torque pulls the big 4x4 around.

[burnin oil]

I know the Dart block is strong but there is nothing wrong with a good factory block. The only one I have lost so far was full of water during the winter. She cracked hard. The motor in my truck was originally built when I was in high school and had the crap beat out of it. Finally busted 4 pistons. A few years later it was rebuilt again (good cylinder walls with no scratches so it stayed 30 over) and has seen way more 7k RPM shifts, not to mention the speed shift that the pedal stuck to the floor. 3 years later compression is still good but oil pressure is going down. I think it is worn cam bearings as I have swapped it 4 times on this build and it didn't show up until the Comp solid went in. Anyways that was all on the same 30 over block. I plan to shelf this one for now and put together a 509 block from 1974. If it takes 1/3 the abuse of the other 400 I will not complain. I think that 500HP is reliable for the factory block.

[Captainfab]

Any new 400/406 builds going on or updates to previous builds?

[parrisc19844x4_468]

Here is my 400 build going in 78 GMC SWB 4x4. 3.42 gears guessing weight is 5k.
Gas mileage is not important. Not going to drive it that much, weekly crusie in.
I am not building this myself, I have a local builder doing that.

511 400 block recent bored to 406. All normal machine work

Scat 9000 Series Cast Steel crank 3.750 x 5.7

Keith Black Hypereutectic Pistons

034 bowtie heads. 64 cc. 202 intake 160 exhaust 184cc intake runners
rockers and springs came with the heads.
Steam holes need to be drilled yet.

Comp Cam Thumpr Pro-Plasma Nitrided lift .489I/.476E.
Intake duration 235 Exhaust duaration 249

ARP block studs and ARP bolts.

My builder thinks that I should go to a 680 or 750 cfm carb. Based on a calulater
he used he thought it need around 650 to 700 cfm. What do you guys think?
Any other suggestions?

[GASoline71]

Depends on what RPM the engine will operate. If you will see some upper RPM pulls a 750 will be great. Hell a 750 cfm like a 3310 would be perfect if you ask me.

I'll tell you though... that Thumpr cam is gonna want a crap load of initial timing. Probably close to 22 to 25 degrees advanced. Got a buddy yarding the Thumpr out of his rig in exchange for a Comp XE cam. Only pulls 5" to 6" of vacuum at idle.

Gary

[Captainfab]

I agree with going with a different cam, especially in a 4x4 with 3.42 gears. What size tires will you be running? You need an engine that produces low to mid range power, with emphasis on low range, not mid to top end power. That single plane intake is not the best for low end power either. A dual plane would be preferable. Did you read post #1 of this thread where I described the 400 we built for my son's 4x4?

[kwmech]

I made a mention in another thread about building up a 400 for my suburban later on this spring. I think I will go after a Dart block to start with

http://www.jegs.com/i/Dart/301/31162211/10002/-1

considering also the dart cyl heads in the 72cc .

http://dartheads.com/dart-product/ir...-165cc-sbc-ss/

Going to keep the TBI and have it re-worked by Harris Chips

Just build up a clean relatively stock stump puller 9-1 compression with about a 266 or 268 computor friendly roller cam

[parrisc19844x4_468]

Originally Posted by Captainfab

I agree with going with a different cam, especially in a 4x4 with 3.42 gears. What size tires will you be running? You need an engine that produces low to mid range power, with emphasis on low range, not mid to top end power. That single plane intake is not the best for low end power either. A dual plane would be preferable. Did you read post #1 of this thread where I described the 400 we built for my son's 4x4?

I did and thanks for that. I went for that cam based on the article in hot rod mag a few years ago. http://www.hotrod.com/articles/ccrp-...ster-for-2500/

The intake manifold pictured is on that was in on the deal I made for the heads. I do have access to a single plane intake as well.
My plans are to change the carrier to a Eaton truetrac , depending on what we find when we open up the differental.

What if I was to say that I may change the gears to 4.10. Would that change your thought on the cam?

The tires are 15 x 32

[Captainfab]

Just because a cam is used in a magazine article does not mean it is the best to use. The Thumper cams are designed to mainly make noise. The first cam they used is a very old school grind and it made nearly as much power as the Thumper. You can buy that old school cam with lifters for about half the cost of the Thumper cam alone.There are much better grinds available for your application than the Thumper line of cams. I would suggest one of the Comp Cams Extreme 4x4 cams.

With a more sensible cam, you could likely keep your 3.42 gears since you are running only 32" tires. Although if you were to change gears I wouldn't go any lower than 3.73 with those tires and with running a TH350.

Originally Posted by parrisc19844x4_468

I did and thanks for that. I went for that cam based on the article in hot rod mag a few years ago. http://www.hotrod.com/articles/ccrp-...ster-for-2500/

The intake manifold pictured is on that was in on the deal I made for the heads. I do have access to a single plane intake as well.
My plans are to change the carrier to a Eaton truetrac , depending on what we find when we open up the differental.

What if I was to say that I may change the gears to 4.10. Would that change your thought on the cam?

The tires are 15 x 32

[jjzepplin]

I run a Comp 4x4 extreme in my 406. Couldn't be happier. (I have run Competition Cams in all my rides) Slight idle lump but that could be the Holley 4x4 Avenger. Air gap intake with water porting going to the rear of the heads. Full 2.5" exhaust all the way back,circa 2000. Neighbors look at me a little funny when I kick the idle down and that mutha lets out a big nasty roar. Cop across the street has a 67 Buick with a 455 and he came over one day and asked what the heck was under that hood. I showed him the little small block. He says "cute". I said "race"? He said"no".

[parrisc19844x4_468]

Ok, I am going over there today and hopefully I can get more info on the pistons. I do know for sure they are not flat top.

Gas I was planing using the same that I am now with my 355 which is Mobil 91 oct. Right now the trans is a th350 with a 2800 stall. The th350 was built like a 3/4 ton with five plates.

[53chevyforever]

Originally Posted by Captainfab

Just because a cam is used in a magazine article does not mean it is the best to use. The Thumper cams are designed to mainly make noise. The first cam they used is a very old school grind and it made nearly as much power as the Thumper. You can buy that old school cam with lifters for about half the cost of the Thumper cam alone.There are much better grinds available for your application than the Thumper line of cams. I would suggest one of the Comp Cams Extreme 4x4 cams.

With a more sensible cam, you could likely keep your 3.42 gears since you are running only 32" tires. Although if you were to change gears I wouldn't go any lower than 3.73 with those tires and with running a TH350.

Captain .....I agree completely on the thumper cams!

400 small blocks are great torque engines. Back in the day I built one for my 68 camaro. At super chevy sunday it ran 12.21 at 110 shifting at 5,500 rpm and leaving at 2,000 with a 3.73 12 bolt and power steering belt on. The block was .030 over with speed pro flat tops. I used a set of the old 292 turbo gm heads which if I remember correctly had small intake runners. I ran a holley strip dominator intake with a holley 850 double pumper with stock jetting. This was a street car that I drove daily so the cam I used was small. A 272 crane econopower. Idle was around 600 rpm and a slight lope.
How ever it would not run on regular and gas was way better back then...so you guys wanting to run a flat top piston with 64 cc heads and todays pump gas are dreaming if you live in texas and drive on the street to car shows and cruises. That is why on my current build on my 66 c10 I made sure compression is low...yes...you lose some power....but no detonation. The captain is right...alot of difference between a 400 and a 350 with flat top pistons. A 1/4 more stroke and .0125 bore makes alot more compression with the same head. I have had alot of 400 sbc in my life...the first came out of a wrecked 70 impala. I put it in bone stock with the 2 barrel in my 56 belair with a 350 turbo and 3.70 gears. Had great torque with no top end...but still fun.

[jjzepplin]

Took a cruise in Old Yeller today and would not change a thing. Big Block Power from the little small Block. Turns My wife's frown upside down when I punch it!