Help with 406 sbc build

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johnny5
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Help with 406 sbc build

Post by johnny5 »

Building a 406sbc for a 77 k10 4800lbs with some fuel.
Sm465 transmission manual
1st 6.55:1
2nd 3.58:1
3rd 1.70:1
4th 1.10:1
205 transfer case
High range 1.00:1
Low range 1.96:1
May twin stick the t case to have low and high range in 2 wheel drive. Dana 44 front axle ,gm 12bolt rear end. Haven't checked the gear ratios yet. 31/10.5/15 wheels for now may go to 33 in or 35 in tires maybe 14 or 15 in wide and trying to keep the truck low. Will be driven on the street and maybe off road sometimes.
I have two heads dart 007 iron measured 170cc intake looks like 2.02 1.60 valves have not measured the combustion camber yet with a vortec bolt pattern . And a set of aluminum dna performance 200 cc heads 2.02 1.60 valves and I believe advertised 64cc combustion chambers.
For the bottom right now it has a stock 817 2 bolt Block bores are at 4.155" this was bought like this with the dart heads and was ran but had three broke pistons top ring lands maybe ring gap .stock 5.7 rods with arp bolts a stock nodular iron 400 sbc crank. Pistons I believe are uem-kb139-030 1/16th ring 1.433 ch keith black hypereutectics three of pistons top ring lands where busted . Quick measurement of one piston was 4.151 bore 4.155 so much looser than kb recommends. Looks like bores will clean up with a quick hone .
I'm not familiar with truck engine builds and there drivablity . Would like something that can put a smile on my face and atleast keep up with or beat modern 1/2ton pickups which will be hard with the sm465. Really need help on the direction I take with the build trying to do this on the cheap. The concern I have with replacing the piston and keeping the bottom end the same.one the piston to wall clearance. two Idk for sure it was balanced. I was thinking of getting a rod balancing fixture and polishing the beams of the stock rods . But the local machine shop charges $400 to balanced so after getting new pistons it may be a better idea to get a balanced rotating assembly. Also 7500 ft elevation
Last edited by johnny5 on Sun Feb 06, 2022 7:33 pm, edited 2 times in total.
johnny5
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Re: How with 406 sbc build

Post by johnny5 »

Screenshot_20220121-002600_YouTube.jpg
this is a flow of the dna heads from YouTube will likely clean up the casting and polish the combustion cambers
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F-BIRD'88
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Re: Help with 406 sbc build

Post by F-BIRD'88 »

Excessive high compression ratio for pump gas.
A KB168 22cc piston works a lot better with 64 cc heads on a 400sbc. 9.8:1 (0 decked) Yes follow the KB piston top ring gap recomendation also..
Excessive CR resulting in detonation and piston failure is a common failure cause on 383-400sbc builds.
64cc heads eant a dished piston for pump gas on these engines.
The cylinder walls need to be checked for cracks now.
May need some sleeves.
F-BIRD'88
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Re: Help with 406 sbc build

Post by F-BIRD'88 »

kb 168 dished piston is LIGHTER WEIGHT than your KB139.. Which means you can stay in balance by ADDING weight to each new piston pin to get weights same same.
On this dished piston the small end balance pad of the rod end must be checked for clearance with the inside of the piston dish. Any trimming of the rod small end to clear dished piston roof will also effect balance.

If you want a reliable pump gas friendly CR with the KB139 flat top pistons, combine with a 76cc head.
.004" PTw clearance is not a problem with KB pistons.
Get the top ring end gap correct reguardlesd.
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Re: Help with 406 sbc build

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Not being familiar with truck engine builds. would you think the aluminum 200cc chinaman heads which I'm currently polishing the chambers exhaust ports ,and cleaning casting flash off would be better or the little dart 007 ss 170cc 2.02 1.60 heads be the the ticket? I'm thinking a voodoo hft 262/268 cam but once again I'm more of a car guy so I'm not sure of the drive ability here. In my mind a 170cc head on a 406 is to small and would rather use them on a ss 350 later on
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Re: Help with 406 sbc build

Post by johnny5 »

Also believe the 007 heads have larger than 64cc chambers still have not measured. The piston tops do not look like there was detonation . I never drove this engine bought it used.
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Re: Help with 406 sbc build

Post by F-BIRD'88 »

Busted top ring land is detonation damage. Don't kid yourself. 170cc port is great on a 406 where big truck torque is desired.. EG a GM vortec head. Or a Dart 170cc port sr torquer" head. Do not build with excessive compression or you'll be redoing it $$$ all over again.

Its just this simple on 400 sbc builds:
64 cc heads want a -18/-22 cc dished piston.

76 cc heads can use a flat top piston in a 400sbc
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Re: Help with 406 sbc build

Post by rustbucket79 »

I’d use the aluminum heads because they’re a bit less prone to detonation, don’t worry about the runner size, on a 400 they’ll be fine.

Those KB pistons don’t deal with detonation at all, and most people don’t provide nearly enough top ring gap. The FM hypereutectic pistons at least have some lid above the top ring. Or a forged piston. Shoot for a combo with 9.5:1 with a zero deck height. Don’t bother beaming the rods, it’s a waste of time. If you trust them, use them. If you don’t, replacements are cheap from Scat or Eagle. If your crank will polish, use it. If it needs a grind, buy a new Eagle cast, they make one now that will neutral balance with 5.7 rods. You’ll need to balance regardless, since there’s no such thing as a factory manual flywheel for a factory 400 crank, so if you’re reusing the GM crank, you’ll need to modify a neutral flywheel for external balance.

Small dual plane and a small camshaft and you’ll be good to go.
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Re: Help with 406 sbc build

Post by johnny5 »

Thanks guys I'll keep you updated
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Re: Help with 406 sbc build

Post by mag2555 »

With that elevation and its lower pascal number you would move more air into the motor and make better average power by having higher port velocity, as in running less then a 200 CC head!
You can cut a man's tongue from his mouth, but that does not mean he’s a liar, it just shows that you fear the truth he might speak about you!
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Re: Help with 406 sbc build

Post by F-BIRD'88 »

If the DRT007 Dart heads are 67 cc open the chambers up by hand to 73cc if you want to run flat top pistons.
Yup a lot of work but you'll only have to do it once.
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Re: Help with 406 sbc build

Post by F-BIRD'88 »

Measure the Deck clearance at tdc before dissassembly.
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Re: Help with 406 sbc build

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mag2555 wrote: Mon Feb 14, 2022 11:46 am With that elevation and its lower pascal number you would move more air into the motor and make better average power by having higher port velocity, as in running less then a 200 CC head!
Mag where would the power band will better with the 170 cc head vs 200cc head . I think the dart ss heads flow 210 cfm they do have 2.02 valves so they may flow a bit more. the 200cc flow around 250cfm and are decent at low lift flows . That's if I haven't ruined them by polishing the exhaust blending the super deep valve jobs into the combustion chambers and blending the seats into the bowl trying to blend the prp in and cleaning the casting flash . Do you think opening the area near the valve in the combustion chambers to the fire ring on the head gasket be worth doing? Looks like there's a lot of meat tell I get to the fire ring there. The reason I asked is I want this thing to move still and I'll gladly lose some drive ability for that definitely if it's the only way to beat a modern day 1/2 ton.
Last edited by johnny5 on Mon Feb 14, 2022 2:58 pm, edited 2 times in total.
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Re: Help with 406 sbc build

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F-BIRD'88 wrote: Mon Feb 14, 2022 11:59 am If the DRT007 Dart heads are 67 cc open the chambers up by hand to 73cc if you want to run flat top pistons.
Yup a lot of work but you'll only have to do it once.
F-bird I'm all about doing that kinda stuff that's the only reason I wanted to run stock rods was to polish the beems and buy a rod fixture was to nerd out on the little stuff like that. Same with the crank take all the sharp edges off and what not.
Last edited by johnny5 on Mon Feb 14, 2022 3:05 pm, edited 1 time in total.
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Re: Help with 406 sbc build

Post by johnny5 »

F-BIRD'88 wrote: Mon Feb 14, 2022 12:56 pm Measure the Deck clearance at tdc before dissassembly.
It looked darn close to zero if not and I couldn't get the piston to rock.
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