400 in the 68 Chevy

[Bobby277]

Hello all, new to the forum! Have followed a few threads here and there but I finally have more than one question to ask so I thought I'd join.

ANYWAY, I own a 1968 Chevy C20, she's a sweetheart. Lol. I recently acquired a 400 sb and I'd like to build it with my truck in mind, I want to build a tourqe motor.

I am going to go through it with a stock rebuild kit, mild cam, and I'd like to put vortec heads on it.

My questions are is this a solid build for decent tourqe? I'm not looking for huge numbers, maybe 350hp and 400 ftlbs. So is a set up like that appropriate? I want advice on the build.

Second- if I go this route I've heard I'll need to change my pistons to dished because my compression ratio will be to high for pump gas. Any details on that?

Third, opinion on aluminum intake? Carb?

I appreciate all of your replies!

[bigmac73]

will vortec heads work on a 400SBC??, not for sure if you can drill steam holes in those heads? you might want to research that a little bit

also compression ratio will also depend on the Combustion chamber size of the heads you are going to use

[truckster]

Vortec heads will work fine on the 400 SB. You'll need to drill steam holes, but you can use the head gasket as a guide for those.

Your HP/torque goals should be easy with that combination. You'll need a manifold that fits the Vortec heads. Edelbrock makes a Performer for that application. A Quadrajet would be a great carb to have on that as well. The 400 is also externally balanced, so you'll need a different balancer/flex plate.

One thing about the 400 - make sure your cooling system is up to snuff.

You'll love the 400 in your truck.

[Bobby277]

I did know about the steam holes, thank you there, so the performer inkake is a good choice? I have seen it mentioned in other threads here.

[DBD]

I'd do a straight performance overhaul on the 400 shooting for around 9:1 CR and using the Vortec heads. I've drilled the steam holes in them many times - just use the head gasket as a guide. you will need heavily dished pistons to get to a reasonable cr with the 64cc heads.

The performer is a great manifold - one of the very best low-rise dual-plane manifolds out there.

I am not a big fan of the Qjets - they were great carbs, but most of them are in pretty sad shape and for the price of a rebuild you can get a Holley...and have something you can tune.

[Bobby277]

So dished pistons, do you have any numbers for something like that? I'm not exactly sure on what I would need to purchase?

[DBD]

Originally Posted by Bobby277

So dished pistons, do you have any numbers for something like that? I'm not exactly sure on what I would need to purchase?

https://www.uempistons.com/index.php...191448f3d340ec

delivers 9.8 CR with a 64cc head and 5.7 rods...no reason to rebuild the stock, short rods when you can get a set of Scat rods for about the same amount of money...this will REQUIRE premium fuel...your machine shop will have other choices, including speed pro.

the northern auto parts guys have great kits if you buy a few upgrades...but don't buy anything until your machine shop tells you what you need.

[Bobby277]

Premium fuel is kind of a deal breaker, it would be great to have a set up that will run 87 octane, is that possible? That seems like the right direction though. I joined to ask these very questions so I appreciate you all putting up with me!

[wesmigletz]

With a 22cc dish, a .041 thick gasket, a .025" deck height and a 64cc combustion chamber, you will be around 9.3:1 compression. Be careful with rebuilder pistons, they have larger dish volume and sit further in the hole, typically .045" down.

My son's 406 is around 8.0:1 compression with it's rebuilder pistons and stock 76cc head. When he swaps to Vortecs, he will still be around 8.6:1.

[DBD]

Yep, the above is all right on.

[burnin oil]

If the truck is a stick shift the flywheel can be a little difficult. Most of the aftermarkets are real pricey. The cheapest option is have a standard flywheel balanced with the rotating assembly or have the whole thing balanced neutral for using a standard flywheel and balancer. Once you look into the prices the neutral balance is the best way to go. That route will probably take some mallory metal to balance out, pricey, but gives you access to off the shelf parts. Even adding mallory metal would probably work out cheaper than a 400 specific flywheel. Some people say to use the balance plate sandwiched behind the crank but I have never been a big fan of them. Even if using one I would want the whole setup balanced with the plate.

[Bobby277]

I was aware that the 400 is externally balanced, the engine (400) has a flywheel on it already. Would it be possible to use it? My truck is a manual, it's got a Muncie. What would be the least expensive route for pairing them up?

[burnin oil]

Flywheel as in not a flex plate? If so take alot of looks at it and the balancer. 400s did not come from the factory as a stick. That means it is aftermarket or had alot of holes drilled into it to balance out. This works but the motor needs rebalnaced if the flywheel needs replaced. Another thing is the 400 balance plate, aftermarket piece, may have been installed on the motor. Check the balancer and make sure it has the balance groove on it. Someone may have just thrown a flywheel on there and ran with it. Back before I learned about the external balance I learned that hard way this does not work. My motor never vibrated at all but wiped out the bearings really quick! Learned a very expensive lesson!

400s with a stick is a great setup but you need to address the balance deal. So as I was saying above you can balance the rotating assembly (which may take heavy metal), buy an expensive after market flywheel (which should be balanced to the assembly), add the counter wieght (some have had good luck but I do not trust and would balance), or buy an anfter market crank that is internally balanced. All options should be balanced so it becomes which way makes the best sence to you. Once the balance issue is addressed the motor will bolt right in like any other small block. It would be a good idea to check the block for bolt holes next to the balancer for the power steering pump and the the one by the oil filter for the clutches Zbar. All the blocks have the bosses but some were not drilled and tapped. An easy fix when it is out of the truck.

[wesmigletz]

I have one of these SBC 400 Flywheels that I bought for my 400 SBC, but haven't installed the engine in my car yet. It looks like a decent, but heavy, piece. I plan to use it with a mild 400 with Vortec heads, a 262 Voodoo cam, and an A833 4 spd O/D. I'm not worried about the flywheel, because my engine won't go above 5500 RPM.

http://www.oreillyauto.com/site/c/se...RWD&vi=1030352

[Bobby277]

You are right, I need to address the vibration problem to-be! Lol. I really like the sounds of an internally balanced crankshaft. Could you possibly give me more detail on that setup? What would I run on the back of it then? Thanks for all the answers so far guys, this is great help.

[Bobby277]

And if I run 22cc dished pistons, would I also use 5.7 rods? And if so, would that all match up to an internally balanced 400sb crank? If that all is true then that sounds like an ideal internal package. I would just hate to make an expensive mistake, measure twice cut once you know?

[burnin oil]

Internal balance crank makes the 400 like any other small block. Then you run a standard 350 balancer and flywheel. When I did my last 400 I spent a big chunk of change, about $1700, and got a SCAT rotating assembly. Sounds expensive untill you realize that you end up with a forged crank, better rods, forged pistons, rings, and bearings for the price. I do not know if they make a internal balanced cast crank but the 9000 series are very good and cheap. Rod size is determined by the piston used. You can plug you info in Summit racing and look at 400 pistons by rod length. Some people on here will argue this but I would try and keep the compression at 9.5-10:1 but some feel less is better for a mild build. Personally I went with the 22cc dish pistons and think I missed the boat there. With 64cc heads I need to run a thin head gasket to keep my compression up. I should have gone with a 13cc piston and a standard head gasket. A 5.7" rod should fit without problem but a quick mock up will verify this. I never tried a 6" rod but from what I have seen you will have to relieve the block in a few places. Back to pistons. Make sure that you dont get low tension oil rings or the narrow racing ring packages. You want a long service life that doesn't burn oil or leak compression.

[Bobby277]

LETS JUST SAY I went a different route with a performance rebuild kit from summit plus a mild cam and kept my stock 76cc heads for now. I realize they aren't very good heads, but about the vibration thing? If all I replaced were the stock pistons with new- equivilant stock pistons- AND my 400 has the original flex plate, not flywheel, or whatever it is supposed to have, WOULD I have to do anything else to run it with my manual transmission? To address the balance issue?

[truckster]

Originally Posted by Bobby277

LETS JUST SAY I went a different route with a performance rebuild kit from summit plus a mild cam and kept my stock 76cc heads for now. I realize they aren't very good heads, but about the vibration thing? If all I replaced were the stock pistons with new- equivilant stock pistons- AND my 400 has the original flex plate, not flywheel, or whatever it is supposed to have, WOULD I have to do anything else to run it with my manual transmission? To address the balance issue?

You can't run a flex plate with a manual transmission. You need a flywheel for the clutch to act against. A flex plate simply connects the crankshaft to the torque convertor, as well as providing a gear ring for the starter.

[burnin oil]

The balance will only need adressed if the flywheel/flexplate is mismatched. All 400s were automatics so a flexplate with the factory wieght welded on is fine. Now manuals did not exist factory so there is no cheap flywheel. This brings the balance issue into play. The 400s have a unique balancer and flywheel unless it is converted to internal balance. This means verify what it has. Nothing wrong with the stock heads if they can be reworked cheap. My first 400 build had 882 casting heads and was a real runner and got 12-14 mpg. I will caution you on those 23cc pistons and 76cc heads. Your compression will suck bad. My motor was flat top pistons with the 4 eyebrow reliefs and 76cc heads. With a good street cam it ran on 87 octane fuel. It could have used a little more octane though. No detonation but cheap fuel would cause a little dieseling. This combo is a little high on static compression. Being the pistons are being swapped the whole rotating assembly needs rebalanced. Back to the heads. You dont mention budget but it sounds like this is a budget build but heads are where the power is. If getting the heads reworked is going to cost more than $700 bucks you may want to look at better aftermarkets. I only say this because this is almost the starting point of things like iron eagle. By $1100 you hit jegs heads which are actually on par with AFRs. I have done many rebuilds with stockers in the past but would not do it any more. The price is just so close any more that i can justify stretching the budget there. New ishome just lighrt years ahead of the old castings. Decent heads with some hyperytetic pistons are a good street motor recipe.

[Bobby277]

it is a budget build right now but someday i might build this engine with more HP and TQ. for now ill stick with factory heads unmachined. i am also disregarding my previous hp tq numbers. what i am looking at now is this rebuild from summit + a mild cam

http://www.summitracing.com/parts/fe...-000/overview/

and maybe this flywheel?

http://www.summitracing.com/parts/su...Reviews=Newest

and having the rotating assembly ballanced all together. would that work? would i need anything else for the vibration factor?
thanks again for the replies, its really helping.

[carp1329]

I bought a fly wheel for my 400 from jegs for $82 .You will have do drill and tap the block for the clutch ball stud.

[Captainfab]

You do not need that billet flywheel. Why not get the flywheel in the link in post #14? Or if you were to get your rotating assembly balanced, a standard flywheel can be balanced for the engine. If you already have a standard flywheel, you could get the whole assembly balanced for not much more than buying a new externally balanced flywheel.

Not that long ago, I could get a standard flywheel balanced for either a 400 or 454 for $50.00. Unfortunately that machinist retired.

Originally Posted by Bobby277

it is a budget build right now but someday i might build this engine with more HP and TQ. for now ill stick with factory heads unmachined. i am also disregarding my previous hp tq numbers. what i am looking at now is this rebuild from summit + a mild cam

http://www.summitracing.com/parts/fe...-000/overview/

and maybe this flywheel?

http://www.summitracing.com/parts/su...Reviews=Newest

and having the rotating assembly ballanced all together. would that work? would i need anything else for the vibration factor?
thanks again for the replies, its really helping.

[burnin oil]

What was the part number for the 400 flywheel. $582 was the cheapest flywheel they carried awhile back. Flexplates have been dirt cheap for awhile. The price of a flywheel plus the need for a new crank made upgrading to internal balance a no brainer. I previosly had a regular flywheel balanced to a 400 and the machine shop hated me. It looked like swiss cheese!

[Bobby277]

the flywheel mentionend in post number 14 would work i think? and i did find the 83 dollar flywheel online, its on JEGS website. my engine is for sure getting new pistons so ill just call a local machine shop to see what i can get the stock rotating assembly plus my new pistons and flywheel balanced for! that doesnt seem to hard?

i did change my mind on rebuild kits BTW. check it out.

http://www.summitracing.com/parts/fe...-000/overview/

any opinions on cam choice for my revised set up? the engine will have 9.08:1 compression accordiing to summit. or do you think stock cam? when it comes to cam choice i really have no clue what to look for.