I just picked up a 400 small block for my 88 S10 short bed, standard cab, 5 spd. It came from an 82 chevy pickup but it wasn't the original motor. I heard it run and it sounded alright. Its the 3951511 casting - 4 bolt main block. I got the motor complete but I already tore off the accessories, intake, and exhaust manifolds since I won't be using of them.

I want to keep the truck fuel injected but I want to make it reliable for daily driving. I need ideas on the best setups for 400s. What should be done to the block to make sure I have a good foundation to start with. When I give it to the machine shop to get bored out, what else should they do to it?

What are some good combinations to make over 400hp/400torque while still being fuel injected?

They have engine kits all over ebay, what the best combination for a 400 small block? Theres the 400 3.75 stroke crank, 3.48 stroke 350 crank, stock rods, 5.7 rods, 6.0 rods, etc. What all works best?

 

forget the 3.48 stroke, it is pointless to take away cubes needlessly. Have the block checked out well. What is the bore on the block? 400's dont like to take very much boring. Get rid of the heads that came with that engine, unless they are different than original. 2 bolt blocks are stronger, but for the power you are looking at, a 4 bolt is fine.

 

Welcome to TGO!

3 things to keep in mind about the 400 block:

1.) They like to breathe
2.) They can take bigger cams and still retain street manners
3.) Did I mention they like to breathe?

I second what was said. Don't toss away cubes. Use the 3.75" stroke and check the bore diameter.

What's all in and around this engine as it sits? Cam? Heads? Rotating assembly? If it's bone stock, take everything out as it is all smogger garbage.

Also, try the search feature. Lots of 400cid combos out there. I am certain at least one retained a form of FI (NOT a factory TPI or TBI setup).

 

Really the 2 bolt is stronger than a 4 bolt?? Why is that??

What horsepower are 4 bolt main blocks good to?


I tried searching for that stuff but it was seems like I can never find exactly what I'm looking for when I use the search feature...

This motor has EVERYTHING, transmission all the way to the air cleaner.

Why isn't a TPI setup good for a 400?

 

It's not so much that 2 bolts are stronger than 4 bolts; rather, the early blocks, which all happened to have got 4-bolt caps installed on them, have ALOT less metal around the main cap webbing area, than the later blocks did, which all happened to get 2-bolt caps installed onto them.

400 HP at the crank is not a problem for either style of block.

TPI chokes a 305. It will choke a 400 even worse.... like 33% worse, more or less.

Torque is the same thing as energy. Energy comes from burning gasoline molecules. Therefore, the more gasoline molecules you burn, the more energy you obtain. Power (expressed in units of horsepower) is energy per unit time; i.e. the time rate of doing work, also calculated as torque x rotational speed. It takes oxygen to burn gasoline molecules to obtain energy. The most gasoline molecules you can burn to obtain their energy from, is proprtional to the most oxygen atoms you can mix them with. Therefore, power (energy per unit time) is directly proportional to oxygen atoms per unit time. Oxygen atoms are found in air, in strict proportion. Therefore, ultimately, an engine's horsepower output is directly proprtional to its induction system's flow. Period.

TPI doesn't flow. And even worse than that, the same acoustic effect (the "Tuned" in TPI) that produces its main benefit which is increased cylinder fill in a particular band of RPMs, also produces decreased cylinder fill at RPMs above about 1.5 times its "tuned" RPM. Since its "tuned" RPM is about 3600, that means that it has an unsually high peak torque at 3600 RPM, falls off rapidly above that, and produces less torque at RPMs above about 4500 than its (already very poor) raw flow numbers would indicate because of the tuning.

Bottom line: if you want power, don't use TPI. Use some other form of FI. The MiniRam for example is perfect for a high-HP 400. The Stealth Ram is OK but its flow limit is about 425-450 HP, due to its restrictive runners. The Accel Pro Ram is another good one I've used on a big motor (434) with decent results. I've never used the Edelbrock Pro Flow multi-point system, but it looks like it would work well also.

The 3 things you need to make big horsepower with a big inch motor, in order of importance, are:

• 1. Flow;
• 2. Flow; and
• 3. Flow

And in case I forgot to mention it, there should be no restrictions anywhere, that would reduce flow through the induction system. That includes the air cleaner, intake, heads, cam (or rather valve opening generally), and exhaust.

 

A good set of 70cc+ chamber aftermarket heads are the best choice for a 400sbc. With the larger bore they build compression especially with a zero decked block. A nice 200cc runner head 230ish at .05 duration cam and performer rpm air gap manifold. Shift the engine around 6K and you'll be leaving all the high revving 350's in the dust with all the torque of the 400.

A better aftermarket rod is a good idea considering the strength compared to the cost of resizing and better arp bolts in stockers. Use a set of 5.7 with capscrews, shouldn't have any problems with cam clearance, but make sure to check. Use a good machinist and don't cut any corners and you'll be very happy.

 

now why would you run a cam that small in a 400.

I have a 224/230 @0.050 in my vortec headed 350, and i wish i had went alittle bigger.

Depending on the heads, I would run no less than a 240 @0.050 in a performance minded 400.

 

I guess this is a truck and may work it a little, boat, small camper whatever... With say a XE274 it will make killer torque from 2500-5000. Shift it at 6K and it will last along time. No valve float or broken internals. Nice thing about the 400 is it does not need the rpm that a 350 does to make the same power.

If it was a racier motor and had forged internals, a solid roller etc and then rev it to 7500. Inside a bowtie blocik of course.

 

Well I guess this is what I'm gonna do...first I'll strip it down to a block and measure the bores to see how bad everything is. Then send it off to the machine shop to first check for cracks, then check the main bore alignment, then bore out the cylinders .030. If I have a good block to start, then I'll start figuring out what I need.


I'd like to run safely on no more than 93 octane gas, since thats the highest octane around here. I want reliable more than anything, but I'd like to buy only what I need...I'm on a tight budget here... I mean I don't wanna sit here and buy a forged steel crank and all that stuff if I don't really need it.

How much can this stock cast crank take? How many rpm can I wind it out to?

What's a good choice for rods and pistons? I've seen complete rod/piston/ring kits on ebay under $400 I think. They were hypereut pistons and forged rods I believe. What should I use for my application?


What do I do about the steam holes in the heads? Does anyone offer any predrilled heads for 400s? I'm kinda reluctant to buy some nice heads, then have to drill them out or something like that, I'd be afraid of messing them up.

 

if you're really that afraid, you can just get a machine shop to do it.


if they charge you more then $20, they're overcharging you.. lol.

you lay a headgasket down as a template and mark the holes.
drill them out (a hand drill is just fine)
deburr the holes



thats it. with all the tools infront of you and the heads on a bench, it should only take 15mins.....

 

That's with a real dull drill, and stopping twice for cold refreshment.

Here's what the holes look like..... the 2 small holes between each pair of cylinders; 6 holes total per head.

IMO, this is so trivial, that if you have enough mechanical savvy to bolt the heads on, you can handle this easily. It's nothing to be afraid of.

 

RB, is that a thermal coating on that head?

 

Yes

 

I think that 400s don't care to be revved over 5000-5500 rpm unless you do some extra work to the block, crank and rods.

5000 rpm would probably let you run it for a LONG time