Question about a Small Block 400

[Marotrent]

Originally Posted by HOJO

I had a 406 in my 67 camaro and that thing was a monster for what it was. Compression was 10.5. Had a comp cam 501/501 292 duration, not sure what it was at 50. Edelbrock RPM air gap intake and headers. I really loved that thing. Definitely do the 350 rods you won’t regret it.

Yea Im hearing alot about the 350 rods. They are pretty cheap too from what I see.

[Marotrent]

Originally Posted by acammer

Heads are the biggest shortcoming on most old small block Chevy's. A good value-based upgrade is a Vortec head, like Russell James said try to get the compression up in that 10.5:1 range. Decent manifold, good headers, healthy cam, and you'll have nice power and a torque monster. Consider an EFI setup - they are not as expensive as they used to be, and if you're having to replace a carb, manifold, and ignition anyways it's even less of an expense.

Ill be looking into the vortec heads, and I've heard that texas speed has some decent headers and cams for the small blocks. Ill have to look into the intake; also if you have any brands that you can recommend Id appreciate it.

[Marotrent]

Originally Posted by Russell James

The first thing I'd do is tear it completely down. Have a machine shop square up and blueprint the block. Then figure out a piston and head combo to get the compression up around 10.5.

70s engines are notoriously low compression and will never make power until bumping up the compression and getting the heads to flow. And throw away as many cast iron parts as possible... intake, exh manifolds... boat anchors.

Way back in the day 30 some years ago I bought a '76 Trans Am - 455 4 spd. Thought it was going to be an awesome fast thing... turd, couldn't get out of it's own way. Brought it in to my high school auto shop class... teacher taught the whole class about how to make a 70s smog motor make some serious steam. We threw the pistons, heads, cam, intake in the trash. Went 10.5 CR pistons, Ram Air IV heads and cam, headers... it then was a beast. Stock it had 7.5 to 1 CR and heads/cam that flowed about as much as a lawn mower.

A lot of 400s are kinda the same way, smog motors with no compression or head flow. But lots of potential.

Thanks for the help, Ill need all the advice I can get. Ive never build and old school motor before. If there are any brands you can recommend let me know.

[christianchevell]

I used to run 406's, used dart Iron eagle heads on the last one to not have to worry about retorqueing of the aluminum heads...which is best done on aluminum mated to cast iron in intervals of like 25-50k...meaning also the intakes.... Great engine for torque, was why they made them, you how ever need to make sure the steam vent holes are there to vent the steam that can build up between the cylinders as they are Siamese ……….. so yes I had to have them drilled into the heads by machine shops.....heads for SBC fit most things....just not a 400 due to the need for the vents, you have to have the extra holes or crack a block...……. best advice I can give. Circle track guys would try to buy up 400's to destroke them to 377's so they could rev higher, me I was street strip and wanted the displacement. Then of course the guys who wanted the crank for a 383....

[SSE 4 2SS]

Marotrent,

In my opinion, if you want to build an old school small block, I would see if you can trade the 400 for an 010 350 block, with 4 bolt main caps.... There isn't much demand for them anymore and you should be able to find one for an even swap or super cheap... Heck, tell them it's a cool project and they may give it to you.... Things to look for, make sure either the freeze plugs on a potential block were removed, or haven't just been flared... Look closely for any block cracks.... You might want to discuss a swap out if your machine shop finds an issue... Being in South Florida, freezing isn't a big issue, but it does happen.... I aways discussed being able to swap out a block I was purchasing if the machine shop found an issue...

The 400 is a fairly solid block, but it has webbed cylinders, where the 350 has fully independent cylinders. There are water flow jackets all the way around the 350 cylinders, for better heat control.

At that point, after having the block centerline bored and decks trued up, Look for a good forged crank shaft and some lightweight rotating parts, rods, pistons (any forged pistons and rods are going to be adequate as long as they are a reputable company..) I would go with a nice set of aluminum heads, someone mentioned Vortec, and that's fine. There are better flowing heads for high rpm if you want to go that route in my opinion.. (Promaxx Performance Freedom Series is one option, Dart Pro 1 Aluminum heads, or the Brodix IK 200 Aluuminum heads) There are lots of options, these are just a few...

Comp Cams has for years and years (at least since I was in HS, and that was many years ago) offered a fantastic cam package for the small block chevy, ...specifically the Comp Cams Xtreme Energy 268 series. I've installed this cam package in 283's, 305's, 327's and 350's... I've never put one in a 400 because as I mentioned, I'm not a fan of factory fights for adequate cooling... I've only built one 400 ever and it was a bust in my book.... It just didn't perform like the 350's.... Get a double roller cam chain or talk to your machine shop and see what they recommend. Cloyes and Lunati make good pieces....

As was mentioned before, try to get the compression ratio up to 10.5 - 1 and then play with the timing to reduce detonation... Premium fuel helps with that as well....

If you are going with a carb, be honest with the RPM goals... Over carb'ing is just as bad as or worse than under carb'ing... Most small blocks I've built have ended up in the 500-600 cfm range.... I had a gaggle of friends I could borrow carbs from for testing... We would swap out theirs and go make a few hits... If you flat foot nail it from idle, and it bogs badly, it's too much carb in most cases....provided the timing is properly set prior to trying this... This is over simplified and easier to address in person.... This is an opinion, but everyone will mention Holleys, or Edlebrocks, but don't overlook the Quadrajet 4 barrel..... It's a factory carb I know, but with a few tweaks is a solid carb that doesn't have "power valves." Anyone that ever worked on Holleys understands that statement....(One backfire and you're pulling valve bodies in the parking lot.... I carried more spare power valves than most people carried spare fuses, but we never got stuck on the side of the road for more than an hour or so... The new line of Quick Fuels carbs are nice too.... I've only ever had trouble with one of them, sent it back and they replaced it for an unspecified factory blemish...

Headers, unless you are building a show car, mild steel headers are fine.... They'll last for several years at a minimum and are cheap and easy to replace if need be... 1 3/4 Hooker long tubes might be just the ticket for this build....

I would go with a midrange dual plane intake manifold... unless you want to spin it up a lot higher.... Most of your driving isn't at high rpm and so the midrange dual plane is a great all around option.... The Dart 42811000 is a nice piece, or the Brodix HP1. If you desire a single plane, the Edelbrock Victor Jr is a very reliable piece, and has been for many years... There is also the Torker II and the Holley 300-25.

There is no reason to break the bank to make a solid performing small block as long as you shop around and ask questions.... Find a machine shop you like and trust and let them guide you as well....

[Bo White]

My experience has been the 2 bolt main being more durable than the 4 bolt. Ive seen alot more 4 bolt blocks having to be line bored compared to 2 bolt because of more meat being in the web for strength. The factory 4 bolt has the outer bolts going through the weakest part of the web which is one reason why aftermarket goes splayed caps.
Cooling wise youl be good with a 400 asl long as you make sure the steam holes are in the heads.

[SSE 4 2SS]

That's why I specified an 010 block if you can find one....

[Bo White]

The extra nickel helps a touch on the 010 blocks but still prefer 2 bolt blocks.

[SSE 4 2SS]

Originally Posted by Bo White

The extra nickel helps a touch on the 010 blocks but still prefer 2 bolt blocks.

That is why there are choices.... and experiences...

[spyderbuddy]

Originally Posted by SSE 4 2SS

That's why I specified an 010 block if you can find one....

Yea that's a high nickel block
I had one in a Monza
350 4 bolt Main
Forged Crank
350 Pink rods
Forged Flat top pistons with eyebrows
Cloyes double roller then pete jackson gear drive
Camel hump 202/194 Heads
head cut for rocker studs/guides roller rockers crane
Mallory uni-lite disturber wires and coil
two 500 cfm afb carter carb on dual plane quad setup
Hooker headers
was making about 400 hp at the wheels

I won't have a 400 small block the cylinders are Siamese, there are cooling issues with them

[Bo White]

Ive seen plenty of 400s on the street even with "street filled" blocks that didnt have cooling issues. Like I said earlier make sure you have the steam holes in the heads.

[Marotrent]

Originally Posted by SSE 4 2SS

Marotrent,

In my opinion, if you want to build an old school small block, I would see if you can trade the 400 for an 010 350 block, with 4 bolt main caps.... There isn't much demand for them anymore and you should be able to find one for an even swap or super cheap... Heck, tell them it's a cool project and they may give it to you.... Things to look for, make sure either the freeze plugs on a potential block were removed, or haven't just been flared... Look closely for any block cracks.... You might want to discuss a swap out if your machine shop finds an issue... Being in South Florida, freezing isn't a big issue, but it does happen.... I aways discussed being able to swap out a block I was purchasing if the machine shop found an issue...

The 400 is a fairly solid block, but it has webbed cylinders, where the 350 has fully independent cylinders. There are water flow jackets all the way around the 350 cylinders, for better heat control.

At that point, after having the block centerline bored and decks trued up, Look for a good forged crank shaft and some lightweight rotating parts, rods, pistons (any forged pistons and rods are going to be adequate as long as they are a reputable company..) I would go with a nice set of aluminum heads, someone mentioned Vortec, and that's fine. There are better flowing heads for high rpm if you want to go that route in my opinion.. (Promaxx Performance Freedom Series is one option, Dart Pro 1 Aluminum heads, or the Brodix IK 200 Aluuminum heads) There are lots of options, these are just a few...

Comp Cams has for years and years (at least since I was in HS, and that was many years ago) offered a fantastic cam package for the small block chevy, ...specifically the Comp Cams Xtreme Energy 268 series. I've installed this cam package in 283's, 305's, 327's and 350's... I've never put one in a 400 because as I mentioned, I'm not a fan of factory fights for adequate cooling... I've only built one 400 ever and it was a bust in my book.... It just didn't perform like the 350's.... Get a double roller cam chain or talk to your machine shop and see what they recommend. Cloyes and Lunati make good pieces....

As was mentioned before, try to get the compression ratio up to 10.5 - 1 and then play with the timing to reduce detonation... Premium fuel helps with that as well....

If you are going with a carb, be honest with the RPM goals... Over carb'ing is just as bad as or worse than under carb'ing... Most small blocks I've built have ended up in the 500-600 cfm range.... I had a gaggle of friends I could borrow carbs from for testing... We would swap out theirs and go make a few hits... If you flat foot nail it from idle, and it bogs badly, it's too much carb in most cases....provided the timing is properly set prior to trying this... This is over simplified and easier to address in person.... This is an opinion, but everyone will mention Holleys, or Edlebrocks, but don't overlook the Quadrajet 4 barrel..... It's a factory carb I know, but with a few tweaks is a solid carb that doesn't have "power valves." Anyone that ever worked on Holleys understands that statement....(One backfire and you're pulling valve bodies in the parking lot.... I carried more spare power valves than most people carried spare fuses, but we never got stuck on the side of the road for more than an hour or so... The new line of Quick Fuels carbs are nice too.... I've only ever had trouble with one of them, sent it back and they replaced it for an unspecified factory blemish...

Headers, unless you are building a show car, mild steel headers are fine.... They'll last for several years at a minimum and are cheap and easy to replace if need be... 1 3/4 Hooker long tubes might be just the ticket for this build....

I would go with a midrange dual plane intake manifold... unless you want to spin it up a lot higher.... Most of your driving isn't at high rpm and so the midrange dual plane is a great all around option.... The Dart 42811000 is a nice piece, or the Brodix HP1. If you desire a single plane, the Edelbrock Victor Jr is a very reliable piece, and has been for many years... There is also the Torker II and the Holley 300-25.

There is no reason to break the bank to make a solid performing small block as long as you shop around and ask questions.... Find a machine shop you like and trust and let them guide you as well....

Hey thanks alot for the reply! I really needed a couple of decent company's to look up for parts and you gave me a few that I will look into. As for the 400 block, I actually have access to a 350 thats in a 1972 monte carlo as well, I just figured the 400 has higher torque so... why not lol. Im still shopping around but i want 400-450hp which shouldn't be to hard to get.

[Marotrent]

Originally Posted by Bo White

My experience has been the 2 bolt main being more durable than the 4 bolt. Ive seen alot more 4 bolt blocks having to be line bored compared to 2 bolt because of more meat being in the web for strength. The factory 4 bolt has the outer bolts going through the weakest part of the web which is one reason why aftermarket goes splayed caps.
Cooling wise youl be good with a 400 asl long as you make sure the steam holes are in the heads.

Just from the research I've done on the internet most people say that the 400 2 Bolt is stronger than the 4 Bolt. I will make sure the steam holes are in the heads.