Small block 400

[HotRodPC]

I think we may be pulling the motor next weekend. From my knowledge its stock on thr inside. Single hump heads and now a holley 650 on it. If I pull it, it will be a full build pan up. But what I'm getting from you guys is better heads before anything else because it will help get all the power out of other add-ons?

I do believe you're getting the message. I sure like all the input here on this thread. Almost making me want to find a 400 now. I just want to address another issue so you don't get sticker shock and you're prepared for it up front. And other can confirm or deny if they want. Don't be shocked when you realize you're going to spend as much or MORE on the heads than you will for the short block build. It doesn't have to be that way though. I'm seeing the AFR180 aluminum heads is the way to go. But how far away in performance would an OEM rebuilt set of Vortecs do with the added steam holes drilled? Those will get the compression up for certain, but don't exceed the .470 lift unless you want more machine work and at that point, then go for the AFR180's. There are plenty of good cam choices under the .470 lift.

And I would for sure not just add a new set of heads to raise the compression. Chances are this is an older tired high mileage engine with some ring wear. You raise that compression to much, those rings will say fugg it and end up in the oil pan in very short order.

 

[HotRodPC]

Damn it!!! I had a really nice post typed up and hit a wrong button on my computer...

Here's the short version...

Run 5.7 rods in your 400. You need different pistons, but you need them for a 383 also.

Grind the mains down on the 400 crank to the smaller 350 size and run bearing spacers or special bearings.

400's are externally balanced and can have problems at higher rpm's, like 6000+. Buy an internally balanced crank for a 400, for less than $300, or buy a 383 kit intended for a 350 and run the above mentioned bearings and/or spacers.

Any head you can put on your 383 can be put on a 400. Just drill the steam holes and run the right gasket. (Repeating hirsch I believe)

My 400 has never had cooling issues, even during hours of summer heat driving with a slide-in camper in the bed at 3000+ rpm's and the stock cooling system. I just put in a 190* thermostat so it would actually warm up properly.

400's have superior cylinder filling with their bigger 4.125 bore that unshrouds the valves. This means more power potential everywhere in the powerband, for both torque and horsepower. That is the biggest difference in power potential, IMO. Followed by cubic inches.

I love 383's just as much as 400's, and my choice of which to build would be determined by what I have sitting around. Because the OP has a 400, I say build it. If he had a 350, I would be promoting finding another 350 block and building a 383.

The thing I don't like is the comparison of a stock 35+ year old engine to another engine that someone has taken the time, effort, and expense to "build". Of course a 383, or 355 for that matter, that someone has "built" is going to make more power than 400. But you do that same exact "build" to a 400, and the 400 is going to wake up like the other engines. Apples to oranges people. Try doing an apples to apples comparison.

Gm stopped producing the 400 due to gas mileage regulations and the "corporate" engine program. Not because the 400 was a terrible engine.

When I rebuild my 400, I am not using the stock shorter rods. You can buy stock used 5.7 rods cheap. Or the terrible 76cc heads. Most heads will probably be better than my stock ones. But I do plan on using the stock crank and big main bearings. Mine will be a low rpm engine build and the bearings size and externally weighted rotating assembly will not be an issue.

Yes, that's the short version!

Thanks for the input. I agree, that is the short version. I agree, avoid the 76cc heads all you can too. They don't only have 76cc going bad for theirselves. They're also riddled with smog (NOX) bumps in the heads, and very small ports. Of course smog bumps and ports can always be ground out, opened up, and polished, but that's about equal to polishing a turd.

 

[Green79Scottsdale]

I do believe you're getting the message. I sure like all the input here on this thread. Almost making me want to find a 400 now. I just want to address another issue so you don't get sticker shock and you're prepared for it up front. And other can confirm or deny if they want. Don't be shocked when you realize you're going to spend as much or MORE on the heads than you will for the short block build. It doesn't have to be that way though. I'm seeing the AFR180 aluminum heads is the way to go. But how far away in performance would an OEM rebuilt set of Vortecs do with the added steam holes drilled? Those will get the compression up for certain, but don't exceed the .470 lift unless you want more machine work and at that point, then go for the AFR180's. There are plenty of good cam choices under the .470 lift.

And I would for sure not just add a new set of heads to raise the compression. Chances are this is an older tired high mileage engine with some ring wear. You raise that compression to much, those rings will say fugg it and end up in the oil pan in very short order.

I do agree with not just replacing the heads for compression. It sounds like the OP is going to go through all of it, so he will have the opportunity to do the math and get all the parts to line up nicely.

I am in the minority, I believe, when it comes to Vortecs. Yes they are probably the greatest factory heads, but I believe that the majority of aftermarket heads will out perform them. In my eyes Vortecs and AFR represent the bottom and top offerings as far as small block heads go. There are a ton of others in the middle of those two, and some for very intriguing prices. I found some aluminum ones from Summit and Scoggin Dickey for the mid-$800 range. They have bigger runner volumes (not much) and also bigger valves and springs and can support around .550 lift cams. I do not have links right here at work, but I can get them.

Around here, to do the right short block machine work, you are looking at around $1000 to have a complete short block ready to go.

edit: Here is one link... http://www.summitracing.com/parts/pmx-2169/overview/
PROMAXX Performance Freedom Series Small Block Chevy Cylinder Heads
64cc combustion chambers (others available)
185cc intake runners
2.02 intake 1.60 exhaust valves
.575 max lift
$843 to your door
They may not be a well known name, but at one time neither was AFR, or Edelbrock, or Holley, you get the idea. Not much more $$ than Vortecs...

 

[MadOgre]

Thanks guys for the helpful posts. Quick question we swapped that Holley on and now the tranny doesn't want to shift right (crack throttle falls on its face in gear neutral or park its fine, not shifting until 4k revs) trans was fine before we put the carb on. Could something be mis adjusted? Had a buddies dad help me and he did all the tuning and adjustments didn't question it but now it doesn't seem right.

He probably never addressed the TV cable to throttle linkage issue. He very well may have done a good job on the carb but forgot or didn't realize the issue behind the 700r4 TV cable

Do not drive it like that until you have fixed this issue.

The TV cable controls line pressure in relation to where the throttle is. ITs actually a very precise setup in relation to throttle position. So any different geometry from the Quadjet will screw the whole thing up and you get early or late shifts and it may work ok in one part of the throttle and not in another.

Im not sure off the top of my head what pieces are available to correct this for a holley? but there is a specific geometry corrector bracket available when running a 700r4 behind an Edelbrock carb.

You will need to find the Holley version of this.

Guys have burnt up 700r4s in a matter of hours by running with out the TV set correctly!

 

[MadOgre]

Also the cable bracket is just as important as you need to keep the cable straight and square and parallel to the base of the carb from the bracket.

If you can find a TV bracket that bolts between the carb and the intake as a plate they are the best as the height of the intake manifold is no longer an issue and they seem to be very sturdy. You don't want the TV bracket to flex when you apply throttle.

 

[HotRodPC]

I do agree with not just replacing the heads for compression. It sounds like the OP is going to go through all of it, so he will have the opportunity to do the math and get all the parts to line up nicely.

I am in the minority, I believe, when it comes to Vortecs. Yes they are probably the greatest factory heads, but I believe that the majority of aftermarket heads will out perform them. In my eyes Vortecs and AFR represent the bottom and top offerings as far as small block heads go. There are a ton of others in the middle of those two, and some for very intriguing prices. I found some aluminum ones from Summit and Scoggin Dickey for the mid-$800 range. They have bigger runner volumes (not much) and also bigger valves and springs and can support around .550 lift cams. I do not have links right here at work, but I can get them.

Around here, to do the right short block machine work, you are looking at around $1000 to have a complete short block ready to go.

edit: Here is one link... http://www.summitracing.com/parts/pmx-2169/overview/
PROMAXX Performance Freedom Series Small Block Chevy Cylinder Heads
64cc combustion chambers (others available)
185cc intake runners
2.02 intake 1.60 exhaust valves
.575 max lift
$843 to your door
They may not be a well known name, but at one time neither was AFR, or Edelbrock, or Holley, you get the idea. Not much more $$ than Vortecs...

I don't think you're in the minority. Most of us agree the aftermarkets outperform the Vortecs. Just that Vortecs are an inexpensive budget step for some bolt on horsepower from OEM TBI and earlier heads. But you're also right. If you intend to start having machine work and updates done to the Vortecs, by the time you spend the funds on the machine work and updating to bigger valves or handling higher lift cams then you may as well just go for the aftermarket heads since total cost comparison between both isn't to far off now days. Cost of good aftermarket heads has come way down over the years. Used to, you'd be spending close to $1000 PER HEAD for an aluminum aftermarket head. Now days you can get a real nice set of 2 for well under $1000.

 

[Don5]

That is some good advice HR and Green79! You guys are absolutely right. The price of aluminum heads has come down thank goodness. I have heard good things about the Promaxx heads. A lot of guys are using them around here.

Linville as far as the rockers go. Wait until you buy the cam and go with what the manufacturer recommends. Those guys spend gobs of money on research so they would know what rockers to match with the cam.

Best of luck on your build and keep us posted. As you can tell there are quite a few of us that are interested in it including me.

 

[Linville33]

We used the stock bracket for the cables. He just adjusted the cable and think he adjusted to much. If the trans goes gives me an excuse for a trans swap as well

 

[MikeB]

Run 5.7 rods in your 400. You need different pistons, but you need them for a 383 also.

Grind the mains down on the 400 crank to the smaller 350 size and run bearing spacers or special bearings.

400's are externally balanced and can have problems at higher rpm's, like 6000+. Buy an internally balanced crank for a 400, for less than $300, or buy a 383 kit intended for a 350 and run the above mentioned bearings and/or spacers.

If this was meant for the OP, he doesn't care about rod angularity or building a 6,000 RPM motor. 5.565" rods are fine for a stock or even a mild rebuild. Heck, back in the 80s and 90s, John Lingenfelter used those rods for many a high performance 383.

The 400's 2.65" main journals increase rod-to-main journal overlap to compensate for the longer stroke. That, in turn, keeps crankshaft rigidity where it needs to be. It's the same reason the 350's increased stroke required larger main and rod journals than the 283 (3.00") and 327 (3.25"). Even the short stoke 302 (3.00") used the larger 350 journals in 68-69. And we don't see anyone grinding a 350's 2.45" main journals down to 2.30".

Bottom line is there are a lot of tricks to make a 400 rev higher, but none are necessary for making lots of low-RPM torque in a truck. And I'm not even sure 5.7" rods would have much effect on revs or horsepower. Seems like you'd need to make the jump to 6.00" or more to see any difference.

 

[Green79Scottsdale]

If this was meant for the OP, he doesn't care about rod angularity or building a 6,000 RPM motor. 5.565" rods are fine for a stock or even a mild rebuild. Heck, back in the 80s and 90s, John Lingenfelter used those rods for many a high performance 383.

The 400's 2.65" main journals increase rod-to-main journal overlap to compensate for the longer stroke. That, in turn, keeps crankshaft rigidity where it needs to be. It's the same reason the 350's increased stroke required larger main and rod journals than the 283 (3.00") and 327 (3.25"). Even the short stoke 302 (3.00") used the larger 350 journals in 68-69. And we don't see anyone grinding a 350's 2.45" main journals down to 2.30".

Bottom line is there are a lot of tricks to make a 400 rev higher, but none are necessary for making lots of low-RPM torque in a truck. And I'm not even sure 5.7" rods would have much effect on revs or horsepower. Seems like you'd need to make the jump to 6.00" or more to see any difference.

No, that was not meant specifically for the OP and his build. As you said, different tricks to bring it up a level.

If you are not doing any sort machining, the stock stuff is perfectly fine to re-use. But if you need new pistons because of an over bore and are rebuilding the stock rods, might as well pick up a set of used 5.7 rods for $50 and rebuild those. You are going to need new pistons for that overbore, so get them with a new wrist pin location while you are at it. The longer rods might not make a noticeable difference in rpm's or power, but they do reduce the side pressure the piston is exerting on the cylinder walls. That is a major factor over time more than anything. 6.00 rods would be even better, but that is aftermarket stuff and that can get $$!

Before you start doing anything to it, do a good evaluation of what you really from it. How high are you realistically going to spin this thing? What kind of manners do want it to have? What is your budget? The answers will dictate what stock components you can re-use and which ones you should upgrade and how exotic of an upgrade you should do.

I still stand behind this for any rebuild. Unless I missed it, the OP never really got into specifics on what he really wants out of this build. My assumption was that up to this point, everything said is general engine build tips, tricks, and information pretty specific to the 400.

 

[MikeB]

Before you start doing anything to it, do a good evaluation of what you really from it. How high are you realistically going to spin this thing? What kind of manners do want it to have? What is your budget? The answers will dictate what stock components you can re-use and which ones you should upgrade and how exotic of an upgrade you should do.

I missed those comments, and certainly agree with them.

 

[DoubleDingo]

We used the stock bracket for the cables. He just adjusted the cable and think he adjusted to much. If the trans goes gives me an excuse for a trans swap as well

Except that cuts into your budget.

 

[Linville33]

Well I don't really have a set budget just don't wont to spend all my money into the engine and not have any money left for a lift and tires. It is getting a trans swap anyways and I could care less about this 700r4 I'm not a fan of them to say the least

 

[Linville33]

Are the double hump heads any good for these 400s? Buddies dad is an old school guy and was telling me how great the 202 double humps are/were. Don't know much about them

 

[Green79Scottsdale]

Vortecs are still better than double humps. Back in the day double humps were top dog, but not these days.