Small block 400

[hirschdalechevy]

Well, that's true for high lift cams, but NOTHING builds torque at low-mid RPM like stock Vortecs with a cam up to .470" lift or so. And it's not just the CFM rating -- it's the velocity created by the intake runners.

But, then again, I'm prejudiced.

My 355 with GM Voretc heads and roller cam used in HT383 and RamJet 350

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I am not bashing vortec heads at all , but I think they have a intake runner of 170cc and the afr's I ran were 180cc with bigger valves , (202's) and we are talking 400 sbc which draws about 15% more air than a 350 at any rpm range so the 180cc heads work really nice for torque on the bigger cubic inch smallblock's , (383 and up).

You can also run higher compression / higher cylinder pressure with the right cam with aluminum heads , which is more power across the board at any rpm , so in my opinion yes vortec heads are great but the number one head for torque on a big cubed smallblock ? Not for me

 

[hirschdalechevy]

Back to the original poster , linville33 , everybody has there star motor build thats the best so you will get all kinds of info. but its very simple really.

For the most part , bigger cubes , easier to make torque.

figure out your stack compared to deck height , crank throw cut in half , rod length , piston compression height , then square deck the block to match your stack , (pistons at 0 deck).

Then you want a piston with a d dish , less cc for aluminum heads , more cc for iron heads , (you can get away with more compression with aluminum heads) , ( use a compression calculater) for the right cc's dish piston's vs. head cc's. Then you need to run the felpro .039 compressed head gasket's

And there you have it a quench motor that will haul ass 383 or 400.

Cam selection is very important to keep the cylinder pressure as high as you can for pump gas , pick a cam that raise's pressure to high and you will ping like a bitch on pump gas and you can run higher cylinder pressure in a quench motor and even higher with aluminum heads.

If you line up two trucks , same tires , gear's , weight , your's with a vortec motor set up and same cube's afr head set up truck you are going to lose.

Hope this helps you out and make sure you pick a good machine shop , there are more crappy one's than good one's.

The guy I alway's use has built outlaw sprint car motors for year's

 

[hirschdalechevy]

You also may wonder why GM has a crate 383 HP motor and not a 400 ?

Its because the 383 is a better motor

I know you are not a fan of 400's , ( I dig them) but anyway my brother was building his quench 383 at the same time as I was building my 407 with 5.7 rods , (same machine shop) , ( both quench motor's) , he ran trick flow heads and mine were afr 180's. He had a .039 quench and mine was .040 , he had a lunati cam and mine was a comp. ( pretty close spec's but I had a tick more lift).

We both ran 4.56 gear's with 38's , auto trans , and stage 2 jet q-jet carb's

His was a 72 blazer and mine was a 77 step side.

We used to race all the time and I could always beat him by half a truck when everything was perfect , but if he got out in front of me I could not reel him in , thats how close we were.

So , yes 383's and 400's are very close.

Niether one of us had any trouble with either motor's and no cooling issue's with the factory 4 row radiator's

So depending on what parts I had laying around , 350 block or 400 I would build either and not be afraid , both are great imo

 

[MikeB]

I
You can also run higher compression / higher cylinder pressure with the right cam with aluminum heads , which is more power across the board at any rpm...

Aluminum heads can tolerate more cylinder pressure than cast iron because they don't retain as much heat. In fact, they MUST run higher pressures to make the same power as an iron head with the same ports, valves, and combustion chambers. Their main benefit is weight savings. And I'm not knocking them. Wish I could have bought some AFR 180s!

It's interesting that you like 180cc runners on large displacement small blocks. Lots of guys with 383-406 engines think they need 200-220, but an AFR guy at the SEMA show once told me their 180 is the best all-around street head for up to a 406. But it's a matter of their customers wanting larger runners than their engines do.

 

[Green79Scottsdale]

This kind of thread is both why I come to forums, and the reason I stay away from forums. I had a big response typed, but the **** storm ain't worth it.

 

[Linville33]

Alright thanks guys . I was over at my buddies place yesterday to have him help me adjust rocker arms and my steering box. Ended up pulling the old q-jet off of it and now I got a Holley 650 with a 750 kit in it(what his dad said) it has helped it a lot already but the motor will be pulled this summer and start building it with all the info you guys gave me. What rocker arm ratio should I go with though? I can get a set of 1.7 for real cheap but from what I was reading anything of 1.6 could be bad. I was looking into 1.52

 

[MadOgre]

This kind of thread is both why I come to forums, and the reason I stay away from forums. I had a big response typed, but the **** storm ain't worth it.

These threads are great! Everybody learns something. Some myths are proven wrong and some good info is added that everybody learns from.

I don't care if nobody agrees with me its still my opinion. BUT just like in this thread, I have learned a few things and the OP gets to base his decision off of all the banter back and forth which can be quite enlightening often times

 

[HotRodPC]

This kind of thread is both why I come to forums, and the reason I stay away from forums. I had a big response typed, but the **** storm ain't worth it.

You may as well jump in. This forum is one different than many. I see a few things I disagree with in this thread. I see some I do agree with and I see some things new to me that I'll certainly look into.

Sometimes people are just WRONG and they are usually corrected in a humble way here. Unlike many forums or social networks, "That's not true stupid, you're wrong". Sometimes people are taught or told wrong and we'll correct them if they wish to be corrected.

Some things are personal opinion like this thread for example. Sometimes there are opinions from old school guys, sometimes there are opinions from the younger generation that might be up on technology and more new school type. Sometimes there old school guys that have kept up technology or want to be schooled on the new technology.

Point is, the more ideas and suggestion the better. We have our immature fun here, but we're still adults and can agree or disagree like adults. I could tell the guy what to do or what I'd do, but I damn sure won't be offended if he doesn't do as I suggested and noone else should be either. So spill your guts and give your opinion. You're cheating the OP by not posting your opinion or suggestion since that what he's asked for.


In fact, I'm not a big fan of SBC 400's at all. Never have been, but in this case, I suggested he build his current 400 because he has it and it appeared to me budget was a factor figuring he can get buy using his current crank, rods and block. I see pros and cons to both,, but budget being a factor, I think in the end, building the SBC 400 is going to win out. JMO

 

[Green79Scottsdale]

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!

 

[Green79Scottsdale]

I should answer the OP while I am here too...

Depends on how deep you want to get into it. The biggest downfall for it right now is the terrible compression, you are probably at 7.5:1 to 8:1. You are fighting big 76cc chambers in your heads, dished pistons, and who knows how far "down in the hole" your pistons truly are. If you were to blow it apart you can install flat top pistons and zero deck the block. That will really help the efficiency and potential of the engine. If you are leaving it in the truck, different heads with much smaller combustion chambers to bring up the compression would be the best first step. Any intake/header/cam/ignition you add without addressing the efficiency could almost be considered a waste because you are not getting everything out of them. You can get a nice set of new heads on your truck for under or around $1000. You would probably spend that much on an intake, headers, and cam once everything is all added up. That is my opinion, and where I would start.

 

[Linville33]

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?

 

[Green79Scottsdale]

That is where I would start myself. 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.

 

[Linville33]

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.

 

[MadOgre]

What transmission ?

 

[350runner]

700r4

Sent from the dust in front of you!