I have a stock production 400 block I want to build. In checking cylinder wall thickness overall it looks good. However, where the head bolts attach to the block, the cylinder walls have a dimple in the water jacket presumably to clear the drilling/threading tools in production. Most meet the min in this area but a couple of cylinders measure .140 way down low in the bore at about the bottom of the piston stroke. One in particular measures .130. So, after boring it may end up at .115 down low. All the walls get thicker toward the top of the bore and most are ~.200 range. Would you use this block for a ~480hp build? I have tried to have this block ultrasonic tested but there doesn't seem to be anyone in my area who can check it so I am left to use calipers and dividers to check the walls.

I know the common min is .150-.160 for thrust walls but based on the way the 400 block is produced, it seems this would be about the max thickness where the head bolts attach. So there must be some 400 specific guide here. When a builder says a block's cylinder walls "check out pretty good" they don't really state what that exactly means.

The application is a street motor for my 89 IROC with a ~6000 max. Any advice or comments will be appreciated.

 

Spend the money on an aftermarket block.

it will have none of the OEM design flaws and you will not have to worry about using steam holes on new heads. you can also get the block with 350 main journals which frees up some frictional HP and use premium fasteners.

http://www.hotrod.com/techarticles/e...ck_comparison/

When to Buy a New Block?
At what point do you sell your stock block and invest in an aftermarket one? Engine design will dictate an upgrade if you plan to increase the stroke of the crankshaft beyond 3.800 inches or bore it more than 0.060 inch. Look closely at the sonic check results and you'll see how thin the cylinder walls of a stock block are when you bore them to 4.125 inch. Cooling the engine also becomes an issue with an overly large bore. GM rates the original small-block cylinder case at no more than 360 hp, but we've seen them stay together at 600 hp or more by stabilizing the bores with a block fill (www.HardBlok.com is a well known supplier) up to the water jackets. Beyond that, we recommend stepping up to an aftermarket block. If you're starting from scratch, consider the cost of sonic-checking, pressure-testing, and machining an old block before you ignore the option of spending more bucks on a new one. Here's a rundown of what it costs to have Pfaff Engines chuck a block up in its five-axis machining center and boring machine:

•Bore and finish hone cylinders: $194.00
•Machine deck surface: $169.00
•Align hone main bearing journals: $206.00
•Sonic check bores and deck surface: $40.00
•Pressure test cooling system: $115.00


Say What?

Baffled by the terms in this article? Here's the lowdown on the more confusing ones.

Blind Tapped: This refers to boltholes that are drilled and tapped into the block without protruding into an open space, like the water jacket. Non-blind tapped holes require thread sealent on the bolts or studs and are prone to leaking water.

Siamese Bores: Early GM blocks have water passages between each cylinder bore. Late-model and aftermarket blocks have what are called Siamese or conjoined bores, which means there is no coolant passage between them. The metal-to-metal contact of each cylinder wall makes them more stable and prone to staying round under intense cylinder pressure that forced induction provides.

Splayed Bolts: GM passenger car blocks have main caps with bolts threaded straight down into the main webs. GM Bowtie racing blocks and most aftermarket blocks have splayed outer bolts in Nos. 2, 3 and 4 main caps. These bolts thread into the side of the block at an angle, usually around 10 degrees or greater. The side of the block has more material thickness than the bottom of the web, making it a stronger foundation for the bolts to grip.

Priority-Main Oiling: A factory 350 block's oiling system sends oil from the pump to the filter, then to the lifters and then to the cam bearings. The main and rod bearings are the last to receive oil, which isn't a good thing at high rpm or when you first start the engine. Priority main oiling reverses the path the oil takes, giving the main bearings the liquid of life first.


Read more: http://www.hotrod.com/techarticles/e...#ixzz2tJStrBRQ

 

stock 400 blocks run hotter by their very nature so be sure to address the cooling system...

Also if you plan to fill the water jackets to increase the strength you have created a track only car. Even a block with a "short fill" will run hotter I don't care what anyone says. for a street car this is a bad idea.

especially for bottom feeder cars like these that have no grille's the cooling system has to operate perfectly to avoid overheating in traffic.

oversized fans and radiator are needed.

again if this is a track only car you could get by with taking shortcuts.. at the track the engine may live a while before something gives up..

but on street or street/strip car you plan to drive a lot problems with high HP and stock block / cooling system will manifest very quickly and it will fail... then you have the pleasure of doing all over again.. the right way.

 

Sell the stock block to an antique engine collector or someone building a number's matching car, it would be better suited for that.

The aftermarket has much better products for your intended use versus that 1970s. relic. A Dart SHP would be great starting point.

 

Great info, thanks for the input.

Yes, the ideal plan would be to use a SHP or better block. If my budget will allow it that is just what I will do. But there are a lot of 400 production blocks giving good, reliable performance out there so it isn't just a matter of "400 blocks are all junk" rather "what makes a good 400 block".

Does anyone who has used production 400 blocks know what the minimum wall thickness should be under the head bolts?

 

Wow - I've never noticed that! To tell you the truth, I'm not even sure my stock block was even sonic checked. It was a .040" over block when I got it.

The only issue I noticed was short hairline cracks on the head deck between where the steam holes are drilled and the head bolt holes. After reading up on it, seems to be pretty common and doesn't cause issues.

I assume you're talking about 480-ish HP at the fly? Still, a pretty aggressive build….

With my small roots blower set up with the biggest pulley, it only put out around 2 to 2.5 PSI of boost, and I still managed 390 HP at the rear wheels. I roughly figure that's around 460 at the flywheel. The most impressive was getting 495 torque at the rear wheels…but I'm sure the boost had a lot to do with it although these 400's do lay down some serious TQ even NA.

As mentioned by FRMULA88, I did end up going with a bigger aftermarket Griffin rad to keep it cool….

When I first built the thing, I had a 195 degree fan switch, which was a bad move. On a hot day idling around, it just couldn't keep up. I noticed if my water temp got over 210 the engine would begin to smoke. Not sure if it was valve seals opening up that caused it, or the cylinders were distorting. Moral is…keep it cool. I now run a 180 degree T-stat and a 185 fan switch and all was well.

I'm now in the process of adding more boost, and hopefully a better set of heads, so I decided to go "all in" and fork over the additional $$$ for a Dart Little M block. No steam holes, better cooling passages, thicker head deck and cylinder walls - which are siamesed BTW.

All that being said, I think you can get away just fine on a non-boosted build with that power in mind….but if you decide to step it up very much from there, you might be better off with an aftermarket block….

Sorry, a lot of yakking and no real answer to your question...

 

No I apreciate the yakking.

Yes, I am refering to crank hp. And it's not really the "HP" numbers I'm after. Really just a good strong torque curve with some top end. I will compromise somewhat to keep it reliable and streetable.

My target is 360WHP average from peak to peak. (10lbs/HP) I figured I will need the largest CI I can afford to keep it mild manored. Still running power brakes and all accessories. And EFI. That is another reason to keep the low end tame-r.

I have this block, and while there are pros and cons to using it, the large bore is very tempting. I just don't want to sink the $$ into it if there is little probability of it holding up long term.

This is a street car but not a daily driver. Most of it's life is spent between 1500-3500. But if I do want to run it hard or juice a little I don't want the block to give out. Either way I go the machine work and parts are basically the same. I guess I just haven't decided if the $1600 is necessary for piece of mind.

 

In the end, it's your call…but I think it'll hold it myself - depending on how hard you intend to "spray" it occasionally. I've found the 400's are a blast on the street…lots of TQ light-to-light.

And yeah, machine work is machine work no matter which you go with.

 

You need to get it properly checked to verify, but if wall thickness ends up being .115-.140 or thicker in the right areas it should be ok at 480 fly wheel. Check it first then decide if needs bored over and only bore as little as possible to clean things up. Check after bore.

I have seen some builders post 800 hp on other blocks with thicknesses in the .120" range. My friends 400 block was .060 over and still made over 650 hp on spray and lived for years before cracking down lifter valley

 

Don't do it if you can't afford to build something else if it blows. I'm not saying every single one of these blows up, but I talked to my friend specifically about this because he has about 8 of these virgin bore blocks stashed away. He said he's built a LOT of them and the failure rate is about 50%. Half of them work out great, and the other half end up blowing up or just not checking out or need to be bored more than .030 which is skating on thin ice with that block. I have a hard time settling with the extra liability that I have $5K into a motor with a weaker block just to find it splits and chews everything up making it worth pennies for scrap metal I guess.

On a budget? Go with a 383 stroker instead and play it safe. You're not really losing much in comparison to a 406 build. Could also build a nice carbed LQ4/9 LS motor if you can score one for a good deal... otherwise I'd vote for a 468 or 496 stroker using 781 heads or equivalent.

 

Or build a 396-401 stroker in a 350 block. Its doable and extremely torquey. Had a local thirdgen guy with one. 408 actually it was really bored out. Forged crank is money but its a solid street setup. He even sprayed his and it was fine even with small piston height

 

Only reason I didn't mention that is because of budget concerns. I'm going this route on my next refresh, actually. 396 strokers are awesome.

 

For what it's worth my machinist (high end circle track and Pro Stock engines a specialty) turned down the prospect of building my 400. He pointed out a few used cores in his shop and they all suffered the same damage. The cylinder wall split right at the head bolt hole. He mentioned that often it happens with the application of a torque plate prior to machining or when the head bolts are torqued down. The results may not show themselves until the engine has been in use for a bit.
This surprised me and I crafted a letter to Kevin McClelland at Chevy High Performance which was answered in an issue about a dozen years ago. He agreed with my machinist and in his reply suggested that the best option is an aftermarket block. Whether it applies in the OPs case or not I don't know, but once the block has been crack checked, pressure tested, sonic checked and fully machined you're about 2/3rds the cost of a new one.
I've heard a few tales about 400's using coolant or having a cylinder go flat and this may explain a lot of that.
Just relating a little first hand experience. The 2nd engine I ever built was a standard bore 400 with fuelie heads (back in the 70's!) that didn't give me any trouble from a cracking standpoint. This is what prompted me to build another albeit 30 years later. Another that I had, a stocker in my service van, dropped a cylinder and was pulled. Sold that block (with full disclosure) to a fellow and never heard what became of it.

 

Way to thin on that size bore. I look for .180 at finish size, 400 block seem to be a crap shoot at best. I have bolted on a torque plate and have seen the block crack from the bolt hole to the cylinder making the block junk.

I have some pretty good deal on Dart blocks all machined I will send you a PM.

 

Seems the situation is not unique.

 

Thanks so much. I guess my gut is telling me the same thing. And yes, it is a budget issue but hey I'm about to dump ~6-7k in it anyway so it's not like this is a shoe string budget.

I have the stock 2-bolt 350 that came out of it and believe it will make my power goal. I feel that a larger CI will do it more easilly and with better streetability.

 

Lots of horror stories coming out of the woodwork about the dreaded 400 small block. I may have never got mine in the first place if I had heard all of this.

I must have gotten super lucky with mine since is was a 4.165" bore block on boost with no huge issues.

Dirt tracker cars are pretty big around this area, and they've been using these 400 sbc's for literally YEARS and YEARS. If built properly, they'll be as reliable as anything else.

All this being said though, even the dirt trackers have mostly gone with SHP blocks over the past few years for a few reasons….price being one of them. 1500 bucks for an entire new block ready for finish machining is hard to pass up.

Plus, with 350 main cranks which are more readily available, no steam holes required, thicker cylinder walls etc. - just too many things on the "plus" side to not get one.

If the budget you just gave us is correct (6-7K) - why buy a 400 main crank for a used over bored block?

I only built my 400 in the first place because SHP blocks weren't available at the time and it was the stronger 509 casting 2 bolt main.

-So I already have my $$ tied up in a 400 main forged crankshaft, and other internals. If it were today and I was just starting all over….SHP all the way…and I'd even choose it over a used 350 block BTW..

 

To be fair, I know just as many dirt track racers that literally "run 'em till they blow" more than anything. They buy the 400 block KNOWING they're lucky to get a whole season out of it and cheap is the primary focus. Those guys really know how to break stuff, heh...


I honestly believe it's really a gamble and you don't REALLY know until you have the motor in and running/under stress. The guy I mention refused to sell the blocks to ANYONE and I'm like his second son, so he offered one to me if I wanted one but warned me that he doesn't recommend it for the money involved.

I've seen a few really nice running 406 SBC's on a stock block. No problems. I've seen just as many with horrid fractures, splits, dropping the crank, etc. I believe it's a combination of different things, and a little luck tied somewhere in the mix. The question really comes down to - are you willing to risk it to save a little coin? Or potentially lose a lot in trying to save a little? Tough decision, really.

 

We have used GM 400 blocks for Super Gas racing for yrs.None of then gets used without sonic testing and mag'ed, block filled haft way,finished bore/honed with torque plates.Then leakdown tested wkly,torn down at a number of laps and freshen up.

Now this isn't a endorsement to use GM 400 blocks.Please don't misunderstand me.All I am saying is back then when we used then,those are the steps plus of course the normal machine work to make them all square and in line to help make them work.And then the rotating assemblies where not cast.

 

Carl?

 

Yes its Carl

 

Thought that was you! Def recommend a block from you

 

PM me on the block as well with price info.

 

I have a virgin 400sbc.
Stock shortblock (crank rods and cast pistons)
I got it sonic checked and it was ok.
Said it was on the line of needing a bore but we left it.

So we re-ringed it and put new bearings in it.

Best of 12.24@108 in a 3620lb GTA (with me in it) . About 380rwhp
Then I sprayed it with a 125 shot and went 10.97@120 (about 500rwhp)

I was told these 400's are good to about 600 crank hp.

I guess I'll see when I shoot a 150shot to it this summer.

 

A honest and fair portrayal of the aftermarket blocks isn't the bottom priced ones. Truth in the matter is there are a number of options for them that does lead in a price more towards the low $2,000 range with raised cams,BBC cam bearings,etc.Those have to be ordered when you buy the block.So yes,about $1,500 for the basic aftermarket block,but there is much,much,more to it than that in ordering and then on top,finishing it to a running engine.<ARP being one example>

 

Shp was 1799 shipped to your door blueprinted machined ready to assemble from Hinkson auto above when i got mine in 09. Its just like an oem roller block except 2 pc seal but i heard they make a 1 pc.

Dont need all the raised cam stuff tall deck for street build unless you want 440+ inches. Shp holds fine. I'm near if not over 1200 hp in mine although it hasnt yet seen a season, but has seen few years at 800 hp
Too bad dart raised prices 15% this year. That really hurts the budget aspect of it

 

Orr.Here is three pages of what I am talking about.Might very well be guys on here to step up to the plate with a big bat.

http://www.dartheads.com/products/engine-blocks?p=1

 

Doing it over again i would have gotten the lil m myself but never thought i'd be this far. Most however doing na builds or mild street nitrous just cant justify those blocks. Those are more for 800whp and up type builds although i feel confident in the shp to 1000

But there are alot of features available when you go aftermarket. Big inches big cam tunnels big lifter bores all help in making stabile high rpm power

 

Haha…I didn't anticipate being this far either….but I still have a ways to catch up anywhere near you Orr!!

In my case, the Little M was at the right price…right before Dart jacked up their prices..plus it was on sale to boot!

-And I can pretty much guarantee you I won't be pushing 800 whp soon…I was more interested in getting over the few shortcomings the stock 400 block has. I don't see any reason the SHP block won't hold for you….

Kinda curious to see which way the OP (Antman) is gonna go with his build...

 

My friends shp had some issues with caps walking at 758 whp thru th400. Approx 900-950 at motor. Nitrous mule. Nitrous is harder on motors than boost. 250 shot followed by another 100 stage slams those caps around... Even tho i have alot more hp mine seemed to be ok at first diassembly after years of 700-850 hp abuse. Smoother power delivery probably helps

 

Yep,nitrous is hard on engines.

 

Welll it finally dawned on me when I made the comparison to cylinder heads- yeah, you can make factory heads flow ok if you know what you're doing but in the end you have a head limited by the factory's constraints. The aftermarket heads have features wayyyy better than the factory parts, not just higher flow. Likewise, the engine block is limited when you stick with the factory stuff. In my case the 400 block with thin spots leaves too much to chance. I truly believe my factory block would hold up just fine at my power levels ~480bhp torque/street build. But I'm not so confident that I want to take the chance. Plus, my plan is for 400+CI. I believe 420CI will make the power goals and still be streetable, even docile at lower rpm. I plan to cam/head it to peak ~55-5800. I feel that in the end it will be less expensive to build it right one time than to build it twice.

My local shop just quoted me SHP block, Callies crank & rods, Weisco piston short block that'll net 420CI and should be rock solid at this power level. And the price is just a bit more than what Tristar and others are getting for a SHP/cast 406. So, confused1 no need to be confused anymore lol. I told them to order the parts.

And I must say, starting with a 350, the first 30CI is cheap but that next 30CI is way expensive. I probably don't really NEED a big motor to achieve my goal but in the end I'd rather have a Dart 420 than a stock block 383.

 

You put a 210 head on it and cam for 5500-6000, its gonna make more than 400 whp and be very mild

 

Maybe it's time to ditch the old screen name….

 

Lol ok I get it confuzed1. My bad.

 

Oh man this is going to be good.

 

421 Build is the way to go and if specked out correctly can be bad ***.

Here is one I built last year with all the bells and whistles.

http://www.chevelles.com/forums/showthread.php?t=481081

 

I checked out your build and yes it was very impressive. A bit above my goal but very close spec.

I am considering AFR 195 vs 210's for the heads. I see a lot of builds with both. I do want to preserve low rpm and part throttle drivability but my 68 L78 375/396 had HUGE rectangluar port heads and had gread drivability so I think the 210's wouldn't hurt since the CI will be up there.

HSR EFI OEM computer MAF. 1 5/8 shorty headers and single exhaust. These two combined are my choke points and probably limiting my top end power. that is one of the main reasons to keep it a torque build. I'm leaning toward the Comp cams XFI line but have some reservation. The LSA seems too wide for a 420CI motor, even considering the fuel injection. I also don't know whether to use the 230/236 or step up to the next cam (236/242 I think) I need to keep the idle vac up enough for power brakes but don't have experiance with big CI motors. How much overlap is too much? I noticed you ran a solid roller and I'm gonna stick with the hydraulic roller so that is another reason to target a 58-6000 red line. I'm running a TKO 5 speed and 3.27 rear gear.

 

I agree ! Check mine out. This is a drag strip focused build (minimal street use) 12.9:1 SCR ( Race Gas ) Solid roller cam, Brodix 18 degree heads.

 

Nice Numbers and thanks for sharing.

Carl

 

Thanks

For the newbs to engine building.. Notice on the graph where the TQ & HP curves cross? it is around 5200 RPM.

if there is one thing to remember it is this..

HP = TQ*RPM/ 5252

 

That's enough to flip an F-body over backward!
Have you run it yet?

 

indeed I have

10.836 @ 126.83 with plenty left on the table.

A lower rear gear and new tires are planned for the spring.

I posted a vid on the organized racing forum a few months ago.

 

https://www.thirdgen.org/forums/orga...best-pass.html

 

That's a nice first outing with it
Yes, you certainly do have LOTS left in it!
What converter and tranny are you running? I looked/listened to the video; that motor's not happy leaving the line -- it wants more R's !!
Here's mine leaving the line with about your hp and a few more lbs of @ss

It's a stock bottom heads/cam LT1 with a 100 shot.

The video should crack you up - my teenage son doing his best excited robot commentary....lol!

 

Big cars going fast are always fun to watch.

My combo has a
Turbo 400 with a trans brake and manual valve body.
Torque converter is Precision Industries.

I had the 2 step set up with a mild 3000 RPM pill or 3200 I can't remember right now, LOL. the car left hard best I can tell. The 60' can be better but the track prep was marginal at the end of season on a cool & very windy day. I called it a day after 4 passes car was getting sideways on me a few times,


the shift light is set at 6800 which should be it ideal based on the dyno curve.. I can try a 7200 setting and see if it likes that better because it will raise the RPM between shifts. *but I don't want to over rev the motor if I don't have too, the parts will last that much longer.


I know my 3.70 is probably too high.. 4.30 would be better because at the finish line I was only revving at 6000 and it should be on the shift light thru the traps. Also I have 26 tall slick, a 28 tall slick would also help the 60' and work with the 4.30.

But first thing is first, what I really need is some more seat time and better track prep to really baseline the car. I will play with the trans brake and shift light setting first... then the rear gear & tires to dial it in..

sorry for hijacking OPs post I guess the moral is big cube small blocks can be ALOT of fun !

 

Sorry to extend the hijack, but hey let's keep talking about what these highwinding small blocks are capable of!
'88, I wish that dyno run was extended past the peak at 6900. But based on what I see, as long as you have the valvetrain to support it, it will ET much better at about a 7400-7500 rpm shift point. What stall rpm is that PI converter? And yes, more gearing and a taller tire will pay big dividends in the 60'.
Just for example, my power peak is at 6400, I'm running 4.88 gears, 29" tires, an 8" 4200 ATI converter, and shifting at 7100 on motor (6900 on the spray) to keep it in the powerband after the shift. I know you have more cubes and extra torque to help it out when it falls into the next gear, but unless you're running a really loose converter, extend those shift points and you'll see some positive results

 

Because I have 18 degree heads, I have shaft mounted rocker and I spent the money on Crower SS pieces.. Safe to say this motor can / should rev to 7400 with no issues. I guess we didn't want to flog a fresh motor too much on the dyno, but looking at the power band on the graph the HP should still be over 650taking it to 7400. I just want to ease into to it and get used to the car at this power level I thought low 12s was fast.. 10s scared the crap out of me the first time. especially when the rear end shook sideways in the wind..

So that is the first step; more seat time and get the best possible ETs with 3.70 gears to see what the RPM really is going to be at the finish line..

 

I really dont remember the spec on the PI convertor I know I send them the engine specs, dyno chart ans car info.. when I swapped to the 400.

I have to check my paperwork.. I think it's a 3500 stall..

its model #219710.. I need to check those stats.

 

Interesting note on the SHP block vs stock block. The SHP has provision to run the OEM style roller lifters. Since I am planning to run a roller camshaft anyway the cost difference between OEM and retro-fit is $250 (Compcam). So, in the end the Dart block will increase the build by $1050. And if someone wants a production 400 for a mild build then my end cost could go down some more. Regardless, a thousand bucks is a bit of money but worthwhile to me. Of course, the forged stroker kit adds another $700 but in the end it should make a rock solid combination at the expected power level.

HIJACKERS!!! lol