400 SBC Block
 

I snagged a virgin 817 casting 400 block to build a 377 for my dirt modified, but when I talked to the machinist about building it for me, he pretty much said he'd rather not build anything using a stock 400 block.

I know compared to a 350 4 bolt main block (which loses the big bore benefit), bowtie block or Little M, the stock 400 is the weakest of the bunch. However, I figured at no more than 550hp and 7500 rpm with a short stroke, long rod, lightweight flat top rotating assembly in a 2500lb car would live for some time. This guy didn't want to touch a build like this PERIOD even with splayed main caps.

What are everyones opinions about using a stock 400 block with stock caps for this application? How long would it live? Will it live at all? What would safe power and rpm limits be before having to really worry about catastrophic block failure.

Thanks Guys,
Darren

I heard with 4 main bolt modification, they can be pretty reliable, My 400 bock was a 2 bolt with stud girdle that lived at 7500 rpm for 3 yrs. and produced a bit more than 600 hp.

Drag or circle track!!!!!!!!!

Re: 400 SBC Block
 

Over the years we have prepared a lot of 400 blocks and afeter a season of running oly to find a cracks in the decks near the head bolt holes and we have seen cracks in the webbing from the cam tunnel down to the mains. And they are so far out o blue print compared to a good block its not funny.

Dart has the new SHP blocks that can be bored to 4.165 and I beleive we can machine one out, Line honed, decked, blue print bore and plate hone, clearance the lifter bores clean and ship in the U.S. for around 1795.00

We have 4 on order just waiting for them to arrive.

I had a 379ci destroked 400 and ran it for about 3 years until it finally blew up from too tight mains. I have a 422 now using a stock block with Eagle Billet Splayed Caps shift has ranged from 6500-7000 so far without any issue's. The biggest issue I have read and heard is weak cylinder walls. I added just a small amount of hard blok to mine to the bottom of the freeze plugs maybe a little lower. It never gets over 190 even on 90+ degree race days. I think going with a short stroke helps it live too.

I had a good conversation with a respsected engine builder about using a production 400 SBC w/ a 3.375 stroke for a LSR ( Land Speed Racing ) project and he was 100 % against it !!

He said to use an aftermartket block or forget it ............... ln .02

If not for IMCA production block rules, it would be a no brainer to go with an after market block. Unfortunately, that rule prohibits any aftermarket block including bowtie blocks.

From what I'm hearing I can build a 400 production block based 377, but shouldn't expect more than a couple of seasons out of it at most. That sux!

Guess I need to hunt down a good 4 bolt main 350 block and build a good SOLID 383. Anyone have one available?

Thanks for all the replies folks
D

We have had a lot of calls over the years from some of the IMCA guys who have blown up 400 blocks looking for more its kind of a shyty rule as it should not allow a 400 block as it would save the guys some money in the long run.

WOW! was that the understatement of the year LOL.

I do see why they don't allow the aftermarket block though and its because they want to keep guys from building the big motors, thus, forcing the guys who can't afford 2-3 motors per season to use 350 blocks and those who can afford several motors per season to use the weakest SBC block made. I guess their view is if your dumb enough to spend the money to build a big motor with a stock block, shame on you.

If they would just put a displacement rule in, say 410ci or so, then I don't see any reason for the stock block rule AND everyone would have bigger faster longer lasting motors.

JMO

Just a question....Didn't the sprint car guys used to use the factory blocks years ago? I know they are weak but when I was a kid the sprint cars were running 406 -410 ci and I know the top teams had aftermarket blocks but I mean the more local type racers that still ran well. I am speaking of early to mid 80's. Like I said just asking cause I know there are several options NOW for an affordable aftermarket block but what was around back then?

Back then they were not at the power level that are today

we had a stock 2 bolt main 400 block and put the splayed caps and bored / stroked it out to 434 cubes. Block half filled...

It ran 9.60's in a 3100 pound car for 4 seasons (about 800-900 passes)

All we did was freshen it with new rings and bearings every winter. After we ran it we sold it and the guy is still running it now onto his 3rd season.

This is shifting at 6800 and going through just under 7000.

I would build another one in a heartbeat, but there must be a difference in my drag cars from the roundy rounders.

I bet for every 1 block like yours there are a hole bunch more that didn't live .

I would be willing to bet the concrete in the block helped it stay together with the splayed caps not to mention your peak rpm of 7000.
I don't know being an ex drag racer myself I would've never believed a dirt track car would be so hard on parts until I heard some of the horror stories and saw some really well built stuff come apart. Part of it might be the fact that in drag racing you tune the car to peak power (shift point and rpm at the end of the track) so the motor rarely sees rpm past the power peak. Circle track cars see rpm past peak power every lap because every track usually has a pretty big swing over the course of a night between high traction and no traction so the car has to be able to pull hard when the traction is there and yet not be prone to blowing the tires off when the traction goes away.
I would say that if I was buiding a motor to put in a drag car i wouldn't be nearly as scared to build it using the block I have unless I was going to be putting a lot of spray to it.

If It was mine I would use it. Fact is I still buy 400 blocks when I find a good one that is a straight casting. I also buy 400 factory crankshafts if in good shape and are cheap enough. Why? most of my SB customers just will not buy an aftermarket block. WE do a lot of prep on them and have really had good sucess at lower than 700 hp with them. We did have one that at a shade above 800 experienced the main caps moving around. Actually we saw some funny things with oil pressures so tore it down and found the main caps were moving on the block. So now I tell my guys to keep them below 750 hp even with nitrous.

Several of the factory blocks doing 530 to 570 hp in street use in poor boy strokers.

I am not arguing with Carl or disagreeing. He is correct.

Ed

You should have em sonic tested,lots of variations in wall thickness. Find a good one and with 4 bolt mains, maybe a short fill and limit hp and your ok! A friend of mine built a 377 years ago ( drag car) and its still running fine!!! David.

Aside from sonic testing is there anyway to tell visually whether a block is a "good" block or not?

Darren

It will let you know when you max out the HP limit!

Look for core shift around the machined holes, lifter bores, freeze plugs, etc.

We have not found that not to be very accurate compared to a sonic test.

Dart has the new SHP blocks that can be bored to 4.165 and I beleive we can machine one out, Line honed, decked, blue print bore and plate hone, clearance the lifter bores clean and ship in the U.S. for around 1795.00

What is the standard bore on this block Carl?How much do you think it will weigh over an 010 sbc block?

We are going to buy all 4.000 bore blocks and blue print bore them from there and the weight is suppose to be 165 pounds depending on the final bore.

Still waiting for the first ones to arrive.

I was not suggesting that, but can be used to rule out blocks before spending the money.

400 block
 

I have run the 400 block as a 377 and a 406 and I would say that the stock block is good to 575 if you check for core shift and socic test the block. Make sure to have it magnafluxed also as they seem to be prone to cracks in the lifter galley.

We have a 400 2bolt block that was converted to a splayed 4bolt making 703 hp @ 406ci. This is a drag application. There are always many possibilities. We know that this is not recommended by anyone at this power level but we had the parts and so we built it. That said we see evidence of the block moving around a lot, i.e. cylinders not sealing like we would like allowing blow-by leading to oil leaks. And this block has been poured. Would I recommend anyone else doing this, no way unless you know going in what the end result could be. Call Dart you will sleep better at night. :lol: :lol:

Curtis

I'm with Curtis on this you can do it but there are consequences, i run a 377" 2 bolt main and even with a gurddle there's evidence of main cap walk, and even with the block filled to the water pump there's still ring seal problems and i don't think i have much over 600 HP if that. We have a couple 434" that run good, but all the above still happens.
Bottom line if you can afford it go to an after market block, i bit the bullit and bought a Dart little "M" for my 434" that i'm building.

PS, Hink, i hope you guys bought the 350 main blks., since most everyone i know is going that way.Also i saw an ad for the new SHP blocks here on RJ, for about the same prices you mentioned, but i don't think they mentioned fixing the lifter bores.

JMO


Zip.