Visit The Dirt Forum for More Information

Author Topic:   400 4bolts vs 400 2bolt
fridge
Dirt Full Roller

Total posts: 31
posted February 22, 2001 11:51 PM
i was wondering what everyone thought about 400 4bolts compared to 2bolts i know that a 350 4bolt is better, but i heard that in a 400 they aren't because the outside bolt is in between the cylinder walls which are closer because of the bore. thanks

tls88mod
Dirt Roller

Total posts: 24
posted February 23, 2001 09:24 PM
2 bolt 400 blocks are a stronger block because they have more material in them. They also work well if you use splayed main caps.

mtnman
Dirt Roller

Total posts: 8
posted February 24, 2001 02:41 PM
What you heard was correct! My brother tried a 4-bolt a couple of years ago, the first night on it,it blew the crank right out the bottom of the engine.I have never seen an engine self destruct the way that one did.The cause was alot of compression and the weak spot on the outside bolts.He since then went to a 2-boltand it's fine.He also had a Klein engine years ago,it had splayed caps on it,that was a tough engine.That one blew up because the oil line got tore off in the corner(dry sump)at 7000+ rpm.

MOD RACER#93
Dirt Freak

Total posts: 251
posted February 24, 2001 08:27 PM
Hi. While on the subject of 400's, I am going to build a 406 with 6.0 rods, and an internal balanced crank. It is a 2 bolt main. My question is, could
I get away with leaving the block a 2 bolt main??? I think I am going to have around 13:1 comp. They reason I ask is because It's going to really be stretching my budget to have the block set up with splayed main caps and all...Any info would be greatly appreciated....thanks.

jklostermann
Dirt Full Roller

Total posts: 45
posted February 24, 2001 10:11 PM
Mod93,

If you have a 400 2-bolt which is the ideal block to have, you should have if fitted with splayed caps. I don't know of anyone around here that runs a motor without them! You could leave it two bolt I guess if you want to blow the bottom end off the thing. Also check the block for the nickel content. A high nickel content means a stronger block. For all the guys running stock caps check the bottom for a "NF" casting on the bottom of the cap. This stands for Nodulated Forged which is a very strong "stock" cap.

chomme
Dirt Full Roller

Total posts: 52
posted February 27, 2001 01:09 PM UIN: 1986763
Modracer ...

I ran a 400 2 bolt block with a 3.75" brc crankshaft, carrilo rods, and trw 12.5:1 compression pistons. I used ARP studs in the mains and never had a problem. If the budget allows, go splayed...but if not, I wouldn't worry too much about it...I was putting about 540hp out of it (two barrel motor)...

awkwardjeff
Dirt Freak

Total posts: 218
posted February 27, 2001 06:08 PM
Mod racer, The Extra cost of doing a splayed cap block is around $400. but if you need to line hone the block you have now you can deduct another $80. because you would have spent that much to keep it a 2 bolt anyway.
I would NEVER, EVER, think of putting a $2500 crank kit in a block that didn't have splayed caps....by the same token I wouldn't put a cast crank kit in a splayed cap block.you would have too much to loose.....you will spend money on tires, fuel, tear offs, and a ton of other things..........this $400 is CHEAP insurance. If you don't blow the 2 bolt to pieces it will be worth a lot less than if it had splayed caps.
In my opinion splayed caps are the cost of racing, and it's one of the few parts where when you sell the thing you can get your money back........A SPLAYED CAP BLOCK HOLDS IT'S VALUE...........
save money some where else, I'm sure you already have, but look again........Jeff

MOD RACER#93
Dirt Freak

Total posts: 251
posted February 27, 2001 08:09 PM
Yeah, that's kind of what i waz figuring. If your gonna go, go all out. I have found a good machine shop that is capable of doing whatever to a race motor. Just waz wondering though. Thanx for the reply's....

P.S. Jammin where are my points, or stars or whatever?????? I wuz way past full roller....lol.

modbob35
Dirt Roller

Total posts: 9
posted February 28, 2001 08:21 PM
I have a 377, with a 4 bolt main which we have put studs in. 13:1 compression, should a carry a bucket around to pick up parts? I sure hope not!

fridge
Dirt Full Roller

Total posts: 31
posted February 28, 2001 09:05 PM
all i have is a 400 4 bolt block, do you think i should put money into it or just build a 355

GnarlyCar
Dirt Forum Racer

Total posts: 96
posted February 28, 2001 10:50 PM
Sell your 4-bolt 400 block to a street rod guy and go find a 2 bolt one and have it fitted with splayed caps. The outer bolts in the factory 4-bolt makes the main bearing webbing too weak to take the HP that a mod motor will make. Awkward Jeff was right..it's nothing to spend $400 on tires that'll be gone next month, but so many of us are afraid to spend that same $400 on something like a splayed cap block. Seems pretty simple when you really think about it. The cost of racing.. chalk it up as one of the "gotta-haves" like a helmet or sweet graphics job.

Matt

Roadhzrd
Dirt Maniac

Total posts: 101
posted March 01, 2001 02:57 AM UIN: 28276986
$400 sounds kind of high. the caps are $100 for the cheap ones and all they do is bolt them in with the old two bolt holes and step drill with bushings and tap the splayed holes before they align bore.

chomme
Dirt Full Roller

Total posts: 52
posted March 01, 2001 10:05 PM UIN: 1986763
Here is just a suggestion...I was building a late model motor and got into the block and figured...I had a 350 2 bolt block (.010/high nickel block) that was a good core. I wanted to have splayed caps installed, plumbed for dry sump, bored, align honed, decked, cam bearings/freeze plugs, and the lifter bores bronze bushed. I also was going to have the rear of the block checked for squareness and the thing magnafluxed/pressure checked. By the time the machine shop figured out how much it would be, I bought a brand new dart iron eagle block for $180 more...and that is a much stronger block and has all the goodies...splayed caps, thicker cylinders, etc.

GnarlyCar
Dirt Forum Racer

Total posts: 96
posted March 01, 2001 10:21 PM
Chomme,
I was just thinking the same thing earlier today. Seemed to me that after all the sweet tricks we gotta do to a stock block to make it race ready, we'd have spent about the same as a decent aftermarket block with all that stuff already done. You just confirmed my suspicion.. Any chance that the authors of any of our rulebooks will ever figure that out??? Fat chance..

Matt

MOD RACER#93
Dirt Freak

Total posts: 251
posted March 01, 2001 10:33 PM
And keep in mind this is after you carry 2 or 3 blocks to the machine shop to get 1 that the guy will work on....I dont know about were yall are from, but 350's and 400's just dont fall from tree's were im at...Im going to build a 406 just because I have several 400 motors. No good 350's. Well mabey if you wanted to sleve all the cylinders and start over....Has anybody done this?? built a high dollar race motor with sleves in it???

awkwardjeff
Dirt Freak

Total posts: 218
posted March 01, 2001 11:13 PM
quote:
Originally posted by Roadhzrd:
$400 sounds kind of high. the caps are $100 for the cheap ones and all they do is bolt them in with the old two bolt holes and step drill with bushings and tap the splayed holes before they align bore.

roadhzrd, Like anything in life you get what you pay for.......I know a shop that will put the caps in the block, then align the thing for about $250......the problem is that they don't fit the caps properly first.
All blocks are a few thousands different at the parting line for the main caps.....the after market caps need to be set into the block then measured for fit.........the set up in the mill and faced off where needed...
the final fit needs to see the step sit flush, then the outside need .002 clearance.
then drilled and taped.........the cheap shop won't torque the outside of the cap before align boring..........then you take the thing home and torque the bolts.....the bore is about .0005-.00075 out of round....
a 1/2 thou may not sound like much but when the oil clearance is 2 1/2 that 1/2 is 20 percent......and now thats a ton.......
This is why a good shop will charge a fair price........$400 is fair where I'm from.
$250 is no bargin when you have problems...you could have saved the $250 and just raced it with 2 bolt mains.

you can also reuse the same caps from one block to another by clipping the cap and re-fitting the cap to the new block, the problem with this is unless this is a very EXPENSIVE set of caps with all the machine work that needs to be done you are money ahead to just my the new ones
Jeff

[This message has been edited by awkwardjeff (edited March 01, 2001).]

modbob35
Dirt Roller

Total posts: 9
posted March 02, 2001 07:31 PM
Is it the main caps or the block that is weak on the 4 bolt main 400's? Or combination of them both. Already have engine built is there any solutions? Thanks

awkwardjeff
Dirt Freak

Total posts: 218
posted March 03, 2001 01:39 AM
It's in the block, there is nothing you can do to make the block stronger.....If you can measure the webbing at the bottom of the bore they are a bunch thicker in a 2 bolt block.

MOD#11
Dirt Roller

Total posts: 24
posted March 03, 2001 01:38 PM
Just put block filler to the bottom of frost plugs and run it.

Back to the Archives