Red Devil

As y'all know all I've worked on is GM stuff and most of my buddies, and my dad too always insit on a block with 4 bolt mains when we start building a SBC from scratch. My dad says he likes the 4 bolt main blocks from pickup trucks becasue they are stronger. Is this really a big deal? I mean I could understand if you race maybe...But all 340s but the T/A version were 2 bolt mains and plenty of them have been raced hard. So what do y'all think? Is having 4 bolt main bearing caps really a big deal?

Crazy4Carz.Com

Actually the 4 bolt Chevy main cap blocks are not as strong as 2 bolt Mopar blocks. On a chebby the four bolts go into the block in a straight line actually weakening the block webbing. It does have a better hold on the main caps and bearing surface but in exchange for weakening the block. The best way, is to have "splayed" four bolt main caps. This utilizes the factory two bolts and adds another two bolts diagonally into the block creating a better clamping force and strengthening the entire crank assy. This is the way the small block was set up in the Dart we ran in "One Lap of America" two years straight. Any good machine shop can do this for you and ARP sells the bolt/studs to accomplish this. Unless you are going to be spinning this HARD don't waste your money. On a side note the new HEMI Mopar blocks are cross bolted main caps and this makes for the best set-up.

Red Devil

huh, I guess I never knew any of that. Thanks for all the info

67 GTX

Can a shop do that to an old 440?

Crazy4Carz.Com

Yep!

67 GTX

what company sells the caps for this, or do they drill into the old ones?

scotts74birds

C4C, at what rpm range would one consider that for a BB? Mine will be a stoplight hero, 93 oct, 10-10.5 cr. I know I'll probably never see the other side of 6500, but that info may help others.

MReeves

Had a 340 that was stroked to 396 and it had the splayed mains.. Never had a problem with it.... Engine was makeing 750 ponies and ran 9.80's in the quarter mile at 136 miles per hour.. But I treated it very gingerly... Stepped on the gas very slowly and never abused it at all!!!!! Only drove it on Saturday nights and only a 1/4 mile at a time.......

Crazy4Carz.Com

ARP does the bolts/studs, and yes the machine shop will drill through your caps. It is important that they do because of alignment issues.

Crazy4Carz.Com

BWWHHHAAAAAAAA

deadkelly

what cam have you got scotty ? my stock 383 with 509/513 lift & 251@ .050 dur used to rev easy over 6500 . although i try'd not to all the time .
& if you really want to rev it over 7000 rpm you can get stud gurdle kits now that are reasonably priced .

78D200

C4C is right on the money with the 4 bolt mains and how they need to drilled for strength.

I remember seeing Mildon (?) selling 4 bolt mains for Mopar BB motors a while back (few years). Not sure if they still do though. Well worth the money if you plan on building a high torue motor that will see lots of gas pedal.

theomahamoparguy

I believe the Big block 4 bolt mains are "cross bolt mains" like on the 426 hemi. The bolts go in from the side of the block, through the skirt of the block and into the main cap. I've read that they are not too hard to install. You would need one hell of motor to grenade the stock bigblock setup though. This is due to the design of the block. The stock maincaps are sunk in deep into the bottom of the motor. On a 383, you could actually sit the motor on the floor with out the oil pan and the crank wont even touch the floor. The smallblock is a completey different story though.

toad490

The problem on BBs is cap walk at high hp and rpm not grenading. Ally main caps will absorb the harmonics and prevent this. I went overboard and added a girdle. I had the caps and rails decked to the same level. Also did a partial block fill, to the bottom of the ring travel, approximatly to the top of the frost plugs with a 4.25 crank.

deadkelly

is this a street engine ??? what heads & cam you using ???

toad490

DK, yes it'll be run on the street. Heads are Indy 440-1, CNC ported, 2.25 valves. Cam is a solid roller with T&D 1.7 rockers it's .731/267 on the intake and .707/278 on the exhaust (@.050), 11.0 to 1 compression. Lots of good stuff, it took me 4 years of saving to build it and get the supporting parts.

toad490

If you go to this eBay search page you'll see Pro-Gram 4 bolt conversion main caps for SB and BBs and 2 bolt main caps. I don't see how you could ever modify stock caps to accept 4 bolts.
http://motors.shop.ebay.com/i.html?_nkw=mopar++main+caps&_sacat=6028&_trksid=p 4506.m270.l1313&_sop=10&_dmpt=Motors_Car_Truck_Par ts_Accessories&_dmd=1&_odkw=mopar+splayed+main+cap s&_osacat=6028

Or am I missing something? The block does have to be drilled but I think you need the conversion caps.
It also has a listing for a girdle that addresses cap walk and web flexing.

Go to this link for a explanation of ally main caps.

http://www.bcrproducts.com/maincaps.html

67 GTX

does the girdle add any more strength to the block?

toad490

It does to a certain extent but mainly it prevents cap walk. It really is over board with the ally caps but I built it for a blower and I got a really good deal on the cap off of ebay and I allready had the girdle so I did both. The block fill strengthens the block more and absorbs some harmonics.

woody02

in reading all the post,i want to chime in and make sure im correct in what im hearing.for 650+hp i need 4 bolt main kit with aluminum rods?...or is the aluminum caps enough to absorb the vibration,and no need to use 4 bolt main cap kit? im looking at 750-800hp

RustBeltRodder

After looking at my 440 on an engine stand and running a finger under the pan rails there doesn't seem to be enough material around this area for cross bolting to do much good. Mopar Muscle Magazine is doing a 451 build right now with cross bolt caps on a factory 400 block so it will be interesting to see how that works out. I've read factory hemi blocks had extra material cast into this area for cross bolting the middle three caps.