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#1 |
Chance
![]() Join Date: Sep 2001
Location: Belcourt ,ND, USA
Posts: 750
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2 or 4 bolt block
What is the difference between a 2 and 4 bolt block? Which is better or does it even matter?
Chance
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1968 Chevrolet Stepside BB 396 w/TH400 1972 Chevrolet 3/4 Ton 4x4 BB 496 w/TH400 |
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#2 |
67 is sold
Join Date: Apr 2001
Location: Troy, Michigan
Posts: 6,738
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Here is a pic of a 4 bolt main block, 4 bolts hold on the main caps instead of 2. This is a stronger setup then a 2 bolt main setup.
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#3 |
I make Models
![]() Join Date: May 2005
Location: Bucks, PA
Posts: 626
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Depends on your application. If you are just building a cruiser with occasional abuse (from the gas pedal...
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#4 |
Java Mechanic
Join Date: Jun 2005
Location: Martinsburg, WV
Posts: 6,764
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That about covers it. Always use a 4 bolt if money is not an issue but, for the rest of us, unless you are going for a serious build that will get serious use -- save the $$ and use a 2 bolt.
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Keith 11 Lincoln MKT -- Momma's wagon ![]() 13 G37xS -- middle age crazy car 68 C20 Fleetside -- RIP Decorating the whole town up at a cost of $27 .... |
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#5 |
Weekend Warrior
Join Date: Oct 2004
Location: CT
Posts: 1,787
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Small Block 2 bolts are good to about 500 horspower if you put main studs in them.
BigBlock 2 bolts are good to about 650 horspower if you stud them. There aren't many street applications that really need a 4 bolt main motor. A 1-ton truck that does alot of heavy towing or hauling may benefit from a 4-bolt. most street driven trucks don't hook up the rear tires enought to merit the use of a 4-bolt main. alot of people want the 4 for "assurance" or they just like to say "it's a 350 4-bolt main" If you want a 700+ horsepower blown injected motor your going to use an aftermarket block or install splayed main caps anyway (the outside bolts in the above picture are angled out toward the oil pan walls) I personally sell all my 4-bolt main motors to the guys who have to have one...and keep the 2's to myself ![]() j.m.h.o. ![]()
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#6 |
Senior Member
Join Date: Jan 2003
Location: daytonabeach
Posts: 22,956
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4bolts overrated 2 is just fine for 90% of actual usage applications
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#7 |
Account Suspended
Join Date: Oct 2004
Posts: 1,276
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Basicaly for the average Joe ,, all the 4-bolt is is something to brag and one up the other guys with .!!!
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#8 |
Registered User
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Location: SOMERSET KY.
Posts: 6,427
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junkyardjohn 69 1 TON TOW TRUCK // 84 4WD CUCV BLAZER// 85 1 TON 4WD STAKE TRUCK// 86 M1031 5/4 TON 4WD CUCV// ALOT OF OLD TRUCKS FOR ONE OLD MAN TO DRIVE. ![]() LIFE MEMBER OF P.E.T.A (PEOPLE EATING TASTY ANIMALS) DON'T RENT U-HAUL ALWAYS TELL THE TRUTH IT WILL AMAZE PART OF THE PEOPLE & ASTONISH THE REST |
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#9 |
Account Suspended
Join Date: Jun 2005
Location: Maine
Posts: 427
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I'd go four-bolt, too. Better to have toughness, even if you do just cruise around town. That way, when you see a ricer at a stoplight, you know you're ready
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#10 |
Registered User
Join Date: Jul 2001
Location: North Louisiana
Posts: 4,501
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arkracing is dead on the money. From my experience, (10 years circletrack racing), I have only seen one block ever fail, and it was a stock sb 400(about 500-550hp). It was a 2 bolt, but from what I hear, even the 4 bolt sb 400s are weak. If I had a choice between the 2 for an engine with less than 500 hp, I would simply pick the one with the least wear, and with the best casting. For a sb 350 above 500 hp, I would pick the 2 bolt, and add splayed caps, or go aftermarket.
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#11 |
67 is sold
Join Date: Apr 2001
Location: Troy, Michigan
Posts: 6,738
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I guess it depends on how much you can spend on a motor and how you intend to drive it
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#12 |
Weekend Warrior
Join Date: Oct 2004
Location: CT
Posts: 1,787
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just for referance around here in the Northeast: (it is obviuosly different out west since JYJ is getting them so cheap....
![]() 2-bolt bare blocks (at the machine shop) run about $50 4-bolt bare blocks (at the maching shop) run about $100-$125 but anyway it's really a matter of opinion..if you want it to say you got it...then go for it. if it doesn't matter to you then get whatever is the best core. if your racing it go after market or put splayed caps in a 2-bolt.
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#13 | |
Registered User
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Location: SOMERSET KY.
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Quote:
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junkyardjohn 69 1 TON TOW TRUCK // 84 4WD CUCV BLAZER// 85 1 TON 4WD STAKE TRUCK// 86 M1031 5/4 TON 4WD CUCV// ALOT OF OLD TRUCKS FOR ONE OLD MAN TO DRIVE. ![]() LIFE MEMBER OF P.E.T.A (PEOPLE EATING TASTY ANIMALS) DON'T RENT U-HAUL ALWAYS TELL THE TRUTH IT WILL AMAZE PART OF THE PEOPLE & ASTONISH THE REST |
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#14 | |
Weekend Warrior
Join Date: Oct 2004
Location: CT
Posts: 1,787
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Quote:
i'll put about 20 of them in the back of my truck for that kind of $$$...looks like Dean will too. Junkyards are pretty much picked clean here in the Northeast if it is a running motor they want $300-$500 for it and if you could find a bare block or core in a junkyard they run about $100-$150 ![]() ![]() ![]() ![]() ![]() Machine shops are about the easiest place and way to get blocks around here - Seems to be that everyone thinks motors are worth there weight in gold especially Big Blocks ![]()
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#15 | |
Registered User
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Location: SOMERSET KY.
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Quote:
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junkyardjohn 69 1 TON TOW TRUCK // 84 4WD CUCV BLAZER// 85 1 TON 4WD STAKE TRUCK// 86 M1031 5/4 TON 4WD CUCV// ALOT OF OLD TRUCKS FOR ONE OLD MAN TO DRIVE. ![]() LIFE MEMBER OF P.E.T.A (PEOPLE EATING TASTY ANIMALS) DON'T RENT U-HAUL ALWAYS TELL THE TRUTH IT WILL AMAZE PART OF THE PEOPLE & ASTONISH THE REST |
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#16 |
Senior Member
Join Date: Jan 2000
Location: Cincinnati, Ohio
Posts: 1,492
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You sure can't pick up a 4 bolt block for $50.00 at any junkyards around here.....I might need a road trip out west.
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#17 |
Registered User
![]() Join Date: Dec 2004
Location: Gypsum Kansas 67448
Posts: 1,681
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im not sure,it also depends on if you are building a stroker or not,i would rather build a stroker out of a 2 bolt mainly beacuasee if it happens to come apart,you usually only have to get a new pan,and maybe,just maybe a rod,but a 4 bolt will stay together alot longer causing more damage to the bores of the engine,just my .02 but thats from my experience
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#18 |
Senior Member
Join Date: Jan 2003
Location: daytonabeach
Posts: 22,956
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all the yards around here that i've gone to the smallblock chevy engines and most of the ford 9inch rears are pulled and sold wholesale to rebuilders long B-4 anyone has a chance to buy them
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71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY |
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#19 |
Senior Member
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Location: CA
Posts: 5,527
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I want to know why GM went to the trouble of putting 4-bolt mains on engines that only put out somewhere between 175 and 300 horse power. I have a 4-bolt main block sitting in my garage (3970010) that probably only had about 200 HP from the factory.
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#20 | |
Weekend Warrior
Join Date: Oct 2004
Location: CT
Posts: 1,787
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Quote:
they were mainly put in larger trucks 3/4 ton and up - because of the low gearing and the load that these trucks were pulling/hauling it put alot of tension on the crank. i've done a personal study and have found that 99% of the 350 4-bolt blocks have an 8" harmonic balancer from GM - the bigger the balancer the better the ability to control harmonic vibration of the crank. these trucks also very rarely were expected to "break loose" - or spin the tires. there is alot less tension on a motor when it is spining freely than when it is "hooking up" obviosly they came in other applications as well...maybe they had a batch of 4-bolts the day they did a run of the chevelles or whatever. I don't think GM thought out which motor when into the cars. but when it came to trucks most of them 3/4 + 1ton or larger ended up with a 4-bolt that is just my own obversvation and thoughts on the subject. i could be completly wrong but i do know that most all the 4-bolt blocks have a 8" balancer...not all but 99% of the ones that i have seen neway
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#21 |
Nothings as cool as my 72
Join Date: May 2005
Location: Edmonton, AB, Kanuckastan
Posts: 181
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I know I was happy to find out when I pulled my pan off that my 350 has four bolt mains. Aren't 400 small blocks crappy anyways. My truck came with a 400 originally but I guess one of the previous owners put a 350 with for bolt mains so im happy about that. I think that motor has had work done to it, the cylinders are bored over .020. I can't wait until I get it back from the shop and start seeing some progress on my truck.
F.Y.I. - All the new Gen-III small blocks like the 4.8, 5.3, 6.0, LS-1, LS-2, etc. are six bolt mains.
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1972 C10 Longbox In the middle of body off restoration Rebuilt 355, turbo 400, 3.42 12-bolt Rolling chassis finally done and cab mounted. Now onto sanding, bondo and more sanding. ![]() |
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#22 |
Senior Member
Join Date: Dec 1999
Location: Saskatchewan
Posts: 1,050
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chance , the shop that built my 2 bolt main recommended the 2 bolt. They've been racing chevies since the 70's and have been racing Pro Mod for the last 10. As a matter of fact their going to Kansas to race this weekend and Spokane the following weekend.
arkracing "I personally sell all my 4-bolt main motors to the guys who have to have one...and keep the 2's to myself besides if i ever build a motor that needs to be a 4-bolt you can rest assure it will be a World Products or Dart block." ![]()
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#23 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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The 4 bolt verses 2 bolt is totally backwards if you are dealing with the 400 small block. The 2 bolt is stronger in that game.
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#24 |
Account Suspended
Join Date: Oct 2004
Posts: 1,276
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I personaly went the machine shop route. 350 cleaned and magged for 150.00.. Now think about it: it will cost about that from a yard and then your teardown time and transportation, not to mention more money for clean and mag and then if it aint any good back to the yard again and try it one more time but this time you have to pay clean and mag again and hope that is a good one and if not:::::::::::::::::::::::::::::: Just call the machine shop and shop for a cleaned aND MAGGED BLOCK FOR YOUR BUILD.. wATCH OUT FOR THE YARDS.
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#25 |
Registered User
![]() Join Date: Feb 2001
Location: East Central, MO
Posts: 11,336
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This is all good to hear. My 2 bolt 383 stroker is being assembled this week. It's getting studs.
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