350-4 bolt vs 2 bolt
05-12-2007, 07:57 AM
#1
Junior Member
Thread Starter
Join Date: Apr 2007
Location: Vermont
Posts: 56
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1985 Trans Am
Engine: Procharged Small block 355
Transmission: TH-350 modified
Axle/Gears: Richmond 410
350-4 bolt vs 2 bolt
So I just need some clarification on a couple of things. The engine that we want to swap to the firebird comes from a 3rd gen Formula with the 350 TPI which we are converting to carb. Now I know that engine has a 2 bolt main vs a 4 bolt main. We would like to see around 450-550 HP on spray or NA, which is going to hold up longer? We are also going to stroke the engine to a 383. Any help would be appreciated.
Thanks
Bernie
Thanks
Bernie
05-12-2007, 08:14 AM
#2
Member
Join Date: Jul 2006
Location: waterford, MI
Posts: 186
Likes: 0
Received 3 Likes
on
1 Post
Car: 89 RS
Engine: 305 carbed
Transmission: 700R4
Axle/Gears: 3.42 auburn posi
Re: 350-4 bolt vs 2 bolt
Generally a 2 bolt main will hold up to 600 horse in an N/A application. but for force fed engines i'd use a 4 bolt just to be safe. You'll have to worry more about throwing a rod or blowing a hole in the piston before you loose the crank to a broken main cap.
05-12-2007, 12:49 PM
#3
Moderator
Join Date: Jan 2000
Location: Mercedes Norte, Heredia, Costa Rica
Posts: 20,981
Likes: 0
Received 9 Likes
on
8 Posts
Car: 1984 Z28 Hardtop
Engine: 383 Carb
Transmission: 4L60
Axle/Gears: 3.54 Dana 44
Re: 350-4 bolt vs 2 bolt
Either one would be fine. The condition of the block is more important than how many bolts are holding the main caps on.
05-12-2007, 03:17 PM
#4
Junior Member
Join Date: Mar 2007
Location: Chicago 'burbs
Posts: 77
Likes: 0
Received 0 Likes
on
0 Posts
Car: 88 IROC
Engine: carburated 350-- H/C
Transmission: TH350
Axle/Gears: 10 bolt w/ auburn posi and 3.73s
Re: 350-4 bolt vs 2 bolt
if you really want security start with a 2 bolt and have it tapped to be a splayed four bolt. then put some ARP sutds in there.
05-17-2007, 06:02 PM
#5
Member
Join Date: Oct 2006
Location: Allenhurst, GA
Posts: 320
Likes: 0
Received 0 Likes
on
0 Posts
Car: '81 Z-28
Engine: Soon to be a 383
Transmission: Muncie
Axle/Gears: 3.42
Re: 350-4 bolt vs 2 bolt
4 bolt mains tend to crack easier... if you look at where the extra bolts go in, it is putting to much pressure on the weakest spot. Best bet is splayed 4 bolt, which repositions the outer bolts. For the power you are trying for I would splay the outer bolts to be on the safe side, but a 2 bolt should be more than sufficiant for you.
Thread
Thread Starter
Forum
Replies
Last Post
UltRoadWarrior9
Transmissions and Drivetrain
3
09-02-2015 08:24 PM
