2 or 4 bolt block?
- Thread starter Edmond
- Start date
T
tnovot
Guest
Don't know when they started with the four bolt but I built up a 350 four bolt from a 1974 1/2 ton pickup for my T Bucket. (date stamping on bellhousing flange verifies manufature date in 1974)
From what I've read, the 4 bolts have more of a tendency to develop cracks in the main webbing than the 2 bolt blocks so they must be checked carefully when torn down. Two bolt engines are supposedly fine for street use and can handle up to 400 HP.
From what I've read, the 4 bolts have more of a tendency to develop cracks in the main webbing than the 2 bolt blocks so they must be checked carefully when torn down. Two bolt engines are supposedly fine for street use and can handle up to 400 HP.
jmccloud
Well-known member
4 Bolts
Chevy 4 bolt mains (small block) came into use for high performance engines early in the Z28 days ('68-69). Don't know when they became universal though.
My '66 Impala 327 is a 2 bolt and will run with my 95 LT1 when the air density is just right.
Chevy 4 bolt mains (small block) came into use for high performance engines early in the Z28 days ('68-69). Don't know when they became universal though.
My '66 Impala 327 is a 2 bolt and will run with my 95 LT1 when the air density is just right.
G Winter
Well-known member
The 4 bolt main was first used in the z28 302 engine. the next yr it was used in the high preformance 350s 300 plus hp. It was also used in truck and some pickup engines. I have read that the 4 bolt main is really only a benifit in a street engine if you plan on running it 7000 rpm or above. Even the 2 bolt will stand up to those rpm for a short time. If you are searching for a 4 bolt main block ,check the 1970s pickups the were quite common in them. I think it was only the 4 barrel carb engines that were 4 bolts.
- Thread starter
- #5
Ken
Gone but not forgotten
Nope.
- Thread starter
- #7
Ken
Gone but not forgotten
You'll be okay Edmond. If you decide to go four-bolt mains, you can always get a splayed set-up from one of the aftermarket manufacturers, but you shouldn't need it unless you're gonna boost it or spray it. 
Edmond, if you want a little extra insurance, install a set of ARP 2-bolt main studs. $35 a set, or $50 if you've got a windage tray. You'll need to align hone though.
- Thread starter
- #10
Ken said:You'll be okay Edmond. If you decide to go four-bolt mains, you can always get a splayed set-up from one of the aftermarket manufacturers, but you shouldn't need it unless you're gonna boost it or spray it.
That's what I like to hear, Ken. That means I don't have to spend the extra money. Now if that guy out in California with the 87' Z51 can get working on his version of the Vortex intake, I would save even more money...
Ken
Gone but not forgotten
kenwa had a good suggestion about the studs too.
- Thread starter
- #12
Your topic caught my eye because I just bought a set of 2-bolt ARP studs for the 400 small block I'm building. Actually $38.95 from Summit. You probably have a windage tray in yours though.Edmond said:
Are you doing a rebuild this winter?
Ken
- Thread starter
- #14
Ken,
Yes, I'm rebuilding this winter. I'm going to have a machine shop do the short block and take it from there. I guess it's a need of more performance and the winter is the time to do the work. Winter is for fixin' and summer is for drivin'.
Yes, I'm rebuilding this winter. I'm going to have a machine shop do the short block and take it from there. I guess it's a need of more performance and the winter is the time to do the work. Winter is for fixin' and summer is for drivin'.
M
Moonunit 451
Guest
You'll be fine with the 2 bolt, I think I saw you were goin' 383. It's done all the time, some folks "splay" them which is said to be stronger than the 4 bolt, but for street driving, not neccesary 
ALL year's for drivin' my car, she's no garage queen
ALL year's for drivin' my car, she's no garage queen
- Thread starter
- #16
Moonunit 451 said:You'll be fine with the 2 bolt, I think I saw you were goin' 383. It's done all the time, some folks "splay" them which is said to be stronger than the 4 bolt, but for street driving, not neccesary
ALL year's for drivin' my car, she's no garage queen
Yeah, I was going to do the 383 but I decided that I didn't want to spend the extra money for a nice forged 400 crank. Plus, I think I can get more than enough power that I'd ever need out of a 350.
M
Moonunit 451
Guest
Should be NO problems then for sure. What are you gonna do for a cam and intake?
- Thread starter
- #18
Moonunit 451 said:
Moon,
I'm going to port the plenum and the intake manifold myself. I'm going to use Arizona Speed and Marines large tube runners. They're $395 and I heard good things about them, $80 less than the TPIS large tube runners.
As for a cam, I haven't decided yet. 1.6 roller rockers for sure and I'm going to have the heads worked on 2.02 intake and 1.6 exhaust. Since the car is for street driving, I would like a cam in the area of idle-4500 because I don't run the car that hard. It's an auto so I don't get to row through the gears like the manual guys do. It's just a street driver so I don't want to get too far out there. I also need to pass the dreaded emissions testing here in IL.
May also go with the Vortex ram air box if I can come to terms with parting for the $270 unit. :L
I have thought about roller rockers for mine. I have seen on summit they offer two 1.6 ones and 1.52. What is the difference between the two of them? And what ones should I get and what price range am I looking at the ones on summit are like 192.
- Thread starter
- #20
Vettefan87 said:
You get slightly more lift. I wish I had my guide handy because you multiply the 1.6 by another number to determine lift. If you stuck with the 1.52, you would multiply the 1.52 to get the lift of that. I'll try to dig it up.
That's weird cause I just responded to that on the other post we subscribed to!
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