350 4 bolt - The 1947 - Present Chevrolet & GMC Truck Message Board Network

otsenre · 12-03-2007, 04:03 PM

Someone told me all chevy 350s out of 72s came with 4 bolt, I disagreed, can anyone comfirm this block casting is 3970010 Thanks in advance

69halfton · 12-03-2007, 04:13 PM

im not a information buff about stuff these trucks came with from the factory.

but i have herd that all trucks had "truck blocks" which were indeed 4 bolt mains.

my 69 has a four bolt.

red69ss · 12-03-2007, 04:23 PM

I have two 350's with same casting number and I know for sure one is a 2 bolt main, but have not had pan off other one you can check numbers on nastyz28.com ,but you probaly need numbers off pad in front of pass. head .

cdowns · 12-03-2007, 04:29 PM

thats a very common casting number i've seen more of them 2bolts than 4

**too much stuff** · 12-03-2007, 05:33 PM

Casting number is for a 350. Used for many years in low perf. to hi-perf. Could be had in 2 and 4 bolt mains...

*Billla* · 12-06-2007, 11:07 PM

Quote:

Originally Posted by cdowns

thats a very common casting number i've seen more of them 2bolts than 4

There is no way to tell a 2-bolt from 4-bolt SBC externally.
4-bolt mains are not required until 450+ HP *or* 6000+ RPM if studs are used. An align-hone is required if switching to studs
It is not economically practical (IMHO) to install aftermarket 4-bolt caps.

IMHO the best buy is either a late-model roller block (one-piece seal) from your local junkyard or a new GMPP bare block (P/N 10066034) at around $700. The new factory block is a 4.00 finished bore with provision for a roller cam and a two-piece seal. You can drop a lot of money getting an old GEN I block up to spec.

For folks that have never actually seen a high nickel, high tin block - this is what it looks like

timcos · 12-03-2007, 06:03 PM

2 bolts are good blocks. 4 bolt mains are used for high RPM or very high compression....not really needed but if you have 4 bolt does not hurt for daily driver apps.

Tim

1969k10stepside · 12-03-2007, 06:06 PM

Quote:

Originally Posted by otsenre

Someone told me all chevy 350s out of 72s came with 4 bolt

Don't think so in the 10-30 series.What I've heard is that if they were from the C/40 and up series they were 4 bolt but I don't know...I've got a few 350 blocks around,one is a 4 bolt out of my old '69 Camaro I rolled over.If I really needed a 4 bolt I would make one out of a 2 bolt main block and go from there..

PanelDeland · 12-03-2007, 06:23 PM

From what research I have done;the casting # will not tell you whether it is 2 or 4 bolt main.Most performance engine builders prefer the 2 bolt main block even for very high performance because the webs are stronger and the aftermarket 4 bolt has splayed mains making them stronger and the webs remain stronger also.Also most agree that under 500 HP the 2 bolt is plenty strong.I have also been told the rods are weaker than the mains in a small block.

57sailplane · 12-03-2007, 06:55 PM

from the info i have found if your block has a 010 on the side by the motor mounts its is cast with thicker webs for the 4 bolt main.. making it stronger. now it is my understanding that if gm was short on 2 bolts it was not uncomon for them to drill out one of these as a 2 bolt.. it is still stronger than your average 2 bolt. if you put arp studs in a 2 bolt block it will be stro
nger than a 4 bolt...

by the way the picture you see here of my engine is a 3970010 casting block. it has the 010 on the sides and in the back.. it was a 4 bolt. but my machinest made cast iron studs and threaded them into the outer bolt holes with lock tight. then milled off the tops. then it was machined for splayed caps..

**special-K** · 12-04-2007, 09:04 AM

A steel crank is more important that 2-bolt vs 4-bolt.4-bolt stabilize against deflection,but 2 extra holes weaken the casting.So a more rigid crank solves that w/o weaking the block.I`m not saying 4-bolt are weak.I still prefer them.Just saying the emphasis should be on the crank more than which block.A steel crank 4-bolt is the ultimate.

I always heard that truck 350s all had 4-bolts up through`75.A truck block is a hi-perf block.The difference between HD and HP comes from all the other moving parts.

Longhorn Man · 12-04-2007, 09:45 AM

back to the original question, it is not uncommon at all to find a 4 bilt block in a 72 10 - 30 series truck.
It is also not uncommon to find a 10 20 high nickle block in a 72 10 - 30 truck too... which personally, I'd rather have the high nickle than the extra bolts.

mrein3 · 12-04-2007, 12:25 PM

Quote:

Originally Posted by otsenre

Someone told me all chevy 350s out of 72s came with 4 bolt, I disagreed, can anyone comfirm this block casting is 3970010 Thanks in advance

According to the factory stamp on the front pad of the 350 that was in my truck when I bought it, it was out of a 78 truck. It had a 3970010 casting number and 4 bolt mains. I replaced that engine with a 383 that was made out of a 350 that originally was in a 1971 Monte Carlo. It had the same casting number, 3970010, and 2 bolt mains. However, it also had 010 and 020 cast in the block under the timing chain cover.

Accoring to my machine shop guy, who has been doing this long enough to have ordered heads for a 396 out of a catalog BEFORE they were ever sold to the public, for 99% of the people out there 2 or 4 bolts won't matter.

**WorkinLonghorn** · 12-04-2007, 12:53 PM

Quote:

for 99% of the people out there 2 or 4 bolts won't matter.

Probly not,but it sounds better "I got 4 bolt mains!" But I also wonder why the GM engineers opted for 4 bolt on low rev-ing trucks. Personally I always assumed that lugging and low rpm full throttle operation somehow required the up-grade to 4 bolts.Maybe it was just hype.
But hey,when I'm pulling away with 10,000 lbs GVW flat out at 1500 RPM I'm thinking " Damn,good thing I got 4 bolt mains!"

Longhorn Man · 12-04-2007, 12:56 PM

when most ppl run a plow, they hold it at WOT in first, same thing when trying to drag junk through the mud or anything like that.
I do agree though, 99% of these build ups that are more for street than track don't need them.

PanelDeland · 12-04-2007, 04:11 PM

So if you want the ultimate small block you need a 10 20 high nickle block with an 010 on the side and a steel crank.Then you have it machined for a splayed 4 bolt aftermarket main.Or you could just get an aftermarket block with all the above and probably save some money and even get a larger bore/stroke combo.Unless there's a class displacement requirement,or an originality issue building a 350 only makes sense if you already have good parts to build one.If you need a crank you can probably get a stroker for the same as a stock one,most other parts are the same,you can get better aftermarket for about the same money.

Jtrux · 12-04-2007, 05:08 PM

My k5's original block was a 4 bolt.

57sailplane · 12-06-2007, 05:24 PM

the 4 bolt main cap is not installed to strengthen the block. the extra 2 bolts are there to keep your bearing alive. i agree that a forged crank is way better than cast but thats a totally differant story..

what happens and most people dont realize is that under drastic loads or high rpm major amounts of down force are applied to the mains via the piston and rod force down on the crank combined with the resistive force wich would be the load your are towing or you hit the trans brake at launch... the piston and rod want to push downward rotating the crank wile the restive load wants to stop crank rotation thus putting a major down force on the mains wether or not the crank is flexing is to no value to this problem and actually one that flexes will actually counteract the problem cause some of the downward force is taken up by flex.. what the 2 extra bolts are there for are not to keep the cap on but to keep it from squeezing togather.. you see the center of the cap is taking all the down force wich is also the weakest point of the cap. now just a slight flex of the cap downward in the middle is not a problem but if the cap flexes to much the sides of the cap will tend to squeeze inward toward the crank thus causing bearing failure. gm added the extra bolt to help the clamping force between the cap and the block to help eleviate this problem.. it can still slide but not nearly as easy.. that is also why the splayed cap is used because the outer bolt is put in at an angle thus making it near imposible for any cap flex and bearing failure.

so you see for a steet engine being abused wile racing it or pulling the 4 bolt is a better deal.. keep in mind that i have read that an ARP studed 2 bolt is stronger than a stock 4 bolt and probably is cause you would get less flex from the stud and it has more clamping force than just 2 bolts. anyways i hope not to confusing...

12-03-2007, 04:03 PM	#1
otsenre Registered User Join Date: Feb 2007 Location: Colorado Springs, Co Posts: 1,939	350 4 bolt Someone told me all chevy 350s out of 72s came with 4 bolt, I disagreed, can anyone comfirm this block casting is 3970010 Thanks in advance

12-03-2007, 04:13 PM	#2
69halfton Registered User Join Date: Apr 2007 Location: King City, Ontario, Canada Posts: 974	Re: 350 4 bolt im not a information buff about stuff these trucks came with from the factory. but i have herd that all trucks had "truck blocks" which were indeed 4 bolt mains. my 69 has a four bolt. __________________ - Jason If you can turn, Youre not going fast enough. Favorite caption: first car to 200 mph in the 1/4 mile, no parachute, drum brakes all the way around.. ..back when men were men.

12-03-2007, 04:23 PM	#3
red69ss Burnouts are therapeutic Join Date: Jun 2007 Location: lancaster, south carolina Posts: 852	Re: 350 4 bolt I have two 350's with same casting number and I know for sure one is a 2 bolt main, but have not had pan off other one you can check numbers on nastyz28.com ,but you probaly need numbers off pad in front of pass. head . __________________ 1969 CHEVELLE SS 1972 C10 ALMOST DAILY DRIVER 1968 C10 RUSTBUCKET (MISSION IMPOSSIBLE) 1972 PONTIAC LEMANS CONVERTIBLE (WIFE'S CAR) "My wife and I were happy for twenty years. Then we met." - Rodney Dangerfield "The difference between genius and stupidity is that genius has its limits." - Einstein

12-03-2007, 04:29 PM	#4
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: 350 4 bolt thats a very common casting number i've seen more of them 2bolts than 4 __________________ 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

12-03-2007, 05:33 PM	#5
too much stuff Roadtrip! Join Date: Feb 2003 Location: Grand Rapids MN Posts: 13,768	Re: 350 4 bolt Casting number is for a 350. Used for many years in low perf. to hi-perf. Could be had in 2 and 4 bolt mains... __________________ 67 gmc custom lwb dakota truck. Sold...And bought back 69 swb 4x4 project (in progress) 70 c-10 lwb texas truck 70 4x4/BB/bkts/posi/tach(retired) 70 swb (wifes) 70 jimmy camper 71 K-5 factory 2wd 71 cheyenne 4x4/tach/posi/ plow rig 71 Cheyenne20 BB, buckets, tach, tilt, 4 speed 72 jimmy CST wyoming rig 72 jimmy Colorado rig 72 lifted texas 4x4 3/4 ton burb 65 fury conv. 383/auto 65 chrysler 300 "L" 413 auto

12-03-2007, 06:03 PM	#7
timcos Chief Honcho In Charge Join Date: Aug 2006 Location: Bentonville AR Posts: 970	Re: 350 4 bolt 2 bolts are good blocks. 4 bolt mains are used for high RPM or very high compression....not really needed but if you have 4 bolt does not hurt for daily driver apps. Tim __________________ 1992 1500 4x4 Shortbed 1984 Ford F250 Supercab Longbed 6.9L Diesel 1972 K10 Cheyenne Super Fleetside Short Bed - 350 - A/C 1971 VW SuperBeetle 1960 Wife 1984 Son 1986 Son 1989 Son Previous Trucks 1967 C10 SWB (1980-1981) 1971 C10 LWB (1998-2004)

12-03-2007, 06:23 PM	#9
PanelDeland I am a Referee of life. Join Date: Jun 2000 Location: Greensboro N.C. Posts: 13,993	Re: 350 4 bolt From what research I have done;the casting # will not tell you whether it is 2 or 4 bolt main.Most performance engine builders prefer the 2 bolt main block even for very high performance because the webs are stronger and the aftermarket 4 bolt has splayed mains making them stronger and the webs remain stronger also.Also most agree that under 500 HP the 2 bolt is plenty strong.I have also been told the rods are weaker than the mains in a small block. __________________ The 47-present Chevrolet and GMC Truck Message Board Network,it's owners,moderators,members,and associates of any type should not be held responsible for my opinion. You can't fix stupid,not even with duct tape. "My appearance is due to the fact that "GOD" does punish you for having too much fun!" Barrett-Jackson has perfected alchemy,they make rust into gold! "You can lead a horse to water but you can't saddle a duck" "Cleverly disguised as a 'Responsible Adult' "Sometimes your Knight in shining armor is just a retard in tinfoil"

12-03-2007, 06:55 PM	#10
57sailplane Senior Member Join Date: Mar 2004 Location: Nebraska Posts: 583	Re: 350 4 bolt from the info i have found if your block has a 010 on the side by the motor mounts its is cast with thicker webs for the 4 bolt main.. making it stronger. now it is my understanding that if gm was short on 2 bolts it was not uncomon for them to drill out one of these as a 2 bolt.. it is still stronger than your average 2 bolt. if you put arp studs in a 2 bolt block it will be stro nger than a 4 bolt... by the way the picture you see here of my engine is a 3970010 casting block. it has the 010 on the sides and in the back.. it was a 4 bolt. but my machinest made cast iron studs and threaded them into the outer bolt holes with lock tight. then milled off the tops. then it was machined for splayed caps.. Last edited by 57sailplane; 12-03-2007 at 07:00 PM.

12-04-2007, 09:04 AM	#11
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,852	Re: 350 4 bolt A steel crank is more important that 2-bolt vs 4-bolt.4-bolt stabilize against deflection,but 2 extra holes weaken the casting.So a more rigid crank solves that w/o weaking the block.I`m not saying 4-bolt are weak.I still prefer them.Just saying the emphasis should be on the crank more than which block.A steel crank 4-bolt is the ultimate. I always heard that truck 350s all had 4-bolts up through`75.A truck block is a hi-perf block.The difference between HD and HP comes from all the other moving parts. __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~ Last edited by special-K; 12-04-2007 at 11:30 AM.

12-04-2007, 09:45 AM	#12
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: 350 4 bolt back to the original question, it is not uncommon at all to find a 4 bilt block in a 72 10 - 30 series truck. It is also not uncommon to find a 10 20 high nickle block in a 72 10 - 30 truck too... which personally, I'd rather have the high nickle than the extra bolts.

12-04-2007, 12:56 PM	#15
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: 350 4 bolt when most ppl run a plow, they hold it at WOT in first, same thing when trying to drag junk through the mud or anything like that. I do agree though, 99% of these build ups that are more for street than track don't need them.

12-04-2007, 04:11 PM	#16
PanelDeland I am a Referee of life. Join Date: Jun 2000 Location: Greensboro N.C. Posts: 13,993	Re: 350 4 bolt So if you want the ultimate small block you need a 10 20 high nickle block with an 010 on the side and a steel crank.Then you have it machined for a splayed 4 bolt aftermarket main.Or you could just get an aftermarket block with all the above and probably save some money and even get a larger bore/stroke combo.Unless there's a class displacement requirement,or an originality issue building a 350 only makes sense if you already have good parts to build one.If you need a crank you can probably get a stroker for the same as a stock one,most other parts are the same,you can get better aftermarket for about the same money. __________________ The 47-present Chevrolet and GMC Truck Message Board Network,it's owners,moderators,members,and associates of any type should not be held responsible for my opinion. You can't fix stupid,not even with duct tape. "My appearance is due to the fact that "GOD" does punish you for having too much fun!" Barrett-Jackson has perfected alchemy,they make rust into gold! "You can lead a horse to water but you can't saddle a duck" "Cleverly disguised as a 'Responsible Adult' "Sometimes your Knight in shining armor is just a retard in tinfoil"

12-04-2007, 05:08 PM	#17
Jtrux I'm a poor spectator Join Date: Aug 2006 Location: San Antonio, Tx Posts: 2,287	Re: 350 4 bolt My k5's original block was a 4 bolt. __________________ 2006 Jeep Unlimited IMPACT ORANGE 1993 Chevy 2500 4x4 ExCab LWB 454/NV4500 Tow rig 1977 Ford F100 2x4 LWB 1st truck I owned, still have it!!! 1979 Ford F150 4x4 SWB Built Ford Tough!!! 1971 Chevy Blazer 350 / SM465 / NP205 UNDER CONSTRUCTION Soon to have a LQ4 6.0!!!

12-06-2007, 05:24 PM	#18
57sailplane Senior Member Join Date: Mar 2004 Location: Nebraska Posts: 583	Re: 350 4 bolt the 4 bolt main cap is not installed to strengthen the block. the extra 2 bolts are there to keep your bearing alive. i agree that a forged crank is way better than cast but thats a totally differant story.. what happens and most people dont realize is that under drastic loads or high rpm major amounts of down force are applied to the mains via the piston and rod force down on the crank combined with the resistive force wich would be the load your are towing or you hit the trans brake at launch... the piston and rod want to push downward rotating the crank wile the restive load wants to stop crank rotation thus putting a major down force on the mains wether or not the crank is flexing is to no value to this problem and actually one that flexes will actually counteract the problem cause some of the downward force is taken up by flex.. what the 2 extra bolts are there for are not to keep the cap on but to keep it from squeezing togather.. you see the center of the cap is taking all the down force wich is also the weakest point of the cap. now just a slight flex of the cap downward in the middle is not a problem but if the cap flexes to much the sides of the cap will tend to squeeze inward toward the crank thus causing bearing failure. gm added the extra bolt to help the clamping force between the cap and the block to help eleviate this problem.. it can still slide but not nearly as easy.. that is also why the splayed cap is used because the outer bolt is put in at an angle thus making it near imposible for any cap flex and bearing failure. so you see for a steet engine being abused wile racing it or pulling the 4 bolt is a better deal.. keep in mind that i have read that an ARP studed 2 bolt is stronger than a stock 4 bolt and probably is cause you would get less flex from the stud and it has more clamping force than just 2 bolts. anyways i hope not to confusing...



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