Are 350 V8s 4 bolt mains? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**JQ-72** · 06-12-2025, 07:25 PM

Visiting from the 67-72 side. I know all 69-72 truck 350s were 4 bolt main blocks. Did this carry over to the square bodies? I ended up with a 77 Big10 and can’t see the suffix code due to the metal fuel line and alternator being in the way. Thanks.

Pontiac1976 · 06-13-2025, 12:33 AM

Yes they did.

Willie Makeit · 06-13-2025, 09:04 AM

I can't answer about ALL truck 350's being 4 bolt mains, but NOT all 350's are 4 bolt mains.

**kwmech** · 06-13-2025, 11:23 AM

No, not all of them were 4 bolt mains. I think GVW had a play in it. I replaced the 350 in my 1-1/4 ton motor home chassis with a big block. 350 I took out had 4 bolt main and a forged STEEL crankshaft. I expected the 4 bolt but not the crankshaft. I've pulled dozens of engines out of these trucks and it was a mix of 2 and 4

Pontiac1976 · 06-14-2025, 09:25 AM

Ok but most all 4x4 truck 4bolt. But you can get a 2 bolt much cheaper turned into a 4 BOLT that is stronger than the factory true 4 bolt at the mains you should look that up talk to a good shop if you want a factory style 350 strong main caps you want the angle style caps the allow blots to go deeper the block over the true 4bolt factory set up. If that what you're looking into the true 4 bolt factory for. If not save money aftermarket 383 I have seen quite a few factories true 4 bolt tore part down, there not as strong most people hope to think they are.

**Getter-Done** · 06-14-2025, 10:07 AM

On some trucks, I have been able to take just the top Alternator bracket off
and remove the belt then lay the alternator over to the passenger's side
and move the fuel line just enough to see the code.

**kwmech** · 06-16-2025, 10:19 AM

What 'code' is that. Block casting number 3970010 doesn't mean a thing with 2 v 4. Serial number doesn't indicate this either. then there is this thread from over 20 years ago

http://67-72chevytrucks.com/vboard/s...ad.php?p=89226

**cag** · 06-30-2025, 02:48 PM

72 2500, two bolt main

06-12-2025, 07:25 PM	#1
JQ-72 Senior Member Join Date: Feb 2001 Location: Killen, Alabama USA Posts: 3,746	Are 350 V8s 4 bolt mains? Visiting from the 67-72 side. I know all 69-72 truck 350s were 4 bolt main blocks. Did this carry over to the square bodies? I ended up with a 77 Big10 and can’t see the suffix code due to the metal fuel line and alternator being in the way. Thanks. __________________ 72 Cheyenne Super swb. Factory 402/400,tach,posi,AM/FM, A/C. Adding cruise, 8-track 72 Cheyenne Super swb. 350/350 A/C, bucket seats 72 Cheyenne swb. Factory 402/400, tilt, posi, A/C 72 Cheyenne Super K-10. 350/4 spd., posi. 72 Suburban 350/350 tilt, tach, AM/FM, A/C, luggage rack 72 GMC Sierra lwb. 350/350, A/C. medium green/olive interior

06-13-2025, 12:33 AM	#2
Pontiac1976 Registered User Join Date: Oct 2015 Location: Ottawa, Ontario, Canada Posts: 803	Re: Are 350 V8s 4 bolt mains? Yes they did. __________________ 1977 REG cab Long Bed with a 1984 Front Clip, 82 305 .60 over 9.0.1 flat top pistons, 4bbl, TH350, w/84 SS-intake & cam , w/ 1977 big block rad, 1975 gear box, 1984 master w/ metric fittings top & SAE fitting @ portion block, 1975 3.42 gear open diff. Duel 77-87 Factory air cleaner, duel inlet from rad support . Down sized 9' to new 8' Steel flat bed Was a 77 454 w/308 gear. Taken out 550 lbs. up front with motor clip change.

06-13-2025, 09:04 AM	#3
Willie Makeit Registered User Join Date: Oct 2013 Location: Alabama Posts: 1,309	Re: Are 350 V8s 4 bolt mains? I can't answer about ALL truck 350's being 4 bolt mains, but NOT all 350's are 4 bolt mains.

06-13-2025, 11:23 AM	#4
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,941	Re: Are 350 V8s 4 bolt mains? No, not all of them were 4 bolt mains. I think GVW had a play in it. I replaced the 350 in my 1-1/4 ton motor home chassis with a big block. 350 I took out had 4 bolt main and a forged STEEL crankshaft. I expected the 4 bolt but not the crankshaft. I've pulled dozens of engines out of these trucks and it was a mix of 2 and 4

06-14-2025, 09:25 AM	#5
Pontiac1976 Registered User Join Date: Oct 2015 Location: Ottawa, Ontario, Canada Posts: 803	Re: Are 350 V8s 4 bolt mains? Ok but most all 4x4 truck 4bolt. But you can get a 2 bolt much cheaper turned into a 4 BOLT that is stronger than the factory true 4 bolt at the mains you should look that up talk to a good shop if you want a factory style 350 strong main caps you want the angle style caps the allow blots to go deeper the block over the true 4bolt factory set up. If that what you're looking into the true 4 bolt factory for. If not save money aftermarket 383 I have seen quite a few factories true 4 bolt tore part down, there not as strong most people hope to think they are. __________________ 1977 REG cab Long Bed with a 1984 Front Clip, 82 305 .60 over 9.0.1 flat top pistons, 4bbl, TH350, w/84 SS-intake & cam , w/ 1977 big block rad, 1975 gear box, 1984 master w/ metric fittings top & SAE fitting @ portion block, 1975 3.42 gear open diff. Duel 77-87 Factory air cleaner, duel inlet from rad support . Down sized 9' to new 8' Steel flat bed Was a 77 454 w/308 gear. Taken out 550 lbs. up front with motor clip change.

06-14-2025, 10:07 AM	#6
Getter-Done Senior Member Join Date: Dec 2009 Location: TN. Posts: 9,870	Re: Are 350 V8s 4 bolt mains? On some trucks, I have been able to take just the top Alternator bracket off and remove the belt then lay the alternator over to the passenger's side and move the fuel line just enough to see the code. __________________ ________________________________________________________________________________________ ____________________________________________ The early bird gets the worm, But the second mouse gets the cheese 85 Chevy K-20 63 Impala (my high school car) http://67-72chevytrucks.com/vboard/s...Crew Cab Build

06-16-2025, 10:19 AM	#7
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,941	Re: Are 350 V8s 4 bolt mains? What 'code' is that. Block casting number 3970010 doesn't mean a thing with 2 v 4. Serial number doesn't indicate this either. then there is this thread from over 20 years ago http://67-72chevytrucks.com/vboard/s...ad.php?p=89226

06-30-2025, 02:48 PM	#8
cag Active Member Join Date: Aug 2022 Location: winneconne, wisco Posts: 185	Re: Are 350 V8s 4 bolt mains? 72 2500, two bolt main



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