1970 350 Compression ratio - The 1947 - Present Chevrolet & GMC Truck Message Board Network

zac · 02-11-2011, 09:16 AM

Does anybody know what the factory listed the compression ratio for on the 350/4bbl/4spd engine in '70? I think it's the original engine, it has 441 heads with June '70 date code, I can't see the block casting number, but I assume it's the usual 0010. The code stamped on the pad in front is VO622 TBB, which matches. I'm going to guess 9:1. Thanks in advance.

cdowns · 02-11-2011, 09:47 AM

8.5 i think is closer

**Tom Vogel** · 02-11-2011, 10:07 AM

Our 69 3/4 ton GMC with the 300hp 350 was 10to1... that is/was stock. Gas was cheaper and better.

**oldgold70c10** · 02-11-2011, 10:28 AM

From the Specifications and Technical Data at the back of the 1970 10-30 series owner's manual:

Engine 350 V8
Color Code Red
Piston Displacement 350
Compression Ratio 9.0:1
Gross HP 255@4600
Net HP 200@4000
Gross Torque 355@3000
Net Torque 310@2400

Hope that helps!

**special-K** · 02-11-2011, 10:48 AM

10:1 350/300hp truck motor??? I don't think so. Never heard that before. If someone can prove me wrong I'd like to learn something.

cdowns · 02-11-2011, 11:24 AM

that must b the elusive corvette optioned truck

**Dave** · 02-11-2011, 11:24 AM

Compression ratios vary a little from engine to engine, more or less. I'd perform a compression test just see where it's at now.

As far as a factory installed 300 hp and 10.0 compression 350 in '70 in a truck? Never seen one, nor does the GM basic engine data and power teams list any combo. Now a passenger car, that's a different story.

zac · 02-11-2011, 09:33 PM

Quote:

Originally Posted by oldgold70c10

From the Specifications and Technical Data at the back of the 1970 10-30 series owner's manual:

Engine 350 V8
Color Code Red
Piston Displacement 350
Compression Ratio 9.0:1
Gross HP 255@4600
Net HP 200@4000
Gross Torque 355@3000
Net Torque 310@2400

Hope that helps!

This is what I was looking for, thanks! I think the 441 combustion chambers are a little tighter than the 487's that came later. My 350 spun a bearing last November, so I can't test it, or there's really no point. I slowly got that tired motor tuned last summer. I thought I had it about right, and it was a little pingy under load so I figured it was around 9. Of course it's in a K10 Burb with 31" tires and 3.08's so I'm sure that aggravates things. I wanted to use the 487 heads I had, but they were pretty bad, and the extra 441's I had looked good. The machine shop guy looked at the 487's and said "Well, I've seen worse, but you better leave those others ones." So my new motor will have thickish head gaskets and 89 octane, I guess. Thanks again.

todd99 · 02-11-2011, 11:00 PM

71 c20 longhorn custom camper. My motor was completely stock and had 11 to 1 compression, I had to check it twice just to believe it. My heads are stamped with 3978487 K250, not sure if that means anything.

DT1 · 02-12-2011, 12:05 AM

That's nothing! My stock 350 in my 71 is 19:1. That's why I have always had to run premium.

todd99 · 02-12-2011, 12:10 AM

^^^ Are you mocking me?

DT1 · 02-12-2011, 12:18 AM

Quote:

Originally Posted by todd99

^^^ Are you mocking me?

Take it easy chief. I'm not mocking anyone. Just the numbers.
I have never heard of a stock 350 Gen 1 Chevy truck engine anywhere close to that. Maybe I could use a bit of education too.

todd99 · 02-12-2011, 12:21 AM

No worries, I'm not making it up. I am far from the original owner, it's possible someone tampered with it before I bought it. It looked stock.

02-11-2011, 09:16 AM	#1
zac Registered User Join Date: Jul 2008 Location: louisville, ky Posts: 502	1970 350 Compression ratio Does anybody know what the factory listed the compression ratio for on the 350/4bbl/4spd engine in '70? I think it's the original engine, it has 441 heads with June '70 date code, I can't see the block casting number, but I assume it's the usual 0010. The code stamped on the pad in front is VO622 TBB, which matches. I'm going to guess 9:1. Thanks in advance.

02-11-2011, 09:47 AM	#2
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: 1970 350 Compression ratio 8.5 i think is closer __________________ 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

02-11-2011, 10:07 AM	#3
Tom Vogel 2WD Jimmy Join Date: Mar 2005 Location: Davis County, Utah Posts: 2,564	Re: 1970 350 Compression ratio Our 69 3/4 ton GMC with the 300hp 350 was 10to1... that is/was stock. Gas was cheaper and better.

02-11-2011, 10:28 AM	#4
oldgold70c10 Who's got steelies? Join Date: Feb 2006 Location: Morrison, Oklahoma Posts: 1,026	Re: 1970 350 Compression ratio From the Specifications and Technical Data at the back of the 1970 10-30 series owner's manual: Engine 350 V8 Color Code Red Piston Displacement 350 Compression Ratio 9.0:1 Gross HP 255@4600 Net HP 200@4000 Gross Torque 355@3000 Net Torque 310@2400 Hope that helps! __________________ 1969 C10 LWB W/ 250 I6 & 3spd 1970 C10 with '67 small window cab, 68 front end, blue; 305/TH350, 3.08 limited slip rear end, manual brakes, power steering; & 4-wheel drums-My daily driver. 1975 Chevelle Malibu Classic Coupe 350/th350 mint green 1970 C20 Suburban 350/700R4 4.10 gearing green & white 1978 Big 10 Silverado 350/th350, working ac, 2 tone blue-My summer daily driver 1983 GMC 1500 Sierra 305/SM465 2.73 rear end How to add a trip odometer to your 67-72 stock speedometer How to rebuild your Q-Jet My Truck Page My Youtube Channel

02-11-2011, 10:48 AM	#5
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,858	Re: 1970 350 Compression ratio 10:1 350/300hp truck motor??? I don't think so. Never heard that before. If someone can prove me wrong I'd like to learn something. __________________ "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 ~

02-11-2011, 11:24 AM	#6
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: 1970 350 Compression ratio that must b the elusive corvette optioned truck __________________ 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

02-11-2011, 11:24 AM	#7
Dave DND Trucks Join Date: Dec 1999 Location: NW Indiana Posts: 2,391	Re: 1970 350 Compression ratio Compression ratios vary a little from engine to engine, more or less. I'd perform a compression test just see where it's at now. As far as a factory installed 300 hp and 10.0 compression 350 in '70 in a truck? Never seen one, nor does the GM basic engine data and power teams list any combo. Now a passenger car, that's a different story. Last edited by Dave; 02-11-2011 at 11:27 AM.

02-11-2011, 11:00 PM	#9
todd99 Registered User Join Date: Feb 2011 Location: prescott, az Posts: 225	Re: 1970 350 Compression ratio 71 c20 longhorn custom camper. My motor was completely stock and had 11 to 1 compression, I had to check it twice just to believe it. My heads are stamped with 3978487 K250, not sure if that means anything.

02-12-2011, 12:05 AM	#10
DT1 Registered User Join Date: Oct 2009 Location: Gardnerville Nv No Mo Cali!! Posts: 869	Re: 1970 350 Compression ratio That's nothing! My stock 350 in my 71 is 19:1. That's why I have always had to run premium.

02-12-2011, 12:10 AM	#11
todd99 Registered User Join Date: Feb 2011 Location: prescott, az Posts: 225	Re: 1970 350 Compression ratio ^^^ Are you mocking me?

02-12-2011, 12:21 AM	#13
todd99 Registered User Join Date: Feb 2011 Location: prescott, az Posts: 225	Re: 1970 350 Compression ratio No worries, I'm not making it up. I am far from the original owner, it's possible someone tampered with it before I bought it. It looked stock.



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