Chevy Engine codes and such.... - The 1947 - Present Chevrolet & GMC Truck Message Board Network

sd-slider · 07-08-2007, 09:19 PM

Wanted to see what some of you have made of the somewhat "cryptic" nature of the 350 Small Block casting #'s and date codes..

I am getting ready to re-power my 69' Step and needed all of the pertinent info for possible trade-in for core. Here are some #'s I pulled off of the block and heads:

Block Casting # - 3970010 (Date code is: D281)

Head Casting # - 3973487 (Date code is: D281..strange?)

Both date codes appear to be April 28, 1971 based on specs that I have found at various sites and publications. I have also seen varying information that says this could be either a 307, 327, or 350.....anyone have any reliable sources for information on this?

What has me wondering is something as simple as spark plugs.....I picked up some new plugs based on the 71' theory to replace the Autolite "145" plugs that were previously installed(not by me..), and they don't fit. Autolites application specs don't even mention compatibility with any 71' 350's...

Any info or links would be greatly appreciated.

=Slider

dave2953 · 07-08-2007, 09:27 PM

I pulled this from www.mortec.com

Block
3970010....302.....69....4...Z-28 Camaro
3970010....327.....69....2...Trucks and industrial
3970010....350...69-80...2 or 4

Heads
3973487....71-72...350..........1.94/1.5 or 2.02/1.6 valves, was also used on '71 350/330hp LT1, 75cc chamber

sd-slider · 07-08-2007, 09:34 PM

Thanks for the response...

That's what I'm getting as well....any way to tell which one it is? Even the date code isn't helping due to the fact that multiple engine sizes were produced within that range....

Aaaaaaargh!

JimKshortstep4x4 · 07-09-2007, 04:23 AM

If the pad codes on the right front of the engine block are legible, the suffix code will give you more information.

JIm

Blazer1970 · 07-09-2007, 06:30 AM

It is a 350. I have never seen or heard of a 327 using that block casting, and you do not have a 302.

sd-slider · 07-09-2007, 12:06 PM

The suffix is "TBC", if that helps...

dave2953 · 07-09-2007, 12:13 PM

Found this for you:

TBC 1970 350 convfwd cabs, a/t 255 4 C-10 to 3500
TBC 1970 350 m/t, 3 spd 255 4 K-10 & 20
TBC 1979 350 conv. cab, m/t,fed L LS9 165 4 C-10 to 2500

Looks like it's a 350, but I still don't understand why those plugs you bought wouldn't fit??

sd-slider · 07-22-2007, 01:51 PM

Thanks for all the replies and info. It indeed appears to be a 71' 350 w/ heads from the same date code. As for the plugs...that is another adventure.

I've located a new crate 350 that I'm going to drop in. Depending on the shape of the block when I pull 'er out, I may choose to rebuild, or, offer it up as a core. Next step will be to locate a lower geared rear-end so that I can take it on the freeway and not turn 5K at cruising speed....

07-08-2007, 09:19 PM	#1
sd-slider Registered User Join Date: Feb 2007 Location: San Diego Posts: 9	Chevy Engine codes and such.... Wanted to see what some of you have made of the somewhat "cryptic" nature of the 350 Small Block casting #'s and date codes.. I am getting ready to re-power my 69' Step and needed all of the pertinent info for possible trade-in for core. Here are some #'s I pulled off of the block and heads: Block Casting # - 3970010 (Date code is: D281) Head Casting # - 3973487 (Date code is: D281..strange?) Both date codes appear to be April 28, 1971 based on specs that I have found at various sites and publications. I have also seen varying information that says this could be either a 307, 327, or 350.....anyone have any reliable sources for information on this? What has me wondering is something as simple as spark plugs.....I picked up some new plugs based on the 71' theory to replace the Autolite "145" plugs that were previously installed(not by me..), and they don't fit. Autolites application specs don't even mention compatibility with any 71' 350's... Any info or links would be greatly appreciated. =Slider __________________ 1970 GTO 455HO/4spd 1970 C10 Fleetside LB 1969 C20 StepSide LB 1966 Skylark GS (401 Nailhead) *Do YOU feel the need for EXTRA Speed*?

07-08-2007, 09:27 PM	#2
dave2953 Dave's not here, man Join Date: Jun 2004 Location: Winder, Georgia Posts: 2,000	Re: Chevy Engine codes and such.... I pulled this from www.mortec.com Block 3970010....302.....69....4...Z-28 Camaro 3970010....327.....69....2...Trucks and industrial 3970010....350...69-80...2 or 4 Heads 3973487....71-72...350..........1.94/1.5 or 2.02/1.6 valves, was also used on '71 350/330hp LT1, 75cc chamber __________________ - 2014 VW Jetta - 2015 VW Jetta - 1966 Ford F-250 Last edited by dave2953; 07-08-2007 at 09:28 PM.

07-08-2007, 09:34 PM	#3
sd-slider Registered User Join Date: Feb 2007 Location: San Diego Posts: 9	Re: Chevy Engine codes and such.... Thanks for the response... That's what I'm getting as well....any way to tell which one it is? Even the date code isn't helping due to the fact that multiple engine sizes were produced within that range.... Aaaaaaargh! __________________ 1970 GTO 455HO/4spd 1970 C10 Fleetside LB 1969 C20 StepSide LB 1966 Skylark GS (401 Nailhead) *Do YOU feel the need for EXTRA Speed*?

07-09-2007, 04:23 AM	#4
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Re: Chevy Engine codes and such.... If the pad codes on the right front of the engine block are legible, the suffix code will give you more information. JIm __________________ 1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC

07-09-2007, 06:30 AM	#5
Blazer1970 Registered User Join Date: Dec 1999 Location: Old Mission, MI, USA Posts: 2,510	Re: Chevy Engine codes and such.... It is a 350. I have never seen or heard of a 327 using that block casting, and you do not have a 302. __________________ Tim

07-09-2007, 12:06 PM	#6
sd-slider Registered User Join Date: Feb 2007 Location: San Diego Posts: 9	Re: Chevy Engine codes and such.... The suffix is "TBC", if that helps... __________________ 1970 GTO 455HO/4spd 1970 C10 Fleetside LB 1969 C20 StepSide LB 1966 Skylark GS (401 Nailhead) *Do YOU feel the need for EXTRA Speed*?

07-09-2007, 12:13 PM	#7
dave2953 Dave's not here, man Join Date: Jun 2004 Location: Winder, Georgia Posts: 2,000	Re: Chevy Engine codes and such.... Found this for you: TBC 1970 350 convfwd cabs, a/t 255 4 C-10 to 3500 TBC 1970 350 m/t, 3 spd 255 4 K-10 & 20 TBC 1979 350 conv. cab, m/t,fed L LS9 165 4 C-10 to 2500 Looks like it's a 350, but I still don't understand why those plugs you bought wouldn't fit?? __________________ - 2014 VW Jetta - 2015 VW Jetta - 1966 Ford F-250 Last edited by dave2953; 07-09-2007 at 12:15 PM.

07-22-2007, 01:51 PM	#8
sd-slider Registered User Join Date: Feb 2007 Location: San Diego Posts: 9	Re: Chevy Engine codes and such.... Thanks for all the replies and info. It indeed appears to be a 71' 350 w/ heads from the same date code. As for the plugs...that is another adventure. I've located a new crate 350 that I'm going to drop in. Depending on the shape of the block when I pull 'er out, I may choose to rebuild, or, offer it up as a core. Next step will be to locate a lower geared rear-end so that I can take it on the freeway and not turn 5K at cruising speed.... __________________ 1970 GTO 455HO/4spd 1970 C10 Fleetside LB 1969 C20 StepSide LB 1966 Skylark GS (401 Nailhead) *Do YOU feel the need for EXTRA Speed*?



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