Eng Block Identification - The 1947 - Present Chevrolet & GMC Truck Message Board Network

SBPage1 · 03-11-2020, 01:36 PM

Afternoon gang
Need some help. I’m getting ready to rebuild a Chevy Block. The GM code shows a 3914678 eng stamp code, but when I look it up, I find it can either be a 302, 327 or 350. There is another stamp that looks like a VIN number that reads: 18J102400VOI84HM. Can anyone help me decipher this? I’ve researched it and get conflicting answers. Any help will be appreciated!!!

sstock · 03-11-2020, 02:39 PM

It will come down to the casting date on this engine suffix. If it is 1965 or 1968 it is a 327, if it is a 1969 casting it is a 350

SBPage1 · 03-11-2020, 05:02 PM

Thanks SStock

Here is what I found and what my dilemma is in trying to glean the info from the internet. Here is what I found. The casting numbers are the same. I could always measure the stroke, but was trying to save myself some time. I’ve already removed the pistons/crank.

sstock · 03-12-2020, 11:27 PM

Quote:

Originally Posted by SBPage1

Thanks SStock

Here is what I found and what my dilemma is in trying to glean the info from the internet. Here is what I found. The casting numbers are the same. I could always measure the stroke, but was trying to save myself some time. I’ve already removed the pistons/crank.

You are going by the engine casting number, I'm going by the suffix which is HM, which further breaks it down to a 327 if it was indeed casted in 1968

sstock · 03-13-2020, 01:32 PM

Quote:

Originally Posted by SBPage1

Thanks SStock

Here is what I found and what my dilemma is in trying to glean the info from the internet. Here is what I found. The casting numbers are the same. I could always measure the stroke, but was trying to save myself some time. I’ve already removed the pistons/crank.

Yes that casting number puts it in the 4" bore family, the difference only is the crank/rods that got dropped into it. 302 had a 3" stoke, 327 had a 3.25" stroke and 350 had the 3.48 stroke cranks. HM tells you the actual engine application 250 hp 327 or 350 cu inch

LT1 Burb · 03-13-2020, 07:51 AM

If it is the 302 and the car is still around, someone would pay handsomely for that, 68 302's are very scarce.

sstock · 03-13-2020, 01:28 PM

HM engines in 1968 and 69 were 250 hp engines and chevrolet made a kagillion of those., a 302 would have a DZ suffix and now yes you are right good money in one of those.

61K10 · 03-13-2020, 02:34 PM

they didn't make a 350 with small journal crankshaft did they?

jchav62 · 03-13-2020, 05:14 PM

Quote:

Originally Posted by 61K10

they didn't make a 350 with small journal crankshaft did they?

I'm pretty sure they didn't...

**rideblue00** · 03-21-2020, 06:19 PM

Hello, im into tracing chevy numbers. What is your crankshaft casting #? Also post a pic of the different numbers cast into the front block face. I wasnt able to get much yet with the stamped # on the cyl head deck(18J)

SBPage1 · 03-21-2020, 08:56 PM

thanks RideBlue...I’ll dig into it tomorrow. I really want to nail this down.

Many thanks

03-11-2020, 01:36 PM	#1
SBPage1 Registered User Join Date: Nov 2017 Location: Nashville Posts: 62	Eng Block Identification Afternoon gang Need some help. I’m getting ready to rebuild a Chevy Block. The GM code shows a 3914678 eng stamp code, but when I look it up, I find it can either be a 302, 327 or 350. There is another stamp that looks like a VIN number that reads: 18J102400VOI84HM. Can anyone help me decipher this? I’ve researched it and get conflicting answers. Any help will be appreciated!!! Attached Images

03-11-2020, 02:39 PM	#2
sstock Registered User Join Date: Mar 2014 Location: Tacoma Wa Posts: 146	Re: Eng Block Identification It will come down to the casting date on this engine suffix. If it is 1965 or 1968 it is a 327, if it is a 1969 casting it is a 350 __________________ 1953 3100 261cu in, sm420, 3.55 torque tube, omaha orange 1964 GMC 1000 series,custom, 305E, sm420

03-11-2020, 05:02 PM	#3
SBPage1 Registered User Join Date: Nov 2017 Location: Nashville Posts: 62	Re: Eng Block Identification Thanks SStock Here is what I found and what my dilemma is in trying to glean the info from the internet. Here is what I found. The casting numbers are the same. I could always measure the stroke, but was trying to save myself some time. I’ve already removed the pistons/crank. Attached Images

03-13-2020, 07:51 AM	#6
LT1 Burb Registered User Join Date: Sep 2010 Location: Winchester Oregon, formerly Vancouver BC Posts: 2,949	Re: Eng Block Identification If it is the 302 and the car is still around, someone would pay handsomely for that, 68 302's are very scarce.

03-13-2020, 01:28 PM	#7
sstock Registered User Join Date: Mar 2014 Location: Tacoma Wa Posts: 146	Re: Eng Block Identification HM engines in 1968 and 69 were 250 hp engines and chevrolet made a kagillion of those., a 302 would have a DZ suffix and now yes you are right good money in one of those. __________________ 1953 3100 261cu in, sm420, 3.55 torque tube, omaha orange 1964 GMC 1000 series,custom, 305E, sm420

03-13-2020, 02:34 PM	#8
61K10 Registered User Join Date: Feb 2012 Location: pleasant valley--placerville ca Posts: 3,039	Re: Eng Block Identification they didn't make a 350 with small journal crankshaft did they? __________________ 1961 chevy K10 my build is------------61K10 build

03-21-2020, 06:19 PM	#10
rideblue00 Senior Member Join Date: Feb 2010 Location: Lambertville, MI Posts: 1,866	Re: Eng Block Identification Hello, im into tracing chevy numbers. What is your crankshaft casting #? Also post a pic of the different numbers cast into the front block face. I wasnt able to get much yet with the stamped # on the cyl head deck(18J)

03-21-2020, 08:56 PM	#11
SBPage1 Registered User Join Date: Nov 2017 Location: Nashville Posts: 62	Re: Eng Block Identification thanks RideBlue...I’ll dig into it tomorrow. I really want to nail this down. Many thanks



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