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Hello
I'm new here and hope someone will have some insight on what I have recently bought.
I came across this motor on CL, I have been on a search for a 71 numbers correct block for my GMC Sprint SP454.
The date is a perfect match for my truck, or some would call it an El Camino. There are a couple things about this engine that puzzle me so that's where our paths are crossing. At first I thought it was a 71 Corvette LS6 motor, maybe?
Then I thought it was a 1970 LS6 but ? Let me know what you think.
Here's a list of all the numbers involved.
3963512
4 Bolt
964 Main Caps
D 5 71
T0504 CRR. No partial vin
7416 Crank
3963550 TRW Pistons
Starter Pad Stamps - MAC, K
3906629 Oil Pump
3964291 Heads, F 12 70 & B 5 71
3969898, 4492, 0303 date Holley Carb
1111258, 6 H 30 Distributor
Edelbrock C427X Intake
The only thing I can think of is its possibly a CE engine or over the counter sale or ???
Please give me your $2 dollars worth of guessing, no longer 2 cents. Inflation
Thanks
You numbers point to a late 1970 LS-6 (April 71 = 1970 production year) for a Chevelle (CRR)
Think the last year of production for those head was 1970 as well.
Nice engine, carb, crank, heads, etc. for a rebuild foundation.
Can't be a Corvette production LS-6 (All produced late 1971 production year and have Alum heads vs iron)
Last edited by Hammerhead Fred; 05-26-2019 at 08:54 AM.
You numbers point to a late 1970 LS-6 (April 71 = 1970 production year) for a Chevelle (CRR)
Nice engine (and carb) for a rebuild foundation if it's authentic
Can't be a Corvette production LS-6 (All produced late 1971 production year and have Alum heads vs iron)
By April 1971, the 1970 production year was long gone. 1971 production started in August of 1970. CPW and CPX were 71 LS6 codes, so it is not that. Not sure what it is, though.
I'll guess a warranty motor sold over the counter. This was a popular counter sale back in the day. The 11:1 pistons and block #s point to 1970 version, but the block was cast D 5 71 April 1971. That would be correct for your stamp assembly date that indicates a May 4 assembly date with no year. So that makes sense for a 1971 cast & assembly. The carb is an 0303 is a Jan 1973 Holley . Was probably a complete motor, only thing missing is the OEM manifold. Or someone bought the Holley at the same time if it sat on the shelf for 2 years. I also believe a number of these were sold as boat motors thru the 1970s but do not know how to identify one. The Chevelle CRR code was the premier variation of the LS6 with iron heads, and I believe that was the commonly made counter version.
IIRC all the factory assembled 70 Chevelle LS6s cars were produced in a short time frame like Jan -Apr 1970.
Last edited by leigh1322; 05-26-2019 at 10:22 AM.
Reason: update
By April 1971, the 1970 production year was long gone. 1971 production started in August of 1970. CPW and CPX were 71 LS6 codes, so it is not that. Not sure what it is, though.
Yup, you're right - I was off a year.
Then the CRR code stamped in the block cannot be original as that was a 1970 production code stamped into a 1971 casting year.
I would think it would be CE. Not have any code that said what model car it was slated to go into. OTOH I can see them grabbing a pre-stamped engine and selling it as a counter engine.
I have a question about the Holley date code of 0303, isn't the first number the year.
I thought that it was a 70, but the code has 4 numbers instead of 3.
Can you help with the decode.
My understanding is all earlier carbs were 3 digit, 1972 and prior. Those the first digit was the year.
In 1973 they switched to four digit, the first 3 being the Julian date (Jan 30 in your case) and the last one being the year.The 3 being 1973. NastyZ28 says the 3 could also cover 1983 or 1993 as well.
I have a question about the Holley date code of 0303, isn't the first number the year.
I thought that it was a 70, but the code has 4 numbers instead of 3.
Can you help with the decode.
Holley carbs were dated two different ways, three digit and four digit.
Initially, they were all three digit, with the first digit representing the year, the second the month (1-9, 0 for October, A for November & B for December), and the third digit the week of the month. In the early 70's, Holley switched to a four digit date, with the first three being a Julian date, and the forth digit the year.
Leigh1322 beat me in with the answer. I gotta learn to type quicker.
good above advice.. it is a big valve, square port head, 4 bolt main block..
that one 70 head makes it a date mismatched engine, but casting is correct.
don't know the cam, and edelbrock is non factory. my book says closed chamber heads with those pistons you might be pumping 11 to 1.
cam it appropriately, and you should get LS6 performance out of it.
find you a correct intake and you should have a pretty good all GM LS6 setup.
05-25-2019, 05:39 PM
1971 LS6 Engine
