CTW L34 engine

1970camaronut

Veteran Member
Jul 25, 2010
125
Can anyone confirm whether the 1970 CTW engine (automatic) was high performance as per 1970-1975 Chevrolet by the Numbers book. I thought the L34 was a 2 bolt main. Thanks
 

ggtsvnv

Veteran Member
Jun 20, 2002
1,304
Fallon, NV
It is a two bolt main but still has Passanger Hipo cast into the side of the block for what that is worth. I think it would still be considered Hi/po with the two bolt main as if you look at the other 402 cid big blocks from 70 they range from something like 260 horsepower in trucks to 300 horsepower engines in full size cars along with A bodies.
 

ggtsvnv

Veteran Member
Jun 20, 2002
1,304
Fallon, NV
I should add that it might not be the 4 bolt block of the L-78 (nor does it have the heads, solid lifters and other items) but I feel it is still a high performance engine
 

1970camaronut

Veteran Member
Jul 25, 2010
125
The owner states its 4 bolt main and has a picture of it during the rebuild proving it. The CTW is stamped on the pad but not the VIN. I asked for a picture of the Vin # by the oil filter and am awating a reply. He is advertisng it as numbers matching ....with a 4 bolt main. Any additional info? Is yours a CTW?
 

ggtsvnv

Veteran Member
Jun 20, 2002
1,304
Fallon, NV
Mine is a CJI block 402 CID (L34 350 H/P) turbo 400 & is a two bolt main. There are no documented L-78 (375 H/P 402 CID) Turbo 400 Camaro SS's. So I don't think it was an L-78 Camaro block. So unless the CTW block was used in Chevelle SS's with the L-78 with an auto trans (which I don't believe was true;due to all solid lifter engines getting 4speeds to my knowledge) then I would have to think that perhaps the block was machined for 4 bolt mains. I know a small block can be machined for 4 bolt mains, and would think that a big block could be also. Unless by some chance some L-34's were 4 bolt blocks from the factory.
 

flowjoe

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Feb 7, 2006
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ggtsvnv said:
Mine is a CJI block 402 CID (L34 350 H/P) turbo 400 & is a two bolt main. There are no documented L-78 (375 H/P 402 CID) Turbo 400 Camaro SS's. So I don't think it was an L-78 Camaro block. So unless the CTW block was used in Chevelle SS's with the L-78 with an auto trans (which I don't believe was true;due to all solid lifter engines getting 4speeds to my knowledge) then I would have to think that perhaps the block was machined for 4 bolt mains. I know a small block can be machined for 4 bolt mains, and would think that a big block could be also. Unless by some chance some L-34's were 4 bolt blocks from the factory.
OK so Colvin lists CJI as the 350HP 402 w/TH400 but the CTW as the 350HP 402 w/TH400 High Perf which begs the question - what's the diff?

HP & TQ don't change (an L-34 is an L-34) so heads, pistons, intake and carb will all be the same leaving the block and crank to be different. Colvin shows the 3969854 block to be in use for both L-78 & L-34 in '70. There are a lot of different crank numbers so who knows.

Surely GM didn't create a separate suffix code for no reason.

FWIW, I can see some L-34's leaving the factory as 4 bolts just cause (like some L-48s are 4 bolt and some are 2 bolt)same block, same line.
 
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deputyrob

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Jun 22, 2008
866
Canal Fulton Ohio
All L34's were forged crank, 10.25 comp and high lift hydraulic cam. from 65 to 70. but in 65, 66, 67 they used Holley carbs and went to Rochesters in 68. Dunno why the book says on is high perf and one not.
 

flowjoe

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Feb 7, 2006
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deputyrob said:
All L34's were forged crank, 10.25 comp and high lift hydraulic cam. from 65 to 70. but in 65, 66, 67 they used Holley carbs and went to Rochesters in 68. Dunno why the book says on is high perf and one not.
From inception through '67 396 cranks are all forged steel. From '68 forward the low HP units receive cast iron. Of course what GM define as low HP and what we define as low HP are not necessarily the same. So you have a variety of cranks that could have been installed (Casting numbers):

3856223 (6223) - forged steel
3863144 - ??
3874874 - ??
3904815 - iron
3804816 - ??
7115 - forged steel

All from Colvin but not clear what was production and what was not.

I don't think the cab dictates either (as in '68 both L-34 and L-35 use same intake and a Qjet - same piston and CR too - it's the cam that differentiates).

Puzzler till someone else chimes in
 

ggtsvnv

Veteran Member
Jun 20, 2002
1,304
Fallon, NV
flowjoe said:
OK so Colvin lists CJI as the 350HP 402 w/TH400 but the CTW as the 350HP 402 w/TH400 High Perf which begs the question - what's the diff?

HP & TQ don't change (an L-34 is an L-34) so heads, pistons, intake and carb will all be the same leaving the block and crank to be different. Colvin shows the 3969854 block to be in use for both L-78 & L-34 in '70. There are a lot of different crank numbers so who knows.

Surely GM didn't create a separate suffix code for no reason.

FWIW, I can see some L-34's leaving the factory as 4 bolts just cause (like some L-48s are 4 bolt and some are 2 bolt)same block, same line.

I agree completely :cool: and what is the difference? My block does have molded into the side of it "Passanger Hipo" where as I have two other 402 blocks one from a 70 Chevelle Malibu that was a 2bbl engine and it doesn't have the passanger hipo on the side of it nor does the 70 truck block that I have.

On a side note I have heard about the L48 2 bolt main blocks and over the years I have had three different L48's that were 69 & 70's and they were all 4bolt blocks.

So maybe the 70 L-34 came both ways 2 bolt and 4 bolt?
 




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