How do you identify a 366, 396, or 427 steel Crank [Archive] - Chevelle Tech

: How do you identify a 366, 396, or 427 steel Crank


james a larson
Dec 19th, 06, 9:48 AM
On a forged steel crank for 66-70 366, 396, or 427 blocks. How do you tell the difference? are all 6223 cranks for the 396 block?

ED1966SS
Dec 19th, 06, 10:12 AM
One reference book I have has the 6223 listed for 396(65-69)/402(70-71) blocks only. The 366, 396 and 427 did share the 4815 and 4816 cranks and the 396/366/402 shared the 3144 cranks. Only the 6223 were forged I believe.

68chvlss396
Dec 19th, 06, 10:36 AM
Here is a list of 366/396/402/427 cranks from Mortec.

BBC TWO PIECE REAR MAIN OIL SEALS
3.76" STROKE used on '65-'90 Mark IV 366T, 396, 402, 427 or 427T

6223.......396,402,427...forged, 1053 steel
7115.......396,402,427...forged, nitrided, cross-drilled, 5140 steel
3804816....396,402,427...cast
3856223....396...forged
3863114....402...
3863144....396,402...
3874874....396,402...
3879621....427...forged
3882841....396...forged, cross drilled, nitrided
3882842....427...forged, cross drilled, nitrided
3882847....
3882848....
3882849....427...forged
3887114....396...forged, nitrided, 5140 steel
3904815....396,402...cast, nodular iron
3941180....
3942411....
3965746..........semi finished, forged
3993804..........raw, 5140 steel

BIGBLOCK70Z
Dec 19th, 06, 11:28 AM
the 427 crand has hevier counter weights. i know the the 396 crank has a 3/4 " thickness and the 27 has 7/8" on the i think like the third weight back. not possitive right now i will check. but it dont matter if you have it ballanced

David Bates
Dec 19th, 06, 4:41 PM
On a forged steel crank for 66-70 366, 396, or 427 blocks. How do you tell the difference? are all 6223 cranks for the 396 block?

I think you will find that the majority of NOS 366T/427T cranks floating around ebay now are forging number 3856223 and do not have cross drilled mains and are being falsely advertised as 396/427 L78/L72/L88/ZL1 pieces and are several pounds heavier then the corresponding passenger car piece because of the heavier rods and pistons in the tall deck engines. These should not be confused with the "6223" 396/427 passenger car HP forged, nitrided and crossdrilled main cranks which when new have a white, green and purple paint swipe on the front of the #1 throw as does the 7115 L88/ZL1 crank. The counterweights on the 7115 crank were a little heavier than the 6223 crank to offset the added weight of the larger rods (L88's and ZL1's - the only 3.76" stroke engines to use 7/16" rod bolts) and somewhat heavier domed pistons.

BIGBLOCK70Z
Dec 19th, 06, 7:49 PM
396 AND 427 STROKE IS 3.76 AND 454 IS 4.00 BOTH CAME WITH 3/8 AND 7/16 ROD BOLTS THEY MADE A DIMPLE ROD FOR 375 HP 396 WITH 3/8 BOLTS AND DIMPLE RODS WITH 7/16 BOLTS FOR 427'S AND 454'S LIKE ZL1 L88 LS6 AND LS7:thumbsup:

supersport6667
Dec 19th, 06, 9:13 PM
I belive all the early steel cranks were #6223 I dont think they used the #38 7 or 8 digit part# till the late 70's or so. I have a #6223 that a friend took out of a 60's 366 motor. I would think most of the #6223 steel cranks out there today are out of 366/427 tall decks. If U have the motor balanced it shouldnt matter what it came out of all had the same stroke, 3.76.

james a larson
Dec 20th, 06, 10:17 AM
I have heard that on the 366 crank the 3rd counterweight is 3/4" thick, on the 396 the 3rd counterweight is 7/16", and on the 427 the 3rd counterweight is 7/8" due to the difference in weight of the pistons & rods. A previous post has the 396 counterweight at 3/4". Can anyone verify the information regarding the with of the 3rd counterweight? thanks

BIGBLOCK70Z
Dec 20th, 06, 8:27 PM
ok my book says that on the third counterweight it's 3/4 for 396 and 7/8 for 427. the flanges' are the same. it is for the diff weights of the pistons all the rods are the same so to speak. the book is chevrolet by the numbers by alan colvin.

james a larson
Dec 21st, 06, 9:05 PM
Thanks, I got the 7/16th's from an earlier Colvin books, now after looking at the changes for the 2nd edition I see the change on page 81 to 3/4" for the 3rd counterweight. Thanks again

supersport6667
Dec 23rd, 06, 12:22 AM
I opnce upon atime had a 66 427 2bolt main motor had 60,000 original miles and never looked to be apart........I measured the counterwieght that was supposed to be 7/8" and it was 3/4" just like the other #6223 cranks I had. If I have a chance will measure the 366 crank and see what counterwieght is.

james a larson
Dec 23rd, 06, 4:10 PM
Just read somewhere that the 3rd counterweight should be 11/16 for the 396 block. Which is correct 11/16 or 3/4?