I just bought what is supposed to be a 68 427, 435 hp Big block
Block numbers are 3916321 and the stamp code is JA. Is this some kind of early 68 because I can't match the two. and help greatly appreciated.

Thanks Ray

 

Just my .02 cents IF that J is an I it would makes sense. Are you sure its a J?
If its IA -----early 1968-- 427---425 HP--- manual transmission---special high performance
Good luck

 

I don't think chevrolet made a 425HP 427 in 68. They were 390, 400, 435 and of course the 430HP L88.

 

I double checked it is definitely a J.

 

The Corvette black book shows your casting # 3916321 for all the 427 corvettes in 68. Is it a 4 bolt?

 

Whats the casting date? The Corvette black book shows a JA in 67 for a 435HP.

 

The total number on the pad is T7R1526JA

 

Yes it is a 4 bolt main.

 

Look on the right side of the block below the cyl head there will be a casting date there. What is it?

 

It looks like 565.

 

I sorry I don'y think I can help you. A 68 should has a casting date of something like K 17 7. That = 11/17/67. The engine pad should have a stamped date like T1205IR. T=Tonawanda 1205=Dec 5th and IR=435HP 427. Look and see if you have anything like that.

 

Found This.

CODE YEAR MODEL CID HP TRANS
IK 1967 Chevrolet 427 425 Mt AR SHP
IK 1968 Chevrolet 396 325 mt-3 Police
IK 1966 Corvette 427 425 Mt SHP
IL 1968 Corvette 427 390 Mt
IL 1966 Corvette 427 390 Mt
IL 1967 Corvette 427 390 Mt
IM 1966 Corvette 427 390 Mt
IM 1967 Corvette 427 390 Mt
IM 1968 Corvette 427 400 Mt HP
IN 1968 Chevrolet 396 325 PG Police
IN 1966 Chevrolet 396 325 TH
IN 1967 Chevrolet 396 325 TH AR
IO 1968 Chevrolet 427 425 Mt SHP
IO 1967 Chevrolet 427 385 TH AR
IO 1966 Chevrolet 396 325 TH
IO 1968 Corvette 427 400 TH HP
IP 1966 Corvette 427 425 Mt SHP
IQ 1968 Corvette 427 390 TH
IQ 1966 Corvette 427 390 PG
IQ 1967 Corvette 427 390 PG
IR 1966 Corvette 427 390 PG AR
IR 1968 Corvette 427 435 Mt SHP
IR 1967 Corvette 427 390 PG
IS 1967 Chevrolet 427 385 TH AR Impala SS
IS 1968 Chevrolet 427 385 TH
IT 1968 Corvette 427 435 Mt SHP
IT 1967 Corvette 427 435 Mt SHP
IU 1968 Corvette 427 435 Mt SHP
IU 1967 Corvette 427 435 Mt SHP
IV 1966 Chevrolet 396 325 TH
IV 1968 Chevrolet 396 325 TH
IV 1967 Chevrolet 396 325 TH AR
IV 1965 Chevrolet 396 325 TH
IW 1965 Chevrolet 396 325 TH
IX 1967 Chevrolet 427 385 Mt AR Impala SS
JA 1967 Corvette 427 435 Mt SHP*********************************
JA 1969 Chevelle 396 325 Mt
JB 1969 Camaro 396 325 MT
JC 1967 Corvette 427 400 Mt
JC 1969 Chevelle 396 350 Mt HP
JD 1967 Corvette 427 400 PG
JD 1969 Chevelle 396 375 Mt SHP
JE 1969 Chevelle 396 350 TH HP
JE 1967 Corvette 427 435 Mt SHP
JF 1967 Corvette 427 400 Mt
JF 1969 Chevy II 396 350 Mt HP
JF 1969 Camaro 396 350 Mt HP
JG 1969 Camaro 396 325 TH
JG 1967 Corvette 427 400 PG
JH 1969 Chevy II 396 375 Mt SHP
JH 1967 Corvette 427 435 Mt SHP
JH 1969 Camaro 396 375 Mt SHP
JI 1969 Chevy II 396 350 TH HP
JI 1969 Camaro 396 350 TH HP
JJ 1969 Camaro 396 AH Mt
JK 1969 Chevelle 396 325 TH
JL 1969 Camaro 396 375 TH SHP
JL 1969 Chevy II 396 375 TH SHP
JM 1969 Camaro 396 TH alum hd
JM 1969 Chevy II 396 TH
JN 1969 Chevrolet 396 265 Mt
JO 1969 Chevrolet 396 265 TH Police
JP 1969 Chevrolet 396 265 Police
JQ 1969 Chevrolet 396 265 TH
JR 1969 Chevrolet 396 265 Mt Police, hdc
JT 1969 Chevrolet 396 265 Mt hdc
JU 1969 Camaro 396 325 Mt
JU 1969 Chevy II 396 PG
JV 1969 Chevelle 396 325 Mt
KA 1969 Chevy II 396 350 Mt HP
KA 1969 Camaro 396 350 Mt HP
KB 1969 Chevelle 396 350 Mt HP
KC 1969 Chevy II 396 375 Mt SHP
KC 1969 Camaro 396 375 Mt SHP
KD 1969 Chevelle 396 375 Mt SHP
KE 1969 Camaro 396 Mt alum hd
KE 1969 Chevy II 396 Mt
KF 1969 Chevelle 396 375 TH SHP
KG 1969 Chevelle 396 Mt alum hd
KH 1969 Chevelle 396 TH alum hd
KI 1969 Chevelle 396 Mt alum hd
LA 1969 Chevrolet 427 390 Mt HP
LB 1969 Chevrolet 427 335 Mt
LB 1965 Chevrolet 396 325 PG
LC 1969 Chevrolet 427 390 TH HP
LC 1965 Chevrolet 396 325 TH
LD 1969 Chevrolet 427 425 Mt SHP
LE 1969 Chevrolet 427 335 TH
LF 1969 Chevrolet 427 390 TH HP Police
LF 1965 Chevrolet 396 325 Mt
LG 1969 Chevrolet 427 390 Mt HP Police
LH 1969 Chevrolet 427 390 Mt HP
LI 1969 Chevrolet 427 335 TH
LJ 1969 Chevrolet 427 335 TH Police
LK 1969 Chevrolet 427 335 Mt Police
LL 1969 Corvette 427 390 TH HP
LM 1969 Corvette 427 390 Mt HP
LN 1969 Corvette 427 400 TH HP
LO 1969 Corvette 427 430 Mt HD
LP 1969 Corvette 427 435 Mt alum hd
LQ 1969 Corvette 427 400 Mt HP
LR 1969 Corvette 427 435 Mt SHP
LS 1969 Chevrolet 427 425 TH SHP
LT 1969 Corvette 427 435 Mt SHP
LU 1969 Corvette 427 435 Mt alum hd
LV 1969 Corvette 427 430 TH HD
LW 1969 Corvette 427 435 TH alum hd
LX 1969 Corvette 427 435 TH SHD
LY 1969 Chevrolet 427 335 Mt Police
LZ 1969 Chevrolet 427 390 Mt HP Police
MA 1969 Chevrolet 427 335 Mt
MB 1969 Chevrolet 427 390 Mt HP Police
MC 1969 Chevrolet 427 390 Mt HP
MD 1969 Chevrolet 427 425 Mt SHP
ME 1969 Corvette 427 430 Mt
MG 1969 Corvette 427 430 at
MH 1969 Corvette 427 390 Mt
MI 1969 Corvette 427 390 at
MJ 1969 Corvette 427 400 at
MK 1969 Corvette 427 400 Mt
MQ 1968 Chevy II 396 375 Mt HP
MQ 1968 Camaro 396 375 Mt
MQ 1967 Camaro 396 375 Mt
MR 1967 Camaro 396 375 Mt
MR 1968 Chevy II 396 350 TH HP
MR 1968 Camaro 396 350 TH
MR 1969 Corvette 427 430 Mt
MS 1969 Corvette 427 Questionable
MT 1968 Camaro 396 375 Mt
MW 1968 Camaro 396 325 Mt & at
MW 1967 Camaro 396 Mt
MX 1968 Camaro 396 350 Mt
MX 1967 Camaro 396 AR
MX 1968 Chevy II 396 350 Mt HP
MY 1967 Camaro 396 325 TH
MY 1968 Camaro 396 325 TH
MZ 1967 Camaro 396 325 TH

 

thanks for the help i will have to research further.

 

JA = 427-cid 435-hp V-8 with 11.0:1 compression ratio, manual transmission, and three two-barrel carburetor

 

Thanks Ray