I've acquired a 68 396/325 hp motor and need some help deciding what to do. It has 3935401 heads on it which from what I've read are open chamber oval ports out of a truck. I have a set of fresh 063 heads also available. My plans are a lunati 60203 cam, performer rpm intake, headers, etc. My question is, would I be better off using the 063's for better performance? Our 68 has a M20 and 4.10 gears, may be changing to a Turbo 400. 99% street driven but I don't want to embarrass myself if I take it to the track. Thanks in advance and any other suggestions are welcome.
396 Build Help
Ledfoot
1 - 15 of 15 Posts
I've acquired a 68 396/325 hp motor and need some help deciding what to do. It has 3935401 heads on it which from what I've read are open chamber oval ports out of a truck. I have a set of fresh 063 heads also available. My plans are a lunati 60203 cam, performer rpm intake, headers, etc. My question is, would I be better off using the 063's for better performance? Our 68 has a M20 and 4.10 gears, may be changing to a Turbo 400. 99% street driven but I don't want to embarrass myself if I take it to the track. Thanks in advance and any other suggestions are welcome.
1968 RS/SS 396 L78, M22 Muncie, 3:73 12 bolt Posi
Joined
·
332 Posts
Jim,
My opinion I would use the 063's because they are 100cc heads verses the 3935401 with 122cc...If you use the 3935401 heads you are going to lower your compression way to much.
My opinion I would use the 063's because they are 100cc heads verses the 3935401 with 122cc...If you use the 3935401 heads you are going to lower your compression way to much.
1968 RS/SS 396 L78, M22 Muncie, 3:73 12 bolt Posi
Joined
·
332 Posts
Jim,
Also If you use those 3935401 heads you are going to lower CR to 8.32...Way to low for the cam you have...IMO...
Also If you use those 3935401 heads you are going to lower CR to 8.32...Way to low for the cam you have...IMO...
1968 RS/SS 396 L78, M22 Muncie, 3:73 12 bolt Posi
Joined
·
332 Posts
Jim,
I checked with my truck buddies and those heads never came on a 396...The 3935401 heads came off a 427 truck engine. Are you sure you have a 396? If you have the block casting numbers post them...
330864.....68-84...oval...OPEN...396, 402, 366T, 427T, 454 Truck330865.....68-84...oval...OPEN...396, 402, 366T, 427T, 454 Truck330866.....68-78...oval...OPEN...366T, 427T330867.....68-73...oval...OPEN...427T336765.....68-78...oval...OPEN...427T336768.....73-76...oval...OPEN...427T336781.....73-85...oval...OPEN...454, 118cc chamber, 256/114cc ports343771.....68-86...oval...OPEN...366T, 427T, 454343772.....68-86...oval...OPEN...366T, 427T, 454343783.....70-76...oval...OPEN...454 Truck346236.....75-87...oval...OPEN...454, 120cc chamber, 225/116cc ports352625.....70-76...oval...OPEN...454 Truck353049.....73-84...oval...OPEN...454, 122cc chamber, 255/119cc ports366765.....74-78...oval...OPEN...427T473328.....68-69...oval...OPEN...366T3856206....65-66...oval..CLOSED..396, 97cc chamber3856208....65......rect..CLOSED..396/425hp, 109cc chamber 396/375hp "Z-16" Chevelle3856213....66-82...oval..CLOSED..366T, 427T3856260....68......oval..CLOSED..396 Truck3872702....65-66...oval..CLOSED..396, 427, 98cc chamber3873858....65-67...rect..CLOSED..396, 427, 109cc chamber3876875....77-85...oval...OPEN...427T3904390....67......oval..CLOSED..396, 427, 98cc chamber3904391....67......rect..CLOSED..396, 427, 107cc chamber 3904392....67......rect..CLOSED..427, Aluminum, L88, L89, 107cc chamber3904393....68-76...oval...OPEN...366T3908952....67......oval...OPEN...427, "M.Truck", Marine3909802....67......oval..CLOSED..396, 427, 101cc chamber3917215....67-68...oval..CLOSED..396, 427, 101cc chamber3917219....68-85...oval...OPEN...366T, 427T3919840....67-69...rect..CLOSED..396, 427, 107cc chamber3919842....68-69...rect..CLOSED..396, 427, Aluminum L88, L89, 107cc chamber3931063....68-69...oval..CLOSED..396, 402, 427, 101cc chamber3933148....69-84...oval...OPEN...'69 396/265hp, 366T, 427T, 112cc chamber3933149....68-76...oval...OPEN...427T, 122cc chamber3935401....68-76...oval...OPEN...427T3946074....69&71...rect...OPEN...'69 427 L88, ZL1, Aluminum, 118cc chamber '71 454 LS6, "round exhaust port"3964290....69-70...oval..CLOSED..396, 402, 427, 454, 101cc chamber Large or small hex spark plugs used3964291....69-70...rect..CLOSED..396, 402, 427, 454, 109cc chamber Large or small hex spark plugs used3965198....68-69...oval..CLOSED..396 Truck3975950....68-70...oval...OPEN...396, 402 Truck, 366T, 427T3986133....68-85...oval...OPEN...366T, 427T, 454 Truck3986135....69-73...oval...OPEN...366T, 427T3986136....68-84...oval...OPEN...366T, 427T, 454 Truck3993820....71......oval...OPEN...402, 113cc chamber, 255/114 ports3993820....71-84...oval...OPEN...454 Passenger and Trucks, 113cc chamber, 255/114 ports3994026....71......rect...OPEN...454 LS6, 118cc chamber3999241....72......oval...OPEN...402, 454, 113cc chamber6272292....70-78...oval...OPEN...402, 4546272990....70-up...rect...OPEN...454 service replacement, used on some MKIV crate engines
118cc chamber10045427...........rect..........Pontiac/Chevy Aluminum, 91cc chamber Large Port, race10049875...........rect..........Pontiac/Chevy Aluminum Small port, race10051128...........rect..........Bowtie, Aluminum 72cc chambers Symmetrical ports10051129...........rect..........Bowtie, Aluminum "raw" casting, Symmetrical ports10052902...........oval...OPEN...MkIV, 427T10101140...91-up...oval..CLOSED..Gen.V 366T, 427T10114156...91-up...oval...OPEN...Gen.V & VI 454, 118cc chamber10141279...96-up...oval..CLOSED.."Vortec 7400", 100cc chambers10487052...77-90...oval...OPEN...366T12363391...96-up...oval...OPEN...Bowtie, Aluminum, Signature Series, fits MKIV, Gen.V, Gen.VI, 110cc chamber12363401...96-up...rect...OPEN...Bowtie, Aluminum, Signature Series, fits MKIV, Gen.V, Gen.VI, 118cc chamber12560241...98-up...oval..CLOSED.."Vortec 7400", 100cc chambers12562934...00-up...rect...OPEN...Gen. VI 502 Marine 14011077...69-up...rect...OPEN...Aluminum, fits MKIV, "C-port" 118cc chamber, also sold as a "solid" head14044861...84-96...rect..........Bowtie, Aluminum, MkIV, "raised runners", 1st design, 105cc chamber14044861...96-up...rect..........Bowtie, Aluminum, Signature Series, fits MKIV, Gen.V, Gen.VI "raised runners", 2nd design, 115cc chamber14044861...84-96...rect..........Bowtie, Aluminum, MkIV "raw" casting of "861" MKIV 1st design14081045...78-87...oval...OPEN...45414081052...85-87...oval...OPEN...366T, 427T, 454 Truck, Marked "HiPerf"14092359...86-90...oval...OPEN...366T, 427T, Marked "HiPerf"14092360...86-88...oval...OPEN...454 Truck14096188...70-71...rect...OPEN...454 service replacement, also used on later Mark IV LS-6, LS-7
and 454 HO crate motors, 116cc chamber14097088...91-up...rect...OPEN...Gen.V 454/502 HO, 118cc chamber 24502585...97......rect..........Olds/Chevy, DRCE 2, Pro Stock aluminum, for blocks w/4.900" bore centersT = Tall deckOval includes both "peanut" (also called "round") ports and large oval ports
I checked with my truck buddies and those heads never came on a 396...The 3935401 heads came off a 427 truck engine. Are you sure you have a 396? If you have the block casting numbers post them...
BBC HEADS
330864.....68-84...oval...OPEN...396, 402, 366T, 427T, 454 Truck330865.....68-84...oval...OPEN...396, 402, 366T, 427T, 454 Truck330866.....68-78...oval...OPEN...366T, 427T330867.....68-73...oval...OPEN...427T336765.....68-78...oval...OPEN...427T336768.....73-76...oval...OPEN...427T336781.....73-85...oval...OPEN...454, 118cc chamber, 256/114cc ports343771.....68-86...oval...OPEN...366T, 427T, 454343772.....68-86...oval...OPEN...366T, 427T, 454343783.....70-76...oval...OPEN...454 Truck346236.....75-87...oval...OPEN...454, 120cc chamber, 225/116cc ports352625.....70-76...oval...OPEN...454 Truck353049.....73-84...oval...OPEN...454, 122cc chamber, 255/119cc ports366765.....74-78...oval...OPEN...427T473328.....68-69...oval...OPEN...366T3856206....65-66...oval..CLOSED..396, 97cc chamber3856208....65......rect..CLOSED..396/425hp, 109cc chamber 396/375hp "Z-16" Chevelle3856213....66-82...oval..CLOSED..366T, 427T3856260....68......oval..CLOSED..396 Truck3872702....65-66...oval..CLOSED..396, 427, 98cc chamber3873858....65-67...rect..CLOSED..396, 427, 109cc chamber3876875....77-85...oval...OPEN...427T3904390....67......oval..CLOSED..396, 427, 98cc chamber3904391....67......rect..CLOSED..396, 427, 107cc chamber 3904392....67......rect..CLOSED..427, Aluminum, L88, L89, 107cc chamber3904393....68-76...oval...OPEN...366T3908952....67......oval...OPEN...427, "M.Truck", Marine3909802....67......oval..CLOSED..396, 427, 101cc chamber3917215....67-68...oval..CLOSED..396, 427, 101cc chamber3917219....68-85...oval...OPEN...366T, 427T3919840....67-69...rect..CLOSED..396, 427, 107cc chamber3919842....68-69...rect..CLOSED..396, 427, Aluminum L88, L89, 107cc chamber3931063....68-69...oval..CLOSED..396, 402, 427, 101cc chamber3933148....69-84...oval...OPEN...'69 396/265hp, 366T, 427T, 112cc chamber3933149....68-76...oval...OPEN...427T, 122cc chamber3935401....68-76...oval...OPEN...427T3946074....69&71...rect...OPEN...'69 427 L88, ZL1, Aluminum, 118cc chamber '71 454 LS6, "round exhaust port"3964290....69-70...oval..CLOSED..396, 402, 427, 454, 101cc chamber Large or small hex spark plugs used3964291....69-70...rect..CLOSED..396, 402, 427, 454, 109cc chamber Large or small hex spark plugs used3965198....68-69...oval..CLOSED..396 Truck3975950....68-70...oval...OPEN...396, 402 Truck, 366T, 427T3986133....68-85...oval...OPEN...366T, 427T, 454 Truck3986135....69-73...oval...OPEN...366T, 427T3986136....68-84...oval...OPEN...366T, 427T, 454 Truck3993820....71......oval...OPEN...402, 113cc chamber, 255/114 ports3993820....71-84...oval...OPEN...454 Passenger and Trucks, 113cc chamber, 255/114 ports3994026....71......rect...OPEN...454 LS6, 118cc chamber3999241....72......oval...OPEN...402, 454, 113cc chamber6272292....70-78...oval...OPEN...402, 4546272990....70-up...rect...OPEN...454 service replacement, used on some MKIV crate engines
118cc chamber10045427...........rect..........Pontiac/Chevy Aluminum, 91cc chamber Large Port, race10049875...........rect..........Pontiac/Chevy Aluminum Small port, race10051128...........rect..........Bowtie, Aluminum 72cc chambers Symmetrical ports10051129...........rect..........Bowtie, Aluminum "raw" casting, Symmetrical ports10052902...........oval...OPEN...MkIV, 427T10101140...91-up...oval..CLOSED..Gen.V 366T, 427T10114156...91-up...oval...OPEN...Gen.V & VI 454, 118cc chamber10141279...96-up...oval..CLOSED.."Vortec 7400", 100cc chambers10487052...77-90...oval...OPEN...366T12363391...96-up...oval...OPEN...Bowtie, Aluminum, Signature Series, fits MKIV, Gen.V, Gen.VI, 110cc chamber12363401...96-up...rect...OPEN...Bowtie, Aluminum, Signature Series, fits MKIV, Gen.V, Gen.VI, 118cc chamber12560241...98-up...oval..CLOSED.."Vortec 7400", 100cc chambers12562934...00-up...rect...OPEN...Gen. VI 502 Marine 14011077...69-up...rect...OPEN...Aluminum, fits MKIV, "C-port" 118cc chamber, also sold as a "solid" head14044861...84-96...rect..........Bowtie, Aluminum, MkIV, "raised runners", 1st design, 105cc chamber14044861...96-up...rect..........Bowtie, Aluminum, Signature Series, fits MKIV, Gen.V, Gen.VI "raised runners", 2nd design, 115cc chamber14044861...84-96...rect..........Bowtie, Aluminum, MkIV "raw" casting of "861" MKIV 1st design14081045...78-87...oval...OPEN...45414081052...85-87...oval...OPEN...366T, 427T, 454 Truck, Marked "HiPerf"14092359...86-90...oval...OPEN...366T, 427T, Marked "HiPerf"14092360...86-88...oval...OPEN...454 Truck14096188...70-71...rect...OPEN...454 service replacement, also used on later Mark IV LS-6, LS-7
and 454 HO crate motors, 116cc chamber14097088...91-up...rect...OPEN...Gen.V 454/502 HO, 118cc chamber 24502585...97......rect..........Olds/Chevy, DRCE 2, Pro Stock aluminum, for blocks w/4.900" bore centersT = Tall deckOval includes both "peanut" (also called "round") ports and large oval ports
Thanks Mike. The casting numbers are 3916323. The stamping on it in front of the head reads T1OIIXG. Pretty sure it's a 396 2 bolt main from what I've read. The heads have probably been swapped out since they came off a 427 truck motor. The 396 is probably a 10.25 to 1 motor so I'm thinking the 063's should work with the combo that I plan to use. Correct me if I'm wrong. Thanks.
1968 RS/SS 396 L78, M22 Muncie, 3:73 12 bolt Posi
Joined
·
332 Posts
Jim,
3916323 is a 396 (325, 350, 375, 2&4 bolt)...The 325 and 350 Hp motors did come factory with 10.25 to 1 CR...The 375 Hp were 11 to 1 CR motors with a solid cam...If I were to guess you most likely have the 325 or 350 version...
IMO, I would use the 063 heads...
3916323 is a 396 (325, 350, 375, 2&4 bolt)...The 325 and 350 Hp motors did come factory with 10.25 to 1 CR...The 375 Hp were 11 to 1 CR motors with a solid cam...If I were to guess you most likely have the 325 or 350 version...
IMO, I would use the 063 heads...
Joined
·
53 Posts
There was an article in Car Craft about 2 months ago on 396 build ups. It was pretty interesting. Aparently it takes more effort, engineering, know how to squeeze horsepower out of a 396 than to build a stroker motor. I didn't realize how fussy 396's are.
imagine if the extra time money and effort to make a 396 run goes into a larger engine!
Not bad-mouthing a 396, just saying "go 454"
50 cubes extra is 50 horses in a decent street engine...and
500 ft lbs torque, not 410....
Jim, 396 with 063s all day long. Advertised at 10.25:1. Measured CR will be 9.9:1 or there about.
If stock, the pistons will be .023" or there about down in the hole. Run a shim head gasket. Not really to raise the CR (but you gain a tad of compression) but to tighten up the quench. Run .023" DITH with a .040" thick head gasket....you will lose the advantages of quench, and be more prone to detonation. My 454 in the Elky has 10.6:1 measured CR, I run a tight Quench with zero deck and .039" gasket....and a 237/245* hyd roller, no ping or rattle or run-on observed to date though the DCR is more than most would operate with pump gas.
Not bad-mouthing a 396, just saying "go 454"
50 cubes extra is 50 horses in a decent street engine...and
500 ft lbs torque, not 410....
Jim, 396 with 063s all day long. Advertised at 10.25:1. Measured CR will be 9.9:1 or there about.
If stock, the pistons will be .023" or there about down in the hole. Run a shim head gasket. Not really to raise the CR (but you gain a tad of compression) but to tighten up the quench. Run .023" DITH with a .040" thick head gasket....you will lose the advantages of quench, and be more prone to detonation. My 454 in the Elky has 10.6:1 measured CR, I run a tight Quench with zero deck and .039" gasket....and a 237/245* hyd roller, no ping or rattle or run-on observed to date though the DCR is more than most would operate with pump gas.
two ways to work the quench height to the desired .039-.050 range:
zero deck the block and run a .039-.040" compressed gasket
or
leave the pistons .023" or there about doown in the hole like the come from the factory and run the Mr Gasket shim gaskets for their BBC. IIRC, they come in at .019" compressed. This works up to .042 quench.
Generic "Builder" pistons may be further down in the hole than .023":
zero deck the block and run a .039-.040" compressed gasket
or
leave the pistons .023" or there about doown in the hole like the come from the factory and run the Mr Gasket shim gaskets for their BBC. IIRC, they come in at .019" compressed. This works up to .042 quench.
Generic "Builder" pistons may be further down in the hole than .023":
1 - 15 of 15 Posts
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
