325 or 350 horse? [Archive] - Chevelle Tech

: 325 or 350 horse?

Jan 5th, 09, 7:56 PM
I purchased a 1967 396 motor with a 2 bolt main. The block casting number is 3902406. I am unsure if it is a 325 or 350 horse. The head casting numbers are 3904390. Is there any way to tell the difference between the two motors?

Jan 5th, 09, 9:02 PM
The most definitive way is to find the actual 2-letter engine code on the machined pad on the front of the block near the deck (post it here if you find it). In literal terms the only difference beteween the 325 and 350 horse engines are the air cleaner, carb, intake manifold and cam. The 325-horse uses an single snorkel air cleaner and a spread bore Quadrajet carb. The cast iron intake is made to mount the spread bore Quadrajet. The 350 horse uses an open element air cleaner and uses a square bore Holley with the corresponding square bore carb mounting on the intake. Both engines use hydrallic lifters, oval port heads, cast 10.25:1 pistons and 2-bolt mains.

Jan 5th, 09, 9:19 PM
Yes ,get the Engine ID Number -top right in pic

BTW ,Thought 66 had 325,360 & 375hp 396's -no 350hp
And didn't all those have Holley's?

3267A 66 Holley 4-brl 396 Chevelle 325 HP Manual trans
3268A 66 Holley 4-brl 396 Chevelle 325 HP Auto trans
3419AAS 66 Holley 4-brl 396 Chevelle 360 HP
3420A 66 Holley 4-brl 396 Chevelle 360 HP
3608A 66 Holley 4-brl 396 Chevelle 360 HP Auto trans
3609A 66 Holley 4-brl 396 Chevelle 360 HP Manual trans
3613A 66 Holley 4-brl 396 Chevelle 375 HP

Let me know if this info's incorrect - Thanks.

Jan 5th, 09, 11:30 PM
FYI,the later 67-68-69-396/325 & 350hp bbc's all used the same type semi hi rise cast iron intake /a q-jet/same heads/same comp ratio/dif air cleaners/dif ign timing curve/different vac adv/different fuel calibration in the q-jet like sec metering rods/same fuel pump/same spark plugs/ same smaller 7" harm ballencer/etc.

The earlier 65-66 396/325hp & 350hp/360hp motors used a different cast iron intake flanged for a square bore 600 or was it 650 cfm vac sec holley 4 brl carb & steel crank & 4bolt mains,but later 325 & 350hp 396's got nodular iron cranks & 2 bolt mains. The 396/375hp(396/425hp vette limited prod for late 65 too) used a larger 780cfm vac sec carb & AL intake for all yrs mfg'd along with a with a decent solid lifter flat tappet 143 cam & open element air cleaner assembly not to mention 11:0 comp with 4 bolt mains,steel crank,hd 7/16 rods,forged pistons,colder spark plugs/dif ign timing curve & vac adv/larger 8" harm ballencer/etc,but back to main topic here.

The main diff between the 325 & 350 hp 396's in 67-69 was some earlier motors like in 67-early-mid 68 got a steel cranks but late 68 to 69 got nodular iron cranks, the cam,an open element vs single snorkle closed air cleaner assembly,slightly different fuel calibration setup in the q-jets,slightly different ign timing curve in the dist,and a different vac adv. The 70 396/350hp was basically the same as the 67-69 396/350hp motors but it used a new flat cast iron intake from the vette but all else was basically the same other then the cowel ind fresh/cool air setup .

The 1966-69 396/325hp L35 & 1970 402/330hp LS3 cam was an extreemly mild hyd flat tappet with 198/198 deg dur @.05,.398/.398 lift,approx 113-114 LSA (?/forgot exact lsa spec)

The 1967-69 396/350hp L34 & 1970 402/350hp L34 cam called the HI LIFT hyd flat tappet was hotter then the 325hp cam but still nothing to write home about which had 214/218 deg dur @.05,.461/.480 lift,114-115 LSA (? /forgot the exact lsa spec) .

I am sure someone will chime in with anything i missed but i think i covered the main difference between the 396/325hp & 350hp & 360hp motors.


Jan 17th, 09, 2:27 PM
Okay, I checked the engine ID tag on the front of the block. When I originally brought the block home, I thought it said TO92IIV and T12411. I looked at it today it better light and it looks to be TO922IIV and T124511. Can anyone take a look into this please?

Jan 17th, 09, 3:59 PM
you might have another look as the IIV doesn't seem to exist.
If your misreading it ,the IV is a 325 horse engine from 65 through 68

Jan 18th, 09, 2:08 PM
"IV" = 1965, 1967 and 1968 Big Car 325hp/396, 4-barrel and A/T..


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