I just looked up the suffix code on my motor and found it`s a LS3 396/402. The aircleaner says 400CI,300hp but what is the compression for these motors? Is it worth even putting a cam in them? Here is the deck numbers,

TO310CLB

Thanks.

I think they are 8.5 comp. A cam, intake, carb, headers and exhaust would wake it up.

I thought they were low compression also. So what cam would work with a 8.5 compression 396? I was wanting to run a comp 280 if the compression was high enough but now I think that would be the wrong cam. This isn`t my daily driver and even though it`s a truck, it`s not going to be used as a truck. Thanks.

We had very good experiences with the Cam Dynamics Energizer 272 in a '74 454. With street tires and poor traction, the car still ran 13.6s at 102.4 mph. Tuning was nothing more than ballpark, so some gains were still to be had. The cam gives good idle vacuum and doesn't need any special valve train pieces.

If you wanted to pull the heads you could have them milled. It would give you a little or you could cut 090 but you would need to match the intake to the heads. Call crane tech and tell them what you have, Vehicle, motor, Trans, gear, intake, carb, headers and what you want to do with it. Tell them what mods that you are going to do to the vehicle. I am not sure what you want to spend. Hope this helps a little.

Thanks guys. I might just leave it alone and spend the money on my 454 that I`m building into a 489 stroker. I basically want a little lope at idle and good pull up to abou 5500rpms. I`ll do more research on the motor and see what heads are on it, did`nt have time today to pull a valve cover. Anyway, thanks again.

Weren't the tall deck 427 truck blocks used for the stroker 489s?

You must have a '71 or '72. The '70 LS-3 was 330 hp and had a 10.25-1 CR. It was similar in specs to the '69 396 325 hp. I believe the '71 and '72 LS-3 had an 8.5-1 CR as previously mentioned. A mild cam would help a lot as the factory cam in these and 325 hp 396 was very weak. You can't go very much over 220 deg duration @ .050 lift due to the low compression ratio.

Check this tread:

http://www.chevelles.com/forum/ultimatebb.php/topic/4/23893.html#000000

Originally posted by Cam:
Weren't the tall deck 427 truck blocks used for the stroker 489s? The 489 uses a .030 bore with a 4.25 stroke. It`s basicaly the same as a 496 it just has a smaller bore. The 4.25 crank will fit in a standard deck block but thats about as big as you can go.

70ELKYSS, thanks for the link. Interesteg cam suggestion.

Yes, you can use .400" longer rods with stock pistons in them for a better rod/stroke ratio thing, but the header fitment hassle isn't worth the trouble, imho.

Even though guy's do run them fine.

pdq67

The heads are likely 241's or 820's. They are both 113cc's and flow pretty well.
That 280 cam is going to be way too big for this engine. I rebuilt the LS3 in my ’72 3/4 ton LWB (5000lbs, stock converter, 3.54, 31"tires) last year. The compression measured out to be 8.3-1. I used a Lunati 262/272, 207/217, .490/.515 and even it is a touch big for my intended use (towing). It’s a little soft off the line and is still pulling hard at my 5k rpm shift point. I’d guess it wants and additional 500+rpm.
Bone stock with an ailing Q-jet and 140k miles on the clock, the truck just cracked 16’s. With headers & 2.5” exhaust it ran 16 flat @ 87 mph. A new carb helped a bunch, but by this time the engine had one foot in the grave and only turned 16 flat @ 82mph. I haven’t had it back since the rebuild & new cam. It runs pretty well, but the butt-o-meter says don’t get your hopes too high. Too little compression and too much weight.
I was trying to be frugal and convinced myself that it’s sufficient power to tow my boat & car and still return decent mileage off 87 octane (which it does). Having said that, I’m gathering parts to build a 489. Since when is sufficient enough anyhow? :)