picked up a 84 firebird was originally a v6 at least thats what the title says. Guy I got it from said it now has a 350 from 1968 chevy truck I got the casting numbers off the block by the transmission they were 3970010 from what I can tell this is a l48 motor but that's what I'm trying to confirm I know the transmission is a t5 if anyone could point me in the right direction i would appreciate it.

 

being a 010 block it's likely a 350, but could be a 327 or 302 (not bloody likely, but on the VERY outside realm of possible) as I recall. Either you measure how far down the pistons move or you visually see the crank casting # and research it. Again, probably a 350. Not that where it came from matters by now. It's been on the earth 50ish years, anything could have been changed. Looks like typical smogger era heads with aftermarket intake and carb. You could get casting numbers off the heads or look at the pistons to see if they're dished or flat top and that'll give you some idea of performance but it really matters zero. How's it run and drive? Feel good? Leave it and maintain the best it can be. Not fast enough? Build a more modern block and forget about it...

 

3970010 is probably the single most common 4" bore block there is. Yerbasic 70s block used in everything from 160 HP 2-bbl motors to whatever else they built back then. As said, it's most likely a 350 now, but could be a 302, 327, or 383.

Odds of it being an actual "motor" from a vehicle are quantum-mechanically small. At this point in its life it's probably been rebuilt 2 or 3 times, had 6 or 8 sets of heads swapped around on it, etc. Trying to call it a "L48" might be somewhat true if it has 882 or 624 heads on it and a 929 cam (or copy thereof) but it's not like somebody just came up with a "L48" from somewhere, a wrecked car let's say, and that's what it still is, unmodified.

You need casting #s of the heads, and a borescope photo of a piston, to figure out what its potential is.

You also need to take it to the car wash and clean up the whole Exxon Valdez thing it has going on there; and put a REAL SHORT bolt in this hole right here, with a drop of sealer on the threads, to stop it from recurring.

 

Thanks for the info guys and she needs some tlc runs strong the motor and transmission are coming out so I can re paint and fix any problem areas I find i was planning on doing some performance upgrades just started looking into that realm but figured I should find out if the motor is even worth upgrading im not looking to be the fastest guy around just want to make the car have lots of torque so its a fun experience driving it with that all being said would it be worth it to do a set of heads and a cam long tube headers and 3" exhaust also if doing a rebuild with a newer style piston would help i dont mind doing that depending on if the ones in it are old or worn and thanks for the info on the short bolt plug had no idea lol

 

50 year old, flat tappet block with likely crappy pistons and could already be .060 overbore.... I wouldn't put upgrade type money into it. If you're going to upgrade, build a roller cam block, or Ltx or Lsx. Otherwise just get that one running good, low end torque will be it's highlight. Horsepower and fast it probably won't be without way too much money than it's worth.

 

You could try to get the stamped numbers from the flat spot on the block above the passenger side water pump mount if still visible

 

That'll tell you what THE BLOCK came as; won't tell you ONE DAMN THING about whatever THE MOTOR that it's now part of is.

Total waste of time IMO. Once a motor has been "rebuilt", those stampings are WORTHLESS. You can take a BLOCK whose stamping says "LT-1 in a 70½ Z/28" and put 15cc dished pistons with .045" of deck clearance, 624 heads, 929 cam, 2-bbl intake, and coffee-stirrer exhaust manifolds on it, and it'll be JUST LIKE a 160 HP pig out of a 76 Impala except WORSE; or, you can take a BLOCK out of a 76 Impala 2-bbl, zero-deck it to some true flat-tops, put 186 or 492 heads on it, slide a solid roller with 260 - 265° @ .050" and .650" or so of lift into it, and get something COMPLETELY else. All without changing the stampings. You have NO WAY OF KNOWING which way is which, in the case of YOUR PARTICULAR motor.

Don't bother with the "codes". Look at THE PARTS if it really makes any difference to you.

Still in all, it's a crappy 70s block, most likely with all the risk of the $hitty quality control they had back then (which is to say, NONE), no modern roller features, already been rebuilt no telling how many times and might already be .060" over and WORE SLAP OUT, you have NO WAY of knowing until you look. No way of knowing about the QC problems until you build it and have an "oh $hit" moment AFTER ALL THE SPEND when the starter doesn't work or the cam goes flat or it EATS the pump bushing in the transmission or any of those other lovely things that go along with 70s blocks. And at that point, ALL THAT MONEY you just spent, goes into the GARBAGE. Not a desirable outcome.

Fix the efffing oil leak; do SOMETHING about that death-trap rubber fuel line before it kills you or yours; and save your money for a better core to begin building onto, while (hopefully) driving this one to work and back every day.

 

Engine appears to be a 350. You'll need to disassemble it to learn anything more detailed.

 

I agree there is no way of knowing without a tear down and inspection but the stamp will tell you what it started as. It may lead to tell if the heads have been changed which would indicate a definete rebuild. OP asked how to find out what he might have and I was just giving options.
ps, decaffeinated might help as it is the Happy Holiday Season and the OP was just asking for help. Just my opinion

 

There is nothing wrong with the 010 block, it is a good foundation for any build. You can use it as is or upgrade it to whatever you need. Find out the combination is and make changes to suit your future build.