Hey yall I just accuired an 82 chevrolet blazer.  It is fourwheel drive and is powered by a 305.  The vehicle is bone stock.  I know four sure because the previous owners were my grandpa then my uncle.  I need a little bit of info about it if yall dont mind, because this is my first build so here goes:

1. What axles, transmission, transfer case, and gears are under the truck.

2. If I decide to replace the 305 with, say, a 350 will it bolt in to the original motor mounts, and transmission.What would be involved in puting a 350 into this truck.

Thanks for all the help and sorry this is such a long post.

There is nothing wrong with a 305 and it tends to be a lot better on fuel than a 350. It should have a NP208 transfer case and most likley pretty tall axles too. It could have a 3 speed or 4 speed automatic. The biggest perfomance boost you can give it would be to install some 4.10 gears in it or deeper yet if you plan to add big tires. That truck mostlikely has 3.08 or 3.42 gears in it and the regear will help you far more than a swap to a 350 at this stage.  

I have a few more questions.

What axles are under this blazer? I heard it was a corporate 12 bolt rear and a 10 bolt front. 

Are the stock axles stong enough to handle a 350? I want to swap the motor because I think the 305 is locked up. I was thinking of getting a shortblock from gm and then using a performer RPM setup from edelbrock with either a quadrajet or the new AVS carb.

I want to run 33x12.50x15in tires. What gears would you use. I plan to use the blazer as a daily driver and as a weekend toy. I might lock up the back but i read it is better to leave the front open(easier on the front axle), any help in this area would be helpful.

I also heard that a blazer is full time 4x4, I was confused by this so any explanation would be helpful.

I'm new to building a 4x4, this is my 1st one, so thanks for all the help.

It mostlikely has 10 bolts front and rear (front for sure) and it is more tire size than engine size that determines axle limitations generally.  No problem with axles with 33's with either engine. Get too much bigger than 33's though and you start getting into the failure prone areas. (I would not go over 35's myself and would say 33's is a solid compromise)  That year Blazer would be part time 4WD not full time. As far as gearing It depends on tranny, If it is a 3 speed auto with no OD I would say 4.10's with 33's, if it has a 4sp auto with OD I would go 4.56's myself with 33's  

Hey snoman thanks for all the info, it really helps.  I have two more questions for you. 

1.How will 4.10 gears perform on the highway?  This is going to be a daily driven rig so i dont want to hurt on highway performance and fuel mileage much(I drive on the freeway a lot).  I saw another post where a gentalman had some low gears in his suburban and couldnt go over 60. 

2. Will 33x12.50x15 tires fit under a stock height blazer? If not, can it be done will fender mild finder trimming and a set of the bushwacker fenderflairs?

Thanks again for all the help.

The gentleman in question had speedo calibration problems (it was actually doing over 80 by his RPM data) and engine issues.   With 33's and 4.10's it will go as fast is you want to go if engine is in good shape. If you go taller gears with 3.73, overall performance will suffer greatly. As far a fit, if sping are not sagging, the rear will be no problem and the front may rub some turning but a mild lift (2 inches) would cure that.  

4.10 with 33" tires will eat fuel unless you have a OD transmission. 3.73 gears would be ideal with 33" tires for a daily driver with an OD trans. Personally I'd leave it stock 3.08 with 33" tires if i was going to be building a motor for the truck. Save the $1000 bucks from gear swapping and dump it into more motor and a good rear locker.

But if you want to do it right, I would reccomend swapping in 3.73 gears, regardless of trans, if this is your daily driver.

Not so. 33's take extra power to turn and truck is heavy and 4.10 without OD is a good compromise.  With a OD I would say 4.56 without question.  Yes tell him to put in 3.73's with false hopes. If you are that worried about MPG you do not get a 5000lb plus 4x4 and put 33's on it. 3.73 will make it a dog in drive and off road without low range. A 4.10 is th minimum for 33's and good overall performance without OD.  

I've stayed out of this one till now. I drive a 78 Blazer 350 with t350 trany modified 203 case, 35's and 3.73 gears. These gears are way too light for this combo! If I don't swap out the 12bolt for the 14bolt full floater that I realy want, the first chunk of change that comes my way will go to new gears. 4.11's bear minumim, preferably 4.56. Yes this will up the rpm's, but as you said this will put less load on the moter & drive train, & will probably help gas milage on the highway because it wont be lugging the moter as much. Running 65-70 down the road I'm sure the 4brl is starting to crack open. Driveing 55 it has bad mileage, (guesing around 8-10) but 70 down the Interstate it drops out of sight. Anyway buddy take snowmans advice and regear. There was an article in four wheeler a while back that had a chart for recomended gear/tire combos.

the blazer should have an overdrive being that year because weren't it 81 when they started using the 700r4? the 3.08 gears we all know are to high.  I think the 4.10 gears with 33 are good for it.  When off road 3.73 would lack power and would cause you to use more gas around town by a couple miles to the gallon but the 4.10s or even 4.56s will help a whole lot in town or on the trail. And like said before 3.73s on the highway the motor may not be turning fast enough to be in its power range in overdrive and cause a loss of milage.  I think 4.56s will use a little more gas on the highway would not be bad with the overdrive.  But if did not have an overdrive would use alot of gas.   

If it has a OD, you want to go 4.56. The early 700R4's were not too strong in forth gear clutch and subject to overheating when pulled. A 4.10 in OD would yeild about a effective 2.8 rear axle and with 33's it would really lug the tranny and engine, So, in a nut shell, 4.10 min with no OD and 4.56 (or better) with OD.  

I still say 3.73 with no OD and 4.10 with OD for a daily driver.  

For a totally sucky and doggy daily driver to with 33's and one that OD will be worthless on to (if it has it) and the other will be even more gutless overall.  

Hey thanks for all the input, yall have been extreamly helpful.  What kind of locker would yall suggest for my application?  When i regear the rear end i want to do the locker at the same time. 

I need to look at the transmission again to see if it has overdrive because im not sure. The blazer is in my hometown and i'm away at college but if i remember correctly, it does have overdrive.  The blazer was a freebee from my aunt.  I had to drive back to school so I didnt have much time to look it over.

Also, I heard that the 700R4 is a piece of crap.  Whats yalls take?  If this is indeed what i have, should I keep it, or go for a TH400?

If it is a 700R4 the early stock one had problems but the later ones after about 86 were pretty solid. A older one can easily be brought up to new spec on a rebuild. I have 700R4 in a 89 4x4 burb with 170k miles on it and it is stock and still works like new and it has been cross country more than a dozen times as recently as 2003 and it is goin back to Colorado and Wyo in 2005 for several weeks.  I do recommand that you install a aux tranny cooler on one. Where a lot of 700R4 have failed early on is people towing in OD or install big rubber without proper gears and cooler and toasting tranny.  

On the locker, I do not like mechncial locker for the street and they can be nasty on ice too. I suggest a Eaton LSD or maybe a True Trac LSD as a good compromise and no mechincal locker (except a selectable locker) can power both wheels at different speed in a turn and such. It is both same speed or one wheel free wheeling because there are no spider gears in a true locker.