I have at my disposal a 1981 Pontiac Bonneville, it has a junk 307 and whatever tranny it has is shot to. Being a poor college student, i plan on doing a budget engine swap. Id like to do a 350 chevy and get around 400 horse or so. i guees a th350 tranny. Im not sure what rear end this car has, but id like to put 3.73 gears in it with limited slip. I know this car aint the best thing to build a street rod or whatever youd want to call it, but hey..its free. I will most likely put some different rims  on it, probly some cheap cragers or somthing, what is the bolt pattern on these cars? Any and all information is appreciated. Thanks.  

If memory serves me right, the 81 Bonne was the mid-size based on the same chassis as a Grand Prix or Lemans, not the full size Caprice right? If it is the mid-size, your options are pretty much unlimited, all the g-body cars were available with SBC power so all you have to do is find a 305 parts car and use everything to do the swap. The trans is a choice of th350 if you want a 3 speed, or either a 200-4r or 700r4 if you want overdrive, either the 350 or 200-4r will bolt-in, the 700 will require a  shorter driveshaft and crossmember mods. As for the rear end , 3.73 and posi from any Chevy S-10 Blazer/GMC Jimmy 4x4 will work for a cheap set of gears and posi. The bolt pattern for the wheels is 5 on 4 3/4" bolt circle, 1981 should have metric studs. Hope I've helped you.
Steve  

it is a big car...big 4 door. I think it is based of the Caprice, im not sure. Here is a picture of it.


how are my options lookin now?  

OK, B-body it is. Being the same chassis as a Chevy Caprice, you can use any Chevy powered BelAir/Impala/Caprice for a parts car. But here's another thought, find a 455 Olds and Th400 trans, bolt it in using the 307 mounts and have a true torque monster! The bolt pattern should be the same on the wheels (5 on 4 3/4") unless it has a heavy duty package with 12" front rotors and 5on5", the rearend should be the 8.5" corporate axle which uses the same gears and posi as any 2nd generation Camaro/Firebird, and it is a strong reliable rearend. Don't forget all the cop car suspension upgrades, such as stiffer springs and larger sway bars can be bolted on for better handling and firmer ride. The late Caprice (think Impala SS style) still uses the same chassis and the parts may still be available thru the dealer.
I've always loved the roomy interior and ride of these big sleds and they easily accept all traditional GM uprades and will take just about any GM V8.
Steve  

ah, ive thought about goin the 455 route, but i really dont know much about them. Im low on money to do this with as well. I know if i do a 350 chevy, with about 400 horse, and a th350 trans, i could probly do it for aound 4 grand. Unless i find a good used 455, and rebuild it, pep it up a little. But who knows, im still in the planning stage of this beast. Im probly goin to pull the motor this winter if i get to it, clean up the oily mess. Then do lots of research on what i can do for the best bang for the buck. I looked up some pontiac crate motors last night...they were outrageous in price. Any good place to find a used 455, or should i build a new one from scratch?  

ok, as of right now im working on just gettin the blasted thing running. It needs a new fuel pump which i got, just havent put it in yet (25 bucks) why not? But i think im goin to pull out the ac system as it dont work, do i need to have it bleed out of whatever, or should i just disconnect it and let it loose whats left in it (not much if any freeon) also, all the smog b.s. do i need it? i just want to get all unessicary parts out of it. So when i get the new motor ready, it will be that much easier to pull out. Let me know what all i can tear out and have it still run.  

Hi again! OK, first things first, I assume you mean that you want to get the 307 running again. If that's the case, before you go yanking smog and a/c, let's check why it doesn't run now. You say it needs a fuel pump, why? Is it not getting fuel? Remove the breather and look down the carb with the choke open and pump the throttle by hand, watch for two streams of gas while pumping the linkage. First try running a length of 3/8" rubber fuel hose from the fuel pump inlet to a gas can and try to start the motor, this might take some cranking to fill the carb, if it starts the fuel pump is not the problem.Cars of this age are notorious for rotten fuel lines, the pump can't suck fuel from the tank if the lines have cracks or holes in them. Jack it up and follow the large 3/8" steel line from the pump all the way to the tank, checking for wet spots or obvious cracks, don't forget to twist the rubber sections to see if they are cracked and sucking air. The last place is the lines at the sending unit on top of the tank, you'll have to drop the tank to check and repair those.
Is it getting spark? Pull a plug wire off and put a screwdriver in the end of the wire, holding the plastic end of the driver, hold the metal shank about 1/16" from a good clean metal bracket and have someone crank the starter. If you see sparks-OK, if not the problem is in the ignition.
As for removing a/c and smog stuff, once the car is running, take it to a shop and have the a/c evacuated. It will only take 20 minutes and you won't be a redneck for dumping the stuff into the ozone layer (remember, stunts like this is what gets rodders a bad reputation with the government to begin with!) It's also cheap, call around and ask what it costs, tell them you are removing the a/c and don't want a repair, just an evacuation. As for smog stuff, leave it there until you build your replacement motor. Yes, it's ugly and hard to work around, but the carb and ignition are tuned to work with it. Removing it won't give you any measureable increase in power or driveability, unless you know how to tune for the changes. Plus if the car needs a smog test to get registered, have it tested before you pull the stuff. Most of the smog and a/c stuff will be attached to the old motor anyway and can be left on when you pull it out. Trying to take it all off now is just making more work for yourself. Do you really want to go to all the work pulling the rad now to get the a/c condensor out, then have to put the rad back in until you do the swap?
Also some advice, get it running so you can get it to a coin wash, use several cans of degreaser and blast as much crud off the engine compartment and under the front end as possible, it will make life way easier when doing the swap.
Oh, one more thing, when removing the a/c, cut the lines at the rubber sections and plug them with bolts and tighten hose clamps around them. This will keep the system air tight. Most of these older R12 systems only need new lines, a flush and new oil to repair and recharge with R134A. By plugging the lines you will save the evaporator etc. for future repair if you ever decide to put the a/c back in working order or want to sell the car.
Steve  

Thanks for the info. It is gettin spark, i couldent see any fuel gettin pumped into the carb. Basicly, a few months ago i used this car (its my moms old car) when my pathfinder was broke down. I fixed the pathfinder then the car sat since. Bout a month ago i was home, tried to start it, it wouldent. After a while it would, and would run HORRIBLY then clear up. It would start afterwards, but the next day, the same thing, have to work on starting it for 15-20 mins. I got it started yesterday, but today it would not start. We even tried starting fluid. Ive dumped gas in the carb with no results. It tries to start but just wont, most of the time just cranks. Im goin to go tinker with it here in a while, ill see what happens and let you know.  

Okay, i just looked it over. Its gettin fuel. I need new glasses haha. Possibly i didint look good enuf last time i checked it. But its pumping fuel into the carb, it has spark. Why wont it run? It went from starting and running halfway decent, to nothing. This car has damn near 200K on it though.  

Has it been sitting in damp, rainy weather? I would pull the distributor cap and check for moisture. I had a Buick V6 a few years back that would act that way every time it rained, always the same issue... moisture under the cap. Dry it or replace it and try again, also get some STP Dry-n-Go spray and spray the wires if this is the case. Let me know.
Steve  

it hasent really  been wet around here. i know the car has been loosing water, perhaps a head gasket is causin the non start. theres no water in the oil though.