302?

[Alech1979]

I got some questions, I'm planning on buying this 73 bronco from this guy. It has the standard 302 motor. I have absolutely no idea on working on trucks at all but am willing to learn by working on this one. The problem I have is that I searched the web and I hear that the 302 is not a great motor to have when your mudding because of torque issues at low rpms. I see that you can get a 302 to around 300 to 400 hp with a lot of torque at the top of the powerband but I'm worried about torque for towing and yanking people out. I'm not looking to make it go 200mph I want the muscle. I'm willing to put in serious cash and time into this bronco to turn it into a mudding machine, I just want to make sure when I get into trouble I have the power to pull myself or others out of mud pits. I dont know if I'm misinformed or what? Any comments or suggestions about the 302, mods, whatever would sure be appreciated for a newcomer who's going to be in over his head!.

 

[4xfan78]

I think that the 302 has plenty of power. There is alot of aftermarcket items you can get to improve it. The best thing you could do to compensate for low torque problems is to change the gear ratio in the front and rearend.

 

[Seabronc]

The 302 should have plenty of power for your truck. Like 4xfan said gearing will resolve the low end torque problem.

Good luck,

>-

 

[Ktomek06]

There is only a small hp difference between a 302 and a 351 and I have a 302 and I have plenty of power for what i do..plenty of get up and go and I can definatly pull..keep the 302..but a 72' might need a rebuild..it all depends

 

[Alech1979]

thanks guys for all the input.

 

[bluesman17]

302 is strong enough to pull a dodge grand caravanin park with relative ease WHOOPS! supercharge it if you really want to have a lot of torque

 

[Broncoholics]

My 302 .030 over (mostly stock) works well at the low end due to the 5:89 gears. No hesitation at low RPM's at all. I can smoke the 38.5" Swamper SX tires on dry pavement!

Its always the gears, people put on larger tires and expect to keep the power and lose the low end torque. I always figure 4:10 gears for stock tires, 4:56 for 33's, 4:88 for 35-36's. Anything larger than 36's should be up in the 5's. Unless its a freeway queen then you might want a higher ratio and take it in the shorts...

 

[billybroncojr]

I had a worn out 302 in my 72. 4barrel carb and headers were about the only upgrade. It did fine even with the 3.50 gears and 35" Ground Hawgs, it didn't like it but it wasn't the motor running out of power. Gears are everything. If you are looking for low end torque, run a 2 barrel carb. I run with a guy that has 39.5's swampers and a 302/2barrel in his Jeep. That is the only Jeep I would ever own. I have rarely seen him stuck and he usually serves as tow rig at the annual mud fest.

Later,

Jeff

 

[Alech1979]

so by changing the gears, I solve the torque problem; but what do I sacrifice? I always felt that you never get something for nothing. Billy you said changing to a 2 barrel carb would help, would a four be better or would I only be stopping at every other gas station?

P.S. thanks guys for all the info it's really helping me get a mental picture of my new hobby!

Plus, the toy has 3 on the tree. Is it easy to convert it to the floor so it sits next to the transfer case shifter?

 

[Broncoholics]

You can get the kit and install it in a day easy. The bad thing is in 2nd gear the shifter is right up next to your leg. The fix is to get a NP435 for the granny low and strength and don't have the shifter problem. They are cheap and very strong. Get the adapter to the Dana20 t-case from Advanced Adapters and your done. Or get the combo NP435/NP205 out of a 79 Bronco and build a custom cross brace, re-route the exhaust and maybe new drivelines if needed.

 

[bluesman17]

Lower gears mean lower top speed usually, not something to really worry about

 

[billybroncojr]

I would like to add that you need to build it for YOUR specific purpose. Whether you are building for mud, rocks, daily driver or whatever, it needs to suit your specific purpose. Do research before you buy anything for it and decide what you are building it for because every application is different! It may sound strange but it will help you and keep you from spending money on upgrades that you really don't need. If you are building a daily driver and you buy a set of Ground Hawgs, you aren't going to be happy!

Your first step should be determining what you are going to use it for and going from there.

Think about it!

Later,

Jeff

 

[bronco69billy]

The gearing is the key to any low-end torqe problems but also don't forget that a simple cam upgrade wouldn't hurt the problem either. comp cams 280H magnum cam is great for a little extra torqe range. and then go bigger as needed for wheelin.

 

[BLADE262US]

Soemthing else to think about is the weight of the rotating mass . This would be especially helpful if your using a stick . Your 72 motor is a good one to rebuild the crank is very heavy which I would believe to help with the grunt off the git . The newer 302,s 79 and up havd that little lightweight crank in them . Its pretty much nothing but the bearing throws . The older ones 77 or so and back have very meaty cranks that look very similar to the 351w . The light crank is good for quick revs but were not looking for that . The heads on your motor might end up costing you alot to have redone because it probably has soft valve seats in it for running leaded gas so I would say use your block , crank , and rods , And then find a set of heads off an 86 5.0 ** and youll be very happy, The edelbrock performer or my favorite the weiand stealth are very good from idle to around 6500 very usable for a truck . Also dont want to over carborate a 600 cfm carb is fine makes good torque . Try to keep the compression ratio around 9 to 1 so it will run off pump gas without spark knock . /emoticons/[email protected] 2x" width="20" height="20" />

 

[Seabronc]

so by changing the gears, I solve the torque problem; but what do I sacrifice? I always felt that you never get something for nothing. Billy you said changing to a 2 barrel carb would help, would a four be better or would I only be stopping at every other gas station? 
P.S. thanks guys for all the info it's really helping me get a mental picture of my new hobby!

Plus, the toy has 3 on the tree. Is it easy to convert it to the floor so it sits next to the transfer case shifter?

10655[/snapback]

​

A properly set up 4 BBL carb should only use the front two ports unless you are putting a heavy demand on the engine. The additional two ports are there to supply the extra fuel and air needed as the engine starts to require more for power. At normal operations like cruise and street legal acceleration /emoticons/[email protected] 2x" width="20" height="20" /> the secondaries are keept closed thus giving you better gas milage. So even if you are going to stomp it from the light the secondaries shouldn't initially open but shoud be adjusted to open smoothly as the engine needs more air and fuel when the revs climb. Then at cruise they should pretty much close and open for passing and hill climbing. That is how a 4 BBL can give you better milage than a 2 BBL. The 2 BBL has large ports that are open all the time, the 4 BBL has smaller individual ports but when the secondaries open the effective port size increases with demand.

The bottom line is that if the 4 BBL is properly set up, it is far superior to a 2 BBL. In fact there are a lot of complaints about poor milage, but here is one thing that definately has a direct effect. I would venture a guess that if the secondary operation was checked a lot of people would find they open too soon or are oen when they shouldn't be for normal operation.

Also, you need to decide what you want this vehicle for. Offroad only, takes a completely different setup than a high performance vehicle. A general use vehicle that can spend a little time off road and still be a reasonable daily driver requires a different setup and some comprimises, ( the way it was built by Ford for general sale). Off road only, who cares about cruise characteristics, for performance be preared to spend money on parts, FUEL and fines /emoticons/[email protected] 2x" width="20" height="20" /> , you may also be kicked off the road if you can't pass emissions and local laws. For general use work on the things that can improve HP and gas milage while keeping you legal.

Good luck,

>-

 

[xsbronco]

This might help. Its a gear ratio/tire size chart as general rule for I believe 55 mph. colors are for high end torque relations to mph relations at spec'd out rpms

TIRE_SIZE_CHART.doc

 

[Seabronc]

Actually that chart is calibrated at 65 MPH and the colors show where you are running in relation to economy and power based on tire size and differential gear ratio at a 1:1 engine to driveshaft ratio, not in overdrive, (stick shift will be closer to the numbers shown while automatic may be a little higher), a good auto and torque converter will give almost identical numbers though. The red band is the power end, green is comprimise area or general use, and the blue area is best economy operation. It represents the optimal operating range of your engine which is 2300 to 2600 RPM and acceptable is 2000 to 3000 RPM. The green band gives you the best balance between power and economy. Also, the colored bands on that chart should be widened to include the acceptable operting range of the Bronco engines. I believe it is actually for Jeep engines.

The formula for calculating RPM is: gear ratio x speed x 336 / tire diameter so if you normally cruise at 60 MPH with a 3.08 rear end and 33 inch tires your RPM at that speed would very close to 1880 RPM which is outside the acceptable operating range. Effectively making it a power dog. Going to 4.11 would put you back in the green area of the chart at 60.

Have fun,

>-