Picked up a 1970 GMC C3500 dump truck that needs some TLC

[timswi]

How you gonna get that mixture thru those tiny valves and heads? I would use a 305 for a door stop.

Just giving my experience...If you don't like them that's fine.

 

[joemd11]

Wow, you done good! That looks like a great truck for its age. I always liked that body style. Let me know if you run across another one like that!

 

[deerefan]

How you gonna get that mixture thru those tiny valves and heads? I would use a 305 for a door stop.

I love these types of attitudes toward these motors. Makes them cheap for guys like me that know how to make power with them. If you would like, I can explain to you exactly how to get air/fuel thru those tiny valves and heads and make good power doing it if you have the time. While a 350/454 would be ideal, hot rodders know the value of these. We are trying to save the op some money by offering options with the current motor. Other motors to consider are the 366 and 427(truck version). Both are long stroke and hard on fuel but make excellent torque which is perfect for your application. I have a 366 sitting in my shop now out of a 2 ton dump truck, makes 300+tq stock before 2500rpm with 345 @ 2500. Hp is around 250 stock. Once the rebuild is complete it is going into a 1 ton chevy truck used for logging work.

 

[boxygen]

I love these types of attitudes toward these motors. Makes them cheap for guys like me that know how to make power with them. If you would like, I can explain to you exactly how to get air/fuel thru those tiny valves and heads and make good power doing it if you have the time. While a 350/454 would be ideal, hot rodders know the value of these. We are trying to save the op some money by offering options with the current motor. Other motors to consider are the 366 and 427(truck version). Both are long stroke and hard on fuel but make excellent torque which is perfect for your application. I have a 366 sitting in my shop now out of a 2 ton dump truck, makes 300+tq stock before 2500rpm with 345 @ 2500. Hp is around 250 stock. Once the rebuild is complete it is going into a 1 ton chevy truck used for logging work.

I have a chevy pickup with 305. As people have mentioned, not a powerhouse. I put headers on it with a single 3" exhaust and it really woke it up. Cheap and simple. It will now go up hills without downshifting where I had to downshift before. Still not a dragracer but I was really surprised at gains for the investment.

 

[murphy1244]

I love these types of attitudes toward these motors. Makes them cheap for guys like me that know how to make power with them. If you would like, I can explain to you exactly how to get air/fuel thru those tiny valves and heads and make good power doing it if you have the time. While a 350/454 would be ideal, hot rodders know the value of these. We are trying to save the op some money by offering options with the current motor. Other motors to consider are the 366 and 427(truck version). Both are long stroke and hard on fuel but make excellent torque which is perfect for your application. I have a 366 sitting in my shop now out of a 2 ton dump truck, makes 300+tq stock before 2500rpm with 345 @ 2500. Hp is around 250 stock. Once the rebuild is complete it is going into a 1 ton chevy truck used for logging work.

I have a in line 250 six cylinder that would blow the doors off your 305. I had a 1970 307 2bbl carb that stock puts out 200 hp. so your hotrod 305 at 231 hp ain't much here.

 

[Diamondpilot]

My only experience with a 305 was not good. It was a late 80's 1500 GMC 2 wheel drive short bed. It was so low on power or poorly geared you could not hold overdrive and 70mph with the AC on with a empty truck. Forget pulling a load.

For less money you could build a nice 350. They are a dime a dozen.

I agree though, just leave it as is.

Chris

 

[deerefan]

I have a in line 250 six cylinder that would blow the doors off your 305. I had a 1970 307 2bbl carb that stock puts out 200 hp. so your hotrod 305 at 231 hp ain't much here.

The 305 you mentioned in your reply was not built for hp. It was built for torque and reliability. Had the goal been hp, the cam choice, piston choice and head work, as well as induction and timing, would have been set up differently. Now, if you would like to discuss motors I have assembled for as you say "blowing the doors off...." whatever then that will have to be an entirely different thread. I am offering the op solid advice on addressing his concerns for lack of power and trying to save him some money too.

 

[Verticaltrx]

If the motor runs good I'd leave it alone. What I would be looking to do is re-gear the axle back down to 4.56 or even 4.88 gears. Obviously someone swapped in a junkyard rear end, on those old cab-chassis truck rear shocks were an option (which it would have said on the build sheet). Lower gears in the axle would make a huge difference in the perceived power and also make it more useable around the farm.

 

[deerefan]

My only experience with a 305 was not good. It was a late 80's 1500 GMC 2 wheel drive short bed. It was so low on power or poorly geared you could not hold overdrive and 70mph with the AC on with a empty truck. Forget pulling a load.

For less money you could build a nice 350. They are a dime a dozen.

I agree though, just leave it as is.

Chris

Fuel injected or carb? These motors had tiny cams and also were a bit on the lean side. The 86 305 in the GMC I rebuilt had similar issues. I think it was 88 they went to the tbi.

 

[hawkeye08]

My experience when putting in a HEI distributor (or whole engine with HEI) when the truck came with points ignition, is the power to the points style distributor drops to ~6Volts in the run position (from ~12V in the start position). This was necessary for points to make them last longer. The voltage drop is not as great with the HEI, but is still enough to cause problems.

There are kits you can get to take care of it or you can just replace the wire with a non resistor wire.

I have no idea if the owner that did the swap took care of this issue, but here is the basics. HEI Conversion

... and even better Full Power to HEI

Nice find... I wouldn't mind having one of those trucks around to move some dirt occasionally.