I have a 1980 Toyota truck with the original 20R in it.  It leaks oil severely from several places and has high miles so I am looking to rebuild it this summer.  I have never rebuilt an engine before but a buddy will be helping me.  He will have rebuilt two before we start mine.  I would like to get a little more power out of it and from what I understand, a larger cam would help and boring larger valves.  Forgive my newby questions, but is this correct?  Would it be possible?  Not asking if it is worth it, if it doesn't work oh well, if it does I would be very happy.  Yes the truck is sort of a POS but it is my truck.

Other upgrades would eventually be a:
        Performance Holley Carb
        Kit to change from mechanical fuel pump to an electrical pump
        Upgraded shocks
        Whole lot of body work
        Stereo system

Cutting the heads for larger(oddball sized)valves is usually a race only type thing and usually an in the white(using gun terminology) head is used that still needs quite a bit of machine work.  Cam would help as long as you don't go too  large then you gotta start replacing everything else to make efficient use of the cam.   Rebuilding would obviously get it back close to stock ratings. Throw in a very mild street cam and I think it would make a noticeable difference. Swap the exhaust, run a mild intake and rejet the carb and make the ignition slightly hotter probably be a good little runner.

One thing to think about is if you run a pretty hot cam, then you gotta upgrade the fuel system, improve the flow on the intake and exhaust side to make use of the larger cam. You end up with a boggy dog because it either can't get the fuel to it fast enough, feed it enough fuel, or get the burnt fuel mix out of it quick/smoothly enough. Would have to run a hotter ignition to get a good clean/thorough burn of the increased fuel mix. Just food for though. Keep it simple and not too radical and it'll perform great. Biggest mistake most people make is throwing an entirely too large cam into an engine without getting everything else up to snuff to use the profile of the cam to it's potential.

Before you set about having all the work done, you should price it out and see how it compares to just buying a rebuilt long block and then installing the cam of your choice.

I'd also agree on not wasting the money for larger valves. The cyl head on your truck has plenty of port volume to support more hp, and going with larger valves could negatively affect your flow efficency. ( It's not always how much air you move, but how fast you move it that matters)

Thanks for the info guys.  Now I know that I won't increase the valve size since there is no point.  I don't want a street racer, just something with a little more get up and go.

Moparman:  I have checked into a rebuilt long block.  Jasper's (in Seattle I think) has a rebuilt that is a little above spec for $1900 but that cost, then getting it down here, and installing it would be more than I have an want to spend.  Rebuilding it myself would be a learning experience and even if it doesn't work it would be fun trying.  I am going to check into a good rebuild kit soon.  Any ideas on what is a good brand?  Is one from the auto parts store quality enough?  

I will likely get a performance Holley carb so is re-jetting still necessary?  What do you think about changing to the electronic fuel pump?

ATK engine at Napa

Check the link for a rebuilt motor if you're not dead set on building your own. They also have a master rebuild kit for about 700 bucks that has everything you'd need with the exception of the machine work.

The elec. fuel pump wouldn't really be that high of a priority on my list, as you wouldn't be running beyond the capabilities of the std. mechanical pump with what you're looking to do.

The Holley carb is a fine idea, and yes, you will have to futz around with it a bit once you get the motor going to make it all happy.

What he said on both of your questions. You might get lucky with the carb. Sometimes they are close enough from the box to run right but very very rarely.

I friend of mine got 2 rebuilt engines from NAPA and had to replace them both in less than a year so I hesitate to get one from them.  He was mildly experienced in engine rebuilds so I don't know if he did something wrong.  Both were Ford 460's.  

I will likely go with a rebuild kit from somewhere.  Does a rebuild require full removal of the engine?  How much do you think the machining will cost on average?

Unless your really talented with about 10 hands otherwise you'll need to pull the engine.

It used to be around 20 bucks a cylinder the last time I had a block bored. I might have been getting a break from the guy. My dad knew him for a very long time and my grandpa had been doing business with him since the 40s. If it needs line boring(realigning the crank bosses) it would obviously be more.  There not really too much machine work that gets done on a normal street driven engine block.

The heads will be pretty limited to cutting new valve angles and replacing the seats. Maybe have to shave the deck surface to get the plane flat again. If you wanted to just to be safe you can get the head and block magnafluxed and sonic tested for cracks and structural strength. It kinda just depends on the machine shop on how much their prices are. The last set I had done were some old Pontiac Ram Airs from the 60s and it was a little over $200.

I usually try to find an older out of the way machine shop. Because it's usually an older gentlmen who has been a machinist for decades. He has been around the block and knows exactly what to do or will do exactly what you want. Has been around since the Ford Flathead was the hottest and most modern engine around and has a vast knowledge or weaknesses and strengths of all engines and how to machine the parts for them.

To find a good machine shop go find some dirt trackers or drag racers in the area and ask them who they use and you'll be set good.

I will have to ask my mechanic (older guy been in business a really long time) who he used to use for a machine shop.  He used to do total rebuilds but doesn't anymore.  Just doesn't have the business I guess.  Everyone buying new cars when the old one gives out.  Anyway, I have another question.  Since I won't be starting the rebuild until later this summer, would it be okay to run a hotter ignition now or should I wait?  Does a hotter ignition consist of just a coil, just a distributor, or both?  Everyone seems to buy MSR (?) is that a good one?  If I stick with a smaller cam will I need hotter ignition?  And one final one....where does one find a cam that will fit this particular truck?

It won't hurt anything but then again I don't know that you would notice it though either. I would run a better ignition period regardless if I ran a mild or wild cam. It will improve the burn no matter what cam or condition of the engine.

Do you mean MSD ignition? If so yes they are great ignition systems. If I'm not running a magneto I use Mallory. But MSD is great stuff!  As far as finding a cam, I have no idea to be honest. I would check on some 4x4 forum or Toyota truck forum specifically. I'm sure they are there, Toyota trucks seem to have a large loyal following.