ok guys i run demolition derby at my local county fair and i was talking to an engine builder and he said that i could swap my 350 heads with 305 heads and have my 305 heads milled to get a lower cc. that would get me more low end torgue. my question is how can i mill my heads myself. i would like to not spend a bunch of money on this motor. i have already replaced intake came and rockers. any help would be great. thanks.  

Unless you have some precise measuring equipment and a milling machine you can't do this on your own. Milling involves cutting down the entire surface of the cylinder head. Doing this any significant amount with a 305 head is probably a bad idea, I'd say more than .050-.060" is a warning zone. 305 heads are known for thin castings (smog-era engines are in general)...

I know demolition derby cars can and probably will get hot, if you have your radiator taken out and want to finish the race you will up the chances of blowing head gaskets, warping the heads, or even cracking them. This becomes more of an issue the more material you remove. Obviously increasing compression increases combustion temperature as well...

Are you prepared to run higher octane fuel in your 350? This may need to be done depending on exactly what your final compression ratio will be. If you're concerned with just mid-range output the 305 heads probably won't be a bad idea but even with the compression increase a 350 head may make more power on the top.  Very few 305 heads have 1.94" valves, which is standard for a 350 head. Most 350 heads will have slightly larger port volumes as well.  

What heads are you running now? Your best bet is probably gonna be to find a set of smaller chamber non-305 heads.  

GibTG:
Unless you have some precise measuring equipment and a milling machine you can't do this on your own. Milling involves cutting down the entire surface of the cylinder head. Doing this any significant amount with a 305 head is probably a bad idea, I'd say more than .050-.060" is a warning zone. 305 heads are known for thin castings (smog-era engines are in general)...

I know demolition derby cars can and probably will get hot, if you have your radiator taken out and want to finish the race you will up the chances of blowing head gaskets, warping the heads, or even cracking them. This becomes more of an issue the more material you remove. Obviously increasing compression increases combustion temperature as well...

Are you prepared to run higher octane fuel in your 350? This may need to be done depending on exactly what your final compression ratio will be. If you're concerned with just mid-range output the 305 heads probably won't be a bad idea but even with the compression increase a 350 head may make more power on the top.  Very few 305 heads have 1.94" valves, which is standard for a 350 head. Most 350 heads will have slightly larger port volumes as well.

I agree with Gib. Alot of reasons ppl are using 305 heads on 350's are simple. They make cheaps HP, cuz point blank, 305 engines are as plentiful as gas stations overcharging for a gallon of gas. Why buy a set of performance heads for your racecar for 2000 bucks when you can go to Jim's auto recycler yard and get a set of heads with tiny 58cc combustion chambers for 50 bucks and recondition them as needed??? You do NOT want to use 305 heads. Higher compression will give more low-end torque, but with the increase of combustion temperatures, you will more likely blow your engine, before winning a derby. I recommend doing ALOT of research on what other derby racers do to their cars. Most stock SBC's have excellent low RPM Torque, thanks to low lift-low duration cams, however Lunati makes a VooDoo line of cams perfect for your application. They are rated for a powerband of, off-idle-4800 RPM, it is their Truck Avenger. It's main purpose is to create a powerband where gobs of low RPM torque are needed to keep the tires turning under ANY condition. Also you may be able to Google search some performance heads for your application. Also I recommend replacing the 350 possibly with a 383 stroker. A 3.75 in stroke will generate more torque throughout your engine's ENTIRE RPM range than the stock 3.48 in stroke. Since you don't need alot of RPM's you aren't really sacrificing by having a longer stroke.  

right now the heads on it are stock 350 heads....if not 305 heads what others would u sugesst. and another question can you guys explan offset lifters. they are 180 offset.  

Well you could try haveing a machine shop porting your heads to fit a 2.02in intake valve. This will reduce low-RPM torque though. As for a recommendation of what type of head? Try to look up different performance heads online. You'll need to find a head that'll standup to some serious punishment, but one that'll improve your low-RPM torque. Unless your Demo derby track is a mile long, and wide, you'll probably never get out of first gear. Placing a set of High flow heads generally will change your torque and HP to the higher RPM ranges(3000-6000 RPM).This means that when you are being slammed into by other drivers, it'll take longer for your drivetrain to get your car moving from a stop. The longer you are stationary the more you'll get pounded. The problem with buying a set of heads is that heads are one of the MOST expensive parts of an engine. You may want to go with a set of pre-1975 350 heads. They will be pre-smog era and should have thicker castings, allowing you to have them milled easily to get the higher compression.  

Alright, there is some good information floating around here...

Let's get something straight. Is this engine going to see race gas? If so, great, this will help prevent detonation while the engine is hot and allow an increase in compression and the subsequent gains in power where you need them. BUT if high octane fuel is not in the budget I wouldn't mill a set of 305 heads if I used them, it is unnecessary. Depending on what casting number you find the chambers can be anywhere from 52-59 cubic centimeters (there may be even outliers here too). Now depending on what type of piston crown we're dealing with here this will already be at or above the limit of pump premium.

Offset ROLLER lifters are used for high-effort, high rpm, and high horsepower racing applications to move the pushrods away from the intake ports to allow for more cross-sectional area in port "bend" because this can become a limiting factor for the induction system. I've never heard of offset flat tappet lifters. I'm not sure if they can be made because directing force away from the lifters center axis would probably eliminate the rotation that is necessary to prevent flat tappet camshaft failure. If you do indeed have offset roller lifters in this engine I have no idea why you have them, they are completely unnecessary at this level and are only needed with aftermarket aluminum cylinder heads that increase the stock port volume by 40-50% or more.

Buying a set of cylinder heads here may not be the best idea because it's money that could be lost and most aftermarket cylinder heads are devoted to the street/strip, pro street, or drag racing crowd. I can't imagine a vortec would give up much low-end torque but part-throttle is a pretty unknown game. Remember that we need to strike a happy-medium with valve size. If it were true that the smaller the valve that more low-end torque will be produced then GM would've placed 1.00" valves in these engines. You need to strike a balance between the extra cylinder filling with the slow port speeds and low-rpms and maybe even part-throttle. Some 305 heads had 1.94" valves, otherwise most were 1.84" or maybe even late models would be 1.72". If you don't want to dig around for a specific set of heads in a scrapyard just go buy a set of vortecs and hope they don't get destroyed...  

back to those offset roller lifters. the only reason i want to buy them is becasue the guy is selling them for 20 bucks (they are used) and i want roller lifters. now i know the LT1 engines have roller lifters from the factory but i would have to drill and tap 3 hols into my current block and i realy don't want to do that. so i guess my question is will the lifters work in my engine without any modifacations? i would consider puting 202 valves in them that would not bother me in the least. i know that i would have to change exahust valves too that might be my best bet as well to get low end torque. i don't know guys you tell me what are my options. i already have roller lifters and a just over stock came. and a new aluminum intake. i thought about 30 over pistons. like i said im all about suggestions. i have untill next year to build this thing. thanks for any help.  

I know a lot of derby guys will bore their engines out a little bit and leave stock pistons in it.  Does wonders for keeping an engine running a bit longer when the radiator is gone.  Pistons expand to fill the cylinders.

From what I've seen...derby motors are rarely built for power.  They are built to survive at extremely high temperatures.  Unless you've got some incredibly sneaky ways of hiding another radiator...and there are ways of doing so...you'd better plan for it to be toast at the end of the run.  

GibTG:
Alright, there is some good information floating around here...

Let's get something straight. Is this engine going to see race gas? If so, great, this will help prevent detonation while the engine is hot and allow an increase in compression and the subsequent gains in power where you need them. BUT if high octane fuel is not in the budget I wouldn't mill a set of 305 heads if I used them, it is unnecessary. Depending on what casting number you find the chambers can be anywhere from 52-59 cubic centimeters (there may be even outliers here too). Now depending on what type of piston crown we're dealing with here this will already be at or above the limit of pump premium.

Offset ROLLER lifters are used for high-effort, high rpm, and high horsepower racing applications to move the pushrods away from the intake ports to allow for more cross-sectional area in port "bend" because this can become a limiting factor for the induction system. I've never heard of offset flat tappet lifters. I'm not sure if they can be made because directing force away from the lifters center axis would probably eliminate the rotation that is necessary to prevent flat tappet camshaft failure. If you do indeed have offset roller lifters in this engine I have no idea why you have them, they are completely unnecessary at this level and are only needed with aftermarket aluminum cylinder heads that increase the stock port volume by 40-50% or more.

Buying a set of cylinder heads here may not be the best idea because it's money that could be lost and most aftermarket cylinder heads are devoted to the street/strip, pro street, or drag racing crowd. I can't imagine a vortec would give up much low-end torque but part-throttle is a pretty unknown game. Remember that we need to strike a happy-medium with valve size. If it were true that the smaller the valve that more low-end torque will be produced then GM would've placed 1.00" valves in these engines. You need to strike a balance between the extra cylinder filling with the slow port speeds and low-rpms and maybe even part-throttle. Some 305 heads had 1.94" valves, otherwise most were 1.84" or maybe even late models would be 1.72". If you don't want to dig around for a specific set of heads in a scrapyard just go buy a set of vortecs and hope they don't get destroyed...

You are probably right about the valves. I read that wrong from one of my engine books laying around. I didn't find anytihing about valve sizes affecting torque, after I re-read through. However I did find that a stock intake manifold with longer runners can be better suited for low-RPM torque. Although considering no radiator, you might want a cast iron manifold. This way it doesn't warp when the engine gets hot and cools down later after the derby is over.