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I want to upgrade the heads on the 350 engine in my 66 half ton. Would like to either go with 305 H/O heads that would raise my compression or go with vortec heads. I don't know what casting numbers to look for and I know it makes a big difference. Any suggestions ?

From what I've heard for about $400. for vortec heads and $250 for an Edelbrock ,you can still use your carb,you get the best bang for your buck in increased performance. You could possibly find a good set of 194's around or older double hump heads for a couple hundred and use your own carb/manifold.Going the 202 route isn't really worth it for what you pay and get for your money in comparison.

The Vortec bowtie heads are supposed to produce almost the same amount of gains as the Fastburn heads for cheaper. These aren't the same as regular vortec heads, they are basically castiron fastburn heads. I think the machineshop that rebuilt my 261 had Vortec Bowtie heads for $100 or $150 apeice, without valves/guides/seals, springs, rockers... Let me know if you want the guy's name and number.

If a budget is in play here, keep in mind that with vortec heads you will also need rocker arms, valve covers, valve cover studs and a different or modified intake manifold.

Jegs and or Summit have the best prices I've seen so far for vortec heads.

Thanks for the input guys. Any particular casting numbers i should look for ?

I think the vortec heads are a great bolt on head for any older stock 350.

You might want to go to Amazon.com and look for some books on small blocks. There is an interchange book and one for casting numbers. This way you can look at the numbers that you find an know what you are buying. I have these books and find them informative. Here is a search that brought up these books.

http://www.amazon.com/gp/search/ref=br_ss_hs/103-1100170-6642258?platform=gurupa&url=index%3Dblended&keywords=small+block+chevrolet+casting+numbers

Try a google search for fastburn heads or vortec bowtie heads and read up on them. There are several other good gm cast heads out there not to mention aftermarket heads. It's all about valves, combustion chamber design and airflow- Before you start looking through bone yards and swapmeets, try calling a few machine shops in your area and talking about heads with them- Sooner or later you'll find someone with a shop full of what you want who rebuilds them, has a flow bench and can sell them built up or bare at a great price.

Great idea NM51. The last time I went to my machine shop I remember he had heads stacked everywhere all rebuilt. I forgot about him. If I explain to him what i want I bet he can find just the right set. I want more torque. The heads I have now have really big valves and combustion chambers. Great for high RPM work but it kills my low end torque. Thanks for the suggestion !

I've never heard of large valves killing torque. The combustion chamber size will have a direct effect on compression ratio, but it's my opinion that camshaft and intake manifold will have more of an effect on torque than valve size.

Too large of valves can effect torque, but everything in the combination (valve size, cam, intake, exhaust) will effect torque. Many people spends gobs of money on parts that don't compliment each other. All of these components need to be chosen to compliment each other and the use of the engine your building.

Builder make a good point- Everything has to match and gets picked based on what you are trying to do. For a towing engine you want certain things, for a racing engine something different. RV stuff mixed with Racing stuff won't produce what a proper blend would.

I agree about finding the correct combination of parts. I am a little old school and I chose the 350/350 hydraulic cam which is good for midrange to high RPM but you lose some low end torque. I used to do cars that were lighter and you could get away with that. In a truck you need a bit more torque so i should have maybe chosen a different cam. I have big valve heads but the combustion chambers are too big and they don't make much compression. That is why I am thinking a H/O 305 head with smaller valves and smaller combustion chambers would actually make more power at low rpm. I would also consider a vortec head as I hear they flow better.

The valves on 305 heads are too small for any kind of performance.

I agree with Wrenchbender about the 305 heads. Some people have attempted to raise the compression ratio of a 350 by using their smaller combustion chambers, but because of the small bore of the 305, those heads are very limited in the size of valves that can be used.

I tried to make a 305 into a performance motor once. I failed miserably. After that, I decided that there was no substitute for cubic inches and started using 400 smallblock motors, which are still my choice for V8 applications.

Honestly, 55Cabover, I think you'd be much better off with a 350 and Vortec heads or even 882 heads (best of the worst...or worst of the best...whatever) and a camshaft that's designed to maximize torque and a dual-plane intake manifold. I've used both Vortecs and 882s with good results. As Builder mentioned, the Vortecs take unique parts, but when they're used together, they are real good cast iron heads.

Again...if torque is your goal, I'd look at the cam before the heads. It might be worth it to toss an "RV" cam in the motor and see how it runs before going with a different set of heads. But of course, it's your decision.

When reconditioning old heads, you are putting on heads that have already seen 100,000 miles or more in most cases. New heads can be bought for 1 or 2 hundred more. I just did an old set of X58 chevy small block heads. You replace guides, valves, clean and mag, mill and assemble and you spend $400 to $500. You can spend more by replacing old springs. For $600 to $700 you can get a set of vortec heads with all the parts and they are new. You get good results with them too. If I didn't have a specific need (restoration) for the heads, I would think hard before rebuilding them at the prices and performance of new heads.

My friend has a lifted newer (91) Chevy and he put vortec heads on the motor and it made a nice improvement. I think that he switched out some other stuff too, but in the end it was a great performance booster. You might choose to change your intake and carb as well, this is a good time to do it.

A friend put the fastburn heads on his 350 and it made a huge difference. He also had to buy a new intake though. I think its the same with the Vortec Bowtie heads, which are the cheaper cast iron version of the aluminum fastburn heads.

The thing with those heads, aside from the valve sizes, smaller combustion chamber and other things is the heart shaped combustion chamber which causes the air to flow in a certain way.

I would not mind the expense of doing the vortec heads and the new intake if I knew it would give me a significant power gain. Thanks for the testimonials.

"chevy high performance magazine" says they are good for forty horsepower.

The Vortec heads will be an improvement. Probably the best bolt on head for that kind of money.

I don't have any experience with vortec or fastburn heads, but I would strongly caution against using 305 heads on a 350. If I'm not mistaken, 305 heads have a 56cc combustion chamber, versus 64 or 72cc's on the 350 heads. That's a 12.5% reduction in chamber volume, so on a 9:1 engine, it would give you 10.125:1. It sounds like a great way to make power, but without a piston dome and combustion chamber built for that kind of compression, detonation would be likely. Since stock 305 heads are almost universally from smog motors, it's a safe bet that the chamber wasn't built for high-compression. Adding to the problem is the fact that 305's have a much smaller bore than 350's,(3.74" vs. 4") so the chamber is built to fit the smaller hole. This results in a flat ledge surrounding the combustion chamber, which isn't terrible in and of itself, except it causes the chamber to be shaped even less optimally than the same heads on a 305.

Granted, this is all technical theory, and maybe I should have started out by saying, I know from experience it's a bad idea. A friend of mine and I stuck some 305 heads on his 350, and spent the rest of the time he had with the truck fiddling with the timing and filling it with premium gas, because that was the only way to keep it from pinging like mad.

And remember, free advice is worth every penny.

Thanks for the info GMCPauly. That kind of direct experience with the 305 on the 350 was what I was looking for. I think all the info is leading me to vortec heads. At $2.99 a gallon premium is not a great option !