cylinder heads

i have a low compression 350 chev eng. i was wondering if the heads could be milled to get a comprssion of 9.5.i know the intake side would have to be milled to make it fit thanks  

Depends on the head, the low compression smog heads starting in the late 1960s are also thin wall casting and usuallydon't take kindly to milling much with probably .030-.040 being the upper safe limit. This won't get a 9.5 ratio.

These engines have further issues with combustion chamber shape and the depth of the dish in the piston. Neither is conducive to good "squish/quench" which is vital to containing high compression. The S/Q function is mechanical octane as far as the engine is concerned. You need as much of this as you can get at 9.5 with 92 octane fuels.

It would be better to replace the heads with either the earlier camel humps or later heads starting with the L-98 or Swirl Ports. Better still would be aftermarket if you can afford them new. E-bay is a great source of new, rebuilt, or used heads.

The money spent on overhauling and milling a set of smog heads will make a large dent in the cost of new, and will be equal to a decent set of more modern rebuilts.

Nose around at Holley, Edlebrock, GMPP and check out what's available. Here's some extra reading on the subject from CHP's archives;

http://www.chevyhiperformance.com/techarticles/46320/index.html

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http://www.chevyhiperformance.com/techarticles/46326/index.html

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http://www.chevyhiperformance.com/techarticles/46359/index.html

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http://www.chevyhiperformance.com/techarticles/46364/index.html

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http://www.chevyhiperformance.com/techarticles/46370/index.html

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http://www.chevyhiperformance.com/techarticles/46438/index.html

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http://www.chevyhiperformance.com/techarticles/46461/index.html

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http://www.chevyhiperformance.com/techarticles/46467/index.html

 Bogie

For @ $520 a pair you can buy new, fully assembled vortec heads that come with small combustion cambers and you can safely mill them more if you want. Heres more info from Jim Pace  Performance Warehouse-

"The Vortec head out flows the Bow tie head out of the box and is a 20 to 40 horsepower bolt on increase over earlier cast iron small block heads." 

That's a pretty ambiguous statement.  20 to 40hp increase over what... open chamber small-valve smog heads, or Z/28 2.02" 64cc chamber heads?  I love the way some manufacturers state their claims.

That is the best imformation on the heads I have ever seen. Does the 20 H.P gain indicate a stock engine with stock cam? This would be  a indicator for  the 40 with a later cam swap and headers?  

"That is the best imformation on the heads I have ever seen."

I disagree.  I think the information is very misleading.  To claim "x" amount of hp is a bunch of poppycock, unless you know what your baseline starting point is.  

I'd bet a week's salary that if those heads were dyno'd against a set of 1970 out-of-the-box 2.02" 64cc angle plug heads on a healthy small-block... they'd lose.  Conversely, they probably would post ~40hp gain over small-valve, open chamber smog heads.

Caveat Emptor.

When strapped to a dyno horse and with no other bottom end changes the Vortec head will put out an honest 60 more ponies over 70's style smogger heads and 40 more than the same engine with swirlports or L-98 heads. This has been tested and documented on many occasions from several sources including CHP magazine. Typical of Chevrolet horsepower claims for decades 20 to 40 horsepower is a low ball number. However, given these bigger numbers are SAE gross on a dyno horse, the GM numbers are probably closer to SAE net as installed in a real world vehicle.

The down side of Vortec heads is the need to buy an intake that will bolt to them, these are a bit pricey. If you're running a vehicle that needs to stay emission compliant, then you've got a problem with hooking up the EGR, this requires some parts from 96 up vortec engine consisting of the rightside exhaust manifold and a supply pipe. An additional problem for guys running these heads with a carb or TBI on the street is the lack of an exhaust heat crossover under the plenum. This results in poor fuel distribution till the thing gets well warmed up. The Vortec uses engine coolant to heat this area which is much less effective than exhaust heat. Since these heads were made for a port injection engine the lack of heat in this area wasn't a problem in that configuration. 

I would concurr with you that Vortecs run against similar pre-smog camel humps or power pack heads would probably not be that different.

Bogie

I know i'll get my a_s reamed for saying this,but I have used small chamber 305 heads which I had reworked and 1.94 & 1.50 valves put in them for years.I have heard all the bad crap about doing this and I'm sure they have their reasons for saying it.If you don't plan on racing this thing on a semi-daily basis this should be a low buck solution to your problem.These heads are still fairly plentiful at bone yards so you shouldn't have a big problem locating a good set.I'm assuming you are looking for a cheap fix and aren't interested in doing a complete rebuild(which I recommend).As with any small block question on here,you are going to get a lot of different opinions.My advice is to read them all and make your own choice.Lots of intelligent people on here,and I value their input highly.You have already made the best decision......to go with a chevy small block!!

                                              tndscrt

save time and money and go get a set of vortec's from your friendly g.m. dealer...

after you mill the heads u got + do um over (valve job ect) the vortec's and intake are the same money and are new!!! 

they where run against the bowtie race heads and won and the bowties are better than the 70's 202 angle head...

Do you believe that just because you read it, or do you have some other factual information?  Oh, silly me.  

ya i was in the dyno room and helped change the heads on the test engine we used..........................

i saw it with my own 2 eyes...

I've heard that because the vortec heads don't allow lift over .500" that they are only so-so on the street, and that to rework them for the higher lift makes them too expensive.

Is there any accuracy to this?

Over-the-counter "Bow Tie" heads are available with 18* degree valves.  They're even available with splayed valves.  On an all-out sbc, a pair of 1.94" Vortecs wouldn't stand a prayer against these.   

you said 70's heads....

the over the counter 70's bowtie heads are not 18 deg...heads