Stock Cylinder Heads

March 11, 2003

How much does a decent pair of used stock 350 cylinder heads go for? I think it would be cool to try my hand at porting and installing cylinder head goodies on them and seeing the results first hand. Would it be worth the money?

Z-TARD · March 11, 2003

Depends on where you get them. I'd start by looking around at swap meets if you can. Refinished heads can be found reasonably cheap if you look around long enough. You could also search the local junkyards for factory high performance heads. Most high performance heads can be identified by a casting mark on the front and rear of the head that looks like two humps, like on the lower right side of the head below:

Once you have the head removed, be sure to check that it is a large valve head (2.02" intake, 1.6" exhaust) Small valve heads will have 1.94" or 1.7"intake and 1.5" exhaust valves. The valves will almost appear to be touching each other on the large valve variants:

Once the valve covers are off you will be able to read the casting number on the head. There are several different castings that came with the large valves, including:3990462, 3917291, 3927186 (shown in above pic), and 3991492. There are other castings that came with large valves as well. The best way to research this would be to find a small block chevy interchange manual, either at a bookstore or at http://www.motorbooks.com. I hope this helps you out.

Mike

Mike C · March 11, 2003

Figure on spending at LEAST $150 for a good set of small chamber heads with accessory holes. A better book IMO is Vizrads "How to build and modify SBC Cylinder heads" The 461, 462, 290, 291, 040 heads all are WITHOUT accessory bolt holes, which might be important. Stay away from any open chamber heads, even if they do have big 2.02/1.6 valves.

The 186, 492, and 370 castings are all double humps. The 041 has a triangle but is the same basic large runner small chamber head. All of these have the holes.

The 292 head was an over the counter called the turbo head. Pretty good head, but not as good as the newer aftermarket heads.

Best bang for the buck, assuming your old heads will need vatting, valves, guides, surfacing, etc. is to just buy some L31 Vortec heads brand new. Have them modded for better springs/more lift and read Vizards advice on porting these castings. Stock they outflow any of the 60's hi-perf castings, even with big valves.

March 13, 2003

Awesome post Z-Tard, great information.... I stand informed.

March 13, 2003

Hey Scarab...what part of portland you from? I'm from south east.

March 13, 2003

Hey Radtad, I am in Tualatin actually, its about 10 min south

on I-5.

So what kinda hybrid are you playing with? I got a 260Z here,

350, Th350, R200(3.90) its fun when its in one piece

Dan

March 13, 2003

Yeah I drive thru Tualitin on my way home, also visit that once place right next to the Interstate by wendy's . I go to school down in Ashland. I actually have a stock 280z but its future is still uncertain. I'm probably going to get rid of it and save up for a 240z and swap something in. I was under serious pressure to buy it,got my friend to drive me out to see it and it wasn't till after about 3 hours into our trip did he tell me that he missed a final to drive me out there so I felt BAD to say the least. The guy that sold it to me lied out his ass about it. Plus it was really dark when we finaly got there so I was unable to see everything that was wrong with it. Eh it was a learning experience.

March 13, 2003

What year is it? How many miles etc..? does it suffer from serious rustation? Oh yeah, I eat at wendy's all the

time hehehh lol

My brother has a 280Z which is in pretty good shape, if I had

a stock 280 I would run a big turbo with and big juice until I blew it and went V8 conversion

How often do you drive through Tualatin? you should stop

over, we could bs about z's, and u could check out my 260

hybrid

email me

Dan

dannadeau2112@hotmail.com

March 13, 2003

Cool, sent u an email.

grumpyvette · March 14, 2003

http://www.angelfire.com/tx5/randysresume/Headguide.html

http://www.nastyz28.com/sbchevy/sbch.html

http://www.topher.net/~bearman/gmheadcomp.html

heres my quick check list I use when pocket porting, It may help, its sure not everything but it will get you started

(1) open throat to 85%-90% of valve size

(2)cut a 4 angle seat with 45 degree angle .065-.075 wide where the valve seats and about .100 at 60 degrees below and a .030 wide 30 degree cut above and a 20 degree cut above that rolled and blended into the combustion chamber

(3)blend the spark plug boss slightly and lay back the combustion chamber walls near the valves

(4)narrow but dont shorten the valve guide

(5) open and straiten and blend the upper two port corner edges along the port roof

(6) gasket match to/with intake and raise the port roof slightly

(7) back cut valves at 30 degrees

(8) polish valve face and round outer edges slightly

(9)polish combustion chamber surface and blend edges slightly

(10) remove and smooth away all casting flash , keep the floor of the port slightly rough but the roof and walls smoothed but not polished.

(11) use a head gasket to see the max you can open the combustion chamber walls

(12) blend but don,t grind away the short side radias

take the time to read this

http://www.chevyhiperformance.com/techarticles/95518/