[beachbum0]

I know it's been asked a millon times, but I cant find the same,almost but not the same markins of my heads. See a picture of on 305.

 

[cobalt327]

I know it's been asked a millon times, but I cant find the same,almost but not the same markins of my heads. See a picture of on 305.

First- I am not any sort of authority on 305 heads! But according to what I have seen that is very similar if not the same as c/n 416, 434 and 450 heads w/the possible exception of a vertical line that is shown in some renderings of the 416 head.

In any event, there can be slight variations to the end casting identifiers depending on the foundry molds that were used. If you are wanting to know the exact head application or ID, use the casting number under the valve cover.

 

[beachbum0]

Looked them up and thay are 305 1.72/1.50 60 cc 1975 to 80 I also have 305 172//1.50 but hte chaber size is 58 Was wondering ,[want better fuel miles per gallon], if the little smaller chamber, higher comp. would hurt if any?

 

[cobalt327]

Looked them up and thay are 305 1.72/1.50 60 cc 1975 to 80 I also have 305 172//1.50 but hte chaber size is 58 Was wondering ,[want better fuel miles per gallon], if the little smaller chamber, higher comp. would hurt if any?

The intake valve size of these heads- depending on the exact casting number and what they came on originally) can be 1.84". This is a fairly common size on the 416 heads, or so I'm told. So you need to actually measure the intake valve head to be sure of what you have. If this is for a stock engine in a daily driver, this really doesn't matter.

As far as any increase/decrease in performance or economy due to a change in chamber volume, the small amount between a 58cc and 60cc head will not materially affect the way the engine runs or its economy.

That said, these heads, and ANY heads that you may want to use, should ideally be measured for their chamber volumes to be sure they both match each other, and that the chambers weren't milled excessively smaller before you got them. The reason for this is because excessive milling can cause the chambers to be too small- resulting in a too high compression ratio (if you have a stock engine w/dished pistons this won't likely be a problem), excessive milling can cause the decks to become too thin (thin decks can cause reliability issues), and excessive milling can cause fitment issues between the intake manifold and cylinder head ports as well as possible valve train geometry problems (may require new pushrods to correct).

But generally speaking, there's little reason to believe that you couldn't use either set of heads that you've mentioned here today and get the same results. Of course this depends on the condition of the heads themselves. And the condition is way more important for a stock engine than the chamber volume (58 cc vs. 60 cc), and is even more important than valve size.

I would suggest you take them to a machine shop that does cylinder heads on a regular basis and have them checked for valve guide condition, valve sealing, and deck flatness. Then have the 'best' set checked for cracks. This will cost a little more than just buying a set of gaskets and bolting them on, but could save you more than that in the long run.

Good luck.

 

[beachbum0]

I was kinda thinking about geometry issues and overmilling but im not into the math of it all, and you cleared it up for me . I have never cc,d heads, always had heads sent out.Thanks

 

[cobalt327]

http://www.hotrodders.com/forum/ccing-cylinder-heads-171846.html is one of several threads on CC'ing heads at home. You can do a search for others. It's not hard or expensive to do. It'll take a few tries before you get repeatable results but after that it's a breeze!

 

[cobalt327]

I doubt seriously the valve train geometry will need any attention but here is a short page on the subject if you want to take a look at it.

 

[techinspector1]

http://www.hotrodders.com/forum/ccing-cylinder-heads-171846.html is one of several threads on CC'ing heads at home. You can do a search for others. It's not hard or expensive to do. It'll take a few tries before you get repeatable results but after that it's a breeze!

In my opinion, a burette, stand, sealing plate and a jar of Vaseline should be the first tools a fellow buys for himself when he takes on an engine rebuild. You can't figure anything intelligently until you know the exact chamber volumes. Plus the fact that you can cc heads for others and make back the cost of the tools. Cool. :welcome: