milling heads for comp ratio increase
If you have 675 heads, then count on around 68 cc's. Not 60 cc's; the NHRA minimum might be that, but the general factory chamber will be around 68 cc's.
Just know that the Mopar 'factory' CR's are general optimistic... and Chevvy El Camino's but they are gone from the market.
Thanks for post, I read it twice. I didn't like hearing about the 'optimistic CR numbers' Oh dear, more woe. Some of the things you talked about I have already mentioned previously but to save you trawling through the whole thread again I will briefly mention again: The bottom end is all done so I won't be doing anything more on that. I did briefly look at the Holden pistons but they wouldn't fit with these light, full floating rods I had lying around (resized, stress relieved, weight matched and fitted with ARP bolts). I checked the piston height in the bore as 66fs mentioned and they are level with the deck. It is essentially a "re-ringer" with a few extras. The condition when pulled apart was so amazingly clean and obviously low miles, that's why I chose this path of rehone and reusing the pistons (new 273 pistons are hard to get and Egge ones were too expensive for this exercise). Yes I knew that the 2.02 valves in the Edelbrocks were too large for this capacity engine. As for cam, I already had a small solid grind on the shelf not doing anything, around 0.47 lift, and since I wanted this 273 to be a mech cam engine (which a 67 engine should have been), it was perfect. Mopar M1 dual plane with a 1" spacer, small ports on the heads will be port matched to that (not much to remove really).
Yes I looked at getting intake surfaces milled and it is cheaper, $550 compared to about $950, but after reading people's posts here about that I thought it would be a good idea to not touch a brand new intake but rather get all the milling done on the heads. Then I can swap intakes and not worry about altering it and then having an intake that will only fit that engine. I didn't want to be spending $1000 or more on these very average 318 heads, when I can see that Edelbrock complete bolt on ones are only a bit more than that! I suppose in this instance the old 273 with its small capacity is a little limited in what can be done these days (esp down under where old chrysler stuff is often very hard to source - eg closed chamber heads!). Anyway, I have just bought some stainless exhaust valves (single groove) super cheap, they were on special A$60 delivered, set of 8. They are 1.6", so maybe I could decide to put them in , and no great loss if I decide not to. I read that the larger exhaust valve can improve low down torque (from a Mopar head porter) but will have to research that a little more
As 66fs said, I have everything I need for a nice street 273. I could always get the heads milled to the maximum of 10thou, then wouldn't need to worry about the intake, and if I used a 0.021 copper gasket, should bring the comp up a bit more.
66fs - as for using a windage tray, I did think about it but more cost and I already have new ARP main bolts to use. It is not necessary for how I will be driving it, as a normal car mostly - as nm9stheham mentions, it is 90% about the torque and drive-ability factor. However it has a nice DRTC fitted now.
