Here's a stock 273-4 for comparison. Testing the Mopar 273 Power Pak on the Dyno
Rebuilding a 65 273..I need some help.
- Thread starter jdhasa65cuda
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What is the number on the intake runner on your first photo? The runner on the left? Just the last 3 digits are all we need if it's the casting number.
I don't see any letters cast into the heads between the spark plugs. That's where the 340/360 heads cast their X,J,U or the like. But even those require the casting number so you know what you have and you still don't know until you look incase they have been modified.
I'll have to take a cover off and look when the car gets back. Right now it's at the shop getting a whole new suspension.
Looks like 920 casting # . Definitely mechanical rocker gear.
Is there a preferred casting number?
920 is correct for 1967
#315 and #080 are both 64 and 65 273 heads. Both are closed chamber with 1.78/1.50 valves.
#178 and #234 are 66 heads. Both are closed chamber with 1.78/1.50 valves.
#920 are 66 and 67 heads. They are closed chamber with 1.78/1.50 valves.
#675 are 68-69 273 and and 68-74 318 heads. They are open chamber with 1.78/1.50 valves.
#178 and #234 are 66 heads. Both are closed chamber with 1.78/1.50 valves.
#920 are 66 and 67 heads. They are closed chamber with 1.78/1.50 valves.
#675 are 68-69 273 and and 68-74 318 heads. They are open chamber with 1.78/1.50 valves.
You have them. They will flow close to a 360 head at lower lift to about .450" with what you were going to do. Not J or X heads though. I think Mopar Official posted porting and flows on a set of 920's?
I think so. I should have bookmarked that post.
Thanks, I did have that bookmarked but not in my favorites. Time consuming to find as I have 27 pages of bookmarks and many are favorites. Wish they could be arranged alphabetically or had a search function there.
Wow!
Very good info. It seems the heads I have are good ones. But would I not be better served just buying a set of 302 castings and prepping them and just doing a head swap? they already have the hardened seats. Are they La heads or magnum heads?
302's are prone to cracking and don't have much if any benefit over the 920's. 302's are LA heads.
Sorry I am stepping on 66fs with my answers.
302's are LA, but you need them ported by someone who knows what they are doing to reach those big numbers. That is why the 273 racers run 1.84 intake valves in early 273 heads. Don't worry about hard exhaust seats, I just run stainless steel exhaust valves instead.
Never a problem, I am slow and usually down in the basement working by now.
I'm not fast any more. I am half assed though.
1.6" ext valves or?
Let's get back to what you are trying to achieve here. Just a little more power? Might as well stay where you are with all the bolt on's you have already. A slight cam change won't get you much more and at what cost? The next step up with a size-ably bigger cam that will make a difference will require higher compression and more cylinder head. Now, You are already at +.060 over right? Unless you are able to kist scuff hone the block and replace the pistons for some high compression ones you are on a sinking ship. You are already maxed out. Oh you could have the block sonic checked and bored again with custom built pistons. $$$$ Or you could have the block sleeved to bring it back to standard. (also $$) See where I am going here? You can put in a slightly bigger cam (like I mentioned, don't go too big) and be happy with the performance. Simply put, you are at the point, unless you go all out, nothing you do is going to make a lot of difference from where you are now. That's my take.
I think for now I'm going to add a small cam and the valve springs to match. This engine is only for this summer. I am building a 340 into a 426 but it won't be done for another year plus I need to get my sub frame connectors installed first. I plan on driving this car daily and through at least a dozen States this summer.
That sounds like a plan. I was where you are now many times with my 273. I finally decided to just rebuild it to close to stock specs and enjoy the ride. It doesn't burn tires for a city block but I am too old for that anyway. It is pretty peppy and get's almost 20mpg on the highway. I have driven it north to Minneapolis numerous times and it has been a good one. I see so many here that overbuild and then don't enjoy the ride anymore. I have friends that have built pretty stout hot rods and they don't drive them much more than 20 miles away from home unless it's in a enclosed trailer. Sorry, not me. Not how I roll.
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