The heads are off, swap them or not..

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CultClassik

CultClassik

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As promised in the "1965 273" thread here's a new one from me, I know you've all been super excited about this. :blob:

Don't know a lot about the engine specs, but assume it's pretty much stock. Casting numbers make it and the heads a 68+ model.

Here's pics of the pertinent parts. Pistons look to be .030 over, Sealed Power or similar. I'm assuming that's a stock type piston?

pistono.jpg


Heads, also stock? You tell me.

headpfj.jpg


combchamber.jpg


I have the comp xe268 cam to go in here, and was going to have some mild milling and porting done on these heads (casting 2843675).

I can probably grab a set of 66-67 273 heads (yeah I just practically gave mine away not thinking I was going to be doing this work). So for the extra couple hundred bucks to have those done instead, 3 angle valve job since they'll need to be done anyway, and if I'm really feeling crazy maybe upgrade valves (perhaps use the intake valves from these heads and step up the exhaust valves?)....is it worth it? I mean if it will give me .5 to 1 point of compression, seems like the way to go assuming the ports flow pretty much the same? I don't want to go anad spend a thousand bucks on stupid bottom of the barrel heads, but I'm looking to get the best bang for my buck of course.

Input please :) thanks guys!
 
Swap heads??? Those are 2.02 valves, ain't-'em?

I'd guess those are high compression "Commando" pistons or better. What's the deck height?
 
67Dart273 said:
Swap heads??? Those are 2.02 valves, ain't-'em?

I'd guess those are high compression "Commando" pistons or better. What's the deck height?
Click to expand...

Always glad to get responses from you!

Actually I think the cutouts are misleading. The battery in my caliper seems to have died, but the intake valve measures about 1.75 across so I'm assuming they are stock 1.78 valves, unfortunately.

I'm going to check the compression hight. Just from eyeballing the carbon ring in the cylinder looks to be around 1/3 of an inch, possibly more. If these are the pistons I think they are, compression distance will be 1.720.
 
!!DOH!! When I looked at that photo, it looked to me as if what turns out to be the seat/ head underneath was part of the valve. Made it look larger
 
Now don't think I wasn't thinking "wow stupid me how could I not notice that, this is a nice bonus to find as opposed to huge dished pistons I usually find". I went back and looked at them and for a second I was all pumped...but, no. Haha!
 
Yeah I've read that at least the 1970+ 318's gave 8.5:1 compression WITH flat tops, awesome :) plus the Sealed Power ones look just like this in pics.

Does anybody have an opinion on those 66-67 273 heads? I was going to have the existing ones milled in hopes of gaining around a half point of compression.

If the 273 heads will flow the same, but give a half point on their own....hey I'll mill those and get around a full point, so at the very least I should be running approx 9.5:1 which I can live with in this engine!

I just need to make an informed decision, given that these heads really don't NEED any work - whereas if I use the 273 heads they will need a rebuild for sure, adding a couple hundred bucks to the cost of this little side project, and I'm sure that these will not be super easy to unload for decent money, so I'm not counting on them to help me re-coup expenses building another set of heads.
 
Remember if you run 273 heads you are limited on what intake that you can run. Bolt holes don't line up.
 
Well, not much input, but from what I gather the 273 heads flow as good if not better than these (and 302 heads), same valve sizes, and are closed chamber 57cc so I'm going for it. Luckily the guy I sold my 273 heads to is going to sell them back to me. I think this will be a nice setup. I'll report back in a few weeks once it's running again and hopefully I'll also have the carb tuned and have dyno numbers.
 
mplex2000 said:
Well, not much input, but from what I gather the 273 heads flow as good if not better than these (and 302 heads), same valve sizes, and are closed chamber 57cc so I'm going for it. Luckily the guy I sold my 273 heads to is going to sell them back to me. I think this will be a nice setup. I'll report back in a few weeks once it's running again and hopefully I'll also have the carb tuned and have dyno numbers.
Click to expand...

I would use the 675 heads for all out porting. If you just wanna utilize the closed chamber, u can get similar numbers with both heads. If you want to use 360 intakes 'more choices' then gasket match the heads toa 360 gasket.
 
All 273/318 1.78-1.5 heads flow about the same, enough for about 300-325hp.
 
Sweet, thanks man. And actually with milling I hope to be in the 9.5 to 10 range on compression. Mild porting, may do 1.60 exhaust valves and most likely a 3 angle.

If I could squeeze close to 300 at the wheels out of the mighty mighty teen I'd be tickled pink.
 
OOH is this a 318, those are 273 numbers I'll do ya 318
 
They flow close, but not the same. Closed chambers will hinder flow some... At least that's what I see on my flow bench.
Also there is a lot more casting inconsistancies with the older 273 castings 'core shift'
 
You might be able to run a J head , but i know you cannot run an X head , i tried it years ago , when i was about 18 .Found out after i run it the block has got to be notched for the large intake valve .The valve actually hits the block .But since the stock valve is 1.78 and the J is 1.80 prob work with the right head gasket. I would just get the original ones done.
 
kt340sport said:
You might be able to run a J head , but i know you cannot run an X head , i tried it years ago , when i was about 18 .Found out after i run it the block has got to be notched for the large intake valve .The valve actually hits the block .But since the stock valve is 1.78 and the J is 1.80 prob work with the right head gasket. I would just get the original ones done.
Click to expand...

You might be thinking of X heads on a 273 - they will work fine on a 318.

Either way, J or X heads were not being considered because they would result in even lower compression. This isn't going to be a 400hp engine (or let's be honest, probably not even 300). It's probably not going to see much more than 5000 RPM...I don't think it will need tons of flow. If I were building a 318 from scratch I'd use my X heads with a better set of pistons, but that isn't the case here.

The 273 closed chamber heads (which I picked up and the ports appear identical to the 318 heads I pulled off the engine) with a little port clean up and milling should probably do the trick!
 
I am swapping in a set 920s myself on my 273. Just got them and boy are the ports going to need a gasket match to match my intake.
 
The 273 heads have the smallest chambers (67cc I believe), should give you the highest compression, although the later heads flow better. The '66-67 273 "920" heads have the more desirable bolt angles giving you better intake manifold choices.
 
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