Trying a lil different combo on my 318 ...

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Franklin Crisp

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Hello, I'm just wondering how my 318 will run with a set of late 273 Heads (about 60cc) and a 340 cam, aluminum intake & 4bbl... dual exhaust in 69 Dart? Hopefully someone has tried this combo and loved it cuz I'm about to ... I know it's not big power but hopeful it will be respectfully powerful for a 318! Thanks y'all!!
 
Similar to the #302 casting heads but not sure about the "swirl" effect the 302 is supposed to have. Should better that 70's 318 heads. The 273 heads do not have hardened valve seats. Use a thin head gasket to boost compression even more.
 
Yes! I forgot to mention the thin head gaskets .029 I hear... I'd like to find some 302 casting heads but junk yard one's might be cracked and part stores are having a hard time finding me those.. sooo, since I had some 273 heads I went for the small chambers for the compression gains.. we'll see what happens..
 
Franklin Crisp said:
Hello, I'm just wondering how my 318 will run with a set of late 273 Heads (about 60cc) and a 340 cam, aluminum intake & 4bbl... dual exhaust in 69 Dart? Hopefully someone has tried this combo and loved it cuz I'm about to ... I know it's not big power but hopeful it will be respectfully powerful for a 318! Thanks y'all!!
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It will work. I'd put hardened seats in those heads for todays gas. Let us know the results :)
And welcome
 
Franklin Crisp said:
Hello, I'm just wondering how my 318 will run with a set of late 273 Heads (about 60cc) and a 340 cam, aluminum intake & 4bbl... dual exhaust in 69 Dart? Hopefully someone has tried this combo and loved it cuz I'm about to ... I know it's not big power but hopeful it will be respectfully powerful for a 318! Thanks y'all!!
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What number heads do you have?
 
when I spun my 273/4 con rod bearing, I dropped in a 318 short block. Same 65 heads, went with a Herbert stage 2 cam (CE2N 205/215 [email protected], 425/445, 112LC, 1000-5000 close to a 340 auto I suppose) and a performer intake, (wallowed out holes and everything). That motor kicked *** in that light car. So your 318 that thinks its a 340 in 273 dress may be just fine.
 
Like above^^^^ I think it will run just fine.Not Big Block power but a good runner. Mine is a 273, running a 441/441 216 @ .050 , performer intake,600 AFB. The photo was taken before TTI's and duals. Not a power house but a good runner. I am running 2.76 gears so it has allot of top end.

IMG_2602.jpg
 
2843675 is the casting.. I guess I'm gonna go on and do a valve job on these things & change springs to match cam...everything i read says stay around .450" lift with those small valves... im used to alot more racy stuff but maybe this lil engine will surprise me.... I'm gonna go with thinner head gasket to with hopes of 9.1 CR... to bad I can't find a dual point distributor somewhere..... lol....
 
Franklin Crisp said:
2843675 is the casting.. I guess I'm gonna go on and do a valve job on these things & change springs to match cam...everything i read says stay around .450" lift with those small valves... im used to alot more racy stuff but maybe this lil engine will surprise me.... I'm gonna go with thinner head gasket to with hopes of 9.1 CR... to bad I can't find a dual point distributor somewhere..... lol....
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Those are the later open chamber heads. With stock 2 barrel pistons and todays thinnest head gaskets you probably will end up wit around 8.5/1. The open chamber heads are the same heads used on the 68-71 318's. The #302 heads are closed chamber and will bump your compression a half point or so plus they flow better. 273 heads like the #920's (you want 1966 and up) are the same valve size as the 318 heads but are closed chamber.
 
I see.....Yea, I wish I had some of thoss 302s handy... im having those 273 heads shaved like 10/15 or so.. that will help the compression....maybe I'll have 8.75 to 1? Oh-well this slightly warmed over 318 is really just a quickly to get the car back on the road.... I have a 340 block I might do something with later on..... thanks for the tip!!
 
Franklin Crisp said:
2843675 is the casting.. I guess I'm gonna go on and do a valve job on these things & change springs to match cam...everything i read says stay around .450" lift with those small valves... im used to alot more racy stuff but maybe this lil engine will surprise me.... I'm gonna go with thinner head gasket to with hopes of 9.1 CR... to bad I can't find a dual point distributor somewhere..... lol....
Click to expand...

I have and accel dual point distributor if your are serious, I will sell it cheap, pm me.
 
Franklin Crisp said:
Hello, I'm just wondering how my 318 will run with a set of late 273 Heads (about 60cc) and a 340 cam, aluminum intake & 4bbl... dual exhaust in 69 Dart? Hopefully someone has tried this combo and loved it cuz I'm about to ... I know it's not big power but hopeful it will be respectfully powerful for a 318! Thanks y'all!!
Click to expand...
I just re-read your original post. Are you changing heads because of performance increase or is there something wrong with the stock heads?
 
toolmanmike said:
I just re-read your original post. Are you changing heads because of performance increase or is there something wrong with the stock heads?
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Well actually those stock 318 heads are junk... (long story) but I still have a decent fix-able set of 273 heads that came on this 69 Dart so i started reading that they're basically the same accept for like very low CC volume chambers like 60? Figure that will help a bit more with compression along with a thin head gasket... otherwise I would probley have just fixed up my old 318 heads....
 
The 675 head chambers are typically around 68 cc's like TMM said. Where some confusion comes in is with the NHRA MINIMUM chamber specs; that may be where the 60 cc number is coming in. And some of the closed chamber 273 heads were in the low 60 cc's range IIRC.

Your 675 heads are open chamber types and can be milled; each .005" reduces the chamber by 1 cc. So if you wanted to have 60 cc heads, then mill them .040". The intake or intake side of the head should also be milled to maintain intake matchup.

If you go to 60 cc chambers that way and use a .028" thick Mr Gasket 1121G head gasket, then you will be around 8.6.-8.7 for static CR IF you have the car 318 pistons. Measure as precisely as you can how far the pistons are down in the bore from deck height when a piston is at the very top of it's stroke. The car pistons are around .080" down in the hole and the lower compression truck pistons are oer .100" down in the hole. (I can't recall how much over .100"...seems like some are as much as .150" down on the hole.)

Bigger exhaust manifolds will help compliment everything else too too if you can swing that.

And just so you will know.... the typical published Mopar CR numbers always seem to be about 3/4 of a point higher than real standard production CR numbers, with very few exceptions.
 
Now my thing is selecting a Cam that will be respectful but not to big.. everything I find says .450" or so - not much more then that.. maybe a cheap Summit Cam? The reviews are good ... Gotta buy springs to... I'm leaning toward that ... anyway that's my deal so far...
 
Franklin Crisp said:
Now my thing is selecting a Cam that will be respectful but not to big.. everything I find says .450" or so - not much more then that.. maybe a cheap Summit Cam? The reviews are good ... Gotta buy springs to... I'm leaning toward that ... anyway that's my deal so far...
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Ok, I see.. well, maybe 450" cam is to big then if my heads aren't going to allow me much compression.... sounds like to much money to blow on 273 small valve heads anyways... I've got some 915 J heads that are in good shape but those also will kill my compression on a stock 318... like in the 7s.... wow. It's all a Hot Mess! Lol.... just want something like 9.5 CR without big problems or bunches of cash on aftermarket heads... sounds like 8 1/4 CR will be a struggle.... but it is what it is....
 
That 318 engine is out of a 1976 Van .... so your probley right pistons way down in the hole... last A body i built ended up with a 426 Wedge motor and that was fun and easy! Tryna to find a mild combo for this 318 is becoming very difficult... but I'm not going Big Block this time....
 
Don't over engineer things. A 318 with a small cam, 4 barrel intake and carb, 340 manifolds and nice exhaust will run very respectable with a stock torque converter. A bigger cam needs a higher stall converter and or taller rear gears. The 273's and 318's don't have the luxury of tons of low end torque unless left close to stock. The experts say cylinder head flow outperforms increased compression every time..
 
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