340X heads

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Hi. I have a set of 340x heads that I was thinking of putting on my 318, along with a 268 comp cam, tti headers and an edelbrock carb and intake will this combination work ok ,or should I go with a different set of heads?

thanks,Robbie
 
I think the X heads will be too much. Also different compression ratios...etc...Someone else will explain better!
 
You'll loose around 1 point in compression switching to the larger 340/360 heads. Your choices are, Rework the 318 heads, Find some 302 casting 318 heads and do them, Swap on some Magnum heads, or mill the X heads.

I think the Magnum heads are the best for bang for the buck.
 
find a set of 360 heads (the x heads might work im not sure) and get them plained down to get the compression down to where you need it! these heads will flow a lot better than 318 heads! with plained heads a nice cam, intake and headers that car will move!!!
 
You need to mill a good chunk of the heads to get compression up though. He would be better off starting with a Magnum head which all ready has a closed chamber to raise compression. Plus the ports are better.
 
farmer260 said:
find a set of 360 heads (the x heads might work im not sure) and get them plained down to get the compression down to where you need it! these heads will flow a lot better than 318 heads! with plained heads a nice cam, intake and headers that car will move!!!
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All 340-360 heads are very similar and theres near zero difference between a J and X head. Save the intake valve in some J's.

While farmer260 is correct in the 360 head flowing more, it is in how it's done and whatit is on that will prove to be a power maker or turd. I have to disagree here on a 340 - 360 head on a mild 318. The port volume is huge. This makes the air and fuel slow moving and un-vaporized, especially at low speed. You'll need some really high RPM to get the heads to work well for you. And it is not in the driving range of the cam, your choosing.

The 318 heads with some work done will provided a higher velocity air and fuel movment and a finer and more fully vaporized air and fuel charge for a better burn in the cylinder. This IS power!

For a on the cheap improvement, (340 - 360 heads) it is OK, but if you have a few bucks to spend, spend on upping the anti on the 318 head or do a Magnum head swap.
Like Adam said, the 318's "302" head should be sought out. But even some basic port work on a late 70's or 80's smog head will show a nice improvment.

(IMO go with a 1.88 intake valve. Stainless steel if you can. Like a Ferra )
 
Since no one seems to be able to read your post properly, I will give you my best shot. You stated you HAVE "X" heads, so we should assume you are not a millionaire, and want to use them. I did this swap on a '72 Barracuda, and had great results. We shaved the heads enough to clean them up,added a comp cam(Extreme Energy),some cheap headers,stock 340 intake,and that was it. I saw a huge improvement in the car through the whole range. To make this work better,you will have to spend some bucks on a deeper cut of the heads(for compression,as stated),a good bowl job, and opening up the intake side of the chamber, and cylinder to improve flow past the valve.
 
MtNemoMopar said:
Since no one seems to be able to read your post properly, I will give you my best shot.
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How do you figure no one read it correctly ? I knew he all ready had the X heads, I just think he would be better of going a different route. Which is exactly what he asked.


or should I go with a different set of heads?

thanks,Robbie
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He could also sell the X heads to some one that needs a set for there resto and flip the money in to something else.
 
Yep I would sell the Xs too, get the magnums you will be happier, better pedal feel on the street at low end. You compression will be good and you can get good money for the Xs, invest it in a cheaper set of heads and i think as Adam said that is a good way to go.

Yep the Xs will work too, but i think you will be ahead and happy with the smaller heads for a budget street car?

But it it is high power big bucks then stay on course and mill like about
.040 - .050 or so to get the compression back into the corrrect range.
 
I think only the 273s have the valve clearance problems but its something to check for sure.
 
273 have a problem with a 1.88 valve. A bore notch is needed and is described in the engines book.

MtNemoMopar;
I re-read my post and edited the post with the "In bold" letters posted here to clear things up.

For a on the cheap improvement, (340 - 360 heads) it is OK, but if you have a few bucks to spend, spend on upping the anti on the 318 head or do a Magnum head swap.
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I just want to also add I have also done what you have said and it was fine and just like you stated.
 
I also think he would be better off selling the x heads and use the money to get a closed chamber head that would be better matched to his combination.
 
Did someone mention 302 Heads???? I'm going to be selling these soon.
 
I put on a set of MP 360 high swirl heads with the 2.02 intakes. Muscle Motors told me it "should be OK but no sure bet. So far 700 miles and no problems.

I milled my heads .030 to 63cc chambers, my 1979 318 heads had 69cc chambers. My cranking compression went from 130 psi to 160 psi.

Motor seems to run better at all speeds, I am happy. Now those newer 360 heads have a bit smaller intake ports, not sure how the X heads would have been.
 
Another thing about running the X heads on a street car is the lack of hardened seats and unleaded gas. A later model head with hardened seats would be more practical.
 
I have milled j-heads on my 318. it runs pretty well. I did keep the ports stock, i should have just polished them up a little bit. But yes, without much mods the 318 can't move as much air as the 360 ports deliver at low speeds. Volume vs Velocity, however high end its pretty decent. I'd like to try some edelbrock magnum heads on my car before i run them on my 360, just to see.

I do have 3500stall, and 3.91 r&p to help with any 'lack in low end' :D
 
I do have 3500stall, and 3.91 r&p to help with any 'lack in low end'
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LOL @ Goody.
Thats the best way to get the 360 heads to work on a teen. It's not a bad deal. The car will go and be fun.
 
GoodysGotaCuda said:
I have milled j-heads on my 318. it runs pretty well. I did keep the ports stock, i should have just polished them up a little bit. But yes, without much mods the 318 can't move as much air as the 360 ports deliver at low speeds. Volume vs Velocity, however high end its pretty decent. I'd like to try some edelbrock magnum heads on my car before i run them on my 360, just to see.

I do have 3500stall, and 3.91 r&p to help with any 'lack in low end' :D
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AdamR said:
Goody, arent your heads milled also ?
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Yes. =P~
 
I hear ya brother. My 318 was also running that time in my '73 Cuda 4spd. years back. I see your video has great footage of what exactly stress relief is all about.
 
I have milled 360 heads on my 318, 1.88/1.60. They are also ported. My dart runs a 1.78 60ft, but I have a 3500 stall with 4.10 gears.
 
I've got a set of 360 heads that have been cleaned up and would rather have a set of X heads for my 340. maybe you would be interested in a swap?
 
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