318 with big valved or 340/360 heads

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rosco426

rosco426

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The more I'm reading and learning on here (which is a lot) I'm getting the understanding that using 340/360 heads or any heads with 2.02/1.6 valves is too much for a 318.

Now I'm already planning on putting a set of LA-X heads with 2.02/1.6 onto a 318 (was originally building a 360) I will hopefully start building shortly. I have got the KB flat tops will help bring the comp up a bit but would people prefer to use something else or stick with these heads. Keeping in mind it isn't as easy to find parts down here in Australia.

At the same time, I'm planning on doing a quick rebuild on a 318 in my wagon and may have stumbled on a short motor and heads ported out and ready for big valves (2.02/1.6). I'm just planning a mild build with around 1HP per C.I. Long term I would love to bolt a turbo on to the side but probably a year or two away at best. What would you guys suggest I do here, use the heads with big valves or just get a set of 318 heads I have ported and go smaller valves?

Appreciate any help and advice.
 
If you can get those flat tops up close to a zero deck, and use the thinnest headgaskets, it wont be too bad. But the big thing is to be conservative with the intake closing point. You can get the StaticCR up to 8.5 or so, but to keep the DynamicCR up takes an early closing intake. I should think in this case the 1.88 valves would be sufficient.But if you already have the 2.02s, no biggie. If you go too big on the cam, the bottom end gets sluggish.Gears and a higher stall TC can get you through that. But if youre running a stickshift, its a PITA, cause you always have to slip the clutch so much to get moving.The soft Dcr also makes sub-2000rpm soft, so you will be spending more time in the lower gears, which gets somewhat tiresome.Best is then to go automatic, and a slightly higher stall TC.
Or get a custom cam ground with an early closing intake but a bunch of lift. That would probably require a fair bit of valvespring to keep the parts together, so the rpm might have to be limited.
Its always easier to get the Dcr up on a teener with a smaller chambered head.
With a teener and flat-tops,it seems a guy is forever making sacrifices.
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Rosco, its not the big valves so much that are a problem, but rather its the big chambers that come along with those valves.
A .030over teener has a swept volume of 661CC. Pistons down in the hole.067 are 13.4CC. The gasket @.039 is 8.5CC.Eyebrows in the pistons are about 5CC.So thats 26.9CC so far. Add 70CC for the big chambers and doing the math thats a Static C/R of 7.7. And thats were a sluggish bottom end lives.
Now with a teener head of 60CC, the math comes to 8.6 now we are getting somewhere.
But if you machine the decks to get zero decks, that throws those 13.4CC away, so now the small heads make 9.86, and the big heads still make 8.9. With these higher Scr numbers a larger than stock cam can be introduced and the Dynamic C/R doesnt fall into the basement quite so fast. Its the low Dcr that makes for a sluggish off-idle response. The Scr is merely the target to build to, to get the Dcr you need.
Machining the decks leads to fitment issues.
As for me I would spend the money on a custom set of pistons instead. I would get pop-ups and fit them to the big chambers/big valves that you already have, and try and build a tight quench into there.Then you can target more serious compression and snappy bottom end response would be the result of that. And how much time in your driving experience is spent getting off the line? And how many of us dont love frying the tyres? Yup,we are kindofaddicted.
Just so I dont mislead you, a high Dcr is not mandatory.It seems guys have had good success with Dcrs as low as 8/1, and occasionaly less.I myself am running just under 9/1 DCr. 9 is snappy. 7 is soft. In between you have to pay close attention to the intake closing point.
So again, run what you brung. If most of your driving is sub 4000rpm, run the teener stuff including the cam. If you want to foray into 6000regularly, the X heads can make good power up there. Between 4000 and 5000 could be either, and it really amounts to how much softness you are willing to suffer. But then, if you dont like the big-chamber softness, you can always slam the teener heads back on. (I have successfully reused the .039 blue Felpros a couple of times, and the intakes as well.)
 
I always put in larger valves. It makes little sense to me not to. But - for a 318 port - I think the 2.02 intake is too large. You should be able to locate 1.88 intake valves in stock form that you can have a back cut put on, or pony up for a more performance oriented stainless deal. Depending on the shop, if they are capable of doing 5 angle cutter valve jobs - have that done. Then just gasket match the entries to the larger 340/360 size so you can run a decent intake. It's not perfect, but it will work.
 
Ok I hear this to big a valve thing all the time or your port is to large torque will suffer. Yes and no. The 327 had 2.02 valves and was known as HIGH RPM engine but actually had decent torque the 340 good torque and a HIGH RPM engine. The new Chevy ls series of engines the new HEMI the new FORD coyote all have good torque and are all REVY if you will..
These latest examples all have great cfm and port velocities. Plus other gadgetry to increase torque.
A 2.02 will not kill torque IF THE CORRECT CAM IS SELECTED. Meaning smaller than you would have selected with a restricted head/valve combination. I built a 340 with stock 1.88 heads and a 484 purple cam it was doggy and rpm limited springs were speced correctly. I swapped to stock non ported non machined Eddie head for 340s. It picked up torque and rpm,air flow is good and with port velocity its better yet.
Our family truck, or black sheep as it's called, has a 360 stock heads had 1.88 valves. We built another set of heads same cam 2.02 valves more torque and more Rpm and changed to a smaller cam when a lobe started to go flat. More torque down low and still revved to 6000+.
What I'm saying is with a big valve small displacement engine their is less room for error with your cam selection to get a great combination of torque and horse power OR really RPM.
 
I perhaps misunderstood - but I though the OP was talking about using 318 heads. A 2.02 valve in a 318 sized port is a waste of effort. In a 340/360 head, I agree 100%, and my ported 340/360 heads get 2.05s.
 
rosco426 said:
The more I'm reading and learning on here (which is a lot) I'm getting the understanding that using 340/360 heads or any heads with 2.02/1.6 valves is too much for a 318.
Click to expand...

I don't know who told you that, but i would suggest that they are mistaken.

I run 2.02/1.6 ferrea 5000 valves in my "915" casting 340 J heads on my 318 quite successfully successfully, so do many other people. (a 340 is only 7% more displacement than a 318 )

The main thing to be sure of is that you get adequate compression for your combination, through the use of aftermarket pistons and/or machining of the deck/heads.
 
Hi,

so if it were me, i would choose the RHS Heads with the standard 1,92 'Valves or the 1.88.
For me the 2.02 Valves makes no sense, only if you want to rev. the Engine 80% above 5000Rpm.
The difference between 1.92 ro 2.02 is not really noticable. Maybe on a Dyno and above 5500 Rpm.

I build a 416 with the RHS Heads. First time with the big valves and a 268° Lunati cam.
It was really great.
After i changed to new RHS Heads with the smaller 1.92 Valves with the same rest of the setup,
the Engine awakes alot earlyer in RPM and pulled very strong up to 6500.
So you will have noticable more torque in lower RPMs.
My Dart was a manual transmission Car.

So my decision would be defnatly the 1.92 or 1.88
The bigger valves are not worth the money imo.

At least you sayd you don´t want to build a race engine!
 
There's nothing at all wrong with 340/360 heads on a 318, and if you want to make much more than 300 HP they're a great place to start.

340/360 heads have a larger combustion chamber volume than 318 heads which will reduce compression ratio. BUT combustion chamber volume can be reduced by skimming the heads.

Larger valves will have the effect of increasing low lift flow. Too much low lift flow is a bit like too much oral sex, a nice problem to have.

Increasing low lift flow will give you more "area under the curve" which will behave like a larger cam. Consider valve size when choosing intake duration. Better to select a cam for your heads rather than heads for your cam.

There are practical limits to the size of valve that can be installed in a particular cylinder head beyond what will physically fit. Think of the valve as the door at the end of a corridor. At some point the door is as big as the corridor and making it larger is of no benefit. With 318 heads, 1.88 (360 size) intake valves are about this point. Will 2.02 valves fit? Yes. Will the engine make more power? Probably not, so don't pay extra. 340/360 heads have a larger port (corridor) so a larger valve can be be fitted. In this case a 2.02 will be better than a 1.88. Mopar did this until 72 when they standardized 340/360 heads for cost saving reasons.

Another thing to consider when putting large valves in a 318 is shrouding. Here it's like putting a wall right next to the doorway. A larger door isn't as effective because the wall is there. So while putting 2.02 valves in 340/360 heads will be an improvement, some of that improvement is lost to the smaller bore of the 318. Will 2.02 valves fit? Yes. Will the engine make more power? Maybe, but the increase will not be as much as putting the larger valves in a 340 or 360. Don't pay much extra.

All talk of improvements by fitting larger valves assumes the bowl is opened and blended to match the larger valve diameter. Such as a 70 degree bottom cut and hand blending.

It sounds like you plan to build a fairly mild street 318. The LA-X heads will certainly get you where you want to be, but so will a set of 340/360 heads (318 heads with larger valves will work also). Consider your budget and future plans. I don't know what parts cost down under, but a set of 360 heads milled to increase compression would be the least expensive alternative up here.
 
While I didn't build my engine this way, this is the combination the previous owner just completed on my 69 Dart before I took it off of his hands. My car has the original 318 bottom end, but it has forged, flat top pistons installed. It also has 2.02 heads off of a 360. The car also has a mild purple cam (I believe .474). The heads have been shaved to increase compression. Currently, the car runs close to 10:1 compression. It is clearly a car built to run on the top end, but it still has more than enough bottom end to get up and go. I plan to remedy the bottom end problem by removing the stock rear end gear that the car still has on board. I guess my point is you can still do some good things with big valves in a 318, so long as it is done right.
 
Thanks for all the advice guys, lots to read and understand!

The 318 I'm building for the car over here <--- will be with the LA-X heads and 2.02/1.6 valves since I've had them for a few years sitting in boxes waiting. They will have the KB167 flat tops and will deck the block. I'm hoping I can get the comp up to around 10:1 from what I understand can happen, but will just need more money spent on machining. I'm going to use the XE268 comp cams with 1.6 rockers so I hope I haven't gone for too much with this stick.

For the other 318 it sounds like I'll do a basic rebuild with a mild cam (Mancini B rebuild kit, Sealed Power flat tops and a XE262 cam) or plan the motor out with the intention of running a turbo on it which I could possibly do anyway with the basic rebuild I just mentioned but that is probably a topic for a new thread.

Thanks again guys and sorry for what may be some dumb questions, I'm not the most mechanically minded guy in the world.
 
I've run 2.02" intake valves on 318's before with 340/360 heads, they will run better with just the head swap alone...

However, if you just put the larger port heads on, it will lower your compression some. If you put in 10.5 compression pistons, then with the 340/360 heads, it will bring it down to a nice 9.2 compression so you can even run on cheap pump gas...

the larger port heads will increase horsepower over the stock 318 heads...
 
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