Cylinder head decision for 318
- Thread starter C2ndLTpigeon
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PRH
Well-Known Member
Personally, I wouldn’t spend the money on putting “big” cylinder heads on a low CR 318.
Have the current stock heads refurbished, mild bowl and pinch work, upgrade the spring/seal package...... install a suitable cam..... and run it.
Use the $$$ that was going to be spent buying the “big” heads towards buying a suitable 360 core instead....... for when you actually want to make some power.
Have the current stock heads refurbished, mild bowl and pinch work, upgrade the spring/seal package...... install a suitable cam..... and run it.
Use the $$$ that was going to be spent buying the “big” heads towards buying a suitable 360 core instead....... for when you actually want to make some power.
Look for a pair of 920's. Close to the 302's but no cracking issues that I have heard of. Smaller ports (273-318) and small closed chamber.
The guy is trying to build hp last thing I'd put on is any 273/318 head, Could go with magnum but they crack too but at least they make power, He's willing to spend money on decent head don't get why not do that.
You either take a small chambered head for compression and port it to get the flow you need or you buy a small chambered aluminum head to get there. I get a charge out of the guys with a stock short block, pistons .060 in the hole and put a set of large open chamber 360 heads (for the flow) and throw in a big duration cam. The static compression is in the high 7's at best. Not the best combination
PRH
Well-Known Member
I understand the “buying bigger heads for use down the road” argument.
The problem is, it often ends up just not working out very well on the “temporary” motor.
It can easily be a step backwards, or if you’re lucky, it’s only an expensive lateral move.
So, as the “first step”....... it ends up as a lousy bang for the buck move.
If the stock heads/cam for stock heads is properly executed, then it takes away some of the urgency to get the next motor finished up....... which might allow you to make a few “upgrades” in the process.
The problem is, it often ends up just not working out very well on the “temporary” motor.
It can easily be a step backwards, or if you’re lucky, it’s only an expensive lateral move.
So, as the “first step”....... it ends up as a lousy bang for the buck move.
If the stock heads/cam for stock heads is properly executed, then it takes away some of the urgency to get the next motor finished up....... which might allow you to make a few “upgrades” in the process.
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Been in a few cars/trucks with low cr 318 short block with 360 and even fully ported 340 TA heads large cam etc.. none were dogs.
My cousin even had to run a low cr 318 short block in his late model stock car cause his 340 spun a bearing and had no problem keeping up with the fast pack just didn't the extra to pull ahead.
My cousin even had to run a low cr 318 short block in his late model stock car cause his 340 spun a bearing and had no problem keeping up with the fast pack just didn't the extra to pull ahead.
PRH
Well-Known Member
Stock heads are what.....130ish cc?
Those are 179cc.
Stock 340/360 under 160cc.
I doubt that’s going to do much to enhance to low speed performance of a mild low cr 318.
But......I’ll tell you right up front.
I’ve never done it (because I don’t believe it’s the right way to go about it).
So...... if the OP goes for it...... maybe I’ll learn something from his taking that course of action.
The other thing is..... are those LAX heads available again?
Not that long ago, they weren’t.
Those are 179cc.
Stock 340/360 under 160cc.
I doubt that’s going to do much to enhance to low speed performance of a mild low cr 318.
But......I’ll tell you right up front.
I’ve never done it (because I don’t believe it’s the right way to go about it).
So...... if the OP goes for it...... maybe I’ll learn something from his taking that course of action.
The other thing is..... are those LAX heads available again?
Not that long ago, they weren’t.
PRH
Well-Known Member
I have plenty of experience putting 360 heads on 318’s....... for race cars.
I had them making hp numbers in the 380 range with unported heads and stock iron 360-2bbl intake manifolds.
I’m just not sure I’d take the same approach with a low CR 318 in a DD type application with mild rear gearing and a low-ish stall speed converter.
However, I’m happy to observe the OP take a different path than I would.
But, I wouldn’t put Indy 440-1’s on a low CR 383/400/440 with a small cam either, even if they were a great choice for a 12.1 512 I planned on building at some point in the future........ for the same reasons.
I had them making hp numbers in the 380 range with unported heads and stock iron 360-2bbl intake manifolds.
I’m just not sure I’d take the same approach with a low CR 318 in a DD type application with mild rear gearing and a low-ish stall speed converter.
However, I’m happy to observe the OP take a different path than I would.
But, I wouldn’t put Indy 440-1’s on a low CR 383/400/440 with a small cam either, even if they were a great choice for a 12.1 512 I planned on building at some point in the future........ for the same reasons.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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More 2cents
In my younger years I did put the bigport heads and 340 cam into a LOW-CR 318..... twice;once for another guy and once for me. and both were DOGS below 3000, going to less doggy with rpm, but sortof ok as the rpm finally woke up.
I have refused to do it ever afterward.
In my cases
the bottom got so soft, the stock TC stall dropped several hundred rpm, and 2.94s were impossibly slow until 42 mph in first gear/70 in second. I got me a 2800 to get off the line, but it did not much for the slow acceleration. That took 3.91s to liven up.
And here's how that combo looks@930ft elevation;
Static compression ratio of 8:1.
Effective stroke is 2.57 inches.
Your dynamic compression ratio is 6.43:1 .
Your dynamic cranking pressure is 117.59 PSI.
V/P (Volume to Pressure Index) is 87
VP of 87!!!!
You know what else has a VP of 87? I'll tell you, here's a stock 1969 - 225cuber
Static compression ratio of 8.4:1.
Effective stroke is 3.62 inches.
Your dynamic compression ratio is 7.49:1 .
Your dynamic cranking pressure is 145.00 PSI.
V/P (Volume to Pressure Index) is 86
Surely one of you have floored one of those a time or two...
In any case, 86VP sucks!, with a 1700TC and 2.94s. On the street, it took a 2800 and 3.23s just for me to stop laughing at how impossibly weak the bottom end was. And 3.91s only made it a lil more bearable, bringing the power onset to 32mph in first gear.
I did not keep that combo very long.
I returned it to stock and put in in the corner for another day, then sold the X-heads.
Everybody over the age of 60 must have done this at least once in their lifetimes,lol. I did it twice. I guess I was a slow learner.......
that was my experience.
I also, one time, put the entire 318 top-end and cam, into/onto a 340, making it a high compression big-bore 318, which I then dropped into a 65 Valiant wagon. Down South those are called Darts I think.
I installed fenderwell headers and dual 2 inch pipes with Thrush shorty straight thrus ( hey that was ~mid 70s and I mightabeen 25ish)./ Yes I left the 1969 2bbl on it. I used the 273 adjustable gear on the solid barbell lifters, on the 318 cam.
That was a funtastic lil screamer. I don't remember what gears were in the wagon, but the "posi" didn't last long . Nor did the 273-904lol. Actually the 7.25 outlasted the trans by a good bit. After the trans fried, I gave the car to my little brother, together with a spare slanty I had. The deal was I got the 340/904 back. And I did. He drove that poor lil car for a few years afterwards, on the same 7.25,lol..
more anecdotal pennies.
As a streeter;
I'll take the screaming hi-compression lo-po 340, over a lo-compression, big-cam, I don't care what heads, 318, any time.
In my younger years I did put the bigport heads and 340 cam into a LOW-CR 318..... twice;once for another guy and once for me. and both were DOGS below 3000, going to less doggy with rpm, but sortof ok as the rpm finally woke up.
I have refused to do it ever afterward.
In my cases
the bottom got so soft, the stock TC stall dropped several hundred rpm, and 2.94s were impossibly slow until 42 mph in first gear/70 in second. I got me a 2800 to get off the line, but it did not much for the slow acceleration. That took 3.91s to liven up.
And here's how that combo looks@930ft elevation;
Static compression ratio of 8:1.
Effective stroke is 2.57 inches.
Your dynamic compression ratio is 6.43:1 .
Your dynamic cranking pressure is 117.59 PSI.
V/P (Volume to Pressure Index) is 87
VP of 87!!!!
You know what else has a VP of 87? I'll tell you, here's a stock 1969 - 225cuber
Static compression ratio of 8.4:1.
Effective stroke is 3.62 inches.
Your dynamic compression ratio is 7.49:1 .
Your dynamic cranking pressure is 145.00 PSI.
V/P (Volume to Pressure Index) is 86
Surely one of you have floored one of those a time or two...
In any case, 86VP sucks!, with a 1700TC and 2.94s. On the street, it took a 2800 and 3.23s just for me to stop laughing at how impossibly weak the bottom end was. And 3.91s only made it a lil more bearable, bringing the power onset to 32mph in first gear.
I did not keep that combo very long.
I returned it to stock and put in in the corner for another day, then sold the X-heads.
Everybody over the age of 60 must have done this at least once in their lifetimes,lol. I did it twice. I guess I was a slow learner.......
that was my experience.
I also, one time, put the entire 318 top-end and cam, into/onto a 340, making it a high compression big-bore 318, which I then dropped into a 65 Valiant wagon. Down South those are called Darts I think.
I installed fenderwell headers and dual 2 inch pipes with Thrush shorty straight thrus ( hey that was ~mid 70s and I mightabeen 25ish)./ Yes I left the 1969 2bbl on it. I used the 273 adjustable gear on the solid barbell lifters, on the 318 cam.
That was a funtastic lil screamer. I don't remember what gears were in the wagon, but the "posi" didn't last long . Nor did the 273-904lol. Actually the 7.25 outlasted the trans by a good bit. After the trans fried, I gave the car to my little brother, together with a spare slanty I had. The deal was I got the 340/904 back. And I did. He drove that poor lil car for a few years afterwards, on the same 7.25,lol..
more anecdotal pennies.
As a streeter;
I'll take the screaming hi-compression lo-po 340, over a lo-compression, big-cam, I don't care what heads, 318, any time.
mygasser
Well-Known Member
I had 360 J heads on a stock rebuilt 318 with the slugs down in the hole and it was a DOG! Made good torque, but it was a dog. Put a set of stock 318 heads on it and it ran much better.
302 heads set up for stock eliminater. Acid wash porting (I forget what’s actually called).
PRH
Well-Known Member
From 1990- Re-ringed 318+.040(started with a previously rebuilt used motor), cast rebuilder pistons, mild ported mid-70’s 318 heads, stock valves, 340 cam, performer, 650dp, headers.
Easy peasy.
Also, easily improved upon a bit with a little different cam.
Easy peasy.
Also, easily improved upon a bit with a little different cam.
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It looks like extrude honed.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
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69 is a different 318. that one was rated 9.4 Scr, and with a 318 cam is a great engine. And I wonder what gears/stall were in that D?
Back in about 74, I put a junk-yard 340 top-end onto a 69 Satellite 318, with the 340 cam, and with a 4.10 rear gear change, it was smoking hot.
check it with clay to be sure.
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