The mighty 318! Help with compression, and head/piston combos…or even a stroker!

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AspenRTiskindafun

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Hello! Im one of those guys who really likes the 318, 400 crank with only a cam, intake, carb and flat tops that actually reach within 20 thou of the quench pad in 302 heads is the street build I had a while back in my 61 lancer. I want to go farther though and want some tips as I have a better skill set now, and a better understanding of how these engines make power but I’m no genius.

Now I’m not some top of the line engine builder, I’ve rebuild engines back to stock but customizing them? Never anything internal.


i have two plans (and don’t tell me to get another motor, I want to use the 318). Both use the 318, I’m capable of building these engines, I want static compression to be no less than 10.5 to 1 and no higher than 11.5-12 to 1.

If you know exactly what parts will give me that compression ratio please tell me, or what parts may put me in the ball park!

Plan 1: stroker kit to a 390 (4.0” stroke) and some 302 close chamber heads or depending on compression numbers maybe X or J heads with the bigger valves for the longer stroke. My questions here are, what would street drivability be like here? What compression ratios can I expect between the 302’s and the open chamber larger valve heads? The 302 valves definitely aren’t a bottle neck of any sort.

Plan 2: Kb pistons makes the 167 flat top which seems to be the closest to 0 deck I can find in my experience having rebuilt a few before with mold upgrades, these with the 302’s seem like they’d hopefully produce the numbers I’m looking for (450 crank because I had that number from a customers engine who supplied all the parts, I believ the aluminum heads they had made the biggest diff)

Plan 2B: kb399 domed pistons but I have a problem with these. If they don’t fit the closed chamber heads I’d rather switch to flat tops than switch to a more open head. The 399 if I ground down the spark plug area like some 340 and 360 aftermarket domed pieces I bet it will fit. That’s if they hit at all and I understand this combo will not be okay with pump gas (most likely, if the 302’s fit I can use the quench pad to help detonation but still)

I want to know if anyone’s ever ran 399’s on the heads I mentioned or ran 399’s at all. What did you think? How was clearance?

And do you think I’ll get higher compression using open heads and domed pistons or 0 deck flat tops with closed chamber 302s?

As I said before, the 318 is a must. I’m open to open chamber heads if someone explains why it’d make good power.

The few things I do know:
At work the guy who does the headwork and has build many a small block mopar says the stock valves are fine to 5500rpm but the ports are restrictive, now I know how to port so I’ll be doing that.
I don’t want to notch the bores in the block. Also what’re your 318 power build numbers? At the shop our most powerful was 590 crank NA with a 318, cam pistons heads sprints intake carb headers yada yada. My goal is 475 crank, hopefully a little under 400 at the wheels if not 400 mentioned in the beginning I have pieves together multiple 318’s with those numbers but I didn’t pick the parts I just assembled them. Anything ultra high performance I still need more certs and experience first.

TLDR: what combo workk get me minimum 450 crank on a 318, stroker? Flat tops and closed chamber or domes and open chamber?

!!!!This is for a dodge aspen R/T with original stripes and blacked out chrome, factory lip spoiler and all the louvres!!!
Found a burgundy interior for it as well out of a junk 2 door because the rt has nothing good inside besides the dasg
 
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Time to start reconsidering your parts.
KB 167 and 399 are for a 3.31 crank, not a 4.00 inch crank. Forget zero deck, your rings will be popping out of the bore.
302 heads are adequate for a nice 318, but asking them to supply enough air for a 390+ cu. in. engine that you want to get 475 horse out of is going to be quite a stretch to put it mildly; ported or not.
 
Professor Fate said:
Time to start reconsidering your parts.
KB 167 and 399 are for a 3.31 crank, not a 4.00 inch crank. Forget zero deck, your rings will be popping out of the bore.
302 heads are adequate for a nice 318, but asking them to supply enough air for a 390+ cu. in. engine that you want to get 475 horse out of is going to be quite a stretch to put it mildly; ported or not.
Click to expand...
You missed the part where I said multiple times I’d either stroke it, or go with higher comp pistons. I may not be the best engine builder but I’ve put together quite a few ol American v8’s. Those pistons will only work on a stock stroke, I was asking if people had tried the 399’s before as I can find people everywhere including myself who have used 167s. Whatever pistons come in the stroker kit are what would be used but I’m not sure stroking it is the best idea. Also asked in my post for anyone with experience with a 390 stroker or closed chamber heads with 399s, or worked with 399s at all. Curious if I’ll get higher compression with domes and open chamber, or flat tops the correct amount in the hole (18 thousandths what the quench pad calls for). So my post was asking questions about people’s experiences and if anybody has ever run a 399 with 302 or 920 heads

I had it listed as “plan 1 stroker”

“plan 2. Pistons and head work”

Also for air flow the 920’s which have the smallest valves don’t starve a 318 of any air until you pass around 6,000rpm, 302’s even higher. The small displacement is your friend on that front and with a decent intake and ported heads there’s no airflow bottleneck until you crest 6k.

For mine I’d like low-mid range torque (have some cams in mind generally around 485-500 lift intake 480-500 lift exhaust, duration equal around 252-262 and 8-10 degree lobe separation,
For mid range torque I want some overlap. It’s a cam size I’m familiar with and it makes much better low end torque than it should on paper and I don’t want anything high rpm, I’m tryna not crest 5.500k with it.
 
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Professor Fate said:
Time to start reconsidering your parts.
KB 167 and 399 are for a 3.31 crank, not a 4.00 inch crank. Forget zero deck, your rings will be popping out of the bore.
302 heads are adequate for a nice 318, but asking them to supply enough air for a 390+ cu. in. engine that you want to get 475 horse out of is going to be quite a stretch to put it mildly; ported or not.
Click to expand...
And I promise it’s not that big of a stretch, that’s a normal number we come to at the shop with stock heads that I ported out for the customer. Also polish rods and crank but I personally don’t think that’s necessary. I’m talking crank, I’d like 400rwhp which for a small block of any of the big 3 isn’t really asking much at all I picked that number because it’s on the lower side of what leaves our shop.
 

AspenRTiskindafun said:
And I promise it’s not that big of a stretch, that’s a normal number we come to at the shop with stock heads that I ported out for the customer. Also polish rods and crank but I personally don’t think that’s necessary. I’m talking crank, I’d like 400rwhp which for a small block of any of the big 3 isn’t really asking much at all I picked that number because it’s on the lower side of what leaves our shop.
Click to expand...

400 rwhp is at least 480 at the crank.

I wouldn’t use a 302 head with a gun to my head. You can do a set of Speedmasters and make more power.

You can easily use a 2.08 valve on a 3.940 bore. It’s not a small block Chevy. The valves open on the bore centerline.

You might as well stroke it because finding a piston that is at least acceptable for compression and has a ring pack that isn’t from the 1950’s for a stock stroke 318 is about impossible.

Compression ratio can be obtained with either an open chamber head or a closed chamber head.

If you are going to get the compression over 11:1 on pump gas you need to be willing to do everything you can to make it run correctly on pump gas. And not just run a cam 5 sizes too big to make it run.

That includes the cooling system and timing curve. And be willing to spend a couple of days on an engine dyno to sort that out.

You need a better plan and that plan starts with ditching the boat anchor 302 heads. Once you make that decision you can start filling in the rest of the pieces of the engine.

And you have to decide if you really want 400 rwhp. If you do, that magnifies your cam, carb, intake manifold no header decisions all the more critical.
 
*sniff*
*sniff*

this all smells very familiar....

Do domed KYB 399’s interfere with 302 cast heads?

Debating between 399’s and 167’s, nothing is getting decked just cleaned and built in the garage, I’ve had great experience with 167’s but I believe with the right choice of cam as long as the 399’s don’t interfere with the 302’s I could run premium still and not get detonation. On the flip...
www.forabodiesonly.com
 
:popcorn: Once someone actually figures this out it will be the second coming. :lol: :thumbsup:
 
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My response is……..I’m hitting the easy button(cuz it seems like the OP knows what he wants, and why argue about it)….……:thumbsup:
 
Yup, sounds like you've already got all your answers "at your shop" and you do it all the time, so why ask here?
Build it and let us know how it goes.
 
If your shop builds 590 hp 318's why you asking us ?

Heads is what makes an engine, why limit yourself with 302 heads.

Compression ratio, why is it either or ? the larger the displacement the easier it is to get cr so your best bet is add a 4" stroke.

What's the most cr you have successfully ran ? like Turk said to run on the edge you have to have everything just right, is and extra point or so of cr really worth it if there's a reasonable chance you could have a pinging mess of an engine ?
 
AspenRTiskindafun said:
And I promise it’s not that big of a stretch, that’s a normal number we come to at the shop with stock heads that I ported out for the customer. Also polish rods and crank but I personally don’t think that’s necessary. I’m talking crank, I’d like 400rwhp which for a small block of any of the big 3 isn’t really asking much at all I picked that number because it’s on the lower side of what leaves our shop.
Click to expand...
Surely you have dyno sheets from the engine and or flow test results from those heads, please post them. We’d all love to have a look.
 
AspenRTiskindafun said:
TLDR: what combo workk get me minimum 450 crank on a 318, stroker? Flat tops and closed chamber or domes and open chamber?
Click to expand...
By it's trapspeed of 93 in the Eighth, my 367 combo is making a theoretical 430 crank hp. I'm doing it with alloy heads, 11/1 Scr, and a Hi-lift 230/110 cam, and a Mopar 4-speed.
That 230 cam, is IMO, really a bit too big for my purpose.
I was happier with the previous 223/230/110 cam

To make it Streetable,
I run a low gear equivalent to a 4.10
and an overdrive to turn the 3.55s into 2.77s

the point being, with a specific engine displacement, the more power you want to achieve, the more rpm yur gunna have to turn, which means the bigger your cam will have to be, which, if you saddle that hi-rpm beast with low-rpm gears, you'll only ever get to that high rpm ONCE, on the way to 65mph, unless yur ok with risking yur driving privileges; cuz if they take away your license, now you got an expensive lawn ornament.
The point being;
have you given thought to the big picture?

Finally, I can tell you that, my previous iteration, by it's Quartermile trapspeed was making 335 hp, and it was everybit as much fun on the street. It lacked for nothing, was very happy on the hiway, made great fuel economy, and she was my DD for about 5 years. The only reason that cam is not still in there today, is because the cam lost lobes one day, right after an oil change. and I mean right away.

If you build a stroker for torque, with a well matched cam and cylinder pressure, I doubt you'd ever be unhappy. Power on the street is mostly for bragging rights.
However, along with a stroker comes those traction issues.

My all time favorite combo for over 50 years is still my Second kick at the can. This was an HO 340 short, with a complete 318 topend on it including the 2bbl 318 cam. The only performance parts on it were the fenderwell headers. I installed this into a 65 V100 Wagon. A real lightweight. I bet that engine never made over 250 hp, but it was sheer delight. Not fast, not quick, but a real pleasure to drive, I was 22, and driving was all I ever wanted to do; I drove that thing everywhere, until the factory A904 gave up..
By that time, I was married and I gave the car to my younger brother, who put it back to a slanty..

I just want to say one thing more; If your willing to convert your 318 into a 392, then it's a 392 not a 318. Why in heck do you want to start with a small bore? What's the attraction to 318s? You can't call it a 318 anymore cuz it's NOT a 318!
You got a bet going at work?
Yur Grandpapa had a 318 Coronet that burned the tires to 85mph?
What's the deal
You want to be different?
OK Fine, stroke a 273, lol. Or better yet, just supercharge something, lol.
Cuz the road you are taking is gonna get really really expensive. Everything behind that stroker will need to be hotrodded to take the power, and in the end, your tires are gonna be the weakest link, or the cooling system will be. it's gunna be one or the other, more likely is both..
There is almost no feeling worse than not being able to drive your car because it won't run cool enough.. I mean finding your wife in bed with your best friend is probably at least as worst. IDK , lol.
 
My advice to anyone wanting to build a potent stock stroke or stroker is to save 10- 15 grand before starting the build.
I suggest buying the cylinder heads first and build from there. Trick flow preferably.
 
AJ/FormS said:
By it's trapspeed of 93 in the Eighth, my 367 combo is making a theoretical 430 crank hp. I'm doing it with alloy heads, 11/1 Scr, and a Hi-lift 230/110 cam, and a Mopar 4-speed.
That 230 cam, is IMO, really a bit too big for my purpose.
I was happier with the previous 223/230/110 cam

To make it Streetable,
I run a low gear equivalent to a 4.10
and an overdrive to turn the 3.55s into 2.77s

the point being, with a specific engine displacement, the more power you want to achieve, the more rpm yur gunna have to turn, which means the bigger your cam will have to be, which, if you saddle that hi-rpm beast with low-rpm gears, you'll only ever get to that high rpm ONCE, on the way to 65mph, unless yur ok with risking yur driving privileges; cuz if they take away your license, now you got an expensive lawn ornament.
The point being;
have you given thought to the big picture?

Finally, I can tell you that, my previous iteration, by it's Quartermile trapspeed was making 335 hp, and it was everybit as much fun on the street. It lacked for nothing, was very happy on the hiway, made great fuel economy, and she was my DD for about 5 years. The only reason that cam is not still in there today, is because the cam lost lobes one day, right after an oil change. and I mean right away.

If you build a stroker for torque, with a well matched cam and cylinder pressure, I doubt you'd ever be unhappy. Power on the street is mostly for bragging rights.
However, along with a stroker comes those traction issues.

My all time favorite combo for over 50 years is still my Second kick at the can. This was an HO 340 short, with a complete 318 topend on it including the 2bbl 318 cam. The only performance parts on it were the fenderwell headers. I installed this into a 65 V100 Wagon. A real lightweight. I bet that engine never made over 250 hp, but it was sheer delight. Not fast, not quick, but a real pleasure to drive, I was 22, and driving was all I ever wanted to do; I drove that thing everywhere, until the factory A904 gave up..
By that time, I was married and I gave the car to my younger brother, who put it back to a slanty..

I just want to say one thing more; If your willing to convert your 318 into a 392, then it's a 392 not a 318. Why in heck do you want to start with a small bore? What's the attraction to 318s? You can't call it a 318 anymore cuz it's NOT a 318!
You got a bet going at work?
Yur Grandpapa had a 318 Coronet that burned the tires to 85mph?
What's the deal
You want to be different?
OK Fine, stroke a 273, lol. Or better yet, just supercharge something, lol.
Cuz the road you are taking is gonna get really really expensive. Everything behind that stroker will need to be hotrodded to take the power, and in the end, your tires are gonna be the weakest link, or the cooling system will be. it's gunna be one or the other, more likely is both..
There is almost no feeling worse than not being able to drive your car because it won't run cool enough.. I mean finding your wife in bed with your best friend is probably at least as worst. IDK , lol.
Click to expand...
I never got the stroker 318, if your gonna to all that expense for more cid, I'd want the extra cid that a stroker 340/360 will give plus the extra breathing room.

To me the two main reasons you build a 318, 1st one you got a running 318 and you want to add basic performance (4bbl, rv cam, exhaust, tune) to me a no brainer. 2nd you want make the hp at a higher rpm than a similar 360 will cause you like rpms. Obviously there's others like under dog but I really don't see it being one especially under 500 hp.
 
Here why you go with better heads (top end).
Even though it's a 355 Chev, All 3 high hp and rpm top ends make make more power than stock everywhere and basically each other, the gains weren't just at the top rpms, lots of midrange gains also.

1748484915786.png
 
junkyardhero said:
*sniff*
*sniff*

this all smells very familiar....

Do domed KYB 399’s interfere with 302 cast heads?

Debating between 399’s and 167’s, nothing is getting decked just cleaned and built in the garage, I’ve had great experience with 167’s but I believe with the right choice of cam as long as the 399’s don’t interfere with the 302’s I could run premium still and not get detonation. On the flip...
www.forabodiesonly.com
Click to expand...
Like a dog's butt?
 
fishmens67 said:
If you wouldn't mind yodeling the parts used for this mystery 590 horse 318.
Click to expand...
I think this is what we all yearned for as young men the mystery recipe for hot rodding a 318 sure we all tried in our own ways and it was fun but it wasnt enough at some point and we moved on... some to 340 some to 360 some to B and RB big blocks ah yes memories.
 
PRH said:
I disagree.

Pure BS? Sure.

But def not grade A.
Click to expand...
definitely marks off for lack of creativity and subterfuge

so like harbor freight levels of bullshittery, not snap-on quality nonsense.

funny how many are gonna take the bait here
 
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